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Current Biology
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ISSN (Print) 0960-9822 - ISSN (Online) 1879-0445
Published by Elsevier Homepage  [3183 journals]
  • CTENO64 Is Required for Coordinated Paddling of Ciliary Comb Plate in
           Ctenophores
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Kei Jokura, Daisuke Shibata, Katsushi Yamaguchi, Kogiku Shiba, Yumiko Makino, Shuji Shigenobu, Kazuo InabaSummaryCtenophores, or comb jellies, are one of the earliest branching basal metazoan groups, whose phylogenetic position continues to be controversial. They have eight rows of iridescent structures, called comb plates, which are huge multiciliated paddle-like structures used for locomotion and uniquely found in this group of animals [1]. Despite a number of morphological and physiological studies over the past 50 years, the molecular nature of comb plates remains completely unknown. Here, we identified a protein CTENO64 that is specifically localized in the comb plates. This protein is only found in ctenophores and not in other animals or eukaryotic species that possess multiciliary cells or tissues. It is localized to regions, called compartmenting lamella (CL), which are uniquely seen in ctenophore multicilia, connecting adjacent cilia in the comb plates. Knockdown of the CTENO64 gene did not affect the formation of comb plates but caused the loss or misformation of CLs and the disruption of ciliary orientation, resulting in aberrant and non-planar waveforms in the mid-distal region of the comb plates. We propose that CLs have been convergently acquired in ctenophores to overcome the hydrodynamic constraints of possessing extremely long multicilia. Our findings provide the initial step in unveiling the molecular structure and evolutionary significance of ciliary comb plates and shed light not only on the hidden biology of ctenophores but also on the unique evolutionary pathway of these animals.Video Graphical Graphical abstract for this article
       
  • The RopGEF KARAPPO Is Essential for the Initiation of Vegetative
           Reproduction in Marchantia polymorpha
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Takuma Hiwatashi, Honzhen Goh, Yukiko Yasui, Li Quan Koh, Hideyuki Takami, Masataka Kajikawa, Hiroyuki Kirita, Takehiko Kanazawa, Naoki Minamino, Taisuke Togawa, Mayuko Sato, Mayumi Wakazaki, Katsushi Yamaguchi, Shuji Shigenobu, Hidehiro Fukaki, Tetsuro Mimura, Kiminori Toyooka, Shinichiro Sawa, Katsuyuki T. Yamato, Takashi UedaSummaryMany plants can reproduce vegetatively, producing clonal progeny from vegetative cells; however, little is known about the molecular mechanisms underlying this process. Liverwort (Marchantia polymorpha), a basal land plant, propagates asexually via gemmae, which are clonal plantlets formed in gemma cups on the dorsal side of the vegetative thallus [1]. The initial stage of gemma development involves elongation and asymmetric divisions of a specific type of epidermal cell, called a gemma initial, which forms on the floor of the gemma cup [2, 3]. To investigate the regulatory mechanism underlying gemma development, we focused on two allelic mutants in which no gemma initial formed; these mutants were named karappo, meaning “empty.” We used whole-genome sequencing of both mutants and molecular genetic analysis to identify the causal gene, KARAPPO (KAR), which encodes a ROP guanine nucleotide exchange factor (RopGEF) carrying a plant-specific ROP nucleotide exchanger (PRONE) catalytic domain. In vitro GEF assays showed that the full-length KAR protein and the PRONE domain have significant GEF activity toward MpROP, the only ROP GTPase in M. polymorpha. Moreover, genetic complementation experiments showed a significant role for the N- and C-terminal variable regions in gemma development. Our investigation demonstrates an essential role for KAR/RopGEF in the initiation of plantlet development from a differentiated cell, which may involve cell-polarity formation and subsequent asymmetric cell division via activation of ROP signaling, implying a similar developmental mechanism in vegetative reproduction of various land plants.Graphical Graphical abstract for this article
       
  • Iterative and Complex Asymmetric Divisions Control Cell Volume Differences
           in Ciona Notochord Tapering
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Konner Winkley, Spencer Ward, Wendy Reeves, Michael VeemanSummaryThe notochord of the invertebrate chordate Ciona forms a tapered rod at tailbud stages consisting of only 40 cylindrical cells in a single-file column. This tapered shape involves differences in notochord cell volume along the anterior-posterior axis. Here, we quantify sibling cell volume asymmetry throughout the developing notochord and find that there are distinctive patterns of unequal cleavage in all 4 bilateral pairs of A-line primary notochord founder cells and also in the B-line-derived secondary notochord founder cells. A quantitative model confirms that the observed patterns of unequal cleavage are sufficient to explain all the anterior-posterior variation in notochord cell volume. Many examples are known of cells that divide asymmetrically to give daughter cells of different size and fate. Here, by contrast, a series of subtle but iterative and finely patterned asymmetric divisions controls the shape of an entire organ. Quantitative 3D analysis of cell shape and spindle positioning allows us to infer multiple cellular mechanisms driving these unequal cleavages, including polarized displacements of the mitotic spindle, contributions from the shape of the mother cell, and late changes occurring between anaphase and abscission that potentially involve differential cortical contractility. We infer differential use of these mechanisms between different notochord blastomeres and also between different rounds of cell division. These results demonstrate a new role for asymmetric division in directly shaping a developing organ and point toward complex underlying mechanisms.
       
  • Neuropsin (OPN5) Mediates Local Light-Dependent Induction of Circadian
           Clock Genes and Circadian Photoentrainment in Exposed Murine Skin
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Ethan D. Buhr, Shruti Vemaraju, Nicolás Diaz, Richard A. Lang, Russell N. Van GelderSummaryNearly all mammalian tissues have functional, autonomous circadian clocks, which free-run with non-24 h periods and must be synchronized (entrained) to the 24 h day. This entrainment mechanism is thought to be hierarchical, with photic input to the retina entraining the master circadian clock in the suprachiasmatic nuclei (SCN) and the SCN in turn synchronizing peripheral tissues via endocrine mechanisms. Here, we assess the function of a population of melanocyte precursor cells in hair and vibrissal follicles that express the photopigment neuropsin (OPN5). Organotypic cultures of murine outer ear and vibrissal skin entrain to a light-dark cycle ex vivo, requiring cis-retinal chromophore and Opn5 gene function. Short-wavelength light strongly phase shifts skin circadian rhythms ex vivo via an Opn5-dependent mechanism. In vivo, the normal amplitude of Period mRNA expression in outer ear skin is dependent on both the light-dark cycle and Opn5 function. In Opn4−/−; Pde6brd1/rd1 mice that cannot behaviorally entrain to light-dark cycles, the phase of skin-clock gene expression remains synchronized to the light-dark cycle, even as other peripheral clocks remain phase-locked to the free-running behavioral rhythm. Taken together, these results demonstrate the presence of a direct photic circadian entrainment pathway and direct light-response elements for clock genes in murine skin, similar to pathways previously described for invertebrates and certain non-mammalian vertebrates.
       
  • Genomic Basis of Circannual Rhythm in the European Corn Borer Moth
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Genevieve M. Kozak, Crista B. Wadsworth, Shoshanna C. Kahne, Steven M. Bogdanowicz, Richard G. Harrison, Brad S. Coates, Erik B. DopmanSummarySynchronizing the annual timing of physiological, morphological, and behavioral transitions with seasons enables survival in temperate environments [1]. The capacity to adjust life history timing and track local seasonal cycles can facilitate geographic expansion [2], adaptation [3], and tolerance [4, 5, 6] during rapid environmental change. Understanding the proximate causes of variation in seasonal timing improves prediction of future response and persistence [7, 8]. However, relatively little is known about the molecular basis generating this diversity [9], particularly in Lepidoptera, a group with many species in decline [10, 11]. In insects, the stress-tolerant physiological state of diapause enables coping with seasonal challenges [1, 12, 13, 14, 15]. Seasonal changes in photoperiod and temperature are used to synchronize diapause with winter, and timing of diapause transitions varies widely within and among species [9, 16]. Changes in spring diapause termination in the European corn borer moth (Ostrinia nubilalis) have allowed populations to respond to shorter winters and emerge ∼3 weeks earlier in the year [17]. Multiple whole-genome approaches suggest two circadian clock genes, period (per) and pigment-dispersing factor receptor (Pdfr), underlie this polymorphism. Per and Pdfr are within interacting quantitative trait loci (QTL) and differ in allele frequency among individuals that end diapause early or late, with alleles maintained in high linkage disequilibrium. Our results provide testable hypotheses about the physiological role of circadian clock genes in the circannual timer. We predict these gene candidates will be targets of selection for future adaptation under continued global climate change [18].Graphical Graphical abstract for this article
       
  • Flies Regulate Wing Motion via Active Control of a Dual-Function Gyroscope
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Bradley H. Dickerson, Alysha M. de Souza, Ainul Huda, Michael H. DickinsonSummaryFlies execute their remarkable aerial maneuvers using a set of wing steering muscles, which are activated at specific phases of the stroke cycle [1, 2, 3]. The activation phase of these muscles—which determines their biomechanical output [4, 5, 6]—arises via feedback from mechanoreceptors at the base of the wings and structures unique to flies called halteres [7, 8, 9]. Evolved from the hindwings, the tiny halteres oscillate at the same frequency as the wings, although they serve no aerodynamic function [10] and are thought to act as gyroscopes [10, 11, 12, 13, 14, 15]. Like the wings, halteres possess minute control muscles whose activity is modified by descending visual input [16], raising the possibility that flies control wing motion by adjusting the motor output of their halteres, although this hypothesis has never been directly tested. Here, using genetic techniques possible in Drosophila melanogaster, we tested the hypothesis that visual input during flight modulates haltere muscle activity and that this, in turn, alters the mechanosensory feedback that regulates the wing steering muscles. Our results suggest that rather than acting solely as a gyroscope to detect body rotation, halteres also function as an adjustable clock to set the spike timing of wing motor neurons, a specialized capability that evolved from the generic flight circuitry of their four-winged ancestors. In addition to demonstrating how the efferent control loop of a sensory structure regulates wing motion, our results provide insight into the selective scenario that gave rise to the evolution of halteres.
       
  • The Human Basolateral Amygdala Is Indispensable for Social Experiential
           Learning
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Lisa A. Rosenberger, Christoph Eisenegger, Michael Naef, David Terburg, Jorique Fourie, Dan J. Stein, Jack van HonkSummaryTrust and betrayal are central to our social world, and adaptive responses to generous and selfish behavior are crucial to our economic and social well-being [1]. We learn about others’ trustworthiness through trial and error during repeated interactions [2]. By reinforcing and suppressing behavior during positive and negative interactions with conspecifics, rodent research has established a crucial role for the basolateral amygdala (BLA) in social experiential learning [3, 4]. The human BLA has undergone a reorganization with massive expansion relative to other amygdala nuclei [5], and there is no translational research on its role in experiential learning. The human amygdala is traditionally researched as a single structure [6], neglecting the sub-nuclei’s structural und functional differences [7], which might explain inconsistent findings in research on social interactions [8, 9]. Here, we study whether the human BLA is necessary for social and non-social experiential learning by testing a group of five humans with selective bilateral damage to the BLA. We compared their learning behavior in a repeated trust game, and a non-social control task, to healthy, matched controls. Crucially, BLA-damaged subjects, unlike control subjects, completely failed to adapt their investments when interacting with a trustworthy and an untrustworthy partner. In the non-social task, BLA-damaged subjects learned from positive outcomes but differed from the controls by not learning from negative outcomes. Our data extend findings in rodent research by showing that the human BLA is essential for social experiential learning and provide confirmatory evidence of divergent mechanisms for differentially valenced outcomes in non-social learning.
       
