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Current Biology
Journal Prestige (SJR): 4.296
Citation Impact (citeScore): 5
Number of Followers: 288  
 
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ISSN (Print) 0960-9822 - ISSN (Online) 1879-0445
Published by Elsevier Homepage  [3177 journals]
  • Activation of Kappa Opioid Receptor Regulates the Hypothermic Response to
           Calorie Restriction and Limits Body Weight Loss
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Rigo Cintron-Colon, Christopher W. Johnson, J. Rafael Montenegro-Burke, Carlos Guijas, Lila Faulhaber, Manuel Sanchez-Alavez, Carlos A. Aguirre, Kokila Shankar, Mona Singh, Andrea Galmozzi, Gary Siuzdak, Enrique Saez, Bruno ContiSummaryMammals maintain a nearly constant core body temperature (Tb) by balancing heat production and heat dissipation. This comes at a high metabolic cost that is sustainable if adequate calorie intake is maintained. When nutrients are scarce or experimentally reduced such as during calorie restriction (CR), endotherms can reduce energy expenditure by lowering Tb [1, 2, 3, 4, 5, 6]. This adaptive response conserves energy, limiting the loss of body weight due to low calorie intake [7, 8, 9, 10]. Here we show that this response is regulated by the kappa opioid receptor (KOR). CR is associated with increased hypothalamic levels of the endogenous opioid Leu-enkephalin, which is derived from the KOR agonist precursor dynorphin [11]. Pharmacological inhibition of KOR, but not of the delta or the mu opioid receptor subtypes, fully blocked CR-induced hypothermia and increased weight loss during CR independent of calorie intake. Similar results were seen with DIO mice subjected to CR. In contrast, inhibiting KOR did not change Tb in animals fed ad libitum (AL). Chemogenetic inhibition of KOR neurons in the hypothalamic preoptic area reduced the CR-induced hypothermia, whereas chemogenetic activation of prodynorphin-expressing neurons in the arcuate or the parabrachial nucleus lowered Tb. These data indicate that KOR signaling is a pivotal regulator of energy homeostasis and can affect body weight during dieting by modulating Tb and energy expenditure.Graphical Graphical abstract for this article
       
  • Activity in Lateral Visual Areas Contributes to Surround Suppression in
           Awake Mouse V1
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Joris Vangeneugden, Enny H. van Beest, Michael X Cohen, Jeannette A.M. Lorteije, Sreedeep Mukherjee, Lisa Kirchberger, Jorrit S. Montijn, Premnath Thamizharasu, Daniela Camillo, Christiaan N. Levelt, Pieter R. Roelfsema, Matthew W. Self, J. Alexander HeimelSummaryNeuronal response to sensory stimuli depends on the context. The response in primary visual cortex (V1), for instance, is reduced when a stimulus is surrounded by a similar stimulus [1, 2, 3]. The source of this surround suppression is partially known. In mouse, local horizontal integration by somatostatin-expressing interneurons contributes to surround suppression [4]. In primates, however, surround suppression arises too quickly to come from local horizontal integration alone, and myelinated axons from higher visual areas, where cells have larger receptive fields, are thought to provide additional surround suppression [5, 6]. Silencing higher visual areas indeed decreased surround suppression in the awake primate by increasing responses to large stimuli [7, 8], although not under anesthesia [9, 10]. In smaller mammals, like mice, fast surround suppression could be possible without feedback. Recent studies revealed a small reduction in V1 responses when silencing higher areas [11, 12] but have not investigated surround suppression. To determine whether higher visual areas contribute to V1 surround suppression, even when this is not necessary for fast processing, we inhibited the areas lateral to V1, particularly the lateromedial area (LM), a possible homolog of primate V2 [13], while recording in V1 of awake and anesthetized mice. We found that part of the surround suppression depends on activity from lateral visual areas in the awake, but not anesthetized, mouse. Inhibiting the lateral visual areas specifically increased responses in V1 to large stimuli. We present a model explaining how excitatory feedback to V1 can have these suppressive effects for large stimuli.
       
  • A Genome-wide Screen Reveals that Reducing Mitochondrial DNA Polymerase
           Can Promote Elimination of Deleterious Mitochondrial Mutations
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Ason C.-Y. Chiang, Eleanor McCartney, Patrick H. O'Farrell, Hansong MaSummaryA mutant mitochondrial genome arising amid the pool of mitochondrial genomes within a cell must compete with existing genomes to survive to the next generation. Even weak selective forces can bias transmission of one genome over another to affect the inheritance of mitochondrial diseases and guide the evolution of mitochondrial DNA (mtDNA). Studies in several systems suggested that purifying selection in the female germline reduces transmission of detrimental mitochondrial mutations [1, 2, 3, 4, 5, 6, 7]. In contrast, some selfish genomes can take over despite a cost to host fitness [8, 9, 10, 11, 12, 13]. Within individuals, the outcome of competition is therefore influenced by multiple selective forces. The nuclear genome, which encodes most proteins within mitochondria, and all external regulators of mitochondrial biogenesis and dynamics can influence the competition between mitochondrial genomes [14, 15, 16, 17, 18], yet little is known about how this works. Previously, we established a Drosophila line transmitting two mitochondrial genomes in a stable ratio enforced by purifying selection benefiting one genome and a selfish advantage favoring the other [8]. Here, to find nuclear genes that impact mtDNA competition, we screened heterozygous deletions tiling ∼70% of the euchromatic regions and examined their influence on this ratio. This genome-wide screen detected many nuclear modifiers of this ratio and identified one as the catalytic subunit of mtDNA polymerase gene (POLG), tam. A reduced dose of tam drove elimination of defective mitochondrial genomes. This study suggests that our approach will uncover targets for interventions that would block propagation of pathogenic mitochondrial mutations.Graphical Graphical abstract for this article
       
  • The Early Ediacaran Caveasphaera Foreshadows the Evolutionary Origin of
           Animal-like Embryology
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Zongjun Yin, Kelly Vargas, John Cunningham, Stefan Bengtson, Maoyan Zhu, Federica Marone, Philip DonoghueSummaryThe Ediacaran Weng’an Biota (Doushantuo Formation, 609 Ma old) is a rich microfossil assemblage that preserves biological structure to a subcellular level of fidelity and encompasses a range of developmental stages [1]. However, the animal embryo interpretation of the main components of the biota has been the subject of controversy [2, 3]. Here, we describe the development of Caveasphaera, which varies in morphology from lensoid to a hollow spheroidal cage [4] to a solid spheroid [5] but has largely evaded description and interpretation. Caveasphaera is demonstrably cellular and develops within an envelope by cell division and migration, first defining the spheroidal perimeter via anastomosing cell masses that thicken and ingress as strands of cells that detach and subsequently aggregate in a polar region. Concomitantly, the overall diameter increases as does the volume of the cell mass, but after an initial phase of reductive palinotomy, the volume of individual cells remains the same through development. The process of cell ingression, detachment, and polar aggregation is analogous to gastrulation; together with evidence of functional cell adhesion and development within an envelope, this is suggestive of a holozoan affinity. Parental investment in the embryonic development of Caveasphaera and co-occurring Tianzhushania and Spiralicellula, as well as delayed onset of later development, may reflect an adaptation to the heterogeneous nature of the early Ediacaran nearshore marine environments in which early animals evolved.Graphical Graphical abstract for this article
       
  • WASP Restricts Active Rac to Maintain Cells’ Front-Rear Polarization
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Clelia Amato, Peter A. Thomason, Andrew J. Davidson, Karthic Swaminathan, Shehab Ismail, Laura M. Machesky, Robert H. InsallSummaryEfficient motility requires polarized cells, with pseudopods at the front and a retracting rear. Polarization is maintained by restricting the pseudopod catalyst, active Rac, to the front. Here, we show that the actin nucleation-promoting factor Wiskott-Aldrich syndrome protein (WASP) contributes to maintenance of front-rear polarity by controlling localization and cellular levels of active Rac. Dictyostelium cells lacking WASP inappropriately activate Rac at the rear, which affects their polarity and speed. WASP’s Cdc42 and Rac interacting binding (“CRIB”) motif has been thought to be essential for its activation. However, we show that the CRIB motif’s biological role is unexpectedly complex. WASP CRIB mutants are no longer able to restrict Rac activity to the front, and cannot generate new pseudopods when SCAR/WAVE is absent. Overall levels of Rac activity also increase when WASP is unable to bind to Rac. However, WASP without a functional CRIB domain localizes normally at clathrin pits during endocytosis, and activates Arp2/3 complex. Similarly, chemical inhibition of Rac does not affect WASP localization or activation at sites of endocytosis. Thus, the interaction between small GTPases and WASP is more complex than previously thought—Rac regulates a subset of WASP functions, but WASP reciprocally restricts active Rac through its CRIB motif.Graphical Graphical abstract for this article
       
  • Genetic Reprogramming of Positional Memory in a Regenerating Appendage
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Ying-Ting Wang, Tzu-Lun Tseng, Yu-Chia Kuo, Jr-Kai Yu, Yi-Hsien Su, Kenneth D. Poss, Chen-Hui ChenSummaryCertain vertebrates such as salamanders and zebrafish are able to regenerate complex tissues (e.g., limbs and fins) with remarkable fidelity. However, how positional information of the missing structure is recalled by appendage stump cells has puzzled researchers for centuries. Here, we report that sizing information for adult zebrafish tailfins is encoded within proliferating blastema cells during a critical period of regeneration. Using a chemical mutagenesis screen, we identified a temperature-sensitive allele of the gene encoding DNA polymerase alpha subunit 2 (pola2) that disrupts fin regeneration in zebrafish. Temperature shift assays revealed a 48-h window of regeneration, during which positional identities could be disrupted in pola2 mutants, leading to regeneration of miniaturized appendages. These fins retained memory of the new size in subsequent rounds of amputation and regeneration. Similar effects were observed upon transient genetic or pharmacological disruption of progenitor cell proliferation after plucking of zebrafish scales or head or tail amputation in amphioxus and annelids. Our results provide evidence that positional information in regenerating tissues is not hardwired but malleable, based on regulatory mechanisms that appear to be evolutionarily conserved across distantly related phyla.Graphical Graphical abstract for this article
       
  • Serotonergic Modulation of Walking in Drosophila
    • Abstract: Publication date: Available online 27 November 2019Source: Current BiologyAuthor(s): Clare E. Howard, Chin-Lin Chen, Tanya Tabachnik, Rick Hormigo, Pavan Ramdya, Richard S. MannSummaryTo navigate complex environments, animals must generate highly robust, yet flexible, locomotor behaviors. For example, walking speed must be tailored to the needs of a particular environment. Not only must animals choose the correct speed and gait, they must also adapt to changing conditions and quickly respond to sudden and surprising new stimuli. Neuromodulators, particularly the small biogenic amine neurotransmitters, have the ability to rapidly alter the functional outputs of motor circuits. Here, we show that the serotonergic system in the vinegar fly, Drosophila melanogaster, can modulate walking speed in a variety of contexts and also change how flies respond to sudden changes in the environment. These multifaceted roles of serotonin in locomotion are differentially mediated by a family of serotonergic receptors with distinct activities and expression patterns.Graphical Graphical abstract for this article
       
  • Reaching Consensus in Polarized Moral Debates
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Joaquin Navajas, Facundo Álvarez Heduan, Juan Manuel Garrido, Pablo A. Gonzalez, Gerry Garbulsky, Dan Ariely, Mariano SigmanSummaryThe group polarization phenomenon is a widespread human bias with no apparent geographical or cultural boundaries [1]. Although the conditions that breed extremism have been extensively studied [2, 3, 4, 5], comparably little research has examined how to depolarize attitudes in people who already embrace extreme beliefs. Previous studies have shown that deliberating groups may shift toward more moderate opinions [6], but why deliberation is sometimes effective although other times it fails at eliciting consensus remains largely unknown. To investigate this, we performed a large-scale behavioral experiment with live crowds from two countries. Participants (N = 3,288 in study 1 and N = 582 in study 2) were presented with a set of moral scenarios and asked to judge the acceptability of a controversial action. Then they organized in groups of three and discussed their opinions to see whether they agreed on common values of acceptability. We found that groups succeeding at reaching consensus frequently had extreme participants with low confidence and a participant with a moderate view but high confidence. Quantitative analyses showed that these “confident grays” exerted the greatest weight on group judgements and suggest that consensus was driven by a mediation process [7, 8]. Overall, these findings shed light on the elements that allow human groups to resolve moral disagreement.
       
  • Neural Correlates of the Conscious Perception of Visual Location Lie
           Outside Visual Cortex
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Sirui Liu, Qing Yu, Peter U. Tse, Patrick CavanaghSummaryWhen perception differs from the physical stimulus, as it does for visual illusions and binocular rivalry, the opportunity arises to localize where perception emerges in the visual processing hierarchy. Representations prior to that stage differ from the eventual conscious percept even though they provide input to it. Here, we investigate where and how a remarkable misperception of position emerges in the brain. This “double-drift” illusion causes a dramatic mismatch between retinal and perceived location, producing a perceived motion path that can differ from its physical path by 45° or more. The deviations in the perceived trajectory can accumulate over at least a second, whereas other motion-induced position shifts accumulate over 80–100 ms before saturating. Using fMRI and multivariate pattern analysis, we find that the illusory path does not share activity patterns with a matched physical path in any early visual areas. In contrast, a whole-brain searchlight analysis reveals a shared representation in anterior regions of the brain. These higher-order areas would have the longer time constants required to accumulate the small moment-to-moment position offsets that presumably originate in early visual cortical areas and then transform these sensory inputs into a final conscious percept. The dissociation between perception and the activity in early sensory cortex suggests that consciously perceived position does not emerge in what is traditionally regarded as the visual system but instead emerges at a higher level.
       
  • Establishment of Wolbachia Strain wAlbB in Malaysian Populations of Aedes
           aegypti for Dengue Control
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Wasi A. Nazni, Ary A. Hoffmann, Ahmad NoorAfizah, Yoon Ling Cheong, Maria V. Mancini, Nicholas Golding, Ghazali M.R. Kamarul, Mohd A.K. Arif, Hasim Thohir, Halim NurSyamimi, M. Zabari ZatilAqmar, Mazni NurRuqqayah, Amran NorSyazwani, Azmi Faiz, Francis-Rudin M.N. Irfan, Subramaniam Rubaaini, Nasir Nuradila, Nasir M.N. Nizam, Saidin M. Irwan, Nancy M. Endersby-HarshmanSummaryDengue has enormous health impacts globally. A novel approach to decrease dengue incidence involves the introduction of Wolbachia endosymbionts that block dengue virus transmission into populations of the primary vector mosquito, Aedes aegypti. The wMel Wolbachia strain has previously been trialed in open releases of Ae. aegypti; however, the wAlbB strain has been shown to maintain higher density than wMel at high larval rearing temperatures. Releases of Ae. aegypti mosquitoes carrying wAlbB were carried out in 6 diverse sites in greater Kuala Lumpur, Malaysia, with high endemic dengue transmission. The strain was successfully established and maintained at very high population frequency at some sites or persisted with additional releases following fluctuations at other sites. Based on passive case monitoring, reduced human dengue incidence was observed in the release sites when compared to control sites. The wAlbB strain of Wolbachia provides a promising option as a tool for dengue control, particularly in very hot climates.
       