  • Flagellum Removal by a Nectar Metabolite Inhibits Infectivity of a
           Bumblebee Parasite
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Hauke Koch, James Woodward, Moses K. Langat, Mark J.F. Brown, Philip C. StevensonSummaryPlant phytochemicals can act as natural “medicines” for animals against parasites [1, 2, 3]. Some nectar metabolites, for example, reduce parasite infections in bees [4, 5, 6, 7]. Declining plant diversity through anthropogenic landscape change [8, 9, 10, 11] could reduce the availability of medicinal nectar plants for pollinators, exacerbating their decline [12]. Existing studies are, however, limited by (1) a lack of mechanistic insights into how phytochemicals affect pollinator diseases and (2) the restriction to few, commercially available chemicals, thereby potentially neglecting plants with the biggest antiparasitic effects. To rapidly identify plants with the greatest potential as natural bee medicines, we developed a bioactivity-directed fractionation assay for nectar metabolites. We evaluated 17 important nectar plants against the bumblebee pathogen Crithidia bombi (Trypanosomatidae) [13, 14, 15, 16, 17]. The most bioactive species was heather (Calluna vulgaris), the second most productive UK nectar plant [10]. We identified 4-(3-oxobut-1-enylidene)-3,5,5-trimethylcyclohex-2-en-1-one (callunene) from heather nectar as a potent inhibitor of C. bombi. Wild bumblebees (Bombus terrestris) foraging on heather ingest callunene at concentrations causing complete C. bombi inhibition. Feeding on callunene was prophylactic against infections. We show that C. bombi establishes infections by flagellar anchoring to the ileum epithelium. Short-term callunene exposure induced flagellum loss in C. bombi choanomastigotes, resulting in a loss of infectivity. We conclude that plant secondary metabolites can disrupt parasite flagellum attachment, revealing a mechanism behind their prophylactic effects. The decline of heathlands [18, 19, 20, 21] reduces the availability of natural bee “medicine” and could exacerbate the contribution of diseases to pollinator declines.Video
       
  • Profilin-Mediated Actin Allocation Regulates the Growth of Epithelial
           Microvilli
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): James J. Faust, Bryan A. Millis, Matthew J. TyskaSummaryTransporting epithelial cells, like those that line the intestinal tract, are specialized for solute processing and uptake. One defining feature is the brush border, an array of microvilli that serves to amplify apical membrane surface area and increase functional capacity. During differentiation, upon exit from stem-cell-containing crypts, enterocytes build thousands of microvilli, each supported by a parallel bundle of actin filaments several microns in length. Given the high concentration of actin residing in mature brush borders, we sought to determine whether enterocytes were resource (i.e., actin monomer) limited in assembling this domain. To examine this possibility, we inhibited Arp2/3, the ubiquitous branched actin nucleator, to increase G-actin availability during brush border assembly. In native intestinal tissues, Arp2/3 inhibition led to increased microvilli length on the surface of crypt, but not villus, enterocytes. In a cell culture model of brush border assembly, Arp2/3 inhibition accelerated the growth and increased the length of microvilli; it also led to a redistribution of F-actin from cortical lateral networks into the brush border. Effects on brush border growth were rescued by treatment with the G-actin sequestering drug, latrunculin A. G-actin binding protein, profilin-1, colocalized in the terminal web with G-actin, and knockdown of this factor compromised brush border growth in a concentration-dependent manner. Finally, the acceleration in brush border assembly induced by Arp2/3 inhibition was abrogated by profilin-1 knockdown. Thus, brush border assembly is limited by G-actin availability, and profilin-1 directs unallocated actin monomers into microvillar core bundles during enterocyte differentiation.
       
  • Unconventional Cell Division Cycles from Marine-Derived Yeasts
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Lorna M.Y. Mitchison-Field, José M. Vargas-Muñiz, Benjamin M. Stormo, Ellysa J.D. Vogt, Sarah Van Dierdonck, James F. Pelletier, Christoph Ehrlich, Daniel J. Lew, Christine M. Field, Amy S. GladfelterSummaryFungi have been found in every marine habitat that has been explored; however, the diversity and functions of fungi in the ocean are poorly understood. In this study, fungi were cultured from the marine environment in the vicinity of Woods Hole, MA, USA, including from plankton, sponge, and coral. Our sampling resulted in 35 unique species across 20 genera. We observed many isolates by time-lapse, differential interference contrast (DIC) microscopy and analyzed modes of growth and division. Several black yeasts displayed highly unconventional cell division cycles compared to those of traditional model yeast systems. Black yeasts have been found in habitats inhospitable to other life and are known for halotolerance, virulence, and stress resistance. We find that this group of yeasts also shows remarkable plasticity in terms of cell size control, modes of cell division, and cell polarity. Unexpected behaviors include division through a combination of fission and budding, production of multiple simultaneous buds, and cell division by sequential orthogonal septations. These marine-derived yeasts reveal alternative mechanisms for cell division cycles that seem likely to expand the repertoire of rules established from classic model system yeasts.Graphical Graphical abstract for this article
       
  • Centralspindlin Recruits ALIX to the Midbody during Cytokinetic Abscission
           in Drosophila via a Mechanism Analogous to Virus Budding
    • Abstract: Publication date: Available online 10 October 2019Source: Current BiologyAuthor(s): Anette Lie-Jensen, Kristina Ivanauskiene, Lene Malerød, Ashish Jain, Kia Wee Tan, Jon K. Laerdahl, Knut Liestøl, Harald Stenmark, Kaisa HaglundSummaryAbscission, the final step of cytokinesis, cleaves the thin intercellular bridge connecting the two daughter cells [1, 2, 3, 4, 5, 6]. The scaffold protein ALIX is a core component of the abscission machinery with an evolutionarily conserved role in midbody recruitment of ESCRT-III [7, 8, 9, 10, 11], which mediates the final cut [1, 2, 3, 4, 5, 8, 9, 10, 12, 13, 14]. In mammalian cells, the centralspindlin complex recruits the major midbody organizer CEP55 that directly binds and recruits ALIX and ESCRT-I [7, 8, 9, 15, 16, 17], which in turn cooperatively recruit ESCRT-III [8, 9, 18]. However, CEP55 is missing in Drosophila melanogaster and other invertebrates [6, 9, 19], and it is unknown how the abscission machinery is recruited to the midbody in the absence of CEP55. Here, we address how Drosophila ALIX is recruited to the midbody. Surprisingly, ALIX localizes to the midbody via its V-domain, independently of the GPPX3Y motif in the proline-rich region that recruits human ALIX [8, 9]. We elucidate that the centralspindlin component Pavarotti (H.s.MKLP1) interacts with the V-domain of ALIX to recruit it to the midbody. Specifically, our results indicate that an LxxLF motif in Pavarotti directly interacts with a conserved hydrophobic pocket in the ALIX V-domain, which in human ALIX binds (L)YPXnL/LxxLF motifs of virus proteins [20, 21, 22, 23, 24, 25, 26, 27, 28]. Thus, our study identifies that ALIX is recruited by an analogous mechanism during abscission in Drosophila as during virus budding in mammalian cells and an ancestral role for centralspindlin in recruiting the abscission machinery to the midbody.Graphical Graphical abstract for this article
       
  • Alex Mogilner
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Alex Mogilner
       
  • Abrupt Change in Climate and Biotic Systems
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Filippo Botta, Dorthe Dahl-Jensen, Carsten Rahbek, Anders Svensson, David Nogués-BravoFifty years ago, Willi Dansgaard and colleagues discovered several abrupt climate change events in Greenland during the last glacial period. Since then, several ice cores retrieved from the Greenland ice sheet have verified the existence of 25 abrupt climate warming events now known as Dansgaard–Oeschger events. These events are characterized by a rapid 10–15°C warming over a few decades followed by a stable period of centuries or millennia before a gradual return to full glacial conditions. Similar warming events have been identified in other paleo-archives in the Northern hemisphere. These findings triggered wide interest in abrupt climate change and its impact on biological diversity, but ambiguous definitions have constrained our ability to assign biotic responses to the different types of climate change. Here, we provide a coherent definition for different types of climatic change, including ‘abrupt climate change’, and a summary of past abrupt climate-change events. We then review biotic responses to abrupt climate change, from the genetic to the ecosystem level, and show that abrupt climatic and ecological changes have been instrumental in shaping biodiversity. We also identify open questions, such as what causes species resilience after an abrupt change. However, identifying causal relationships between past climate change and biological responses remains difficult. We need to formalize and unify the definition of abrupt change across disciplines and further investigate past abrupt climate change periods to better anticipate and mitigate the impacts on biodiversity and society wrought by human-made climate change.
       
  • Challenges and Opportunities for Soil Biodiversity in the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Stefan Geisen, Diana H. Wall, Wim H. van der PuttenBiodiversity on Earth is strongly affected by human alterations to the environment. The majority of studies have considered aboveground biodiversity, yet little is known about whether biodiversity changes belowground follow the same patterns as those observed aboveground. It is now established that communities of soil biota have been substantially altered by direct human activities such as soil sealing, agricultural land-use intensification, and biological invasions resulting from the introduction of non-native species. In addition, altered abiotic conditions resulting from climate change have also impacted soil biodiversity. These changes in soil biodiversity can alter ecosystem functions performed by the soil biota, and therefore, human-induced global changes have a feedback effect on ecosystem services via altered soil biodiversity. Here, we highlight the major phenomena that threaten soil biodiversity, and we propose options to reverse the decline in soil biodiversity. We argue that it is essential to protect soil biodiversity as a rich reservoir that provides insurance against the changes wrought by the Anthropocene. Overall, we need to better understand the determinants of soil biodiversity and how they function, plan to avoid further losses, and restore soil biodiversity where possible. Safeguarding this rich biotic reservoir is essential for soil sustainability and, ultimately, the sustainability of human society.
       
  • Climate Change, Human Impacts, and Coastal Ecosystems in the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Qiang He, Brian R. SillimanCoastal zones, the world’s most densely populated regions, are increasingly threatened by climate change stressors — rising and warming seas, intensifying storms and droughts, and acidifying oceans. Although coastal zones have been affected by local human activities for centuries, how local human impacts and climate change stressors may interact to jeopardize coastal ecosystems remains poorly understood. Here we provide a review on interactions between climate change and local human impacts (e.g., interactions between sea level rise and anthropogenic land subsidence, which are forcing Indonesia to relocate its capital city) in the coastal realm. We highlight how these interactions can impair and, at times, decimate a variety of coastal ecosystems, and examine how understanding and incorporating these interactions can reshape theory on climate change impacts and ecological resilience. We further discuss implications of interactions between climate change and local human impacts for coastal conservation and elucidate the context when and where local conservation is more likely to buffer the impacts of climate change, attempting to help reconcile the growing debate about whether to shift much of the investment in local conservation to global CO2 emission reductions. Our review underscores that an enhanced understanding of interactions between climate change and local human impacts is of profound importance to improving predictions of climate change impacts, devising climate-smart conservation actions, and helping enhance adaption of coastal societies to climate change in the Anthropocene.
       
  • Conservation of Tropical Forests in the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): David P. Edwards, Jacob B. Socolar, Simon C. Mills, Zuzana Burivalova, Lian Pin Koh, David S. WilcoveIf current trends continue, the tropical forests of the Anthropocene will be much smaller, simpler, steeper and emptier than they are today. They will be more diminished in size and heavily fragmented (especially in lowland wet forests), have reduced structural and species complexity, be increasingly restricted to steeper, less accessible areas, and be missing many heavily hunted species. These changes, in turn, will greatly reduce the quality and quantity of ecosystem services that tropical forests can provide. Driving these changes will be continued clearance for farming and monoculture forest plantations, unsustainable selective logging, overhunting, and, increasingly, climate change. Concerted action by local and indigenous communities, environmental groups, governments, and corporations can reverse these trends and, if successful, provide future generations with a tropical forest estate that includes a network of primary forest reserves robustly defended from threats, recovering logged and secondary forests, and resilient community forests managed for the needs of local people. Realizing this better future for tropical forests and people will require formalisation of land tenure for local and indigenous communities, better-enforced environmental laws, the widescale roll-out of payments for ecosystem service schemes, and sustainable intensification of under-yielding farmland, as well as global-scale societal changes, including reduced consumerism, meat consumption, fossil fuel reliance, and population growth. But the time to act is now, while the opportunity remains to protect a semblance of intact, hyperdiverse tropical forests.
       
  • The Potential for Rapid Evolution under Anthropogenic Climate Change
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Renee A. Catullo, John Llewelyn, Ben L. Phillips, Craig C. MoritzUnderstanding how natural populations will respond to rapid anthropogenic climate change is one of the greatest challenges for ecologists and evolutionary biologists. Much research has focussed on whether physiological traits can evolve quickly enough under rapidly increasing temperatures. While the simple Breeder’s equation helps to understand how extreme temperatures and genetic variation might drive within-population evolution under climate change, it does not consider two key areas: how different forms of phenotypic plasticity interact and variation among populations. Plasticity can modify the exposure to climatic extremes and the strength of selection from those extremes, while differences among populations provide adaptive diversity not apparent within them. Here, we focus on terrestrial vertebrates and, with a case study on a tropical lizard, demonstrate the complex interplay between spatial, genetic and plastic contributions to variation in climate-relevant physiological traits. We identify several problems that need to be better understood: which traits are under selection in a changing climate; the different forms of plasticity relevant to population persistence and rapid evolution; plastic versus genetic contributions to geographic variation in climate-associated traits and whether plasticity can be harnessed to promote persistence of species. Given ongoing uncertainties around whether natural populations can evolve rapidly enough to persist, we advocate the use of field trials aimed at increasing rates of adaptation, especially in systems known to be strongly impacted by human-driven changes in climate.
       
  • Psychology and climate change
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Susan Clayton
       
  • Fishing through the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Robert S. Steneck, Daniel Pauly
       
  • Extinction in the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Samuel T. Turvey, Jennifer J. Crees
       
  • Deep learning for environmental conservation
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Aakash Lamba, Phillip Cassey, Ramesh Raja Segaran, Lian Pin KohSummaryThe last decade has transformed the field of artificial intelligence, with deep learning at the forefront of this development. With its ability to ‘self-learn’ discriminative patterns directly from data, deep learning is a promising computational approach for automating the classification of visual, spatial and acoustic information in the context of environmental conservation. Here, we first highlight the current and future applications of supervised deep learning in environmental conservation. Next, we describe a number of technical and implementation-related challenges that can potentially impede the real-world adoption of this technology in conservation programmes. Lastly, to mitigate these pitfalls, we discuss priorities for guiding future research and hope that these recommendations will help make this technology more accessible to environmental scientists and conservation practitioners.
       
  • Rethinking the food system for human health in the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Guy M. Poppy, Jenny BaverstockSummaryThe current global food system is becoming increasingly unsustainable and is having negative impacts on planetary and human health. It is essential that human health is placed at the centre of a redesigned food system, as that will also help ensure planetary health.
       
  • The insect apocalypse, and why it matters
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Dave GoulsonSummaryThe majority of conservation efforts and public attention are focused on large, charismatic mammals and birds such as tigers, pandas and penguins, yet the bulk of animal life, whether measured by biomass, numerical abundance or numbers of species, consists of invertebrates such as insects. Arguably, these innumerable little creatures are far more important for the functioning of ecosystems than their furry or feathered brethren, but until recently we had few long-term data on their population trends. Recent studies from Germany and Puerto Rico suggest that insects may be in a state of catastrophic population collapse: the German data describe a 76% decline in biomass over 26 years, while the Puerto Rican study estimates a decline of between 75% and 98% over 35 years. Corroborative evidence, for example from butterflies in Europe and California (which both show slightly less dramatic reductions in abundance), suggest that these declines are not isolated. The causes are much debated, but almost certainly include habitat loss, chronic exposure to pesticides, and climate change. The consequences are clear; insects are integral to every terrestrial food web, being food for numerous birds, bats, reptiles, amphibians and fish, and performing vital roles such as pollination, pest control and nutrient recycling. Terrestrial and freshwater ecosystems will collapse without insects. These studies are a warning that we may have failed to appreciate the full scale and pace of environmental degradation caused by human activities in the Anthropocene.
       
  • Multiple threats imperil freshwater biodiversity in the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): David DudgeonSummaryAppropriation of fresh water to meet human needs is growing, and competition among users will intensify in a warmer and more crowded world. This essay explains why freshwater ecosystems are global hotspots of biological richness, despite a panoply of interacting threats that jeopardize biodiversity. The combined effects of these threats will soon become detrimental to humans since provision of ecosystem services, such as protein from capture fisheries, can only be sustained if waters remain healthy. Climate change poses an insidious existential threat to freshwater biodiversity in the Anthropocene, but immediate risks from dams, habitat degradation and pollution could well be far greater.
       
  • Noise pollution
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Hans Slabbekoorn
       
  • The ecological cost of pets
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Peter P. Marra
       
  • The Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): William F. LauranceBill Laurance introduces the Anthropocene epoch marked by humans invariably altering Earth’s bio- and geosphere.
       
  • Plastic world
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Cyrus MartinSummaryWe produce our own weight in plastic every year. Much of this is single-use packaging that often finds its way to the ocean where it causes harm to marine life. New research has focused attention in particular on microplastics, which are ubiquitous in the environment and literally rain down on us from above. Cyrus Martin reports.
       
  • The future is urbanised
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Michael GrossSummaryThe human population is shaping the planet like never before. Although this transformation started with agriculture, the focus is now switching to cities as humanity is rapidly becoming more urbanised. Thus, the environmental and sustainability challenges of this century will all have to be addressed in the context of more than 4 billion people living in cities. Michael Gross reports.
       
  • Spectres of the Anthropocene
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Florian Maderspacher
       
  • Animal Eyes: Filtering Out the Background
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Venkata Jayasurya Yallapragada, Benjamin A. PalmerSummaryAnimals use photonic structures in their eyes to form images, enhance sensitivity and provide camouflage. A recent exciting discovery shows that the eyes of some larval mantis shrimp possess photonic crystals that function as color filters to detect bioluminescence.
       
  • Evolution: New Protist Predators under the Sun
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Morgan J. Colp, John M. ArchibaldSummaryA lineage of predatory, non-photosynthetic protists related to red algae has been discovered, changing the way we think about the biology of the first photosynthetic eukaryotes.
       
  • Motion Vision: A New Mechanism in the Mammalian Retina
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Anna Vlasits, Tom BadenSummaryIn animal eyes, the detection of slow global image motion is crucial to preventing blurry vision. A new study reveals how a mammalian global motion detector achieves this through ‘space–time wiring’ at its dendrites.
       
  • Nucleolus: A Liquid Droplet Compartment for Misbehaving Proteins
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Simon Alberti, Serena CarraSummaryA new study reports an unexpected function of the nucleolus as a protein quality control compartment for misfolded and aggregation-prone proteins. These findings have important implications for protein misfolding diseases.
       
  • Auditory Perception: Relative Universals for Musical Pitch
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Daniel Pressnitzer, Laurent DemanySummaryDo members of a remote Amazonian tribe and Boston-trained musicians share similarities in their mental representations of auditory pitch' According to an impressive new set of psychoacoustic evidence they do, a finding which highlights the universal importance of relative pitch patterns.
       
  • Water Balance: Abstaining from Obtaining While Retaining
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Sandra L. MartinSummaryAnimals tightly regulate blood volume and solute concentrations. Water balance is usually achieved by a combination of managing intake and excretion but sometimes both drinking and urination are inconvenient. Hibernators have perfected internal mechanisms to maintain water balance without either.
       
  • Goal-Oriented Behaviour: The Ventral Tegmental Area in Motivated Movements
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Laura Masullo, Marco TripodiSummaryThe ventral tegmental area is a midbrain region known for the involvement of its dopaminergic neurons in encoding reward-related features, value and motivational states. New research suggests a role for inhibitory neurons of the ventral tegmental area in the orchestration of head movements, which might be instrumental in guiding animals towards spatial targets during motivated behaviour.
       
  • Molecular Evolution: RNA Splicing Machinery Moonlights in Junk Removal
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Scott W. Roy, Bradley A. BowserSummaryA close relative of vertebrates solves the problem of gene-disrupting transposable element insertions by splicing them out at the RNA level. Why is such an elegant solution so rare across eukaryotes'
       
  • Cognitive Neuroscience: No Gain, Much Pain
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): Tobias KalenscherSummaryWhat do hard intellectual work and intense physical training have in common' New research suggests that both types of effort exhaust the brain’s executive control system, leading to reduced excitability of the lateral prefrontal cortex and stronger preference for immediate rewards in economic decision-making.
       
  • Evolution of thought and emotion
    • Abstract: Publication date: 7 October 2019Source: Current Biology, Volume 29, Issue 19Author(s): György Buzsáki
       
  • Systemic Root-Shoot Signaling Drives Jasmonate-Based Root Defense against
           Nematodes
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Guoting Wang, Chaoyi Hu, Jie Zhou, Ya Liu, Jiaxing Cai, Caizhe Pan, Yu Wang, Xiaodan Wu, Kai Shi, Xiaojian Xia, Yanhong Zhou, Christine H. Foyer, Jingquan YuSummaryShoot-root communication is crucial for plant adaptation to environmental changes. However, the extensive crosstalk between shoots and roots that controls the synthesis of jasmonates (JAs), in order to enhance defense responses against rhizosphere herbivores, remains poorly understood. Here, we report that the root-knot nematode (RKN) Meloidogyne incognita induces the systemic transmission of electrical and reactive oxygen species (ROS) signals from attacked tomato roots to the leaves, leading to an increased accumulation of JAs in the leaves. Grafting of 1.0-cm stem sections from mutants lacking GLUTAMATE RECEPTOR-LIKE 3.5 or the mutants deficient in RESPIRATORY BURST OXIDASE HOMOLOG 1 abolished the RKN-induced electrical signals and associated ROS and JA accumulation in the upper stems and leaves with attenuated resistance to RKN. Furthermore, the absence of systemic transmission of electrical and ROS signals compromised the activation of mitogen-activated protein kinases (MPKs) 1/2 in leaves. Silencing MPK1 or MPK2 abolished RKN-induced accumulation of JAs and associated resistance. These findings reveal a systemic signaling loop that integrates electrical, ROS, and JA signals to enhance the resistance in distal organs via root-shoot-root communication.Graphical Graphical abstract for this article
       
  • Functionally Distinct Gamma Range Activity Revealed by Stimulus Tuning in
           Human Visual Cortex
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Eleonora Bartoli, William Bosking, Yvonne Chen, Ye Li, Sameer A. Sheth, Michael S. Beauchamp, Daniel Yoshor, Brett L. FosterSummaryNeocortical gamma activity has long been hypothesized as a mechanism for synchronizing brain regions to support visual perception and cognition more broadly. Although early studies focused on narrowband gamma oscillations (∼20–60 Hz), recent work has emphasized a more broadband “high-gamma” response (∼70–150+ Hz). These responses are often conceptually or analytically treated as synonymous markers of gamma activity. Using high-density intracranial recordings from the human visual cortex, we challenge this view by showing distinct spectral, temporal, and functional properties of narrow and broadband gamma. Across four experiments, narrowband gamma was strongly selective for gratings and long-wavelength colors, displaying a delayed response onset, sustained temporal profile, and contrast-dependent peak frequency. In addition, induced narrowband gamma oscillations lacked phase consistency across stimulus repetitions and displayed highly focal inter-site synchronization. In contrast, broadband gamma was consistently observed for all presented stimuli, displaying a rapid response onset, transient temporal profile, and invariant spectral properties. We exploited stimulus tuning to highlight the functional dissociation of these distinct signals, reconciling prior inconsistencies across species and stimuli regarding the ubiquity of visual gamma oscillations during natural vision. The occurrence of visual narrowband gamma oscillations, unlike broadband high gamma, appears contingent on specific structural and chromatic stimulus attributes intersecting with the receptive field. Together, these findings have important implications for the study, analysis, and functional interpretation of neocortical gamma-range activity.Graphical Graphical abstract for this article
       
  • Earthworms Coordinate Soil Biota to Improve Multiple Ecosystem Functions
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Ting Liu, Xiaoyun Chen, Xin Gong, Ingrid M. Lubbers, Yangyang Jiang, Wen Feng, Xianping Li, Joann K. Whalen, Michael Bonkowski, Bryan S. Griffiths, Feng Hu, Manqiang LiuSummaryEarthworms have been perceived as benevolent soil engineers since the time of Charles Darwin, but several recent syntheses link earthworm activities to higher greenhouse gas emissions, less soil biodiversity, and inferior plant defense against pests. Our study provides new field-based evidence of the multiple direct and indirect impacts of earthworms on ecosystem functions within an ecological multifunctionality framework (i.e., aggregated measures of the ability of ecosystems to simultaneously provide multiple ecosystem functions). Data from a 13-year field experiment describing 21 ecosystem functions showed that earthworm presence generally enhanced multifunctionality by indirect rather than direct effects. Specifically, earthworms enhanced multifunctionality by shifting the functional composition toward a soil community favoring the bacterial energy channel and strengthening the biotic associations of soil microbial and microfaunal communities. However, earthworm-mediated changes in soil physical structure, pH, and taxonomic diversity were not related to multifunctionality. We conclude that the coordinated actions of earthworms and their associated soil biota were responsible for the maintenance of multifunctionality at high levels in this rice-wheat cropping system. Management of crop residue inputs and reduction of soil physicochemical disturbances should encourage beneficial earthworm effects and support multiple ecosystem services that are vital to sustainable agriculture.Graphical Graphical abstract for this article
       
  • Ultrasonic Neuromodulation via Astrocytic TRPA1
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Soo-Jin Oh, Jung Moo Lee, Hyun-Bum Kim, Jungpyo Lee, Sungmin Han, Jin Young Bae, Gyu-Sang Hong, Wuhyun Koh, Jea Kwon, Eun-Sang Hwang, Dong Ho Woo, Inchan Youn, Il-Joo Cho, Yong Chul Bae, Sungon Lee, Jae Wan Shim, Ji-Ho Park, C. Justin LeeSummaryLow-intensity, low-frequency ultrasound (LILFU) is the next-generation, non-invasive brain stimulation technology for treating various neurological and psychiatric disorders. However, the underlying cellular and molecular mechanism of LILFU-induced neuromodulation has remained unknown. Here, we report that LILFU-induced neuromodulation is initiated by opening of TRPA1 channels in astrocytes. The Ca2+ entry through TRPA1 causes a release of gliotransmitters including glutamate through Best1 channels in astrocytes. The released glutamate activates NMDA receptors in neighboring neurons to elicit action potential firing. Our results reveal an unprecedented mechanism of LILFU-induced neuromodulation, involving TRPA1 as a unique sensor for LILFU and glutamate-releasing Best1 as a mediator of glia-neuron interaction. These discoveries should prove to be useful for optimization of human brain stimulation and ultrasonogenetic manipulations of TRPA1.Graphical Graphical abstract for this article
       
  • Neuronal O-GlcNAcylation Improves Cognitive Function in the Aged Mouse
           Brain
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Elizabeth G. Wheatley, Eddy Albarran, Charles W. White, Gregor Bieri, Cesar Sanchez-Diaz, Karishma Pratt, Cedric E. Snethlage, Jun B. Ding, Saul A. VilledaSummaryMounting evidence in animal models indicates potential for rejuvenation of cellular and cognitive functions in the aging brain. However, the ability to utilize this potential is predicated on identifying molecular targets that reverse the effects of aging in vulnerable regions of the brain, such as the hippocampus. The dynamic post-translational modification O-linked N-Acetylglucosamine (O-GlcNAc) has emerged as an attractive target for regulating aging-specific synaptic alterations as well as neurodegeneration. While speculation exists about the role of O-GlcNAc in neurodegenerative conditions, such as Alzheimer’s disease, its role in physiological brain aging remains largely unexplored. Here, we report that countering age-related decreased O-GlcNAc transferase (OGT) expression and O-GlcNAcylation ameliorates cognitive impairments in aged mice. Mimicking an aged condition in young adults by abrogating OGT, using a temporally controlled neuron-specific conditional knockout mouse model, recapitulated cellular and cognitive features of brain aging. Conversely, overexpressing OGT in mature hippocampal neurons using a viral-mediated approach enhanced associative fear memory in young adult mice. Excitingly, in aged mice overexpressing neuronal OGT in the aged hippocampus rescued in part age-related impairments in spatial learning and memory as well as associative fear memory. Our data identify O-GlcNAcylaton as a key molecular mediator promoting cognitive rejuvenation.Graphical Graphical abstract for this article
       