  • Mechanisms of Convergent Egg Provisioning in Poison Frogs
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Eva K. Fischer, Alexandre B. Roland, Nora A. Moskowitz, Charles Vidoudez, Ndimbintsoa Ranaivorazo, Elicio E. Tapia, Sunia A. Trauger, Miguel Vences, Luis A. Coloma, Lauren A. O’ConnellSummaryParental provisioning of offspring with physiological products (nursing) occurs in many animals, yet little is known about the neuroendocrine basis of nursing in non-mammalian species. Within amphibians, maternal provisioning has evolved multiple times, with mothers of some species feeding unfertilized eggs to their developing offspring until tadpoles complete metamorphosis [1, 2, 3]. We conducted field studies in Ecuador and Madagascar to ask whether convergence at the behavioral level provides similar benefits to offspring and relies on shared neural mechanisms in dendrobatid and mantellid poison frogs. At an ecological level, we found that nursing allows poison frogs to provide chemical defenses to their tadpoles in both species. At the neural level, nursing was associated with increased activity in the lateral septum and preoptic area, demonstrating recruitment of shared brain regions in the convergent evolution of nursing within frogs and across vertebrates [4]. In contrast, only mantellids showed increased oxytocin neuron activity akin to that in nursing mammals [5], suggesting evolutionary versatility in molecular mechanisms. Our findings demonstrate that maternal provisioning provides similar potential benefits to offspring and relies on similar brain regions in poison frog species with convergently evolved toxicity and maternal care.Video Graphical Graphical abstract for this article
       
  • Defined Cell Types in Superior Colliculus Make Distinct Contributions to
           Prey Capture Behavior in the Mouse
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Jennifer L. Hoy, Hannah I. Bishop, Cristopher M. NiellSummaryThe superior colliculus (SC) plays a highly conserved role in visual processing and mediates visual orienting behaviors across species, including both overt motor orienting [1, 2] and orienting of attention [3, 4]. To determine the specific circuits within the superficial superior colliculus (sSC) that drive orienting and approach behavior toward appetitive stimuli, we explored the role of three genetically defined cell types in mediating prey capture in mice. Chemogenetic inactivation of two classically defined cell types, the wide-field (WF) and narrow-field (NF) vertical neurons, revealed that they are involved in distinct aspects of prey capture. WF neurons were required for rapid prey detection and distant approach initiation, whereas NF neurons were required for accurate orienting during pursuit as well as approach initiation and continuity. In contrast, prey capture did not require parvalbumin-expressing (PV) neurons that have previously been implicated in fear responses. The visual coding and projection targets of WF and NF cells were consistent with their roles in prey detection versus pursuit, respectively. Thus, our studies link specific neural circuit connectivity and function with stimulus detection and orienting behavior, providing insight into visuomotor and attentional mechanisms mediated by superior colliculus.Graphical Graphical abstract for this article
       
  • Autoregulation of RCO by Low-Affinity Binding Modulates Cytokinin Action
           and Shapes Leaf Diversity
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Mohsen Hajheidari, Yi Wang, Neha Bhatia, Francesco Vuolo, José Manuel Franco-Zorrilla, Michal Karady, Remco A. Mentink, Anhui Wu, Bello Rilwan Oluwatobi, Bruno Müller, Raffaele Dello Ioio, Stefan Laurent, Karin Ljung, Peter Huijser, Xiangchao Gan, Miltos TsiantisSummaryMechanisms through which the evolution of gene regulation causes morphological diversity are largely unclear. The tremendous shape variation among plant leaves offers attractive opportunities to address this question. In cruciferous plants, the REDUCED COMPLEXITY (RCO) homeodomain protein evolved via gene duplication and acquired a novel expression domain that contributed to leaf shape diversity. However, the molecular pathways through which RCO regulates leaf growth are unknown. A key question is to identify genome-wide transcriptional targets of RCO and the DNA sequences to which RCO binds. We investigate this question using Cardamine hirsuta, which has complex leaves, and its relative Arabidopsis thaliana, which evolved simple leaves through loss of RCO. We demonstrate that RCO directly regulates genes controlling homeostasis of the hormone cytokinin to repress growth at the leaf base. Elevating cytokinin signaling in the RCO expression domain is sufficient to both transform A. thaliana simple leaves into complex ones and partially bypass the requirement for RCO in C. hirsuta complex leaf development. We also identify RCO as its own target gene. RCO directly represses its own transcription via an array of low-affinity binding sites, which evolved after RCO duplicated from its progenitor sequence. This autorepression is required to limit RCO expression. Thus, evolution of low-affinity binding sites created a negative autoregulatory loop that facilitated leaf shape evolution by defining RCO expression and fine-tuning cytokinin activity. In summary, we identify a transcriptional mechanism through which conflicts between novelty and pleiotropy are resolved during evolution and lead to morphological differences between species.Graphical Graphical abstract for this article
       
  • An Inhibitory Lateral Hypothalamic-Preoptic Circuit Mediates Rapid
           Arousals from Sleep
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Anne Venner, Roberto De Luca, Lauren T. Sohn, Sathyajit S. Bandaru, Anne M.J. Verstegen, Elda Arrigoni, Patrick M. FullerSummaryAmong the neuronal populations implicated in sleep-wake control, the ventrolateral preoptic (VLPO) nucleus has emerged as a key sleep-promoting center. However, the synaptic drives that regulate the VLPO to control arousal levels in vivo have not to date been identified. Here, we show that sleep-promoting galaninergic neurons within the VLPO nucleus, defined pharmacologically and by single-cell transcript analysis, are postsynaptic targets of lateral hypothalamic GABAergic (LHGABA) neurons and that activation of this pathway in vivo rapidly drives wakefulness. Ca2+ imaging from LHGABA neurons indicate that they are both wake and rapid eye movement (REM)-sleep active. Consistent with the potent arousal-promoting property of the LHGABA → VLPO pathway, presynaptic inputs to LHGABA neurons originate from several canonical stress- and arousal-related network nodes. This work represents the first demonstration that direct synaptic inhibition of the VLPO area can suppress sleep-promoting neurons to rapidly promote arousal.Graphical Graphical abstract for this article
       
  • Auditory Perceptual History Is Propagated through Alpha Oscillations
    • Abstract: Publication date: Available online 21 November 2019Source: Current BiologyAuthor(s): Hao Tam Ho, David C. Burr, David Alais, Maria Concetta MorroneSummaryPerception is a proactive, “predictive” process, in which the brain relies, at least in part, on accumulated experience to make best guesses about the world to test against sensory data, updating the guesses as new experience is acquired. Using novel behavioral methods, the present study demonstrates the role of alpha rhythms in communicating past perceptual experience. Participants were required to discriminate the ear of origin of brief sinusoidal tones that were presented monaurally at random times within a burst of uncorrelated dichotic white noise masks. Performance was not constant but varied with delay after noise onset in an oscillatory manner at about 9 Hz (alpha rhythm). Importantly, oscillations occurred only for trials preceded by a target tone to the same ear, either on the previous trial or two trials back. These results suggest that communication of perceptual history generates neural oscillations within specific perceptual circuits, strongly implicating behavioral oscillations in predictive perception and with formation of working memory.Graphical Graphical abstract for this article
       
  • Evolution: A Mosaic-type Centromere in an Early-Diverging Fungus
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Bungo AkiyoshiSummaryCentromeres in eukaryotes can be classified into three categories: point centromeres, regional centromeres, or holocentric. Now, a hybrid-type centromere is found in a pathogenic fungus that lacks the key kinetochore component CENP-A.
       
  • Heterogeneity in Palaeolithic Population Continuity and Neolithic
           Expansion in North Africa
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Gerard Serra-Vidal, Marcel Lucas-Sanchez, Karima Fadhlaoui-Zid, Asmahan Bekada, Pierre Zalloua, David ComasSummaryNorth Africa is located at the crossroads of the Mediterranean Sea, the Middle East, and the Sahara Desert. Extensive migrations and gene flow in the region have shaped many different cultures and ancestral genetic components through time [1, 2, 3, 4, 5, 6]. DNA data from ancient Moroccan sites [7, 8] has recently shed some light to the population continuity-versus-replacement debate, i.e., the question of whether current North African populations descend from Palaeolithic groups or, on the contrary, subsequent migrations swept away all pre-existing genetic signal in the region. In the present study, we analyze 21 complete North African genomes and compare them with extant and ancient genome data in order to address the demographic continuity-versus-replacement debate, to assess whether these demographic events were homogeneous (including Berber and Arabic-speaking groups), and to explore the effect of Neolithization and posterior migration waves. The North African genetic pool is defined as a melting pot of genetic components, including an endemic North African Epipalaeolithic component at low frequency that forms a declining gradient from Western to Eastern North Africa. This scenario is consistent with Neolithization having shaped most of the current genetic variation in the region when compared to posterior back-to-North-Africa migration waves such as the Arabization. A common and distinct genetic history of the region is shown, with internal different proportions of genetic components owing to differential admixture with surrounding groups as well as to genetic drift due to isolation and endogamy in certain populations.
       
  • Rhizosphere-Associated Pseudomonas Suppress Local Root Immune Responses by
           Gluconic Acid-Mediated Lowering of Environmental pH
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Ke Yu, Yang Liu, Ramon Tichelaar, Niharika Savant, Ellen Lagendijk, Sanne J.L. van Kuijk, Ioannis A. Stringlis, Anja J.H. van Dijken, Corné M.J. Pieterse, Peter A.H.M. Bakker, Cara H. Haney, Roeland L. BerendsenSummaryThe root microbiome consists of commensal, pathogenic, and plant-beneficial microbes [1]. Most members of the root microbiome possess microbe-associated molecular patterns (MAMPs) similar to those of plant pathogens [2]. Their recognition can lead to the activation of host immunity and suppression of plant growth due to growth-defense tradeoffs [3, 4]. We found that 42% of the tested root microbiota, including the plant growth-promoting rhizobacteria Pseudomonas capeferrum WCS358 [5, 6] and Pseudomonas simiae WCS417 [6, 7], are able to quench local Arabidopsis thaliana root immune responses that are triggered by flg22 [8], an immunogenic epitope of the MAMP flagellin [9], suggesting that this is an important function of the root microbiome. In a screen for WCS358 mutants that lost their capacity to suppress flg22-induced CYP71A12pro:GUS MAMP-reporter gene expression, we identified the bacterial genes pqqF and cyoB in WCS358, which are required for the production of gluconic acid and its derivative 2-keto gluconic acid. Both WCS358 mutants are impaired in the production of these organic acids and consequently lowered their extracellular pH to a lesser extent than wild-type WCS358. Acidification of the plant growth medium similarly suppressed flg22-induced CYP71A12pro:GUS and MYB51pro:GUS expression, and the flg22-mediated oxidative burst, suggesting a role for rhizobacterial gluconic acid-mediated modulation of the extracellular pH in the suppression of root immunity. Rhizosphere population densities of the mutants were significantly reduced compared to wild-type. Collectively, these findings show that suppression of immune responses is an important function of the root microbiome, as it facilitates colonization by beneficial root microbiota.
       
  • Dark Ophiuroid Biodiversity in a Prospective Abyssal Mine Field
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Magdalini Christodoulou, Timothy D. O’Hara, Andrew F. Hugall, Pedro Martinez ArbizuSummaryThe seafloor contains valuable mineral resources, including polymetallic (or manganese) nodules that form on offshore abyssal plains. The largest and most commercially attractive deposits are located in the Clarion Clipperton Fracture Zone (CCZ), in the eastern Pacific Ocean (EP) between Hawaii and Mexico, where testing of a mineral collection system is set to start soon [1]. The requirement to establish pre-mining environmental management plans has prompted numerous recent biodiversity and DNA barcoding surveys across these remote regions. Here we map DNA sequences from sampled ophiuroids (brittle stars, including post-larvae) of the CCZ and Peru Basin onto a substantial tree of life to show unprecedented levels of abyssal ophiuroid phylogenetic diversity including at least three ancient (>70 Ma), previously unknown clades. While substantial dark (unobserved) biodiversity has been reported from various microbial meta-barcoding projects [2, 3], our data show that we have considerably under-estimated the biodiversity of even the most conspicuous mega-faunal invertebrates [4] of the EP abyssal plain.Graphical Graphical abstract for this article
       
  • Social Context Enhances Hormonal Modulation of Pheromone Detection in
           Drosophila
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Sachin Sethi, Hui-Hao Lin, Andrew K. Shepherd, Pelin C. Volkan, Chih-Ying Su, Jing W. WangSummaryCritical to evolutionary fitness, animals regulate social behaviors by integrating signals from both their external environments and internal states. Here, we find that population density modulates the courtship behavior of male Drosophila melanogaster in an age-dependent manner. In a competitive mating assay, males reared in a social environment have a marked advantage in courting females when pitted against males reared in isolation. Group housing promotes courtship in mature (7-day) but not immature (2-day) males; this behavioral plasticity requires the Or47b pheromone receptor. Using single-sensillum recordings, we find that group housing increases the response of Or47b olfactory receptor neurons (ORNs) only in mature males. The effect of group housing on olfactory response and behavior can be mimicked by chronically exposing single-housed males to an Or47b ligand. At the molecular level, group housing elevates Ca2+ levels in Or47b ORNs, likely leading to CaMKI-mediated activation of the histone-acetyl transferase CBP. This signaling event in turn enhances the efficacy of juvenile hormone, an age-related regulator of reproductive maturation in flies. Furthermore, the male-specific Fruitless isoform (FruM) is required for the sensory plasticity, suggesting that FruM functions as a downstream genomic coincidence detector in Or47b ORNs—integrating reproductive maturity, signaled by juvenile hormone, and population density, signaled by CBP. In all, we identify a neural substrate and activity-dependent mechanism by which social context can directly influence pheromone sensitivity, thereby modulating social behavior according to animals’ life-history stage.Graphical Graphical abstract for this article
       