  • Complementary Task Structure Representations in Hippocampus and
           Orbitofrontal Cortex during an Odor Sequence Task
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Jingfeng Zhou, Marlian Montesinos-Cartagena, Andrew M. Wikenheiser, Matthew P.H. Gardner, Yael Niv, Geoffrey SchoenbaumSummaryBoth hippocampus (HPC) and orbitofrontal cortex (OFC) have been shown to be critical for behavioral tasks that require use of an internal model or cognitive map, composed of the states and the relationships between them, which define the current environment or task at hand. One general idea is that the HPC provides the cognitive map, which is then transformed by OFC to emphasize information of relevance to current goals. Our previous analysis of ensemble activity in OFC in rats performing an odor sequence task revealed a rich representation of behaviorally relevant task structure, consistent with this proposal. Here, we compared those data to recordings from single units in area CA1 of the HPC of rats performing the same task. Contrary to expectations that HPC ensembles would represent detailed, even incidental, information defining the full task space, we found that HPC ensembles—like those in OFC—failed to distinguish states when it was not behaviorally necessary. However, hippocampal ensembles were better than those in OFC at distinguishing task states in which prospective memory was necessary for future performance. These results suggest that, in familiar environments, the HPC and OFC may play complementary roles, with the OFC maintaining the subjects’ current position on the cognitive map or state space, supported by HPC when memory demands are high.
       
  • Reconstructing the Transcriptional Ontogeny of Maize and Sorghum Supports
           an Inverse Hourglass Model of Inflorescence Development
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Samuel Leiboff, Sarah HakeSummaryAssembling meaningful comparisons between species is a major limitation in studying the evolution of organismal form. To understand development in maize and sorghum, closely related species with architecturally distinct inflorescences, we collected RNA-seq profiles encompassing inflorescence body-plan specification in both species. We reconstructed molecular ontogenies from 40 B73 maize tassels and 47 BTx623 sorghum panicles and separated them into transcriptional stages. To discover new markers of inflorescence development, we used random forest machine learning to determine stage by RNA-seq. We used two descriptions of transcriptional conservation to identify hourglass-like stages during inflorescence development. Despite a relatively short 12 million years since their last common ancestor, we found maize and sorghum inflorescences are most different during their hourglass-like stages of development, following an inverse-hourglass model of development. We discuss whether agricultural selection may account for the rapid divergence signatures in these species and the observed separation of evolutionary pressure and developmental reprogramming.Graphical Graphical abstract for this article
       
  • Bumble Bee Workers Give Up Sleep to Care for Offspring that Are Not Their
           Own
    • Abstract: Publication date: Available online 3 October 2019Source: Current BiologyAuthor(s): Moshe Nagari, Ariel Gera, Sara Jonsson, Guy BlochSummarySleep is ubiquitous in vertebrates and invertebrates, and its loss is typically associated with reduced performance, health, or survival, for reasons that are yet unclear [1, 2, 3]. Nevertheless, some animals can reduce sleep for increasing foraging time [4], under predation risk [5, 6, 7, 8], during seasonal migration [9, 10, 11], or for having greater mating opportunities [12, 13]. Here, we tested the hypothesis that social bumble bee (Bombus terrestris) workers give up sleep for improving brood care. We combined video recordings, detailed behavioral analyses, sleep-deprivation experiments, and response-threshold assessments to characterize the sleep behavior of worker bees and showed that immobility bouts of ≥5 min provide a reliable proxy for sleep. We next used this index to study sleep with an automated video-based activity monitoring system. We found that isolated workers severely reduce sleep time in the presence of both larvae that need to be fed and pupae that do not. Reduced sleep was also correlated with around-the-clock activity and wax-pot building, which are typical for nest-founding mother queens. Cocoons, from which we removed the pupae, elicited a similar but transient sleep loss in tending workers, suggesting that the pupa effect on sleep is mediated by pheromonal signals. Sleep time increased following brood removal but remained lower compared to control bees, suggesting that the brood modulated sleep need. This first evidence for brood modulation of sleep in an insect suggests that plasticity in sleep can evolve as a mechanism to improve care for dependent juveniles, even in social insect workers that do not care for their own offspring.
       
  • Single-Turnover Activation of Arp2/3 Complex by Dip1 May Balance
           Nucleation of Linear versus Branched Actin Filaments
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Connor J. Balzer, Andrew R. Wagner, Luke A. Helgeson, Brad J. NolenSummaryArp2/3 complex nucleates branched actin filaments important for cellular motility, endocytosis, meiosis, and cellular differentiation [1, 2, 3, 4]. Wiskott-Aldrich syndrome proteins (WASPs), the prototypical Arp2/3 complex activators, activate Arp2/3 complex only once it is bound to the side of an actin filament [5, 6]. This ensures WASP-activated Arp2/3 complex only nucleates branched actin filaments but means branched actin networks must be seeded with an initial preformed filament. Dip1 and other WISH/DIP/SPIN90 family proteins activate Arp2/3 complex without preformed filaments [7], creating seed filaments that activate WASP-bound Arp2/3 complex [8]. Importantly, Dip1-mediated activation of Arp2/3 complex creates linear filaments instead of branches [7]. Cells may therefore need to limit Dip1 activity relative to WASP to preserve the dendritic nature of actin networks, although it is unclear whether such regulatory mechanisms exist. Here, we use total internal reflection fluorescence (TIRF) microscopy to show that Dip1 causes actin assembled with WASP and Arp2/3 complex to form disconnected networks with many linear filaments rather than highly branched arrays. We discover a key biochemical difference between Dip1 and WASP that may limit linear filament nucleation in cells; although WASP must be released for nucleation, Dip1 stays associated with Arp2/3 complex on the pointed ends of nucleated actin filaments, so Dip1 is consumed in the reaction. Using live-cell imaging of fission yeast, we provide evidence that Dip1 is a single-turnover activator of Arp2/3 complex in vivo, revealing a mechanism by which Dip1 can initiate branched actin networks at endocytic sites without disrupting their branched architectures.
       
  • Neuro-computational Impact of Physical Training Overload on Economic
           Decision-Making
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Bastien Blain, Cyril Schmit, Anaël Aubry, Christophe Hausswirth, Yann Le Meur, Mathias PessiglioneSummaryOvertraining syndrome is a form of burnout, defined in endurance athletes by unexplained performance drop associated with intense fatigue sensation. Our working hypothesis is that the form of fatigue resulting from physical training overload might share some neural underpinnings with the form of fatigue observed after prolonged intellectual work, which was previously shown to affect the cognitive control brain system. Indeed, cognitive control may be required to prevent any impulsive behavior, including stopping physical effort when it hurts, despite the long-term goal of improving performance through intense training. To test this hypothesis, we induced a mild form of overtraining in a group of endurance athletes, which we compared to a group of normally trained athletes on behavioral tasks performed during fMRI scanning. At the behavioral level, training overload enhanced impulsivity in economic choice, which was captured by a bias favoring immediate over delayed rewards in our computational model. At the neural level, training overload resulted in diminished activation of the lateral prefrontal cortex, a key region of the cognitive control system, during economic choice. Our results therefore provide causal evidence for a functional link between enduring physical exercise and exerting cognitive control. Besides, the concept of cognitive control fatigue bridges the functional consequences of excessive physical training and intellectual work into a single neuro-computational mechanism, which might contribute to other clinical forms of burnout syndromes.
       
  • Spatiotemporally Asymmetric Excitation Supports Mammalian Retinal Motion
           Sensitivity
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Akihiro Matsumoto, Kevin L. Briggman, Keisuke YoneharaSummaryThe detection of visual motion is a fundamental function of the visual system. How motion speed and direction are computed together at the cellular level, however, remains largely unknown. Here, we suggest a circuit mechanism by which excitatory inputs to direction-selective ganglion cells in the mouse retina become sensitive to the motion speed and direction of image motion. Electrophysiological, imaging, and connectomic analyses provide evidence that the dendrites of ON direction-selective cells receive spatially offset and asymmetrically filtered glutamatergic inputs along motion-preference axis from asymmetrically wired bipolar and amacrine cell types with distinct release dynamics. A computational model shows that, with this spatiotemporal structure, the input amplitude becomes sensitive to speed and direction by a preferred direction enhancement mechanism. Our results highlight the role of an excitatory mechanism in retinal motion computation by which feature selectivity emerges from non-selective inputs.Graphical Graphical abstract for this article
       
  • Newly Identified Nematodes from Mono Lake Exhibit Extreme Arsenic
           Resistance
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Pei-Yin Shih, James Siho Lee, Ryoji Shinya, Natsumi Kanzaki, Andre Pires-daSilva, Jean Marie Badroos, Elizabeth Goetz, Amir Sapir, Paul W. SternbergSummaryExtremophiles have much to reveal about the biology of resilience, yet their study is limited by sampling and culturing difficulties [1, 2, 3]. The broad success and small size of nematodes make them advantageous for tackling these problems [4, 5, 6]. We investigated the arsenic-rich, alkaline, and hypersaline Mono Lake (CA, US) [7, 8, 9] for extremophile nematodes. Though Mono Lake has previously been described to contain only two animal species (brine shrimp and alkali flies) in its water and sediments [10], we report the discovery of eight nematode species from the lake, including microbe grazers, parasites, and predators. Thus, nematodes are the dominant animals of Mono Lake in species richness. Phylogenetic analysis suggests that the nematodes originated from multiple colonization events, which is striking, given the young history of extreme conditions at Mono Lake [7, 11]. One species, Auanema sp., is new, culturable, and survives 500 times the human lethal dose of arsenic. Comparisons to two non-extremophile sister species [12] reveal that arsenic resistance is a common feature of the genus and a preadaptive trait that likely allowed Auanema to inhabit Mono Lake. This preadaptation may be partly explained by a variant in the gene dbt-1 shared with some Caenorhabditis elegans natural populations and known to confer arsenic resistance [13]. Our findings expand Mono Lake’s ecosystem from two known animal species to ten, and they provide a new system for studying arsenic resistance. The dominance of nematodes in Mono Lake and other extreme environments and our findings of preadaptation to arsenic raise the intriguing possibility that nematodes are widely pre-adapted to be extremophiles.Graphical Graphical abstract for this article
       
  • Planar Cell Polarity Effector Proteins Inturned and Fuzzy Form a Rab23 GEF
           Complex
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Andreas Gerondopoulos, Helen Strutt, Nicola L. Stevenson, Tomoaki Sobajima, Tim P. Levine, David J. Stephens, David Strutt, Francis A. BarrSummaryA subset of Rab GTPases have been implicated in cilium formation in cultured mammalian cells [1, 2, 3, 4, 5, 6]. Rab11 and Rab8, together with their GDP-GTP exchange factors (GEFs), TRAPP-II and Rabin8, promote recruitment of the ciliary vesicle to the mother centriole and its subsequent maturation, docking, and fusion with the cell surface [2, 3, 4, 5]. Rab23 has been linked to cilium formation and membrane trafficking at mature cilia [1, 7, 8]; however, the identity of the GEF pathway activating Rab23, a member of the Rab7 subfamily of Rabs, remains unclear. Longin-domain-containing complexes have been shown to act as GEFs for Rab7 subfamily GTPases [9, 10, 11, 12]. Here, we show that Inturned and Fuzzy, proteins previously implicated as planar cell polarity (PCP) effectors and in developmentally regulated cilium formation [13, 14], contain multiple longin domains characteristic of the Mon1-Ccz1 family of Rab7 GEFs and form a specific Rab23 GEF complex. In flies, loss of Rab23 function gave rise to defects in planar-polarized trichome formation consistent with this biochemical relationship. In cultured human and mouse cells, Inturned and Fuzzy localized to the basal body and proximal region of cilia, and cilium formation was compromised by depletion of either Inturned or Fuzzy. Cilium formation arrested after docking of the ciliary vesicle to the mother centriole but prior to axoneme elongation and fusion of the ciliary vesicle and plasma membrane. These findings extend the family of longin domain GEFs and define a molecular activity linking Rab23-regulated membrane traffic to cilia and planar cell polarity.Graphical Graphical abstract for this article
       
  • Light-Mediated Circuit Switching in the Drosophila Neuronal Clock
           Network
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Matthias Schlichting, Patrick Weidner, Madelen Diaz, Pamela Menegazzi, Elena Dalla Benetta, Charlotte Helfrich-Förster, Michael RosbashSummaryThe circadian clock is a timekeeper but also helps adapt physiology to the outside world. This is because an essential feature of clocks is their ability to adjust (entrain) to the environment, with light being the most important signal. Whereas cryptochrome-mediated entrainment is well understood in Drosophila, integration of light information via the visual system lacks a neuronal or molecular mechanism. Here, we show that a single photoreceptor subtype is essential for long-day adaptation. These cells activate key circadian neurons, namely the large ventral-lateral neurons (lLNvs), which release the neuropeptide pigment-dispersing factor (PDF). RNAi and rescue experiments show that PDF from these cells is necessary and sufficient for delaying the timing of the evening (E) activity in long-day conditions. This contrasts to PDF that derives from the small ventral-lateral neurons (sLNvs), which are essential for constant darkness (DD) rhythmicity. Using a cell-specific CRISPR/Cas9 assay, we show that lLNv-derived PDF directly interacts with neurons important for E activity timing. Interestingly, this pathway is specific for long-day adaptation and appears to be dispensable in equinox or DD conditions. The results therefore indicate that external cues cause a rearrangement of neuronal hierarchy, which contributes to behavioral plasticity.
       