  • Injury Activates a Dynamic Cytoprotective Network to Confer Stress
           Resilience and Drive Repair
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Helen Weavers, Will Wood, Paul MartinSummaryIn healthy individuals, injured tissues rapidly repair themselves following damage. Within a healing skin wound, recruited inflammatory cells release a multitude of bacteriocidal factors, including reactive oxygen species (ROS), to eliminate invading pathogens. Paradoxically, while these highly reactive ROS confer resistance to infection, they are also toxic to host tissues and may ultimately delay repair. Repairing tissues have therefore evolved powerful cytoprotective “resilience” machinery to protect against and tolerate this collateral damage. Here, we use in vivo time-lapse imaging and genetic manipulation in Drosophila to dissect the molecular and cellular mechanisms that drive tissue resilience to wound-induced stress. We identify a dynamic, cross-regulatory network of stress-activated cytoprotective pathways, linking calcium, JNK, Nrf2, and Gadd45, that act to both “shield” tissues from oxidative damage and promote efficient damage repair. Ectopic activation of these pathways confers stress protection to naive tissue, while their inhibition leads to marked delays in wound closure. Strikingly, the induction of cytoprotection is tightly linked to the pathways that initiate the inflammatory response, suggesting evolution of a fail-safe mechanism for tissue protection each time inflammation is triggered. A better understanding of these resilience mechanisms—their identities and precise spatiotemporal regulation—is of major clinical importance for development of therapeutic interventions for all pathologies linked to oxidative stress, including debilitating chronic non-healing wounds.Graphical Graphical abstract for this article
       
  • The Sublaterodorsal Tegmental Nucleus Functions to Couple Brain State and
           Motor Activity during REM Sleep and Wakefulness
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Zoltan A. Torontali, Jimmy J. Fraigne, Paul Sanghera, Richard Horner, John PeeverSummaryAppropriate levels of muscle tone are needed to support waking behaviors such as sitting or standing. However, it is unclear how the brain functions to couple muscle tone with waking behaviors. Cataplexy is a unique experiment of nature in which muscle paralysis involuntarily intrudes into otherwise normal periods of wakefulness. Cataplexy therefore provides the opportunity to identify the circuit mechanisms that couple muscle tone and waking behaviors. Here, we tested the long-standing hypothesis that muscle paralysis during cataplexy is caused by recruitment of the brainstem circuit that induces muscle paralysis during REM sleep. Using behavioral, electrophysiological, and chemogenetic strategies, we found that muscle tone and arousal state can be decoupled by manipulation of the REM sleep circuit (the sublaterodorsal tegmental nucleus [SLD]). First, we show that silencing SLD neurons prevents motor suppression during REM sleep. Second, we show that activating these same neurons promotes cataplexy in narcoleptic (orexin−/−) mice, whereas silencing these neurons prevents cataplexy. Most importantly, we show that SLD neurons can decouple motor activity and arousal state in healthy mice. We show that SLD activation triggers cataplexy-like attacks in wild-type mice that are behaviorally and electrophysiologically indistinguishable from cataplexy in orexin−/− mice. We conclude that the SLD functions to engage arousal-motor synchrony during both wakefulness and REM sleep, and we propose that pathological recruitment of SLD neurons could underlie cataplexy in narcolepsy.
       
  • The Biology of General Anesthesia from Paramecium to Primate
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Max B. Kelz, George A. MashourGeneral anesthesia serves a critically important function in the clinical care of human patients. However, the anesthetized state has foundational implications for biology because anesthetic drugs are effective in organisms ranging from paramecia, to plants, to primates. Although unconsciousness is typically considered the cardinal feature of general anesthesia, this endpoint is only strictly applicable to a select subset of organisms that are susceptible to being anesthetized. We review the behavioral endpoints of general anesthetics across species and propose the isolation of an organism from its environment — both in terms of the afferent arm of sensation and the efferent arm of action — as a generalizable definition. We also consider the various targets and putative mechanisms of general anesthetics across biology and identify key substrates that are conserved, including cytoskeletal elements, ion channels, mitochondria, and functionally coupled electrical or neural activity. We conclude with a unifying framework related to network function and suggest that general anesthetics — from single cells to complex brains — create inefficiency and enhance modularity, leading to the dissociation of functions both within an organism and between the organism and its surroundings. Collectively, we demonstrate that general anesthesia is not restricted to the domain of modern medicine but has broad biological relevance with wide-ranging implications for a diverse array of species.
       
  • Synaptic Plasticity: Close Encounters of the Tonic and Phasic Kind
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Karen L. Cunningham, J. Troy LittletonSummaryNeuronal circuits have the capacity to maintain relatively constant activity in the face of perturbations that alter excitability or synaptic properties. A new study demonstrates that different classes of neurons co-innervating the same postsynaptic target express homeostatic plasticity with unique presynaptic features.
       
  • Cell Biology: Hacking Alpha Satellites out of the HAC
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Alexander B. Willis, Daniel R. FoltzSummaryHuman artificial chromosomes (HACs) are a potentially powerful technique for genomic engineering, but their use is limited by the repetitive centromeric alpha-satellite DNA needed to form a centromere. A new study presents a method to induce HAC centromere formation on non-repetitive templates through sequence-directed CENP-A nucleosome seeding.
       
  • Tissue Repair: Guarding against Friendly Fire
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Paul Hiebert, Sabine WernerSummaryFollowing tissue injury, cells produce reactive molecules that fight off invading pathogens, but these factors might also damage the host tissue. A new study has characterized a network of defense pathways that synergize to protect cells from collateral damage and drive repair.
       
  • Evolution: Adapting to a Warming World
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Marcel E. VisserSummaryTo be able to cope with climate change, species need to evolve. Demonstrating such evolution in wild populations is notoriously difficult. Replication of a 21-year-old experiment demonstrates that a long-distance migratory songbird has genetically adapted to climate change.
       
  • Plant Biology: To Live, or Not to Live, That Is the Question
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Alice Y. CheungSummaryOrganisms tread a fine line in balancing the decision to maintain cellular homeostasis or promote cell death to allow for renewal during development or halt the spread of a life-threatening crisis. Recent studies suggest a labyrinth of receptor kinase–cyclic nucleotide-gated ion channel connections mediates life-and-death decisions in plants.
       
  • Neuroscience: Sleep Fragmentation Impairs Memory Formation
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): William J. JoinerSummarySleep deprivation has long been known to impair cognition, but it has been difficult to distinguish whether loss or disruption of sleep is responsible. Now it appears that merely interrupting sleep is sufficient to interfere with memory formation.
       
  • Axonal Development: RhoA Restrains but Does Not Specify
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Anton Omelchenko, Bonnie L. FiresteinSummaryNeurons develop polarity by the formation of specialized dendritic and axonal structural compartments. A new report now provides evidence that reveals how neurons regulate the initiation and further maintenance of axonal growth, challenging our currently held view of RhoA function in axogenesis.
       
  • Chronobiology: The Circadian Clock under Extreme Photoperiods
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): David DoleželSummaryCircadian clocks are time-measuring devices found in a majority of organisms synchronizing their behavior and metabolism with the day–light cycle. What happens in extreme latitudes, where the environmental conditions can be harsh at any time of day'
       
  • Ciliate Biology: The Graceful Hunt of a Shape-Shifting Predator
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Kirsty Y. WanSummaryEven single-celled eukaryotes are capable of highly complex behaviors. A new study reveals how one unicellular predator actively manipulates and remodels its unique cytoskeletal morphology to achieve rapid shape changes and a remarkable hunting strategy.
       
  • A left-handed fern twiner in a Permian swamp forest
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Weiming Zhou, Dandan Li, Josef Pšenička, C. Kevin Boyce, Jun WangSummaryThe twining habit is a climbing strategy that helps slender plants grow upward by using circumnutation around other plants. In geological history, climbing may have already been present in the first Middle Devonian forests, as indicated by possible climbers among aneurophytalean progymnosperms [1] and lycopsids [2]. By the late Carboniferous, climbing was both more common and diverse — preserved in swamp forests with modes of attachment ranging from aerial roots to appendages modified into hooks and tendrils on the leaves [3]. However, all of these diagnoses of a climbing habit are based upon either indirect morphological characteristics of the purported climber or on direct physical contact with a host plant, but without direct preservation of twining [3,4]. Permineralized epiphytes have been preserved in the Carboniferous [5], but the interpretation of scars purported to have been caused by twiners that have been found on trunk compressions of potential host-plants has been questioned [5] (see Supplemental Information). Direct preservation of a climber engaged in true twining around a host has only been documented in the Miocene Shanwang Formation of Eastern China, albeit with the identity of the twiner difficult to establish and likely to be a self-twiner [6]. Here, we report a climbing fern engaged in left-handed twining around a seed plant from the early Permian Wuda Tuff fossil Lagerstätte of Inner Mongolia, China [7]. Moreover, the host plant is likely to also be a climber based on its overall form. Such a climber-climbing-a-climber phenomenon signals the potential ecological complexity of late Paleozoic forests.
       
  • Predation by non-bioluminescent firefly larvae on a tepui-summit endemic
           toad
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Philippe J.R. Kok, Loïc van Doorn, Raheleh DezfoulianSummaryTepuis are Precambrian sandstone tabletop mountains in South America that can reach up to ∼3,000 m in elevation. Their highest summits are both physiographically and ecologically isolated from the surrounding upland savannah and lush tropical rainforest, and they face particularly hostile, challenging environmental conditions [1,2] (Figure 1A). Taxa thriving on high tepui summits must adapt to resource-limited and highly competitive ecosystems. The toad genus Oreophrynella is exclusively found on tepui slopes and summits [3] and is particularly well-adapted to the tepui top environment. We here report on an unanticipated and possibly large-scale predation on this endemic toad by non-bioluminescent firefly larvae.
       
  • Animal domesticators
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Rohan M. Brooker, William E. Feeney
       
  • Helder Maiato
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Helder Maiato
       
  • Why we should care about bats
    • Abstract: Publication date: 18 November 2019Source: Current Biology, Volume 29, Issue 22Author(s): Michael GrossSummaryA quarter of all mammalian species are bats, but we still know less about them than about many other groups of mammals. Their complex and diverse hunting, migration, and social behaviours leave many mysteries yet to be solved. Their ability to carry virus diseases such as Ebola without getting ill makes it all the more urgent to understand their ways. Michael Gross reports.
       
  • Intracellular Infection of Diverse Diatoms by an Evolutionary Distinct
           Relative of the Fungi
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Aurélie Chambouvet, Adam Monier, Finlay Maguire, Sarah Itoïz, Javier del Campo, Philippe Elies, Bente Edvardsen, Wenche Eikreim, Thomas A. RichardsSummaryThe Fungi are a diverse kingdom, dominating terrestrial environments and driving important ecologies. Although fungi, and the related Opisthosporidia, interact with photosynthetic organisms on land and in freshwater as parasites, symbionts, and/or saprotrophic degraders [1, 2], such interactions in the marine environment are poorly understood [3, 4, 5, 6, 7, 8]. One newly identified uncultured marine lineage has been named novel chytrid-like-clade-1 (NCLC1) [4] or basal-clone-group-I [5, 6]. We use ribosomal RNA (rRNA) encoding gene phylogenies to demonstrate that NCLC1 is a distinct branch within the Opisthosporidia (Holomycota) [7]. Opisthosporidia are a diverse and largely uncultured group that form a sister branch to the Fungi or, alternatively, the deepest branch within the Fungi, depending on how the boundary to this kingdom is inferred [9]. Using culture-free lineage-specific rRNA-targeted fluorescent in situ hybridization (FISH) microscopy, we demonstrate that NCLC1 cells form intracellular infection of key diatom species, establishing that intracellular colonization of a eukaryotic host is a consistent lifestyle across the Opisthosporidia [8, 9, 10, 11]. NCLC1 infection-associated loss and/or envelopment of the diatom nuclei infers a necrotrophic-pathogenic interaction. Diatoms are one of the most diverse and ecologically important phytoplankton groups, acting as dominant primary producers and driving carbon fixation and storage in many aquatic environments [12, 13, 14]. Our results provide insight into the diversity of microbial eukaryotes that interact with diatoms. We suggest that such interactions can play a key role in diatom associated ecosystem functions, such as the marine carbon pump through necrotrophic-parasitism, facilitating the export of diatoms to the sediment [15, 16].Graphical Graphical abstract for this article
       
  • Polymodal Nociception in Drosophila Requires Alternative Splicing
           of TrpA1
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Pengyu Gu, Jiaxin Gong, Ye Shang, Fei Wang, Kendra T. Ruppell, Zhiguo Ma, Amy E. Sheehan, Marc R. Freeman, Yang XiangSummaryTranscripts of noxious stimulus-detecting TrpA1 channels are alternatively spliced. Despite the importance of nociception for survival, the in vivo significance of expressing different TrpA1 isoforms is largely unknown. Here, we develop a novel genetic approach to generate Drosophila knockin strains expressing single TrpA1 isoforms. Drosophila TrpA1 mediates heat and UVC-triggered nociception. We show that TrpA1-C and TrpA1-D, two alternative isoforms, are co-expressed in nociceptors. When examined in heterologous cells, both TrpA1-C and TrpA1-D are activated by heat and UVC. By contrast, analysis of knockin flies reveals the striking functional specificity; TrpA1-C mediates UVC-nociception, whereas TrpA1-D mediates heat-nociception. Therefore, in vivo functions of TrpA1-C and TrpA1-D are different from each other and are different from their in vitro properties. Our results indicate that a given sensory stimulus preferentially activates a single TrpA1 isoform in vivo and that polymodal nociception requires co-expression of TrpA1 isoforms, providing novel insights of how alternative splicing regulates nociception.Graphical Graphical abstract for this article
       
  • A Putative Mechanism for Magnetoreception by Electromagnetic Induction in
           the Pigeon Inner Ear
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Simon Nimpf, Gregory Charles Nordmann, Daniel Kagerbauer, Erich Pascal Malkemper, Lukas Landler, Artemis Papadaki-Anastasopoulou, Lyubov Ushakova, Andrea Wenninger-Weinzierl, Maria Novatchkova, Peter Vincent, Thomas Lendl, Martin Colombini, Matthew J. Mason, David Anthony KeaysSummaryA diverse array of vertebrate species employs the Earth’s magnetic field to assist navigation. Despite compelling behavioral evidence that a magnetic sense exists, the location of the primary sensory cells and the underlying molecular mechanisms remain unknown [1]. To date, most research has focused on a light-dependent radical-pair-based concept and a system that is proposed to rely on biogenic magnetite (Fe3O4) [2, 3]. Here, we explore an overlooked hypothesis that predicts that animals detect magnetic fields by electromagnetic induction within the semicircular canals of the inner ear [4]. Employing an assay that relies on the neuronal activity marker C-FOS, we confirm that magnetic exposure results in activation of the caudal vestibular nuclei in pigeons that is independent of light [5]. We show experimentally and by physical calculations that magnetic stimulation can induce electric fields in the pigeon semicircular canals that are within the physiological range of known electroreceptive systems. Drawing on this finding, we report the presence of a splice isoform of a voltage-gated calcium channel (CaV1.3) in the pigeon inner ear that has been shown to mediate electroreception in skates and sharks [6]. We propose that pigeons detect magnetic fields by electromagnetic induction within the semicircular canals that is dependent on the presence of apically located voltage-gated cation channels in a population of electrosensory hair cells.Graphical Graphical abstract for this article
       
  • Interplay between Developmental Flexibility and Determinism in the
           Evolution of Mimetic Heliconius Wing Patterns
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Carolina Concha, Richard W.R. Wallbank, Joseph J. Hanly, Jennifer Fenner, Luca Livraghi, Edgardo Santiago Rivera, Daniel F. Paulo, Carlos Arias, Marta Vargas, Manu Sanjeev, Colin Morrison, David Tian, Paola Aguirre, Sabrina Ferrara, Jessica Foley, Carolina Pardo-Diaz, Camilo Salazar, Mauricio Linares, Darli Massardo, Brian A. CountermanSummaryTo what extent can we predict how evolution occurs? Do genetic architectures and developmental processes canalize the evolution of similar outcomes in a predictable manner? Or do historical contingencies impose alternative pathways to answer the same challenge? Examples of Müllerian mimicry between distantly related butterfly species provide natural replicates of evolution, allowing us to test whether identical wing patterns followed parallel or novel trajectories. Here, we explore the role that the signaling ligand WntA plays in generating mimetic wing patterns in Heliconius butterflies, a group with extraordinary mimicry-related wing pattern diversity. The radiation is relatively young, and numerous cases of wing pattern mimicry have evolved within the last 2.5–4.5 Ma. WntA is an important target of natural selection and is one of four major effect loci that underlie much of the pattern variation in the group. We used CRISPR/Cas9 targeted mutagenesis to generate WntA-deficient wings in 12 species and a further 10 intraspecific variants, including three co-mimetic pairs. In all tested butterflies, WntA knockouts affect pattern broadly and cause a shift among every possible scale cell type. Interestingly, the co-mimics lacking WntA were very different, suggesting that the gene networks that pattern a wing have diverged considerably among different lineages. Thus, although natural selection channeled phenotypic convergence, divergent developmental contexts between the two major Heliconius lineages opened different developmental routes to evolve resemblance. Consequently, even under very deterministic evolutionary scenarios, our results underscore a surprising unpredictability in the developmental paths underlying convergence in a recent radiation.Graphical Graphical abstract for this article
       
  • An Acoustic Password Enhances Auditory Learning in Juvenile Brood
           Parasitic Cowbirds
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Matthew I.M. Louder, Christopher N. Balakrishnan, Amber A.N. Louder, Robert J. Driver, Sarah E. London, Mark E. HauberSummaryHow does a naive, young animal decide from which adults to learn behavior' Obligate brood parasitic birds, including brown-headed cowbirds (Molothrus ater), face a particular challenge in learning species-specific behaviors; they lay their eggs in the nest of another species, and juveniles are raised without exposure to adult conspecifics. Nevertheless, male cowbirds need to learn a conspecific song to attract appropriate mates, and female cowbirds need to learn to identify conspecific males for mating. Traditionally, it was thought that parasitic bird species rely purely on instinctual species recognition [1, 2, 3, 4], but an alternative is that a species-specific trait serves as a “password” [5], a non-learned cue for naive animals that guides decisions regarding from whom to learn. Here, we tested the hypothesis that the adult “chatter call” enhances the learning of specific songs in juvenile cowbirds. We exposed acoustically naive juvenile male and female cowbirds to songs paired with chatter calls and found that the chatter call enhanced song production learning in males and induced a neurogenomic profile of song familiarity in females, even for heterospecific songs. Thus, a combination of experience-independent and -dependent mechanisms converges to explain how young cowbirds emerge from another species’ nest yet learn behaviors from conspecifics. Identifying whether such password-based mechanisms relate to perceptual and behavioral learning in non-parasitic taxa will contribute to our general understanding of the development of social recognition systems.
       
  • Dichotomy of Dosage Compensation along the Neo Z Chromosome of the Monarch
           Butterfly
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Liuqi Gu, Patrick F. Reilly, James J. Lewis, Robert D. Reed, Peter Andolfatto, James R. WaltersSummaryMechanisms of sex chromosome dosage compensation (SCDC) differ strikingly among animals. In Drosophila flies, chromosome-wide transcription is doubled from the single X chromosome in hemizygous (XY) males, whereas in Caenorhabditis nematodes, expression is halved for both X copies in homozygous (XX) females [1, 2]. Unlike other female-heterogametic (WZ female and ZZ male) animals, moths and butterflies exhibit sex chromosome dosage compensation patterns typically seen only in male-heterogametic species [3]. The monarch butterfly carries a newly derived Z chromosome segment that arose from an autosomal fusion with the ancestral Z [4]. Using a highly contiguous genome assembly, we show that gene expression is balanced between sexes along the entire Z chromosome but with distinct modes of compensation on the two segments. On the ancestral Z segment, depletion of H4K16ac corresponds to nearly halving of biallelic transcription in males, a pattern convergent to nematodes. Conversely, the newly derived Z segment shows a Drosophila-like mode of compensation, with enriched H4K16ac levels corresponding to doubled monoallelic transcription in females. Our work reveals that, contrary to the expectation of co-opting regulatory mechanisms readily in place, the evolution of plural modes of dosage compensation is also possible along a single sex chromosome within a species.Graphical Graphical abstract for this article
       
  • The Genomic Impact of European Colonization of the Americas
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Linda Ongaro, Marilia O. Scliar, Rodrigo Flores, Alessandro Raveane, Davide Marnetto, Stefania Sarno, Guido A. Gnecchi-Ruscone, Marta E. Alarcón-Riquelme, Etienne Patin, Pongsakorn Wangkumhang, Garrett Hellenthal, Miguel Gonzalez-Santos, Roy J. King, Anastasia Kouvatsi, Oleg Balanovsky, Elena Balanovska, Lubov Atramentova, Shahlo Turdikulova, Sarabjit Mastana, Damir MarjanovicSummaryThe human genetic diversity of the Americas has been affected by several events of gene flow that have continued since the colonial era and the Atlantic slave trade. Moreover, multiple waves of migration followed by local admixture occurred in the last two centuries, the impact of which has been largely unexplored. Here, we compiled a genome-wide dataset of ∼12,000 individuals from twelve American countries and ∼6,000 individuals from worldwide populations and applied haplotype-based methods to investigate how historical movements from outside the New World affected (1) the genetic structure, (2) the admixture profile, (3) the demographic history, and (4) sex-biased gene-flow dynamics of the Americas. We revealed a high degree of complexity underlying the genetic contribution of European and African populations in North and South America, from both geographic and temporal perspectives, identifying previously unreported sources related to Italy, the Middle East, and to specific regions of Africa.
       
  • A Novel Katanin-Tethering Machinery Accelerates Cytokinesis
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Takema Sasaki, Motosuke Tsutsumi, Kohei Otomo, Takashi Murata, Noriyoshi Yagi, Masayoshi Nakamura, Tomomi Nemoto, Mitsuyasu Hasebe, Yoshihisa OdaSummaryCytokinesis is fundamental for cell proliferation [1, 2]. In plants, a bipolar short-microtubule array forms the phragmoplast, which mediates vesicle transport to the midzone and guides the formation of cell walls that separate the mother cell into two daughter cells [2]. The phragmoplast centrifugally expands toward the cell cortex to guide cell-plate formation at the cortical division site [3, 4]. Several proteins in the phragmoplast midzone facilitate the anti-parallel bundling of microtubules and vesicle accumulation [5]. However, the mechanisms by which short microtubules are maintained during phragmoplast development, in particular, the behavior of microtubules at the distal zone of phragmoplasts, are poorly understood. Here, we show that a plant-specific protein, CORTICAL MICROTUBULE DISORDERING 4 (CORD4), tethers the conserved microtubule-severing protein katanin to facilitate formation of the short-microtubule array in phragmoplasts. CORD4 was specifically expressed during mitosis and localized to preprophase bands and phragmoplast microtubules. Custom-made two-photon spinning disk confocal microscopy revealed that CORD4 rapidly localized to microtubules in the distal phragmoplast zone during phragmoplast assembly at late anaphase and persisted throughout phragmoplast expansion. Loss of CORD4 caused abnormally long and oblique phragmoplast microtubules and slow expansion of phragmoplasts. The p60 katanin subunit, KTN1, localized to the distal phragmoplast zone in a CORD4-dependent manner. These results suggest that CORD4 tethers KTN1 at phragmoplasts to modulate microtubule length, thereby accelerating phragmoplast growth. This reveals the presence of a distinct machinery to accelerate cytokinesis by regulating the action of katanin.Graphical Graphical abstract for this article
       
  • A Historical-Genetic Reconstruction of Human Extra-Pair Paternity
    • Abstract: Publication date: Available online 14 November 2019Source: Current BiologyAuthor(s): Maarten H.D. Larmuseau, Pieter van den Berg, Sofie Claerhout, Francesc Calafell, Alessio Boattini, Leen Gruyters, Michiel Vandenbosch, Kelly Nivelle, Ronny Decorte, Tom WenseleersSummaryPaternity testing using genetic markers has shown that extra-pair paternity (EPP) is common in many pair-bonded species [1, 2]. Evolutionary theory and empirical data show that extra-pair copulations can increase the fitness of males as well as females [3, 4]. This can carry a significant fitness cost for the social father, who then invests in rearing offspring that biologically are not his own [5]. In human populations, the incidence and correlates of extra-pair paternity remain highly contentious [2, 6, 7]. Here, we use a population-level genetic genealogy approach [6, 8] to reconstruct spatiotemporal patterns in human EPP rates. Using patrilineal genealogies from the Low Countries spanning a period of over 500 years and Y chromosome genotyping of living descendants, our analysis reveals that historical EPP rates, while low overall, were strongly impacted by socioeconomic and demographic factors. Specifically, we observe that estimated EPP rates among married couples varied by more than an order of magnitude, from 0.4% to 5.9%, and peaked among families with a low socioeconomic background living in densely populated cities of the late 19th century. Our results support theoretical predictions that social context can strongly affect the outcomes of sexual conflict in human populations by modulating the incentives and opportunities for engaging in extra-pair relationships [9, 10, 11]. These findings show how contemporary genetic data combined with in-depth genealogies open up a new window on the sexual behavior of our ancestors.
       
  • Gap Junction Coupling Shapes the Encoding of Light in the Developing
           Retina
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Franklin Caval-Holme, Marla B. FellerSummaryDetection of ambient illumination in the developing retina prior to maturation of conventional photoreceptors is mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) and is critical for driving several physiological processes, including light aversion, pupillary light reflexes, and photoentrainment of circadian rhythms. The strategies by which ipRGCs encode variations in ambient light intensity at these early ages are not known. Using unsupervised clustering of two-photon calcium responses followed by inspection of anatomical features, we found that the population activity of the neonatal retina could be modeled as six functional groups that were composed of mixtures of ipRGC subtypes and non-ipRGC cell types. By combining imaging, whole-cell recording, pharmacology, and anatomical techniques, we found that functional mixing of cell types is mediated in part by gap junction coupling. Together, these data show that both cell-autonomous intrinsic light responses and gap junction coupling among ipRGCs contribute to the proper encoding of light intensity in the developing retina.Graphical Graphical abstract for this article
       
  • Uncertainty and Surprise Jointly Predict Musical Pleasure and Amygdala,
           Hippocampus, and Auditory Cortex Activity
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Vincent K.M. Cheung, Peter M.C. Harrison, Lars Meyer, Marcus T. Pearce, John-Dylan Haynes, Stefan KoelschSummaryListening to music often evokes intense emotions [1, 2]. Recent research suggests that musical pleasure comes from positive reward prediction errors, which arise when what is heard proves to be better than expected [3]. Central to this view is the engagement of the nucleus accumbens—a brain region that processes reward expectations—to pleasurable music and surprising musical events [4, 5, 6, 7, 8]. However, expectancy violations along multiple musical dimensions (e.g., harmony and melody) have failed to implicate the nucleus accumbens [9, 10, 11], and it is unknown how music reward value is assigned [12]. Whether changes in musical expectancy elicit pleasure has thus remained elusive [11]. Here, we demonstrate that pleasure varies nonlinearly as a function of the listener’s uncertainty when anticipating a musical event, and the surprise it evokes when it deviates from expectations. Taking Western tonal harmony as a model of musical syntax, we used a machine-learning model [13] to mathematically quantify the uncertainty and surprise of 80,000 chords in US Billboard pop songs. Behaviorally, we found that chords elicited high pleasure ratings when they deviated substantially from what the listener had expected (low uncertainty, high surprise) or, conversely, when they conformed to expectations in an uninformative context (high uncertainty, low surprise). Neurally, we found using fMRI that activity in the amygdala, hippocampus, and auditory cortex reflected this interaction, while the nucleus accumbens only reflected uncertainty. These findings challenge current neurocognitive models of music-evoked pleasure and highlight the synergistic interplay between prospective and retrospective states of expectation in the musical experience.
       
  • Sensorimotor Transformations in the Zebrafish Auditory System
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Martin Privat, Sebastián A. Romano, Thomas Pietri, Adrien Jouary, Jonathan Boulanger-Weill, Nicolas Elbaz, Auriane Duchemin, Daphne Soares, Germán SumbreSummaryOrganisms use their sensory systems to acquire information from their environment and integrate this information to produce relevant behaviors. Nevertheless, how sensory information is converted into adequate motor patterns in the brain remains an open question. Here, we addressed this question using two-photon and light-sheet calcium imaging in intact, behaving zebrafish larvae. We monitored neural activity elicited by auditory stimuli while simultaneously recording tail movements. We observed a spatial organization of neural activity according to four different response profiles (frequency tuning curves), suggesting a low-dimensional representation of frequency information, maintained throughout the development of the larvae. Low frequencies (150–450 Hz) were locally processed in the hindbrain and elicited motor behaviors. In contrast, higher frequencies (900–1,000 Hz) rarely induced motor behaviors and were also represented in the midbrain. Finally, we found that the sensorimotor transformations in the zebrafish auditory system are a continuous and gradual process that involves the temporal integration of the sensory response in order to generate a motor behavior.Graphical Graphical abstract for this article
       
  • Target-wide Induction and Synapse Type-Specific Robustness of Presynaptic
           Homeostasis
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Özgür Genç, Graeme W. DavisSummaryPresynaptic homeostatic plasticity (PHP) is an evolutionarily conserved form of adaptive neuromodulation and is observed at both central and peripheral synapses. In this work, we make several fundamental advances by interrogating the synapse specificity of PHP. We define how PHP remains robust to acute versus long-term neurotransmitter receptor perturbation. We describe a general PHP property that includes global induction and synapse-specific expression mechanisms. Finally, we detail a novel synapse-specific PHP expression mechanism that enables the conversion from short- to long-term PHP expression. If our data can be extended to other systems, including the mammalian central nervous system, they suggest that PHP can be broadly induced and expressed to sustain the function of complex neural circuitry.
       