  • Precise Coordination of Three-Dimensional Rotational Kinematics by Ventral
           Tegmental Area GABAergic Neurons
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Ryan N. Hughes, Glenn D.R. Watson, Elijah A. Petter, Namsoo Kim, Konstantin I. Bakhurin, Henry H. YinSummaryThe ventral tegmental area (VTA) is a midbrain region implicated in a variety of motivated behaviors. However, the function of VTA GABAergic (Vgat+) neurons remains poorly understood. Here, using three-dimensional motion capture, in vivo electrophysiology, calcium imaging, and optogenetics, we demonstrate a novel function of VTAVgat+ neurons. We found three distinct populations of neurons, each representing head angle about a principal axis of rotation: yaw, roll, and pitch. For each axis, opponent cell groups were found that increase firing when the head moves in one direction and decrease firing in the opposite direction. Selective excitation and inhibition of VTAVgat+ neurons generate opposite rotational movements. Thus, VTAVgat+ neurons serve a critical role in the control of rotational kinematics while pursuing a moving target. This general-purpose steering function can guide animals toward desired spatial targets in any motivated behavior.Graphical Graphical abstract for this article
       
  • Shared Song Detector Neurons in Drosophila Male and Female Brains Drive
           Sex-Specific Behaviors
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): David Deutsch, Jan Clemens, Stephan Y. Thiberge, Georgia Guan, Mala MurthySummaryMales and females often produce distinct responses to the same sensory stimuli. How such differences arise—at the level of sensory processing or in the circuits that generate behavior—remains largely unresolved across sensory modalities. We address this issue in the acoustic communication system of Drosophila. During courtship, males generate time-varying songs, and each sex responds with specific behaviors. We characterize male and female behavioral tuning for all aspects of song and show that feature tuning is similar between sexes, suggesting sex-shared song detectors drive divergent behaviors. We then identify higher-order neurons in the Drosophila brain, called pC2, that are tuned for multiple temporal aspects of one mode of the male’s song and drive sex-specific behaviors. We thus uncover neurons that are specifically tuned to an acoustic communication signal and that reside at the sensory-motor interface, flexibly linking auditory perception with sex-specific behavioral responses.Graphical Graphical abstract for this article
       
  • Behavioral and Cortical Correlates of Self-Suppression, Anticipation, and
           Ambivalence in Rat Tickling
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Shimpei Ishiyama, Lena V. Kaufmann, Michael BrechtSummaryThe relationship between tickling, sensation, and laughter is complex. Tickling or its mere anticipation makes us laugh, but not when we self-tickle. We previously showed rat somatosensory cortex drives tickling-evoked vocalizations and now investigated self-tickle suppression and tickle anticipation. We recorded somatosensory cortex activity while tickling and touching rats and while rats touched themselves. Allo-touch and tickling evoked somatotopic cortical excitation and vocalizations. Self-touch induced wide-ranging inhibition and vocalization suppression. Self-touch also suppressed vocalizations and cortical responses evoked by allo-touch or cortical microstimulation. We suggest a global-inhibition model of self-tickle suppression, which operates without the classically assumed self versus other distinction. Consistent with this inhibition hypothesis, blocking cortical inhibition with gabazine abolished self-tickle suppression. We studied anticipation in a nose-poke-for-tickling paradigm. Although rats nose poked for tickling, they also showed escaping, freezing, and alarm calls. Such ambivalence (“Nervenkitzel”) resembles tickle behaviors in children. We conclude that self-touch-induced GABAergic cortical inhibition prevents self-tickle, whereas anticipatory layer 5 activity drives anticipatory laughter.Video
       
  • LLG2/3 Are Co-receptors in BUPS/ANX-RALF Signaling to Regulate Arabidopsis
           Pollen Tube Integrity
    • Abstract: Publication date: Available online 26 September 2019Source: Current BiologyAuthor(s): Zengxiang Ge, Yuling Zhao, Ming-Che Liu, Liang-Zi Zhou, Lele Wang, Sheng Zhong, Saiying Hou, Jiahao Jiang, Tianxu Liu, Qingpei Huang, Junyu Xiao, Hongya Gu, Hen-Ming Wu, Juan Dong, Thomas Dresselhaus, Alice Y. Cheung, Li-Jia QuSummaryIn angiosperms, two sperm cells are transported and delivered by the pollen tube to the ovule to achieve double fertilization. Extensive communication takes place between the pollen tube and the female tissues until the sperm cell cargo is ultimately released. During this process, a pollen tube surface-located receptor complex composed of ANXUR1/2 (ANX1/2) and Buddha’s Paper Seal 1/2 (BUPS1/2) was reported to control the maintenance of pollen tube integrity by perceiving the autocrine peptide ligands rapid alkalinization factor 4 and 19 (RALF4/19). It was further hypothesized that pollen-tube rupture to release sperm is caused by the paracrine RALF34 peptide from the ovule interfering with this signaling pathway. In this study, we identified two Arabidopsis pollen-tube-expressed glycosylphosphatidylinositol-anchored proteins (GPI-APs), LORELEI-like-GPI-anchored protein 2 (LLG2) and LLG3, as co-receptors in the BUPS-ANX receptor complex. llg2 llg3 double mutants exhibit severe fertility defects. Mutant pollen tubes rupture early during the pollination process. Furthermore, LLG2 and LLG3 interact with ectodomains of both BUPSs and ANXURs, and this interaction is remarkably enhanced by the presence of RALF4/19 peptides. We further demonstrate that the N terminus (including a YISY motif) of the RALF4 peptide ligand interacts strongly with BUPS-ANX receptors but weakly with LLGs and is essential for its biological function, and its C-terminal region is sufficient for LLG binding. In conclusion, we propose that LLG2/3 serve as co-receptors during BUPS/ANX-RALF signaling and thereby further establish the importance of GPI-APs as key regulators in plant reproduction processes.
       
  • Developmental Biology: Embryonic Movement Influences Sex Determination in
           a Turtle
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Geoffrey M. While, Erik WapstraMany ectotherms behaviourally thermoregulate to maintain their body temperatures within an optimal range. A new study suggests that turtle embryos developing inside eggs also have this capacity, and that this can have significant implications for sex determination.
       
  • How Targeted Memory Reactivation Promotes the Selective Strengthening
           of Memories in Sleep
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Penelope A. Lewis, Daniel BendorOver the last ten years, scientists have developed a method called targeted memory reactivation (TMR) for selectively strengthening memories during sleep. Prior to this, memory manipulation during sleep was at most a plot device in science fiction movies, but a large corpus of studies now demonstrates that TMR is both reliable and effective. TMR studies hypothesize that this method taps into normal consolidation mechanisms that require the repeated replay of memories during sleep. This idea has recently been supported by several new studies demonstrating that TMR upregulates the reactivation of cued memories, and that such upregulation predicts subsequent memory performance. This new body of work provides a unique window onto many properties of memory reactivation and helps to close the gap between our understanding of replay in rodents, where it has been visualised at the neural level for many years, and humans, where such studies are only just starting to become possible. We will discuss this new literature and highlight the vast potential of these new methods for future research.
       
  • A New Unifying Account of the Roles of Neuronal Entrainment
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Peter Lakatos, Joachim Gross, Gregor ThutRhythms are a fundamental and defining feature of neuronal activity in animals including humans. This rhythmic brain activity interacts in complex ways with rhythms in the internal and external environment through the phenomenon of ‘neuronal entrainment’, which is attracting increasing attention due to its suggested role in a multitude of sensory and cognitive processes. Some senses, such as touch and vision, sample the environment rhythmically, while others, like audition, are faced with mostly rhythmic inputs. Entrainment couples rhythmic brain activity to external and internal rhythmic events, serving fine-grained routing and modulation of external and internal signals across multiple spatial and temporal hierarchies. This interaction between a brain and its environment can be experimentally investigated and even modified by rhythmic sensory stimuli or invasive and non-invasive neuromodulation techniques. We provide a comprehensive overview of the topic and propose a theoretical framework of how neuronal entrainment dynamically structures information from incoming neuronal, bodily and environmental sources. We discuss the different types of neuronal entrainment, the conceptual advances in the field, and converging evidence for general principles.
       
  • Transposition: A CRISPR Way to Get Around
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Tatiana Dimitriu, Ben Ashby, Edze R. WestraCRISPR-Cas systems provide sequence-specific immunity against selfish genetic elements in prokaryotes. Now, two studies show that transposon-encoded variants can guide sequence-specific transposition. These findings have important practical implications but also raise questions of why and how this strategy would benefit transposons.
       
  • Neuroscience: A New Golden Age for Neurourology
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Stephen A. ZdericThe pons contains neurons that control urinary bladder function. Using the modern tools of neurobiology, new studies reveal a heterogeneous population of neurons which interact with higher centers and the sacral and lumbar spinal cord to coordinate complex voiding behaviors.
       
  • Motion Perception: Slow Development of Center-Surround Suppression
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Ying Lin, Duje TadinNew evidence on the development of center-surround suppression in human infants shows that this key feature of visual motion perception does not emerge until seven months of age. This raises questions about the development of basic visual functions thought to derive from surround suppression.
       
  • Prey Capture: Becoming Invisible When You Move
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Johannes M. ZankerConspicuous skin patterns attract the attention of predators, but are thought also to act as protective mimicry during movement. A new behavioural study of mantises has found that the responses of these insect predators to a striped dummy target are reduced when the target is moving at high speed.
       
  • Plant Biology: Evolution of Volatile-Mediated Plant–Plant
           Interactions
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Matthias ErbA new study shows that long-term herbivore exclusion modulates volatile-induced herbivore resistance in tall goldenrod, thus providing evidence for herbivory driving the evolution of volatile-mediated plant–plant interactions in nature.
       
  • Neocortical Cell Classes: Essential Contributions
           from Electrophysiology
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Thilo WomelsdorfNeocortical cells form classes that likely take on unique functional roles in the cortical microcircuit. A new study finds that, with sufficient sampling, the electrophysiological signature of cells distinguishes four cell classes across primate frontal and parietal cortex.
       
  • Plant Genomics: Evolution and Development of a Major Crop Parasite
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Peter J.N. Stokes, Benjamin K. BlackmanParasitic plants in the genus Striga bedevil crop production throughout Africa and Asia. A new genome assembly reveals how repurposing of developmental pathways, gene gains and losses, and horizonal gene transfer all contributed to the evolution of these destructive pathogens.
       
  • Self/Non-self Recognition: Microbes Playing Hard to Get
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Paul S. DyerFungi can fuse with other individuals to enable cooperative growth, although this process is restricted by certain self/non-self recognition systems. A novel layer of compatibility has now been discovered, acting at the stage of germling cell wall fusion, showing the remarkable complexity of allorecognition in fungi.
       
  • Attachment bonds between domestic cats and humans
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Kristyn R. Vitale, Alexandra C. Behnke, Monique A.R. UdellSummaryWorldwide, domestic cats (Felis silvestris catus) outnumber domestic dogs (Canis familiaris). Despite cats’ success in human environments, dog social cognition has received considerably more scientific attention over the last several decades 1, 2, 3. A key aspect of what has been said to make dogs unique is their proclivity for forming attachment bonds, including secure attachments to humans 1, 3, which could provide scaffolding for the development of human-like socio-cognitive abilities and contribute to success in human environments [3]. Cats, like dogs, can be found living in social groups or solitarily, depending on early developmental factors, resource distribution, and lifetime experiences such as human interaction 1, 2, 4. Despite fewer studies, research suggests we may be underestimating cats’ socio-cognitive abilities [2]. Here we report evidence, using behavioral criteria established in the human infant literature 5, 6, that cats display distinct attachment styles toward human caregivers. Evidence that cats share social traits once attributed to dogs and humans alone would suggest that broader non-canine-specific mechanisms may be needed to explain cross-species attachment and socio-cognitive abilities.
       
  • Xing Xu
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Xing Xu
       
  • Amber
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): David A. Grimaldi
       
  • The race against antibiotics resistance
    • Abstract: Publication date: 23 September 2019Source: Current Biology, Volume 29, Issue 18Author(s): Michael GrossSummaryAntibiotics and resistance traits co-evolved over several hundred million years, shaping the evolution and ecology of microbes and fungi. Within less than a century of using and over-using antibiotics, we have managed to spread resistance genes so far and wide that we are now facing the threat of a dramatic loss of the protection that they have provided until now. Michael Gross reports.
       
  • Galanin Neurons Unite Sleep Homeostasis and α2-Adrenergic Sedation
    • Abstract: Publication date: Available online 19 September 2019Source: Current BiologyAuthor(s): Ying Ma, Giulia Miracca, Xiao Yu, Edward C. Harding, Andawei Miao, Raquel Yustos, Alexei L. Vyssotski, Nicholas P. Franks, William WisdenSummaryOur urge to sleep increases with time spent awake, until sleep becomes inescapable. The sleep following sleep deprivation is longer and deeper, with an increased power of delta (0.5–4 Hz) oscillations, a phenomenon termed sleep homeostasis [1, 2, 3, 4]. Although widely expressed genes regulate sleep homeostasis [1, 4, 5, 6, 7, 8, 9, 10] and the process is tracked by somnogens and phosphorylation [1, 3, 7, 11, 12, 13, 14], at the circuit level sleep homeostasis has remained mysterious. Previously, we found that sedation induced with α2-adrenergic agonists (e.g., dexmedetomidine) and sleep homeostasis both depend on the preoptic (PO) hypothalamus [15, 16]. Dexmedetomidine, increasingly used for long-term sedation in intensive care units [17], induces a non-rapid-eye-movement (NREM)-like sleep but with undesirable hypothermia [18, 19]. Within the PO, various neuronal subtypes (e.g., GABA/galanin and glutamate/NOS1) induce NREM sleep [20, 21, 22] and concomitant body cooling [21, 22]. This could be because NREM sleep’s restorative effects depend on lower body temperature [23, 24]. Here, we show that mice with lesioned PO galanin neurons have reduced sleep homeostasis: in the recovery sleep following sleep deprivation there is a diminished increase in delta power, and the mice catch up little on lost sleep. Furthermore, dexmedetomidine cannot induce high-power delta oscillations or sustained hypothermia. Some hours after dexmedetomidine administration to wild-type mice there is a rebound in delta power when they enter normal NREM sleep, reminiscent of emergence from torpor. This delta rebound is reduced in mice lacking PO galanin neurons. Thus, sleep homeostasis and dexmedetomidine-induced sedation require PO galanin neurons and likely share common mechanisms.Graphical Graphical abstract for this article
       
  • Evolution of the U2 Spliceosome for Processing Numerous and Highly Diverse
           Non-canonical Introns in the Chordate Fritillaria borealis
    • Abstract: Publication date: Available online 19 September 2019Source: Current BiologyAuthor(s): Simon Henriet, Berta Colom Sanmartí, Sara Sumic, Daniel ChourroutSummaryAn overwhelming majority of eukaryotic introns have GT/AG ends, whose identities play a critical role for their recognition and removal by the U2 spliceosome, a well-conserved complex of protein and RNAs. Introns with other splice sites exist at very low frequencies in various genomes, and some of them are processed by the U12 spliceosome. Here, we show that, in the chordate Fritillaria borealis, the majority of old introns have been lost and replaced by introns with highly divergent splice sites. The new introns of F. borealis are exceptionally diverse, though more frequently AG/AC or AG/AT, and features of thousands of them support an origin from transposons. They cannot be processed in human cells, but their splicing is rescued by mutating terminal dinucleotides to GT/AG. With lariat sequencing and splicing inhibitor assays, we show that F. borealis introns are spliced by the U2 spliceosome, which thus evolved to a different selectivity, with neither novel U1 small nuclear RNA (snRNA) types nor major remodeling of its protein and snRNA complements. This genome-wide recolonization by non-canonical introns emphasizes the importance of transposons as a resource of novel introns in a context of massive intron loss. An evolution of the spliceosome may also permit to neutralize harmful transposons through their conversion into introns.Graphical Graphical abstract for this article
       
  • Orexin in the Posterior Paraventricular Thalamus Mediates Hunger-Related
           Signals in the Nucleus Accumbens Core
    • Abstract: Publication date: Available online 19 September 2019Source: Current BiologyAuthor(s): Julie Meffre, Mehdi Sicre, Mohamadou Diarra, Florian Marchessaux, Dany Paleressompoulle, Frederic AmbroggiSummaryAnimals use exteroceptive stimuli that have acquired, through learning, the ability to predict available resources allowing them to engage in adaptive behaviors. Meanwhile, peripheral signals related to internal state (e.g., hunger) provide information about current needs, modulating the ability of exteroceptive stimuli to drive food-seeking behavior [1, 2]. The nucleus accumbens core (NAcC) is essential for encoding the value of reward-predictive cues and controlling the level of behavioral responding [3, 4, 5, 6, 7]. However, the way in which interoceptive information related to physiological needs is integrated in the NAcC remains to be clarified. Located in the lateral and perifornical hypothalamic regions, orexin neurons [8, 9] are implicated in a wide range of functions, including arousal, feeding, and reward seeking [10, 11, 12, 13, 14, 15, 16]. Paraventricular thalamus (PVT) neurons receive a strong orexinergic projection [17] and are excited by orexins [18, 19, 20]. Hence, Kelley et al. [21] proposed that the PVT serves as an integrative relay, conveying hypothalamic energy-balance information to the NAc through its glutamatergic projection. Here, we test whether NAcC encoding of reward-predictive cues is modulated by the integration of posterior PVT (pPVT) orexin-mediated hunger-related signals. Using a cue-driven reward-seeking task, we show that satiety decreases cue responses in NAcC and pPVT neurons. Blockade of pPVT orexin-2 receptors reduces responding in hungry rats. Activation of pPVT neurons, either with local infusion of orexin-A or via optogenetics, positively controls NAcC cue responses and restores behavioral responding in sated rats, highlighting a circuit that integrates reward-predictive cues perceived in the environment with the current metabolic state of the animal.Graphical Graphical abstract for this article
       
  • An Early Arising Role of the MicroRNA156/529-SPL Module in Reproductive
           Development Revealed by the Liverwort Marchantia polymorpha
    • Abstract: Publication date: Available online 19 September 2019Source: Current BiologyAuthor(s): Masayuki Tsuzuki, Kazutaka Futagami, Masaki Shimamura, Chikako Inoue, Kan Kunimoto, Takashi Oogami, Yuki Tomita, Keisuke Inoue, Takayuki Kohchi, Shohei Yamaoka, Takashi Araki, Takahiro Hamada, Yuichiro WatanabeSummaryIn angiosperms, the phase transition from vegetative to reproductive growth involves the de-repression of the squamosa promoter-binding-protein-like (SPL) class of transcription factors, which is negatively regulated by the specific microRNAs (miRNAs/miRs) miR156/529 [1]. Non-vascular land plants also undergo growth-phase transition to the reproductive state, but knowledge regarding the controlling mechanisms is limited. Here, we investigate the reproductive transition in the liverwort Marchantia polymorpha, focusing on the roles of miR529c [2, 3, 4] and MpSPL2. First, we established mir529c-null mutants using CRISPR/Cas9. Even in the absence of far-red light-supplemented long-day condition, which is usually needed to induce reproductive development [5, 6], the mutant thalli developed sexual reproductive organs (gametangia) and produced gametes. Transgenic plants expressing a miR529-resistant MpSPL2 transgene also showed a similar phenotype of reproductive transition in the absence of inductive far-red light signals. In these mutants and transgenic plants, the MpSPL2 mRNA abundance was elevated. Mpspl2ko mutant plants showed successful gamete development and fertilization, which suggests that MpSPL2 is involved in, but not essential for, sexual reproduction in M. polymorpha. Furthermore, analysis of Mpspl2ko mutant and its complemented lines suggests that MpSPL2 may have a role in promotion of reproductive transition. These findings support the notion that the transition to reproductive development in liverworts is controlled by a system similar to that in angiosperms, and the miR156/529-SPL module has common significance in the control of the vegetative-to-reproductive transition during development in many land plants, including liverworts.Graphical Graphical abstract for this article
       
  • Universal and Non-universal Features of Musical Pitch Perception Revealed
           by Singing
    • Abstract: Publication date: Available online 19 September 2019Source: Current BiologyAuthor(s): Nori Jacoby, Eduardo A. Undurraga, Malinda J. McPherson, Joaquín Valdés, Tomás Ossandón, Josh H. McDermottSummaryMusical pitch perception is argued to result from nonmusical biological constraints and thus to have similar characteristics across cultures, but its universality remains unclear. We probed pitch representations in residents of the Bolivian Amazon—the Tsimane', who live in relative isolation from Western culture—as well as US musicians and non-musicians. Participants sang back tone sequences presented in different frequency ranges. Sung responses of Amazonian and US participants approximately replicated heard intervals on a logarithmic scale, even for tones outside the singing range. Moreover, Amazonian and US reproductions both deteriorated for high-frequency tones even though they were fully audible. But whereas US participants tended to reproduce notes an integer number of octaves above or below the heard tones, Amazonians did not, ignoring the note “chroma” (C, D, etc.). Chroma matching in US participants was more pronounced in US musicians than non-musicians, was not affected by feedback, and was correlated with similarity-based measures of octave equivalence as well as the ability to match the absolute f0 of a stimulus in the singing range. The results suggest the cross-cultural presence of logarithmic scales for pitch, and biological constraints on the limits of pitch, but indicate that octave equivalence may be culturally contingent, plausibly dependent on pitch representations that develop from experience with particular musical systems.
       
  • Locomotor and Hippocampal Processing Converge in the Lateral Septum
    • Abstract: Publication date: Available online 19 September 2019Source: Current BiologyAuthor(s): Hannah S. Wirtshafter, Matthew A. WilsonSummaryThe lateral septum (LS) has been implicated in anxiety and fear modulation and may regulate interactions between the hippocampus and regions, such as the VTA, that mediate goal-directed behavior. In this study, we simultaneously record from cells in the LS and the hippocampus during navigation and conditioning tasks. In the LS, we identify a speed and acceleration spiking code that does not map to states of anticipation or reward. Additionally, we identify an overlapping population of LS cells that change firing to cue and reward during conditioning. These cells display sharp wave ripple and theta modulation, spatial firing fields, and responses similar to the hippocampus during conditioning. These hippocampus-associated cells are not disproportionately speed or acceleration modulated, suggesting that these movement correlates are not hippocampally derived. Finally, we show that LS theta coordination is selectively enhanced in hippocampus-associated LS cells during navigation behavior that requires working memory. Taken together, these results suggest a role for the LS in transmitting spatial and contextual information, in concert with locomotor information, to downstream areas, such as the VTA, where value weighting may take place.
       
  • Insect Herbivory Selects for Volatile-Mediated Plant-Plant Communication
    • Abstract: Publication date: Available online 12 September 2019Source: Current BiologyAuthor(s): Aino Kalske, Kaori Shiojiri, Akane Uesugi, Yuzu Sakata, Kimberly Morrell, André KesslerSummaryPlant volatile organic compounds (VOCs) are major vehicles of information transfer between organisms and mediate many ecological interactions [1, 2, 3]. Altering VOC emission in response to herbivore damage has been hypothesized to be adaptive, as it can deter subsequent herbivores [4], attract natural enemies of herbivores [5], or transmit information about attacks between distant parts of the same plant [6, 7, 8, 9]. Neighboring plants may also respond to these VOC cues by priming their own defenses against oncoming herbivory, thereby reducing future damage [10, 11, 12]. However, under which conditions such information sharing provides fitness benefits to emitter plants, and, therefore, whether selection by herbivores affects the evolution of such VOC signaling, is still unclear [13]. Here, we test the predictions of two alternative hypotheses, the kin selection and mutual benefits hypotheses [14], to uncover the selective environment that may favor information sharing in plants. Measuring the response to natural selection in Solidago altissima, we found strong effects of herbivory on the way plants communicated with neighbors. Plants from populations that experienced selection by insect herbivory induced resistance in all neighboring conspecifics by airborne cues, whereas those from populations experiencing herbivore exclusion induced resistance only in neighbors of the same genotype. Furthermore, the information-sharing plants converged on a common, airborne VOC signal upon damage. We demonstrate that herbivory can drive the evolution of plant-plant communication via induction of airborne cues and suggest plants as a model system for understanding information sharing and communication among organisms in general.
       
  • Pattern and Speed Interact to Hide Moving Prey
    • Abstract: Publication date: Available online 12 September 2019Source: Current BiologyAuthor(s): Diana Umeton, Ghaith Tarawneh, Eugenia Fezza, Jenny C.A. Read, Candy RoweSummaryEvolutionary biologists have long been fascinated by camouflage patterns that help animals reduce their chances of being detected by predators [1, 2, 3, 4]. However, patterns that hide prey when they remain stationary, such as those that match their backgrounds [5, 6], are rendered ineffective once prey are moving [7, 8, 9, 10]. The question remains: can a moving animal ever be patterned in a way that helps reduce detection by predators' One long-standing idea is that high-contrast patterns with repeated elements, such as stripes, which are highly visible when prey are stationary, can actually conceal prey when they move fast enough [11, 12, 13, 14]. This is predicted by the “flicker fusion effect,” which occurs when prey move with sufficient speed that their pattern appears to blur, making them appear more featureless and become less conspicuous against the background [2, 8]. However, although this idea suggests a way to camouflage moving prey, it has not been empirically tested, and it is not clear that it would work at speeds that are biologically relevant to a predator [13]. Combining psychophysics and behavioral approaches, we show that speed and pattern interact to determine the detectability of prey to the praying mantis (Sphodromantis lineola) and, crucially, that prey with high-contrast stripes become less visible than prey with background-matching patterns when moving with sufficient speed. We show that stripes can reduce the detection of moving prey by exploiting the spatiotemporal limitations of predator perception, and that the camouflaging effect of a pattern depends upon the speed of prey movement.
       