  • Coordinated Behavioral and Physiological Responses to a Social Signal Are
           Regulated by a Shared Neuronal Circuit
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Erin Z. Aprison, Ilya RuvinskySummarySuccessful reproduction in animals requires orchestration of behavior and physiological processes. Pheromones can induce both “releaser” (behavioral) and “priming” (physiological) effects [1] in vertebrates [2, 3] and invertebrates [4, 5]. Therefore, understanding the mechanisms underlying pheromone responses could reveal how reproduction-related behaviors and physiology are coordinated. Here, we describe a neuronal circuit that couples the reproductive system and behavior in adult Caenorhabditis elegans hermaphrodites. We found that the response of the oogenic germline to the male pheromone requires serotonin signal from NSM and HSN neurons that acts via the mod-1 receptor in AIY and RIF interneurons and is antagonized by pigment-dispersing factor (PDF). Surprisingly, the same neurons and pathways have been previously implicated in regulation of exploratory behavior in the absence of male-produced signals [6]. We demonstrate that male pheromone acts via this circuit in hermaphrodites to reduce exploration and decrease mating latency, thereby tuning multiple fitness-proximal processes. Our results demonstrate how a single circuit could coordinate behavioral and physiological responses to the environment, even those that unfold on different timescales. Our findings suggest the existence of a centralized regulatory mechanism that balances organismal resources between reproductive investment and somatic maintenance.
       
  • Dynamic Regulation of Adult-Specific Functions of the Nervous System by
           Signaling from the Reproductive System
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Erin Z. Aprison, Ilya RuvinskySummaryUnlike juveniles, adult animals engage in suites of behaviors related to the search for and selection of potential mates and mating, including appropriate responses to sex pheromones. As in other species [1], male sex pheromones modulate several behaviors and physiological processes in C. elegans hermaphrodites [2, 3, 4, 5]. In particular, one of these small-molecule signals, an ascaroside ascr#10, causes reduced exploration, more avid mating, and improved reproductive performance (see the accompanying paper by Aprison and Ruvinsky in this issue of Current Biology) [6]. Here, we investigated the mechanism that restricts pheromone response to adult hermaphrodites. Unexpectedly, we found that attainment of developmental adulthood was not alone sufficient for the behavioral response to the pheromone. To modify exploratory behavior in response to male pheromone, adult hermaphrodites also require functional germline and egg-laying apparatus. We show that this dependence of behavior on the reproductive system is due to feedback from the vulva muscles that reports ongoing reproduction to the nervous system. Our results reveal an activity-dependent conduit by which the reproductive system continuously licenses adult behaviors, including appropriate responses to the pheromones of the opposite sex. More broadly, our results suggest that signals from peripheral organs may serve as an important component of assuring age-appropriate functions of the nervous system.
       
  • GEMMA CUP-ASSOCIATED MYB1, an Ortholog of Axillary Meristem Regulators, Is
           Essential in Vegetative Reproduction in Marchantia polymorpha
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Yukiko Yasui, Shigeyuki Tsukamoto, Tomomi Sugaya, Ryuichi Nishihama, Quan Wang, Hirotaka Kato, Katsuyuki T. Yamato, Hidehiro Fukaki, Tetsuro Mimura, Hiroyoshi Kubo, Klaus Theres, Takayuki Kohchi, Kimitsune IshizakiSummaryA variety of plants in diverse taxa can reproduce asexually via vegetative propagation, in which clonal propagules with a new meristem(s) are generated directly from vegetative organs. A basal land plant, Marchantia polymorpha, develops clonal propagules, gemmae, on the gametophyte thallus from the basal epidermis of a specialized receptacle, the gemma cup. Here we report an R2R3-MYB transcription factor, designated GEMMA CUP-ASSOCIATED MYB1 (GCAM1), which is an essential regulator of gemma cup development in M. polymorpha. Targeted disruption of GCAM1 conferred a complete loss of gemma cup formation and gemma generation. Ectopic overexpression of GCAM1 resulted in formation of cell clumps, suggesting a function of GCAM1 in suppression of cell differentiation. Although gemma cups are a characteristic gametophyte organ for vegetative reproduction in a taxonomically restricted group of liverwort species, phylogenetic and interspecific complementation analyses support the orthologous relationship of GCAM1 to regulatory factors of axillary meristem formation, e.g., Arabidopsis REGULATOR OF AXILLARY MERISTEMS and tomato Blind, in angiosperm sporophytes. The present findings in M. polymorpha suggest an ancient acquisition of a transcriptional regulator for production of asexual propagules in the gametophyte and the use of the regulatory factor for diverse developmental programs, including axillary meristem formation, during land plant evolution.Graphical Graphical abstract for this article
       
  • Cell-Cycle Asynchrony Generates DNA Damage at Mitotic Entry in Polyploid
           Cells
    • Abstract: Publication date: Available online 7 November 2019Source: Current BiologyAuthor(s): Maddalena Nano, Simon Gemble, Anthony Simon, Carole Pennetier, Vincent Fraisier, Veronique Marthiens, Renata BastoSummaryPolyploidy arises from the gain of complete chromosome sets [1], and it is known to promote cancer genome evolution. Recent evidence suggests that a large proportion of human tumors experience whole-genome duplications (WGDs), which might favor the generation of highly abnormal karyotypes within a short time frame, rather than in a stepwise manner [2, 3, 4, 5, 6]. However, the molecular mechanisms linking whole-genome duplication to genetic instability remain poorly understood. Using repeated cytokinesis failure to induce polyploidization of Drosophila neural stem cells (NSCs) (also called neuroblasts [NBs]), we investigated the consequences of polyploidy in vivo. Surprisingly, we found that DNA damage is generated in a subset of nuclei of polyploid NBs during mitosis. Importantly, our observations in flies were confirmed in mouse NSCs (mNSCs) and human cancer cells after acute cytokinesis inhibition. Interestingly, DNA damage occurs in nuclei that were not ready to enter mitosis but were forced to do so when exposed to the mitotic environment of neighboring nuclei within the same cell. Additionally, we found that polyploid cells are cell-cycle asynchronous and forcing cell-cycle synchronization was sufficient to lower the levels of DNA damage generated during mitosis. Overall, this work supports a model in which DNA damage at mitotic entry can generate DNA structural abnormalities that might contribute to the onset of genetic instability.Graphical Graphical abstract for this article
       
  • Termite Evolution: A Primal Knock on Wood or a Hearty Mouthful of Dirt
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Michael S. EngelSummaryTermite success is inexorably linked to their diet and symbiotic cellulolytic intestinal microorganisms. A new study reveals that soil feeding may have triggered a turnover in intestinal symbionts, rather than ectosymbiont cultivation, allowing termites to achieve ecological dominance.
       
  • Kif2a Scales Meiotic Spindle Size in Hymenochirus boettgeri
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Kelly E. Miller, Adam M. Session, Rebecca HealdSummarySize is a fundamental feature of biological systems that affects physiology at all levels. For example, the dynamic, microtubule-based spindle that mediates chromosome segregation scales to a wide range of cell sizes across different organisms and cell types. Xenopus frog species possess a variety of egg and meiotic spindle sizes, and differences in activities or levels of microtubule-associated proteins in the egg cytoplasm between Xenopus laevis and Xenopus tropicalis have been shown to account for spindle scaling [1]. Increased activity of the microtubule severing protein katanin scales the X. tropicalis spindle smaller compared to X. laevis [2], as do elevated levels of TPX2, a protein that enriches the cross-linking kinesin-5 motor Eg5 at spindle poles [3]. To examine the conservation of spindle scaling mechanisms more broadly across frog species, we have utilized the tiny, distantly related Pipid frog Hymenochirus boettgeri. We find that egg extracts from H. boettgeri form meiotic spindles similar in size to X. tropicalis but that TPX2 and katanin-mediated scaling is not conserved. Instead, the microtubule depolymerizing motor protein kif2a functions to modulate spindle size. H. boettgeri kif2a possesses an activating phosphorylation site that is absent from X. laevis. Comparison of katanin and kif2a phosphorylation sites across a variety of species revealed strong evolutionary conservation, with X. laevis and X. tropicalis possessing distinct and unique alterations. Our study highlights the diversity and complexity of spindle assembly and scaling mechanisms, indicating that there is more than one way to assemble a spindle of a particular size.Graphical Graphical abstract for this article
       
  • Differential Sperm Motility Mediates the Sex Ratio Drive Shaping Mouse Sex
           Chromosome Evolution
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Claudia Cattoni Rathje, Emma Elizabeth Philippa Johnson, Deborah Drage, Christina Patinioti, Giuseppe Silvestri, Nabeel Ahmed Affara, Côme Ialy-Radio, Julie Cocquet, Benjamin Matthew Skinner, Peter James Ivor EllisSummaryThe mouse sex chromosomes exhibit an extraordinary level of copy number amplification of postmeiotically expressed genes [1, 2], driven by an “arms race” (genomic conflict) between the X and Y chromosomes over the control of offspring sex ratio. The sex-linked ampliconic transcriptional regulators Slx and Sly [3, 4, 5, 6, 7] have opposing effects on global transcription levels of the sex chromosomes in haploid spermatids via regulation of postmeiotic sex chromatin (PMSC) [8, 9, 10, 11] and opposing effects on offspring sex ratio. Partial deletions of the Y chromosome (Yq) that reduce Sly copy number lead to global overexpression of sex-linked genes in spermatids and either a distorted sex ratio in favor of females (smaller deletions) or sterility (larger deletions) [12, 13, 14, 15, 16]. Despite a large body of work studying the role of the sex chromosomes in regulating spermatogenesis (recent reviews [17, 18, 19, 20]), most studies do not address differential fertility effects on X- and Y-bearing cells. Hence, in this study, we concentrate on identifying physiological differences between X- and Y-bearing sperm from Yq-deleted males that affect their relative fertilizing ability and consequently lead to sex ratio skewing. We show that X- and Y-bearing sperm in these males have differential motility and morphology but are equally able to penetrate the cumulus and fertilize the egg once at the site of fertilization. The altered motility is thus deduced to be the proximate cause of the skew. This represents the first demonstration of a specific difference in sperm function associated with sex ratio skewing.
       
  • NODULE INCEPTION Recruits the Lateral Root Developmental Program for
           Symbiotic Nodule Organogenesis in Medicago truncatula
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Katharina Schiessl, Jodi L.S. Lilley, Tak Lee, Ioannis Tamvakis, Wouter Kohlen, Paul C. Bailey, Aaron Thomas, Jakub Luptak, Karunakaran Ramakrishnan, Matthew D. Carpenter, Kirankumar S. Mysore, Jiangqi Wen, Sebastian Ahnert, Veronica A. Grieneisen, Giles E.D. OldroydSummaryTo overcome nitrogen deficiencies in the soil, legumes enter symbioses with rhizobial bacteria that convert atmospheric nitrogen into ammonium. Rhizobia are accommodated as endosymbionts within lateral root organs called nodules that initiate from the inner layers of Medicago truncatula roots in response to rhizobial perception. In contrast, lateral roots emerge from predefined founder cells as an adaptive response to environmental stimuli, including water and nutrient availability. CYTOKININ RESPONSE 1 (CRE1)-mediated signaling in the pericycle and in the cortex is necessary and sufficient for nodulation, whereas cytokinin is antagonistic to lateral root development, with cre1 showing increased lateral root emergence and decreased nodulation. To better understand the relatedness between nodule and lateral root development, we undertook a comparative analysis of these two root developmental programs. Here, we demonstrate that despite differential induction, lateral roots and nodules share overlapping developmental programs, with mutants in LOB-DOMAIN PROTEIN 16 (LBD16) showing equivalent defects in nodule and lateral root initiation. The cytokinin-inducible transcription factor NODULE INCEPTION (NIN) allows induction of this program during nodulation through activation of LBD16 that promotes auxin biosynthesis via transcriptional induction of STYLISH (STY) and YUCCAs (YUC). We conclude that cytokinin facilitates local auxin accumulation through NIN promotion of LBD16, which activates a nodule developmental program overlapping with that induced during lateral root initiation.Graphical Graphical abstract for this article
       
  • Cellular and Neural Responses to Sour Stimuli Require the Proton Channel
           Otop1
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Bochuan Teng, Courtney E. Wilson, Yu-Hsiang Tu, Narendra R. Joshi, Sue C. Kinnamon, Emily R. LimanSummaryThe sense of taste allows animals to sample chemicals in the environment prior to ingestion. Of the five basic tastes, sour, the taste of acids, had remained among the most mysterious. Acids are detected by type III taste receptor cells (TRCs), located in taste buds across the tongue and palate epithelium. The first step in sour taste transduction is believed to be entry of protons into the cell cytosol, which leads to cytosolic acidification and the generation of action potentials. The proton-selective ion channel Otop1 is expressed in type III TRCs and is a candidate sour receptor. Here, we tested the contribution of Otop1 to taste cell and gustatory nerve responses to acids in mice in which Otop1 was genetically inactivated (Otop1-KO mice). We first show that Otop1 is required for the inward proton current in type III TRCs from different parts of the tongue that are otherwise molecularly heterogeneous. We next show that in type III TRCs from Otop1-KO mice, intracellular pH does not track with extracellular pH and that moderately acidic stimuli do not elicit trains of action potentials, as they do in type III TRCs from wild-type mice. Moreover, gustatory nerve responses in Otop1-KO mice were severely and selectively attenuated for acidic stimuli, including citric acid and HCl. These results establish that the Otop1 proton channel plays a critical role in acid detection in the mouse gustatory system, evidence that it is a bona fide sour taste receptor.Graphical Graphical abstract for this article
       
  • Spatial Organization of Expanding Bacterial Colonies Is Affected by
           Contact-Dependent Growth Inhibition
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Michael J. Bottery, Ioannis Passaris, Calvin Dytham, A. Jamie Wood, Marjan W. van der WoudeSummaryIdentifying how microbes are able to manipulate, survive, and thrive in complex multispecies communities has expanded our understanding of how microbial ecosystems impact human health and the environment. The ability of bacteria to negatively affect neighbors, through explicit toxin delivery systems, provides them with an opportunity to manipulate the composition of growing microbial communities. Contact-dependent inhibition (CDI) systems (a Type Vb secretion system) are a distinct subset of competition systems whose contribution to shaping the development of spatially structured bacterial communities are yet to be fully understood. Here, we compare the impact of different CDI systems, at both the single-cell and population level, to determine the key drivers of CDI-mediated competition within spatially structured bacterial populations. Through an iterative approach using both an Escherichia coli experimental system and computational modeling, we show that CDI systems have subtle and system-specific effects at the single-cell level, generating single-cell-wide boundaries between CDI-expressing inhibitor cells and their neighboring targets. Despite the subtle effects of CDI at a single-cell level, CDI systems greatly diminished the ability of susceptible targets to expand their range during colony growth. The inoculum density of the population, together with the CDI system-specific variables of the speed of inhibition after contact and biological cost of CDI, strongly affects CDI-mediated competition. In contrast, the magnitude of the toxin-induced growth retardation of target cells only weakly impacts the composition of the population. Our work reveals how distinct CDI systems can differentially affect the composition and spatial arrangement of bacterial populations.
       