  • Genome Sequence of Striga asiatica Provides Insight into the
           Evolution of Plant Parasitism
    • Abstract: Publication date: Available online 12 September 2019Source: Current BiologyAuthor(s): Satoko Yoshida, Seungill Kim, Eric K. Wafula, Jaakko Tanskanen, Yong-Min Kim, Loren Honaas, Zhenzhen Yang, Thomas Spallek, Caitlin E. Conn, Yasunori Ichihashi, Kyeongchae Cheong, Songkui Cui, Joshua P. Der, Heidrun Gundlach, Yuannian Jiao, Chiaki Hori, Juliane K. Ishida, Hiroyuki Kasahara, Takatoshi Kiba, Myung-Shin KimSummaryParasitic plants in the genus Striga, commonly known as witchweeds, cause major crop losses in sub-Saharan Africa and pose a threat to agriculture worldwide. An understanding of Striga parasite biology, which could lead to agricultural solutions, has been hampered by the lack of genome information. Here, we report the draft genome sequence of Striga asiatica with 34,577 predicted protein-coding genes, which reflects gene family contractions and expansions that are consistent with a three-phase model of parasitic plant genome evolution. Striga seeds germinate in response to host-derived strigolactones (SLs) and then develop a specialized penetration structure, the haustorium, to invade the host root. A family of SL receptors has undergone a striking expansion, suggesting a molecular basis for the evolution of broad host range among Striga spp. We found that genes involved in lateral root development in non-parasitic model species are coordinately induced during haustorium development in Striga, suggesting a pathway that was partly co-opted during the evolution of the haustorium. In addition, we found evidence for horizontal transfer of host genes as well as retrotransposons, indicating gene flow to S. asiatica from hosts. Our results provide valuable insights into the evolution of parasitism and a key resource for the future development of Striga control strategies.
       
  • Photosynthetic Endosymbionts Benefit from Host’s Phagotrophy, Including
           Predation on Potential Competitors
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Sosuke Iwai, Kyosuke Fujita, Yuuki Takanishi, Kota FukushiSummaryIn many endosymbioses, hosts have been shown to benefit from symbiosis, but it remains unclear whether intracellular endosymbionts benefit from their association with hosts [1, 2]. This makes it difficult to determine evolutionary mechanisms underlying cooperative behaviors between hosts and intracellular endosymbionts, such as mutual exchange of vital resources. Here, we investigate the fitness effects of symbiosis on the ciliate host Paramecium bursaria and on the algal endosymbiont Chlorella [3, 4], using experimental microcosms that include the free-living alga Chlamydomonas reinhardtii to mimic ecologically realistic conditions. We demonstrate that both host ciliate and the endosymbiotic algae gain fitness benefits from the symbiosis when another alga C. reinhardtii is present in the system. Specifically, the endosymbiotic Chlorella can grow as the host ciliate feeds and grows on C. reinhardtii, whereas the growth of free-living Chlorella is reduced by its competitor, C. reinhardtii. Thus, we propose that the endosymbiotic algae benefit from the host’s phagotrophy, which allows the endosymbiont to access particulate nutrient sources and to indirectly prey on the potential competitors competing with its free-living counterparts. Even though the ecological contexts in which each partner receives its benefits differ, both partners would gain net fitness benefits in an ecological timescale. Thus, the cooperative behaviors can evolve through fitness feedback (partner fidelity feedback) between the host and the endosymbiont, without need for special partner control mechanisms. The proposed ecological and evolutionary mechanisms provide a basis for understanding cooperative resource exchanges in endosymbioses, including many photosynthetic endosymbioses widespread in aquatic ecosystems.
       
  • Differences in Mitotic Spindle Architecture in Mammalian Neural Stem Cells
           Influence Mitotic Accuracy during Brain Development
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Diana Vargas-Hurtado, Jean-Baptiste Brault, Tristan Piolot, Ludovic Leconte, Nathalie Da Silva, Carole Pennetier, Alexandre Baffet, Véronique Marthiens, Renata BastoSummaryA functional bipolar spindle is essential to segregate chromosomes correctly during mitosis. Across organisms and cell types, spindle architecture should be optimized to promote error-free divisions. However, it remains to be investigated whether mitotic spindle morphology adapts to changes in tissue properties, typical of embryonic development, in order to ensure different tasks, such as spindle positioning and chromosome segregation. We have characterized mitotic spindles in neural stem cells (NSCs) of the embryonic developing mouse neocortex. Surprisingly, we found a switch in spindle morphology from early to late neurogenic stages, which relies on an increase in inner spindle microtubule density and stability. Mechanistically, we identified the microtubule-associated protein TPX2 as one determinant of spindle shape, contributing not only to its robustness but also to correct chromosome segregation upon mitotic challenge. Our findings highlight a possible causal relationship between spindle architecture and mitotic accuracy with likely implications in brain size regulation.Graphical Graphical abstract for this article
       
  • Distinct Mechanisms for Visual and Motor-Related Astrocyte Responses in
           Mouse Visual Cortex
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Michal Slezak, Steffen Kandler, Paul P. Van Veldhoven, Chris Van den Haute, Vincent Bonin, Matthew G. HoltSummaryAstrocytes are a major cell type in the mammalian nervous system, are in close proximity to neurons, and show rich Ca2+ activity thought to mediate cellular outputs. Astrocytes show activity linked to sensory [1, 2] and motor [3, 4] events, reflecting local neural activity and brain-wide neuromodulatory inputs. Sensory responses are highly variable [5, 6, 7, 8, 9, 10], which may reflect interactions between distinct input types [6, 7, 9]. However, the diversity of inputs generating astrocyte activity, particularly during sensory stimulation and behavior, is not fully understood [11, 12]. Using a combination of Ca2+ imaging, a treadmill assay, and visual stimulation, we examined the properties of astrocyte activity in mouse visual cortex associated with motor or sensory events. Consistent with previous work, motor activity activated astrocytes across the cortex with little specificity, reflecting a diffuse neuromodulatory mechanism. In contrast, moving visual stimuli generated specific activity patterns that reflected the stimulus' trajectory within the visual field, precisely as one would predict if astrocytes reported local neural activity. Visual responses depended strongly on behavioral state, with astrocytes showing high amplitude Ca2+ transients during locomotion and little activity during stillness. Furthermore, the amplitudes of visual responses were highly correlated with pupil size, suggesting a role of arousal. Interestingly, while depletion of cortical noradrenaline abolished locomotor responses, visual responses were only reduced in amplitude and their spatiotemporal organization remained intact, suggesting two distinct types of inputs underlie visual responses. We conclude that cortical astrocytes integrate local sensory information and behavioral state, suggesting a role in information processing.
       
  • Capping Protein Insulates Arp2/3-Assembled Actin Patches from Formins
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Ingrid Billault-Chaumartin, Sophie G. MartinSummaryHow actin structures of distinct identities and functions coexist within the same environment is a critical self-organization question. Fission yeast cells have a simple actin cytoskeleton made of four structures: Arp2/3 assembles actin patches around endocytic pits, and the formins For3, Cdc12, and Fus1 assemble actin cables, the cytokinetic ring during division, and the fusion focus during sexual reproduction, respectively. The focus concentrates the delivery of hydrolases by myosin V to digest the cell wall for cell fusion. We discovered that cells lacking capping protein (CP), a heterodimer that blocks barbed-end dynamics and associates with actin patches, exhibit a delay in fusion. Consistent with CP-formin competition for barbed-end binding, Fus1, F-actin, and the linear filament marker tropomyosin hyper-accumulate at the fusion focus in cells lacking CP. CP deletion also rescues the fusion defect of a mutation in the Fus1 knob region. However, myosin V and exocytic cargoes are reduced at the fusion focus and diverted to ectopic foci, which underlies the fusion defect. Remarkably, the ectopic foci coincide with Arp2/3-assembled actin patches, which now contain low levels of Fus1. We further show that CP localization to actin patches is required to prevent the formation of ectopic foci and promote efficient cell fusion. During mitotic growth, actin patches lacking CP similarly display a dual identity, as they accumulate the formins For3 and Cdc12, normally absent from patches, and are co-decorated by the linear filament-binding protein tropomyosin and the patch marker fimbrin. Thus, CP serves to protect Arp2/3-nucleated structures from formin activity.Graphical Graphical abstract for this article
       
  • The Gypsy Endogenous Retrovirus Drives Non-Cell-Autonomous Propagation in
           a Drosophila TDP-43 Model of Neurodegeneration
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Yung-Heng Chang, Josh DubnauSummaryA hallmark of neurodegenerative disease is focal onset of pathological protein aggregation, followed by progressive spread of pathology to connected brain regions. In amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), pathology is often associated with aggregation of TAR DNA-binding protein 43 (TDP-43). Although aggregated TDP-43 protein moves between cells, it is not clear whether and how this movement propagates the degeneration. Here, we have established a Drosophila model of human TDP-43 in which we initiated toxic expression of human TDP-43 focally within small groups of glial cells. We found that this focal onset kills adjacent neurons. Surprisingly, we show that this spreading death is caused by an endogenous retrovirus within the glia, which leads to DNA damage and death in adjacent neurons. These findings suggest a possible mechanism by which human retroviruses such as HERV-K might contribute to TDP-43-mediated propagation of neurodegeneration.Graphical Graphical abstract for this article
       
  • Osmolyte Depletion and Thirst Suppression Allow Hibernators to Survive for
           Months without Water
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Ni Y. Feng, Madeleine S. Junkins, Dana K. Merriman, Sviatoslav N. Bagriantsev, Elena O. GrachevaSummaryThirteen-lined ground squirrels (Ictidomys tridecemlineatus) are obligatory hibernators who can survive over 6 months of the year in underground burrows or laboratory hibernaculum without access to food or water [1]. Hibernation consists of prolonged periods of torpor, lasting up to 18 days, which are characterized by low body temperature and suppressed metabolism. This torpidity is interspersed with short periods of interbout arousal, lasting up to 48 h, during which squirrels temporarily return to an active-like state and lose small amounts of water to urination and evaporation [2]. Water is also lost during torpor due to a positive vapor pressure difference created by the slightly higher temperature of the body compared to its surroundings [2, 3]. Here, we investigate the physiological mechanism of survival during prolonged water loss and deprivation throughout hibernation. By measuring hydration status during hibernation, we show that squirrels remain hydrated during torpor by depleting osmolytes from the extracellular fluid. During brief periods of arousal, serum osmolality and antidiuretic hormone levels are restored, but thirst remains suppressed. This decoupling of thirst and diuresis enables water retention by the kidney while suppressing the drive to leave the safety of the underground burrow in search of water. An acute increase in serum osmolality reinstates water-seeking behavior, demonstrating preservation of the physiological thirst circuit during hibernation. Better mechanistic understanding of internal osmolyte regulation and thirst suppression could translate to advancements in human medicine and long-term manned spaceflight.Graphical Graphical abstract for this article
       
  • Adaptive Evolution Is Common in Rapid Evolutionary Radiations
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Bruno Nevado, Edgar L.Y. Wong, Owen G. Osborne, Dmitry A. FilatovSummaryOne of the most long-standing and important mysteries in evolutionary biology is why biological diversity is so unevenly distributed across space and taxonomic lineages. Nowhere is this disparity more evident than in the multitude of rapid evolutionary radiations found on oceanic islands and mountain ranges across the globe [1, 2, 3, 4, 5]. The evolutionary processes driving these rapid diversification events remain unclear [6, 7, 8]. Recent genome-wide studies suggest that natural selection may be frequent during rapid evolutionary radiations, as inferred from work in cichlid fish [9], white-eye birds [10], new world lupins [11], and wild tomatoes [12]. However, whether frequent adaptive evolution is a general feature of rapid evolutionary radiations remains untested. Here we show that adaptive evolution is significantly more frequent in rapid evolutionary radiations compared to background levels in more slowly diversifying lineages. This result is consistent across a wide range of angiosperm lineages analyzed: 12 evolutionary radiations, which together comprise 1,377 described species, originating from some of the most biologically diverse systems on Earth. In addition, we find a significant negative correlation between population size and frequency of adaptive evolution in rapid evolutionary radiations. A possible explanation for this pattern is that more frequent adaptive evolution is at least partly driven by positive selection for advantageous mutations that compensate for the fixation of slightly deleterious mutations in smaller populations.
       