  • Effects of Sexual Experience and Puberty on Mouse Genital Cortex revealed
           by Chronic Imaging
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Johanna Sigl-Glöckner, Eduard Maier, Naoya Takahashi, Robert Sachdev, Matthew Larkum, Michael BrechtSummaryThe topographic map in layer 4 of somatosensory cortex is usually specified early postnatally and stable thereafter. Genital cortex, however, undergoes a sex-hormone- and sexual-touch-dependent pubertal expansion. Here, we image pubertal development of genital cortex in Scnn1a-Tg3-Cre mice, where transgene expression has been shown to be restricted to layer 4 neurons with primary sensory cortex identity. Interestingly, during puberty, the number of Scnn1a+ neurons roughly doubled within genital cortex. The increase of Scnn1a+ neurons was gradual and rapidly advanced by initial sexual experience. Neurons that gained Scnn1a expression comprised stellate and pyramidal neurons in layer 4. Unlike during neonatal development, pyramids did not retract their apical dendrites during puberty. Calcium imaging revealed stronger genital-touch responses in Scnn1a+ neurons in males versus females and a developmental increase in responsiveness in females. The first sexual interaction is a unique physical experience that often creates long-lasting memories. We suggest such experience uniquely alters somatosensory body maps.Graphical Graphical abstract for this article
       
  • Adaptive Regulation of Motor Variability
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Ashesh K. Dhawale, Yohsuke R. Miyamoto, Maurice A. Smith, Bence P. ÖlveczkySummaryTrial-to-trial movement variability can both drive motor learning and interfere with expert performance, suggesting benefits of regulating it in context-specific ways. Here we address whether and how the brain regulates motor variability as a function of performance by training rats to execute ballistic forelimb movements for reward. Behavioral datasets comprising millions of trials revealed that motor variability is regulated by two distinct processes. A fast process modulates variability as a function of recent trial outcomes, increasing it when performance is poor and vice versa. A slower process tunes the gain of the fast process based on the uncertainty in the task’s reward landscape. Simulations demonstrated that this regulation strategy optimizes reward accumulation over a wide range of time horizons, while also promoting learning. Our results uncover a sophisticated algorithm implemented by the brain to adaptively regulate motor variability to improve task performance.Video Abstract
       
  • Design Principles of Branching Morphogenesis in Filamentous Organisms
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Yoan Coudert, Steven Harris, Bénédicte CharrierThe radiation of life on Earth was accompanied by the diversification of multicellular body plans in the eukaryotic kingdoms Animalia, Plantae, Fungi and Chromista. Branching forms are ubiquitous in nature and evolved repeatedly in the above lineages. The developmental and genetic basis of branch formation is well studied in the three-dimensional shoot and root systems of land plants, and in animal organs such as the lung, kidney, mammary gland, vasculature, etc. Notably, recent thought-provoking studies combining experimental analysis and computational modeling of branching patterns in whole animal organs have identified global patterning rules and proposed unifying principles of branching morphogenesis. Filamentous branching forms represent one of the simplest expressions of the multicellular body plan and constitute a key step in the evolution of morphological complexity. Similarities between simple and complex branching forms distantly related in evolution are compelling, raising the question whether shared mechanisms underlie their development. Here, we focus on filamentous branching organisms that represent major study models from three distinct eukaryotic kingdoms, including the moss Physcomitrella patens (Plantae), the brown alga Ectocarpus sp. (Chromista), and the ascomycetes Neurospora crassa and Aspergillus nidulans (Fungi), and bring to light developmental regulatory mechanisms and design principles common to these lineages. Throughout the review we explore how the regulatory mechanisms of branching morphogenesis identified in other models, and in particular animal organs, may inform our thinking on filamentous systems and thereby advance our understanding of the diverse strategies deployed across the eukaryotic tree of life to evolve similar forms.
       
  • Neuroscience: Tantalized Flies Are Primed for Satiety
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Osama M. Ahmed, Mala MurthySummaryHow animals maintain and switch between distinct motivational states is an important question in neuroscience. New work in Drosophila identifies an excitatory neuronal circuit that builds up mating drive while priming itself for satiety.
       
  • Microbial Ecology: Complex Bacterial Communities Reduce Selection for
           Antibiotic Resistance
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Kevin WoodSummaryCompetition between antibiotic-resistant and -susceptible bacteria is well studied in single-species communities, but less is known about selection for resistance in more complex ecologies. A new experiment shows natural microbial communities can hinder selection by increasing the fitness costs of resistance or by offering protection to drug-sensitive strains.
       
  • Cancer: Context Is Key for E-cadherin in Invasion and Metastasis
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Eric R. FearonSummaryA recent paper demonstrates how tissue context impacts the breast cancer cell phenotype. Loss of the E-cadherin tumor suppressor protein enhanced cell invasion, but inhibited multiple steps in metastatic spread due to the accumulation of reactive oxygen species and induction of apoptosis.
       
  • Zebrafish Neuroscience: Using Artificial Neural Networks to Help
           Understand Brains
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Misha B. AhrensSummaryBrains are notoriously hard to understand, and neuroscientists need all the tools they can get their hands on to have a realistic shot at it. Advances in machine learning are proving instrumental, illustrated by their recent use to shed light on navigational strategies implemented by zebrafish brains.
       
  • Cell Division: Tailoring a Swiftly Scaling Spindle
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Kelly E. Hartsough, Claire E. WalczakSummaryA new study looks across frog species to identify molecular factors important in meiotic spindle scaling.
       
  • Language: Do Bilinguals Think Differently in Each Language'
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Karen EmmoreySummaryWhether the representation of concepts depends on the language used to express them is controversial. A new study with sign–speech bilingual participants has found that neural representations of semantic categories, such as fruit, are shared across languages but individual items, such as apple, are not.
       
  • Developmental Evolution: Downsizing Wings in the Flightless Emu
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Sergio G. Minchey, Douglas B. MenkeSummaryThe vestigial wings of emus are a striking illustration of morphological evolution. A new study points to reduced activity of an essential signaling pathway as a factor in the evolution of the emu’s stunted wings.
       
  • Sleep: Slow Waves Quiet the Fly’s Mind
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Ian D. Blum, Mark N. WuSummarySlow-wave sleep is a marker of sleep need, but its presence and function in non-mammalian species have been controversial. A new study finds sleep-dependent slow wave oscillations in the fruit fly, which act to inhibit sensory input during sleep.
       
  • Evolution of Termite Symbiosis Informed by Transcriptome-Based Phylogenies
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Ales Bucek, Jan Šobotník, Shulin He, Mang Shi, Dino P. McMahon, Edward C. Holmes, Yves Roisin, Nathan Lo, Thomas BourguignonSummaryTermitidae comprises ∼80% of all termite species [1] that play dominant decomposer roles in tropical ecosystems [2, 3]. Two major events during termite evolution were the loss of cellulolytic gut protozoans in the ancestor of Termitidae and the subsequent gain in the termitid subfamily Macrotermitinae of fungal symbionts cultivated externally in “combs” constructed within the nest [4, 5]. How these symbiotic transitions occurred remains unresolved. Phylogenetic analyses of mitochondrial data previously suggested that Macrotermitinae is the earliest branching termitid lineage, followed soon after by Sphaerotermitinae [6], which cultivates bacterial symbionts on combs inside its nests [7]. This has led to the hypothesis that comb building was an important evolutionary step in the loss of gut protozoa in ancestral termitids [8]. We sequenced genomes and transcriptomes of 55 termite species and reconstructed phylogenetic trees from up to 4,065 orthologous genes of 68 species. We found strong support for a novel sister-group relationship between the bacterial comb-building Sphaerotermitinae and fungus comb-building Macrotermitinae. This key finding indicates that comb building is a derived trait within Termitidae and that the creation of a comb-like “external rumen” involving bacteria or fungi may not have driven the loss of protozoa from ancestral termitids, as previously hypothesized. Instead, associations with gut prokaryotic symbionts, combined with dietary shifts from wood to other plant-based substrates, may have played a more important role in this symbiotic transition. Our phylogenetic tree provides a platform for future studies of comparative termite evolution and the evolution of symbiosis in this taxon.
       
  • Olfaction: Repellents that Congest the Mosquito Nose
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Jeffrey A. RiffellSummaryHow does the common insect repellent DEET modify a mosquito’s ability to detect humans' New research using GCaMP-expressing mosquitoes suggests that DEET works differently for different mosquito species. For An. coluzzii, DEET and other non-volatile repellents mask the mosquitoes’ ability to detect odors.
       
  • Genital Cortex: Development of the Genital Homunculus
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Susana Q. LimaSummaryThe cortical representation of male and female genitals, unlike that of the rest of the body, undergoes late expansion during puberty and is modulated by sexual experience. Using chronic imaging, a recent study has shed light on the cellular changes that accompany the sex-hormone- and experience-dependent expansion of the genital cortex.
       
  • The multilevel society of a small-brained bird
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Danai Papageorgiou, Charlotte Christensen, Gabriella E.C. Gall, James A. Klarevas-Irby, Brendah Nyaguthii, Iain D. Couzin, Damien R. FarineSummaryAnimal societies can be organised in multiple hierarchical tiers [1]. Such multilevel societies, where stable groups move together through the landscape, overlapping and associating preferentially with specific other groups, are thought to represent one of the most complex forms of social structure in vertebrates. For example, hamadryas baboons (Papio hamadryas) live in units consisting of one male and one or several females, or of several solitary males, that group into clans. These clans then come together with solitary bachelor males to form larger bands [2]. This social structure means that individuals have to track many different types of relationships at the same time [1,3]. Here, we provide detailed quantitative evidence for the presence of a multilevel society in a small-brained bird, the vulturine guineafowl (Acryllium vulturinum). We demonstrate that this species lives in large, multi-male, multi-female groups that associate preferentially with specific other groups, both during the day and at night-time communal roosts.
       
  • Bedbugs
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Klaus Reinhardt
       
  • Reconstructing trait evolution in plant evo–devo studies
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Pierre-Marc Delaux, Alexander J. Hetherington, Yoan Coudert, Charles Delwiche, Christophe Dunand, Sven Gould, Paul Kenrick, Fay-Wei Li, Hervé Philippe, Stefan A. Rensing, Mélanie Rich, Christine Strullu-Derrien, Jan de VriesSummaryOur planet is teeming with an astounding diversity of plants. In a mere single group of closely related species, tremendous diversity can be observed in their form and function — the colour of petals in flowering plants, the shape of the fronds in ferns, and the branching pattern of the gametophyte in mosses. Diversity can also be found in subtler traits, such as the resistance to pathogens or the ability to recruit symbiotic microbes from the environment. Plant traits can also be highly conserved — at the cellular and metabolic levels, entire biosynthetic pathways are present in all plant groups, and morphological characteristics such as vascular tissues have been conserved for hundreds of millions of years. The research community that seeks to understand these traits — both the diverse and the conserved — by taking an evolutionary point-of-view on plant biology is growing. Here, we summarize a subset of the different aspects of plant evolutionary biology, provide a guide for structuring comparative biology approaches and discuss the pitfalls that (plant) researchers should avoid when embarking on such studies.
       
  • Xinnian Dong
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Xinnian Dong
       
  • Six-legged success stories
    • Abstract: Publication date: 4 November 2019Source: Current Biology, Volume 29, Issue 21Author(s): Michael GrossSummaryInsects represent the majority of today’s animal biodiversity, although many of their species are now at risk from land-use change and pesticides. Given their vast number of species, it is no wonder that science is still busy finding new connections in their ecology and evolution, including in the ways they co-evolve with plants and other organisms. Michael Gross reports.
       
  • Simultaneous Regulation of Cytokinetic Furrow and Nucleus Positions by
           Cortical Tension Contributes to Proper DNA Segregation during Late Mitosis
           
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Anne Pacquelet, Matthieu Jousseaume, Jocelyn Etienne, Grégoire MichauxSummaryCoordinating mitotic spindle and cytokinetic furrow positioning is essential to ensure proper DNA segregation. Here, we present a novel mechanism, which corrects DNA segregation defects due to cytokinetic furrow mispositioning during the first division of C. elegans embryos. Correction of DNA segregation defects due to an abnormally anterior cytokinetic furrow relies on the concomitant and opposite displacements of the furrow and of the anterior nucleus toward the posterior and anterior poles of the embryo, respectively. It also coincides with cortical blebbing and an anteriorly directed cytoplasmic flow. Although microtubules contribute to nuclear displacement, relaxation of an excessive tension at the anterior cortex plays a central role in the correction process and simultaneously regulates cytoplasmic flow as well as nuclear and furrow displacements. This work thus reveals the existence of a so-far uncharacterized correction mechanism, which is critical to correct DNA segregation defects due to cytokinetic furrow mispositioning.Graphical Graphical abstract for this article
       
  • Early Diverging Fungus Mucor circinelloides Lacks Centromeric Histone
           CENP-A and Displays a Mosaic of Point and Regional Centromeres
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): María Isabel Navarro-Mendoza, Carlos Pérez-Arques, Shweta Panchal, Francisco E. Nicolás, Stephen J. Mondo, Promit Ganguly, Jasmyn Pangilinan, Igor V. Grigoriev, Joseph Heitman, Kaustuv Sanyal, Victoriano GarreSummaryCentromeres are rapidly evolving across eukaryotes, despite performing a conserved function to ensure high-fidelity chromosome segregation. CENP-A chromatin is a hallmark of a functional centromere in most organisms. Due to its critical role in kinetochore architecture, the loss of CENP-A is tolerated in only a few organisms, many of which possess holocentric chromosomes. Here, we characterize the consequence of the loss of CENP-A in the fungal kingdom. Mucor circinelloides, an opportunistic human pathogen, lacks CENP-A along with the evolutionarily conserved CENP-C but assembles a monocentric chromosome with a localized kinetochore complex throughout the cell cycle. Mis12 and Dsn1, two conserved kinetochore proteins, were found to co-localize to a short region, one in each of nine large scaffolds, composed of an ∼200-bp AT-rich sequence followed by a centromere-specific conserved motif that echoes the structure of budding yeast point centromeres. Resembling fungal regional centromeres, these core centromere regions are embedded in large genomic expanses devoid of genes yet marked by Grem-LINE1s, a novel retrotransposable element silenced by the Dicer-dependent RNAi pathway. Our results suggest that these hybrid features of point and regional centromeres arose from the absence of CENP-A, thus defining novel mosaic centromeres in this early-diverging fungus.
       
  • Meiotic Kinetochores Fragment into Multiple Lobes upon Cohesin Loss in
           Aging Eggs
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Agata P. Zielinska, Eirini Bellou, Ninadini Sharma, Ann-Sophie Frombach, K. Bianka Seres, Jennifer R. Gruhn, Martyn Blayney, Heike Eckel, Rüdiger Moltrecht, Kay Elder, Eva R. Hoffmann, Melina SchuhSummaryChromosome segregation errors during female meiosis are a leading cause of pregnancy loss and human infertility. The segregation of chromosomes is driven by interactions between spindle microtubules and kinetochores. Kinetochores in mammalian oocytes are subjected to special challenges: they need to withstand microtubule pulling forces over multiple hours and are built on centromeric chromatin that in humans is decades old. In meiosis I, sister kinetochores are paired and oriented toward the same spindle pole. It is well established that they progressively separate from each other with advancing female age. However, whether aging also affects the internal architecture of centromeres and kinetochores is currently unclear. Here, we used super-resolution microscopy to study meiotic centromere and kinetochore organization in metaphase-II-arrested eggs from three mammalian species, including humans. We found that centromeric chromatin decompacts with advancing maternal age. Kinetochores built on decompacted centromeres frequently lost their integrity and fragmented into multiple lobes. Fragmentation extended across inner and outer kinetochore regions and affected over 30% of metaphase-II-arrested (MII) kinetochores in aged women and mice, making the lobular architecture a prominent feature of the female meiotic kinetochore. We demonstrate that a partial cohesin loss, as is known to occur in oocytes with advancing maternal age, is sufficient to trigger centromere decompaction and kinetochore fragmentation. Microtubule pulling forces further enhanced the fragmentation and shaped the arrangement of kinetochore lobes. Fragmented kinetochores were frequently abnormally attached to spindle microtubules, suggesting that kinetochore fragmentation could contribute to the maternal age effect in mammalian eggs.Graphical Graphical abstract for this article
       
  • RhoA Controls Axon Extension Independent of Specification in the
           Developing Brain
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Sebastian Dupraz, Brett J. Hilton, Andreas Husch, Telma E. Santos, Charlotte H. Coles, Sina Stern, Cord Brakebusch, Frank BradkeSummaryThe specification of an axon and its subsequent outgrowth are key steps during neuronal polarization, a prerequisite to wire the brain. The Rho-guanosine triphosphatase (GTPase) RhoA is believed to be a central player in these processes. However, its physiological role has remained undefined. Here, genetic loss- and gain-of-function experiments combined with time-lapse microscopy, cell culture, and in vivo analysis show that RhoA is not involved in axon specification but confines the initiation of neuronal polarization and axon outgrowth during development. Biochemical analysis and super-resolution microscopy together with molecular and pharmacological manipulations reveal that RhoA restrains axon growth by activating myosin-II-mediated actin arc formation in the growth cone to prevent microtubules from protruding toward the leading edge. Through this mechanism, RhoA regulates the duration of axon growth and pause phases, thus controlling the tightly timed extension of developing axons. Thereby, this work unravels physiologically relevant players coordinating actin-microtubule interactions during axon growth.Graphical Graphical abstract for this article
       
  • The Receptor Kinases BAK1/SERK4 Regulate Ca2+ Channel-Mediated Cellular
           Homeostasis for Cell Death Containment
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Xiao Yu, Guangyuan Xu, Bo Li, Luciano de Souza Vespoli, Hai Liu, Wolfgang Moeder, Sixue Chen, Marcos V.V. de Oliveira, Suzane Ariádina de Souza, Wenyong Shao, Bárbara Rodrigues, Yi Ma, Shweta Chhajed, Shaowu Xue, Gerald A. Berkowitz, Keiko Yoshioka, Ping He, Libo ShanSummaryCell death is a vital and ubiquitous process that is tightly controlled in all organisms. However, the mechanisms underlying precise cell death control remain fragmented. As an important shared module in plant growth, development, and immunity, Arabidopsis thaliana BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 (BAK1) and somatic embryogenesis receptor kinase 4 (SERK4) redundantly and negatively regulate plant cell death. By deploying an RNAi-based genetic screen for bak1/serk4 cell death suppressors, we revealed that cyclic nucleotide-gated channel 20 (CNGC20) functions as a hyperpolarization-activated Ca2+-permeable channel specifically regulating bak1/serk4 cell death. BAK1 directly interacts with and phosphorylates CNGC20 at specific sites in the C-terminal cytosolic domain, which in turn regulates CNGC20 stability. CNGC19, the closest homolog of CNGC20 with a low abundance compared with CNGC20, makes a quantitative genetic contribution to bak1/serk4 cell death only in the absence of CNGC20, supporting the biochemical data showing homo- and heteromeric assembly of the CNGC20 and CNGC19 channel complexes. Transcripts of CNGC20 and CNGC19 are elevated in bak1/serk4 compared with wild-type plants, further substantiating a critical role of homeostasis of CNGC20 and CNGC19 in cell death control. Our studies not only uncover a unique regulation of ion channel stability by cell-surface-resident receptor kinase-mediated phosphorylation but also provide evidence for fine-tuning Ca2+ channel functions in maintaining cellular homeostasis by the formation of homo- and heterotetrameric complexes.Graphical Graphical abstract for this article
       
  • Population-Specific Selection on Standing Variation Generated by Lateral
           Gene Transfers in a Grass
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Jill K. Olofsson, Luke T. Dunning, Marjorie R. Lundgren, Henry J. Barton, John Thompson, Nicholas Cuff, Menaka Ariyarathne, Deepthi Yakandawala, Graciela Sotelo, Kai Zeng, Colin P. Osborne, Patrik Nosil, Pascal-Antoine ChristinSummaryEvidence of eukaryote-to-eukaryote lateral gene transfer (LGT) has accumulated in recent years [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14], but the selective pressures governing the evolutionary fate of these genes within recipient species remain largely unexplored [15, 16]. Among non-parasitic plants, successful LGT has been reported between different grass species [5, 8, 11, 16, 17, 18, 19]. Here, we use the grass Alloteropsis semialata, a species that possesses multigene LGT fragments that were acquired recently from distantly related grass species [5, 11, 16], to test the hypothesis that the successful LGT conferred an advantage and were thus rapidly swept into the recipient species. Combining whole-genome and population-level RAD sequencing, we show that the multigene LGT fragments were rapidly integrated in the recipient genome, likely due to positive selection for genes encoding proteins that added novel functions. These fragments also contained physically linked hitchhiking protein-coding genes, and subsequent genomic erosion has generated gene presence-absence polymorphisms that persist in multiple geographic locations, becoming part of the standing genetic variation. Importantly, one of the hitchhiking genes underwent a secondary rapid spread in some populations. This shows that eukaryotic LGT can have a delayed impact, contributing to local adaptation and intraspecific ecological diversification. Therefore, while short-term LGT integration is mediated by positive selection on some of the transferred genes, physically linked hitchhikers can remain functional and augment the standing genetic variation with delayed adaptive consequences.Graphical Graphical abstract for this article
       
  • Life at High Latitudes Does Not Require Circadian Behavioral Rhythmicity
           under Constant Darkness
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Enrico Bertolini, Frank K. Schubert, Damiano Zanini, Hana Sehadová, Charlotte Helfrich-Förster, Pamela MenegazziSummaryNearly all organisms evolved endogenous self-sustained timekeeping mechanisms to track and anticipate cyclic changes in the environment. Circadian clocks, with a periodicity of about 24 h, allow animals to adapt to day-night cycles. Biological clocks are highly adaptive, but strong behavioral rhythms might be a disadvantage for adaptation to weakly rhythmic environments such as polar areas [1, 2]. Several high-latitude species, including Drosophila species, were found to be highly arrhythmic under constant conditions [3, 4, 5, 6]. Furthermore, Drosophila species from subarctic regions can extend evening activity until dusk under long days. These traits depend on the clock network neurochemistry, and we previously proposed that high-latitude Drosophila species evolved specific clock adaptations to colonize polar regions [5, 7, 8]. We broadened our analysis to 3 species of the Chymomyza genus, which diverged circa 5 million years before the Drosophila radiation [9] and colonized both low and high latitudes [10, 11]. C. costata, pararufithorax, and procnemis, independently of their latitude of origin, possess the clock neuronal network of low-latitude Drosophila species, and their locomotor activity does not track dusk under long photoperiods. Nevertheless, the high-latitude C. costata becomes arrhythmic under constant darkness (DD), whereas the two low-latitude species remain rhythmic. Different mechanisms are behind the arrhythmicity in DD of C. costata and the high-latitude Drosophila ezoana, suggesting that the ability to maintain behavioral rhythms has been lost more than once during drosophilids’ evolution and that it might indeed be an evolutionary adaptation for life at high latitudes.Graphical Graphical abstract for this article
       
  • Coupled Active Systems Encode an Emergent Hunting Behavior in the
           Unicellular Predator Lacrymaria olor
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Scott M. Coyle, Eliott M. Flaum, Hongquan Li, Deepak Krishnamurthy, Manu PrakashSummaryMany single-celled protists use rapid morphology changes to perform fast animal-like behaviors. To understand how such behaviors are encoded, we analyzed the hunting dynamics of the predatory ciliate Lacrymaria olor, which locates and captures prey using the tip of a slender “neck” that can rapidly extend more than seven times its body length (500 μm from its body) and retract in seconds. By tracking single cells in real-time over hours and analyzing millions of sub-cellular postures, we find that these fast extension-contraction cycles underlie an emergent hunting behavior that comprehensively samples a broad area within the cell’s reach. Although this behavior appears complex, we show that it arises naturally as alternating sub-cellular ciliary and contractile activities rearrange the cell’s underlying helical cytoskeleton to extend or retract the neck. At short timescales, a retracting neck behaves like an elastic filament under load, such that compression activates a series of buckling modes that reorient the head and scramble its extensile trajectory. At longer timescales, the fundamental length of this filament can change, altering the location in space where these transitions occur. Coupling these fast and slow dynamics together, we present a simple model for how Lacrymaria samples the range of geometries and orientations needed to ensure dense stochastic sampling of the immediate environment when hunting to locate and strike at prey. More generally, coupling active mechanical and chemical signaling systems across different timescales may provide a general strategy by which mechanically encoded emergent cell behaviors can be understood or engineered.Graphical Graphical abstract for this article
       
  • An Evolutionarily Conserved Receptor-like Kinases Signaling Module
           Controls Cell Wall Integrity During Tip Growth
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Jens Westermann, Susanna Streubel, Christina Maria Franck, Roswitha Lentz, Liam Dolan, Aurélien Boisson-DernierSummaryRooting cells and pollen tubes—key adaptative innovations that evolved during the colonization and subsequent radiation of plants on land—expand by tip growth. Tip growth relies on a tight coordination between the protoplast growth and the synthesis/remodeling of the external cell wall. In root hairs and pollen tubes of the seed plant Arabidopsis thaliana, cell wall integrity (CWI) mechanisms monitor this coordination through the Malectin-like receptor kinases (MLRs), such as AtANXUR1 and AtFERONIA, that act upstream of the AtMARIS PTI1-like kinase. Here, we show that rhizoid growth in the early diverging plant, Marchantia polymorpha, is also controlled by an MLR and PTI1-like signaling module. Rhizoids, root hairs, and pollen tubes respond similarly to disruption of MLR and PTI1-like encoding genes. Thus, the MLR and PTI1-like signaling module that controls CWI during tip growth is conserved between M. polymorpha and A. thaliana, suggesting that it was active in the common ancestor of land plants.Graphical Graphical abstract for this article
       
  • Successive Kinesin-5 Microtubule Crosslinking and Sliding Promote Fast,
           Irreversible Formation of a Stereotyped Bipolar Spindle
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Allen Leary, Shannon Sim, Elena Nazarova, Kristian Shulist, Rachel Genthial, Shun Kai Yang, Khanh Huy Bui, Paul Francois, Jackie VogelSummarySeparation of duplicated spindle poles is the first step in forming the mitotic spindle. Kinesin-5 crosslinks and slides anti-parallel microtubules (MTs), but it is unclear how these two activities contribute to the first steps in spindle formation. In this study, we report that in monopolar spindles, the duplicated spindle poles snap apart in a fast and irreversible step that produces a nascent bipolar spindle. Using mutations in Kinesin-5 that inhibit microtubule sliding, we show that the fast, irreversible pole separation is primarily driven by microtubule crosslinking. Electron tomography revealed microtubule pairs in monopolar spindles have short overlaps that intersect at high angles and are unsuited for ensemble Kinesin-5 sliding. However, maximal extension of a subset of anti-parallel microtubule pairs approaches the length of nascent bipolar spindles and is consistent with a Kinesin-5 crosslinking-driven transition. Nonetheless, microtubule sliding by Kinesin-5 contributes to stabilizing the nascent spindle and setting its stereotyped equilibrium length.Graphical Graphical abstract for this article
       
  • Variation in Tolerance to Parasites Affects Vectorial Capacity of Natural
           Asian Tiger Mosquito Populations
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Guha Dharmarajan, Kathryne D. Walker, Tovi LehmannSummaryGlobally, diseases transmitted by arthropod vectors, such as mosquitoes, remain a major cause of morbidity and mortality [1]. The defense responses of mosquito and other arthropod vectors against parasites are important for understanding disease transmission dynamics and for the development of novel disease-control strategies. Consequently, the mechanisms by which mosquitoes resist parasitic infection (e.g., immune-mediated killing) have long been studied [2, 3]. However, the ability of mosquitoes to ameliorate the negative fitness consequences of infection through tolerance mechanisms (e.g., tissue repair) has been virtually ignored (but see [4, 5]). Ignoring parasite tolerance is especially taxing in vector biology because unlike resistance, which typically reduces vectorial capacity, tolerance is expected to increase vectorial capacity by reducing parasite-mediated mortality without killing parasites [6], contributing to the recurrent emergence of vector-borne diseases and its stabilization and exacerbation. Despite its importance, there is currently no evidence for the evolution of tolerance in natural mosquito populations. Here, we use a common-garden experimental framework to measure variation in resistance and tolerance to dog heartworm (Dirofilaria immitis) between eight natural Aedes albopictus mosquito populations representing areas of low and high transmission intensity. We find significant inter-population variation in tolerance and elevated tolerance where transmission intensity is high. Additionally, as expected, we find that increased tolerance is associated with higher vectorial capacity. Consequently, our results indicate that high transmission intensity can lead to the evolution of more competent disease vectors, which can feed back to impact disease risk.Graphical Graphical abstract for this article
       
  • Economic Decisions through Circuit Inhibition
    • Abstract: Publication date: Available online 31 October 2019Source: Current BiologyAuthor(s): Sébastien Ballesta, Camillo Padoa-SchioppaSummaryEconomic choices between goods are thought to rely on the orbitofrontal cortex (OFC), but the decision mechanisms remain poorly understood. To shed light on this fundamental issue, we recorded from the OFC of monkeys choosing between two juices offered sequentially. An analysis of firing rates across time windows revealed the presence of different groups of neurons similar to those previously identified under simultaneous offers. This observation suggested that economic decisions in the two modalities are formed in the same neural circuit. We then examined several hypotheses on the decision mechanisms. OFC neurons encoded good identities and values in a juice-based representation (labeled lines). Contrary to previous assessments, our data argued against the idea that decisions rely on mutual inhibition at the level of offer values. In fact, we showed that previous arguments for mutual inhibition were confounded by differences in value ranges. Instead, decisions seemed to involve mechanisms of circuit inhibition, whereby each offer value indirectly inhibited neurons encoding the opposite choice outcome. Our results reconcile a variety of previous findings and provide a general account for the neuronal underpinnings of economic choices.
       
  • Spindle-Length-Dependent HURP Localization Allows Centrosomes to Control
           Kinetochore-Fiber Plus-End Dynamics
    • Abstract: Publication date: Available online 24 October 2019Source: Current BiologyAuthor(s): Damian Dudka, Cédric Castrogiovanni, Nicolas Liaudet, Hélène Vassal, Patrick MeraldiSummaryDuring mitosis, centrosomes affect the length of kinetochore fibers (k-fibers) and the stability of kinetochore-microtubule attachments, implying that they regulate k-fiber dynamics. However, the exact cellular and molecular mechanisms of this regulation remain unknown. Here, we created human cells with only one centrosome to investigate these mechanisms. Such cells formed asymmetric bipolar spindles that resulted in asymmetric cell divisions. K-fibers in the acentrosomal half-spindles were shorter, more stable, and had a reduced poleward microtubule flux at minus ends and more frequent pausing events at their plus ends. This indicates that centrosomes regulate k-fiber dynamics both locally at minus ends and far away at plus ends. At the molecular level, we find that the microtubule-stabilizing protein HURP is enriched on the k-fiber plus ends in the acentrosomal half-spindles of cells with only one centrosome. HURP depletion rebalances k-fiber stability and plus-end dynamics in such cells and improves spindle and cell division symmetry. Our data from 3 different cell lines indicate that HURP accumulates on k-fibers inversely proportionally to half-spindle length. We therefore propose that centrosomes regulate k-fiber plus ends indirectly via length-dependent accumulation of HURP.Graphical Graphical abstract for this article
       
  • Notch-Mediated Determination of Hair-Bundle Polarity in Mechanosensory
           Hair Cells of the Zebrafish Lateral Line
    • Abstract: Publication date: Available online 24 October 2019Source: Current BiologyAuthor(s): Adrian Jacobo, Agnik Dasgupta, Anna Erzberger, Kimberly Siletti, A.J. HudspethSummaryThe development of mechanosensory epithelia, such as those of the auditory and vestibular systems, results in the precise orientation of mechanosensory hair cells. After division of a precursor cell in the zebrafish’s lateral line, the daughter hair cells differentiate with opposite mechanical sensitivity. Through a combination of theoretical and experimental approaches, we show that Notch1a-mediated lateral inhibition produces a bistable switch that reliably gives rise to cell pairs of opposite polarity. Using a mathematical model of the process, we predict the outcome of several genetic and chemical alterations to the system, which we then confirm experimentally. We show that Notch1a downregulates the expression of Emx2, a transcription factor known to be involved in polarity specification, and acts in parallel with the planar-cell-polarity system to determine the orientation of hair bundles. By analyzing the effect of simultaneous genetic perturbations to Notch1a and Emx2, we infer that the gene-regulatory network determining cell polarity includes an undiscovered polarity effector.
       
  • Evolutionary Response to Climate Change in Migratory Pied Flycatchers
    • Abstract: Publication date: Available online 24 October 2019Source: Current BiologyAuthor(s): Barbara Helm, Benjamin M. Van Doren, Dieter Hoffmann, Ute HoffmannSummaryClimate change is rapidly advancing spring phenology [1, 2, 3] but at different rates in different species [1, 4]. Whether these advances are solely driven by phenotypic plasticity [2, 5] or also involve evolution is hotly debated (e.g., [5, 6, 7]). In some species, including avian long-distance migrants, plastic responses to early springs may be constrained by inherited circannual timing programs [8, 9], making evolutionary adjustment the only viable mechanism for keeping pace with shifting phenology [5, 10]. This constraint may be contributing to population declines in migratory species [5, 10, 11, 12]. To test whether a migrant’s timing program has evolved [10, 12], we replicated an experimental study of the annual cycle of long-distance migratory pied flycatchers (Ficedula hypoleuca) after 21 years of warming. Flycatchers are a model for studying constrained ecological responses to climate change [6, 10, 12, 13]. We show that the phase of the flycatcher circannual clock controlling spring moult, migration, and reproductive timing advanced by 9 days. A nearby wild population mirrored these changes, concurrently advancing egg-laying by 11 days. Furthermore, the time window during which wild flycatcher reproductive timing was most sensitive to ambient temperature advanced by 0.8 days year–1. These results support a role of phenotypic evolution [14] in changing spring phenology [15, 16]. We suggest that the timing programs of long-distance migratory birds may have greater adaptive potential than previously thought, leaving some scope for evolutionary rescue in a changing climate.
       
  • Attenuated Fgf Signaling Underlies the Forelimb Heterochrony in the Emu
           Dromaius novaehollandiae
    • Abstract: Publication date: Available online 24 October 2019Source: Current BiologyAuthor(s): John J. Young, Phil Grayson, Scott V. Edwards, Clifford J. TabinSummaryPowered flight was fundamental to the establishment and radiation of birds. However, flight has been lost multiple times throughout avian evolution. Convergent losses of flight within the ratites (flightless paleognaths, including the emu and ostrich) often coincide with reduced wings. Although there is a wealth of anatomical knowledge for several ratites, the genetic mechanisms causing these changes remain debated. Here, we use a multidisciplinary approach employing embryological, genetic, and genomic techniques to interrogate the mechanisms underlying forelimb heterochrony in emu embryos. We show that the initiation of limb formation, an epithelial to mesenchymal transition (EMT) in the lateral plate mesoderm (LPM) and myoblast migration into the LPM, occur at equivalent stages in the emu and chick. However, the emu forelimb fails to subsequently proliferate. The unique emu forelimb expression of Nkx2.5, previously associated with diminished wing development, initiates after this stage (concomitant with myoblast migration into the LPM) and is therefore unlikely to cause this developmental delay. In contrast, RNA sequencing of limb tissue reveals significantly lower Fgf10 expression in the emu forelimb. Artificially increasing Fgf10 expression in the emu LPM induces ectodermal Fgf8 expression and a limb bud. Analyzing open chromatin reveals differentially active regulatory elements near Fgf10 and Sall-1 in the emu wing, and the Sall-1 enhancer activity is dependent on a likely Fgf-mediated Ets transcription factor-binding site. Taken together, our results suggest that regulatory changes result in lower expression of Fgf10 and a concomitant failure to express genes required for limb proliferation in the early emu wing bud.
       
  • A Serotonin-Modulated Circuit Controls Sleep Architecture to Regulate
           Cognitive Function Independent of Total Sleep in Drosophila
    • Abstract: Publication date: Available online 24 October 2019Source: Current BiologyAuthor(s): Chang Liu, Zhiqiang Meng, Timothy D. Wiggin, Junwei Yu, Martha L. Reed, Fang Guo, Yunpeng Zhang, Michael Rosbash, Leslie C. GriffithSummaryBoth the structure and the amount of sleep are important for brain function. Entry into deep, restorative stages of sleep is time dependent; short sleep bouts selectively eliminate these states. Fragmentation-induced cognitive dysfunction is a feature of many common human sleep pathologies. Whether sleep structure is normally regulated independent of the amount of sleep is unknown. Here, we show that in Drosophila melanogaster, activation of a subset of serotonergic neurons fragments sleep without major changes in the total amount of sleep, dramatically reducing long episodes that may correspond to deep sleep states. Disruption of sleep structure results in learning deficits that can be rescued by pharmacologically or genetically consolidating sleep. We identify two reciprocally connected sets of ellipsoid body neurons that form the heart of a serotonin-modulated circuit that controls sleep architecture. Taken together, these findings define a circuit essential for controlling the structure of sleep independent of its amount.
       
  • Commonly Used Insect Repellents Hide Human Odors from Anopheles
           Mosquitoes
    • Abstract: Publication date: Available online 17 October 2019Source: Current BiologyAuthor(s): Ali Afify, Joshua F. Betz, Olena Riabinina, Chloé Lahondère, Christopher J. PotterSummaryThe mode of action for most mosquito repellents is unknown. This is primarily due to the difficulty in monitoring how the mosquito olfactory system responds to repellent odors. Here, we used the Q-system of binary expression to enable activity-dependent Ca2+ imaging in olfactory neurons of the African malaria mosquito Anopheles coluzzii. This system allows neuronal responses to common insect repellents to be directly visualized in living mosquitoes from all olfactory organs, including the antenna. The synthetic repellents N,N-diethyl-meta-toluamide (DEET) and IR3535 did not activate Anopheles odorant receptor co-receptor (Orco)-expressing olfactory receptor neurons (ORNs) at any concentration, and picaridin weakly activated ORNs only at high concentrations. In contrast, natural repellents (i.e. lemongrass oil and eugenol) strongly activated small numbers of ORNs in the Anopheles mosquito antennae at low concentrations. We determined that DEET, IR3535, and picaridin decrease the response of Orco-expressing ORNs when these repellents are physically mixed with activating human-derived odorants. We present evidence that synthetic repellents may primarily exert their olfactory mode of action by decreasing the amount of volatile odorants reaching ORNs. These results suggest that synthetic repellents disruptively change the chemical profile of host scent signatures on the skin surface, rendering humans invisible to Anopheles mosquitoes.Graphical Graphical abstract for this article
       
  • Cell Width Dictates Type VI Secretion Tail Length
    • Abstract: Publication date: Available online 17 October 2019Source: Current BiologyAuthor(s): Yoann G. Santin, Thierry Doan, Laure Journet, Eric CascalesSummaryThe type VI secretion system (T6SS) is a multiprotein apparatus that injects protein effectors into target cells, hence playing a critical role in pathogenesis and in microbial communities [1, 2, 3, 4]. The T6SS belongs to the broad family of contractile injection systems (CISs), such as Myoviridae bacteriophages and R-pyocins, that use a spring-like tail to propel a needle loaded with effectors [5, 6]. The T6SS tail comprises an assembly baseplate on which polymerizes a needle, made of stacked Hcp hexamers, tipped by the VgrG-PAAR spike complex and wrapped by the contractile sheath made of TssB and TssC [7, 8, 9, 10, 11, 12, 13]. The T6SS tail is anchored to the cell envelope by a membrane complex that also serves as channel for the passage of the needle upon sheath contraction [14, 15, 16]. In most CISs, the length of the tail sheath is invariable and is usually ensured by a dedicated protein called tape measure protein (TMP) [17, 18, 19, 20, 21, 22]. Here, we show that the length of the T6SS tail is constant in enteroaggregative Escherichia coli cells, suggesting that it is strictly controlled. By overproducing T6SS tail subunits, we demonstrate that component stoichiometry does not participate to the regulation of tail length. The observation of longer T6SS tails when the apparatus is relocalized at the cell pole further shows that tail length is not controlled by a TMP. Finally, we show that tail stops its elongation when in contact with the opposite membrane and thus that T6SS tail length is determined by the cell width.Graphical Graphical abstract for this article
       
  • A Neofunctionalized X-Linked Ampliconic Gene Family Is Essential for Male
           Fertility and Equal Sex Ratio in Mice
    • Abstract: Publication date: Available online 17 October 2019Source: Current BiologyAuthor(s): Alyssa N. Kruger, Michele A. Brogley, Jamie L. Huizinga, Jeffrey M. Kidd, Dirk G. de Rooij, Yueh-Chiang Hu, Jacob L. MuellerSummaryThe mammalian sex chromosomes harbor an abundance of newly acquired ampliconic genes, although their functions require elucidation [1, 2, 3, 4, 5, 6, 7, 8, 9]. Here, we demonstrate that the X-linked Slx and Slxl1 ampliconic gene families represent mouse-specific neofunctionalized copies of a meiotic synaptonemal complex protein, Sycp3. In contrast to the meiotic role of Sycp3, CRISPR-loxP-mediated multi-megabase deletions of the Slx (5 Mb) and Slxl1 (2.3Mb) ampliconic regions result in post-meiotic defects, abnormal sperm, and male infertility. Males carrying Slxl1 deletions sire more male offspring, whereas males carrying Slx and Slxl1 duplications sire more female offspring, which directly correlates with Slxl1 gene dosage and gene expression levels. SLX and SLXL1 proteins interact with spindlin protein family members (SPIN1 and SSTY1/2) and males carrying Slxl1 deletions downregulate a sex chromatin modifier, Scml2, leading us to speculate that Slx and Slxl1 function in chromatin regulation. Our study demonstrates how newly acquired X-linked genes can rapidly evolve new and essential functions and how gene amplification can increase sex chromosome transmission.
       
  • Network-Specific Synchronization of Electrical Slow-Wave Oscillations
           Regulates Sleep Drive in Drosophila
    • Abstract: Publication date: Available online 17 October 2019Source: Current BiologyAuthor(s): Davide Raccuglia, Sheng Huang, Anatoli Ender, M.-Marcel Heim, Desiree Laber, Raquel Suárez-Grimalt, Agustin Liotta, Stephan J. Sigrist, Jörg R.P. Geiger, David OwaldSummarySlow-wave rhythms characteristic of deep sleep oscillate in the delta band (0.5–4 Hz) and can be found across various brain regions in vertebrates. Across phyla, however, an understanding of the mechanisms underlying oscillations and how these link to behavior remains limited. Here, we discover compound delta oscillations in the sleep-regulating R5 network of Drosophila. We find that the power of these slow-wave oscillations increases with sleep need and is subject to diurnal variation. Optical multi-unit voltage recordings reveal that single R5 neurons get synchronized by activating circadian input pathways. We show that this synchronization depends on NMDA receptor (NMDAR) coincidence detector function, and that an interplay of cholinergic and glutamatergic inputs regulates oscillatory frequency. Genetically targeting the coincidence detector function of NMDARs in R5, and thus the uncovered mechanism underlying synchronization, abolished network-specific compound slow-wave oscillations. It also disrupted sleep and facilitated light-induced wakening, establishing a role for slow-wave oscillations in regulating sleep and sensory gating. We therefore propose that the synchronization-based increase in oscillatory power likely represents an evolutionarily conserved, potentially “optimal,” strategy for constructing sleep-regulating sensory gates.Graphical Graphical abstract for this article
       
 
 
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