  • Centromere Dysfunction Compromises Mitotic Spindle Pole Integrity
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Simon Gemble, Anthony Simon, Carole Pennetier, Marie Dumont, Solène Hervé, Franz Meitinger, Karen Oegema, Raphaël Rodriguez, Geneviève Almouzni, Daniele Fachinetti, Renata BastoSummaryCentromeres and centrosomes are crucial mitotic players. Centromeres are unique chromosomal sites characterized by the presence of the histone H3-variant centromere protein A (CENP-A) [1]. CENP-A recruits the majority of centromere components, collectively named the constitutive centromere associated network (CCAN) [2]. The CCAN is necessary for kinetochore assembly, a multiprotein complex that attaches spindle microtubules (MTs) and is required for chromosome segregation [3]. In most animal cells, the dominant site for MT nucleation in mitosis are the centrosomes, which are composed of two centrioles, surrounded by a protein-rich matrix of electron-dense pericentriolar material (PCM) [4]. The PCM is the site of MT nucleation during mitosis [5]. Even if centromeres and centrosomes are connected via MTs in mitosis, it is not known whether defects in either one of the two structures have an impact on the function of the other. Here, using high-resolution microscopy combined with rapid removal of CENP-A in human cells, we found that perturbation of centromere function impacts mitotic spindle pole integrity. This includes release of MT minus-ends from the centrosome, leading to PCM dispersion and centriole mis-positioning at the spindle poles. Mechanistically, we show that these defects result from abnormal spindle MT dynamics due to defective kinetochore-MT attachments. Importantly, restoring mitotic spindle pole integrity following centromere inactivation lead to a decrease in the frequency of chromosome mis-segregation. Overall, our work identifies an unexpected relationship between centromeres and maintenance of the mitotic pole integrity necessary to ensure mitotic accuracy and thus to maintain genetic stability.Graphical Graphical abstract for this article
       
  • Development of Center-Surround Suppression in Infant Motion Processing
    • Abstract: Publication date: Available online 5 September 2019Source: Current BiologyAuthor(s): Yusuke Nakashima, Masami K. Yamaguchi, So KanazawaSummaryMotion direction of a large high-contrast pattern is more difficult to perceive than that of a small one [1]. This counterintuitive perceptual phenomenon is considered to reflect surround suppression, a receptive field property observed in the visual cortex [2, 3, 4, 5]. Here, we demonstrate that this phenomenon can be observed in human infants. Infants at 7 to 8 months of age showed higher sensitivity for a small motion stimulus than for a large one. However, infants under 6 months showed the opposite result; motion sensitivity was higher for a large stimulus. These results suggest that suppressive surround regions beyond classical receptive fields develop in the second half of the first year. Moreover, we examined the size of spatial summation in infants and found that the spatial summation area shrinks from 3 to 8 months of age. Our findings suggest that the summation area for motion is broad with no surround suppression in early infancy and that it narrows and acquires suppressive surround regions in the first year of life, which might reflect the developmental changes in the receptive field structure.
       
  • A Bidimensional Segregation Mode Maintains Symbiont Chromosome Orientation
           toward Its Host
    • Abstract: Publication date: Available online 30 August 2019Source: Current BiologyAuthor(s): Philipp M. Weber, Friedrich Moessel, Gabriela F. Paredes, Tobias Viehboeck, Norbert O.E. Vischer, Silvia BulgheresiSummaryAll living organisms require accurate segregation of their genetic material. However, in microbes, chromosome segregation is less understood than replication and cell division, which makes its decipherment a compelling research frontier. Furthermore, it has only been studied in free-living microbes so far. Here, we investigated this fundamental process in a rod-shaped symbiont, Candidatus Thiosymbion oneisti. This gammaproteobacterium divides longitudinally as to form a columnar epithelium ensheathing its nematode host. We hypothesized that uninterrupted host attachment would affect bacterial chromosome dynamics and set out to localize specific chromosomal loci and putative DNA-segregating proteins by fluorescence in situ hybridization and immunostaining, respectively. First, DNA replication origins (ori) number per cell demonstrated symbiont monoploidy. Second, we showed that sister ori segregate diagonally prior to septation onset. Moreover, the localization pattern of the centromere-binding protein ParB recapitulates that of ori, and consistently, we showed recombinant ParB to specifically bind an ori-proximal site (parS) in vitro. Third, chromosome replication ends prior to cell fission, and as the poles start to invaginate, termination of replication (ter) sites localize medially, at the leading edges of the growing septum. They then migrate to midcell, concomitantly with septation progression and until this is completed. In conclusion, we propose that symbiont ParB might drive chromosome segregation along the short axis and that tethering of sister ter regions to the growing septum mediates their migration along the long axis. Crucially, active bidimensional segregation of the chromosome allows transgenerational maintenance of its configuration, and therefore, it may represent an adaptation to symbiosis.Video Graphical Graphical abstract for this article
       
  • Blue Growth Potential to Mitigate Climate Change through Seaweed
           Offsetting
    • Abstract: Publication date: Available online 29 August 2019Source: Current BiologyAuthor(s): Halley E. Froehlich, Jamie C. Afflerbach, Melanie Frazier, Benjamin S. HalpernSummaryCarbon offsetting—receiving credit for reducing, avoiding, or sequestering carbon—has become part of the portfolio of solutions to mitigate carbon emissions, and thus climate change, through policy and voluntary markets, primarily by land-based re- or afforestation and preservation [1, 2]. However, land is limiting, creating interest in a rapidly growing aquatic farming sector of seaweed aquaculture [3, 4, 5]. Synthesizing data from scientific literature, we assess the extent and cost of scaling seaweed aquaculture to provide sufficient CO2eq sequestration for several climate change mitigation scenarios, with a focus on the food sector—a major source of greenhouse gases [6]. Given known ecological constraints (nutrients and temperature), we found a substantial suitable area (ca. 48 million km2) for seaweed farming, which is largely unfarmed. Within its own industry, seaweed could create a carbon-neutral aquaculture sector with just 14% (mean = 25%) of current seaweed production (0.001% of suitable area). At a much larger scale, we find seaweed culturing extremely unlikely to offset global agriculture, in part due to production growth and cost constraints. Yet offsetting agriculture appears more feasible at a regional level, especially areas with strong climate policy, such as California (0.065% of suitable area). Importantly, seaweed farming can provide other benefits to coastlines affected by eutrophic, hypoxic, and/or acidic conditions [7, 8], creating opportunities for seaweed farming to act as “charismatic carbon” that serves multiple purposes. Seaweed offsetting is not the sole solution to climate change, but it provides an invaluable new tool for a more sustainable future.
       
  • Allorecognition upon Fungal Cell-Cell Contact Determines Social
           Cooperation and Impacts the Acquisition of Multicellularity
    • Abstract: Publication date: Available online 29 August 2019Source: Current BiologyAuthor(s): A. Pedro Gonçalves, Jens Heller, Elise A. Span, Gabriel Rosenfield, Hung P. Do, Javier Palma-Guerrero, Natalia Requena, Michael A. Marletta, N. Louise GlassSummarySomatic cell fusion and conspecific cooperation are crucial social traits for microbial unicellular-to-multicellular transitions, colony expansion, and substrate foraging but are also associated with risks of parasitism. We identified a cell wall remodeling (cwr) checkpoint that acts upon cell contact to assess genetic compatibility and regulate cell wall dissolution during somatic cell fusion in a wild population of the filamentous fungus Neurospora crassa. Non-allelic interactions between two linked loci, cwr-1 and cwr-2, were necessary and sufficient to block cell fusion: cwr-1 encodes a polysaccharide monooxygenase (PMO), a class of enzymes associated with extracellular degradative capacities, and cwr-2 encodes a predicted transmembrane protein. Mutations of sites in CWR-1 essential for PMO catalytic activity abolished the block in cell fusion between formerly incompatible strains. In Neurospora, alleles cwr-1 and cwr-2 were highly polymorphic, fell into distinct haplogroups, and showed trans-species polymorphisms. Distinct haplogroups and trans-species polymorphisms at cwr-1 and cwr-2 were also identified in the distantly related genus Fusarium, suggesting convergent evolution. Proteins involved in chemotropic processes showed extended localization at contact sites, suggesting that cwr regulates the transition between chemotropic growth and cell wall dissolution. Our work revealed an allorecognition surveillance system based on kind discrimination that inhibits cooperative behavior in fungi by blocking cell fusion upon contact, contributing to fungal immunity by preventing formation of chimeras between genetically non-identical colonies.Graphical Graphical abstract for this article
       
  • Dynamic- and Frequency-Specific Regulation of Sleep Oscillations by
           Cortical Potassium Channels
    • Abstract: Publication date: Available online 29 August 2019Source: Current BiologyAuthor(s): Christine M. Muheim, Andrea Spinnler, Tina Sartorius, Roland Dürr, Reto Huber, Clement Kabagema, Peter Ruth, Steven A. BrownSummaryPrimary electroencephalographic (EEG) features of sleep arise in part from thalamocortical neural assemblies, and cortical potassium channels have long been thought to play a critical role. We have exploited the regionally dynamic nature of sleep EEG to develop a novel screening strategy and used it to conduct an adeno-associated virus (AAV)-mediated RNAi screen for cellular roles of 31 different voltage-gated potassium channels in modulating cortical EEG features across the circadian sleep-wake cycle. Surprisingly, a majority of channels modified only electroencephalographic frequency bands characteristic of sleep, sometimes diurnally or even in specific vigilance states. Confirming our screen for one channel, we show that depletion of the KCa1.1 (or “BK”) channel reduces EEG power in slow-wave sleep by slowing neuronal repolarization. Strikingly, this reduction completely abolishes transcriptomic changes between sleep and wake. Thus, our data establish an unexpected connection between transcription and EEG power controlled by specific potassium channels. We postulate that additive dynamic roles of individual potassium channels could integrate different influences upon sleep and wake within single neurons.
       
  • Recurrent Circuitry Sustains Drosophila Courtship Drive While
           Priming Itself for Satiety
    • Abstract: Publication date: Available online 29 August 2019Source: Current BiologyAuthor(s): Stephen X. Zhang, Dragana Rogulja, Michael A. CrickmoreSummaryMotivations intensify over hours or days, promoting goals that are achieved in minutes or hours, causing satiety that persists for hours or days. Here we develop Drosophila courtship as a system to study these long-timescale motivational dynamics. We identify two neuronal populations engaged in a recurrent excitation loop, the output of which elevates a dopamine signal that increases the propensity to court. Electrical activity within the recurrent loop accrues with abstinence and, through the activity-dependent transcription factor CREB2, drives the production of activity-suppressing potassium channels. Loop activity is decremented by each mating to reduce subsequent courtship drive, and the inhibitory loop environment established by CREB2 during high motivation slows the reaccumulation of activity for days. Computational modeling reproduces these behavioral and physiological dynamics, generating predictions that we validate experimentally and illustrating a causal link between the motivation that drives behavior and the satiety that endures after goal achievement.
       
  • The Sensorimotor Basis of Whisker-Guided Anteroposterior Object
           Localization in Head-Fixed Mice
    • Abstract: Publication date: Available online 29 August 2019Source: Current BiologyAuthor(s): Jonathan Cheung, Phillip Maire, Jinho Kim, Jonathan Sy, Samuel Andrew HiresSummaryActive tactile perception combines directed motion with sensory signals to generate mental representations of objects in space. Competing models exist for how mice use these signals to determine the precise location of objects along their face. We tested six of these models using behavioral manipulations and statistical learning in head-fixed mice. Trained mice used a whisker to locate a pole in a continuous range of locations along the anteroposterior axis. Mice discriminated locations to ≤0.5 mm (
       
  • Long-Wavelength Reflecting Filters Found in the Larval Retinas of One
           Mantis Shrimp Family (Nannosquillidae)
    • Abstract: Publication date: Available online 29 August 2019Source: Current BiologyAuthor(s): Kathryn D. Feller, David Wilby, Gianni Jacucci, Silvia Vignolini, Judith Mantell, Trevor J. Wardill, Thomas W. Cronin, Nicholas W. RobertsSummaryBoth vertebrates and invertebrates commonly exploit photonic structures adjacent to their photoreceptors for visual benefits. For example, use of a reflecting structure (tapetum) behind the retina increases photon capture, enhancing vision in dim light [1, 2, 3, 4, 5]. Colored filters positioned lateral or distal to a photoreceptive unit may also be used to tune spectral sensitivity by selective transmission of wavelengths not absorbed or scattered by the filters [6, 7, 8]. Here we describe a new category of biological optical filter that acts simultaneously as both a transmissive spectral filter and narrowband reflector. Discovered in the larval eyes of only one family of mantis shrimp (stomatopod) crustaceans (Nannosquillidae), each crystalline structure bisects the photoreceptive rhabdom into two tiers and contains an ordered array of membrane-bound vesicles with sub-wavelength diameters of 153 ± 5 nm. Axial illumination of the intrarhabdomal structural reflector (ISR) in vivo produces a narrow band of yellow reflectance (mean peak reflectivity, 572 ± 18 nm). The ISR is similar to several synthetic devices, such as bandgap filters, laser mirrors, and (in particular) fiber Bragg gratings used in optical sensors for a wide range of industries. To our knowledge, the stomatopod larval ISR is the first example of a naturally occurring analog to these human-made devices. Considering what is known about these animals’ visual ecology, we propose that these reflecting filters may help improve the detection of pelagic bioluminescence in shallow water at night.Video Graphical Graphical abstract for this article
       
  • HLH-2/E2A Expression Links Stochastic and Deterministic Elements of a Cell
           Fate Decision during C. elegans Gonadogenesis
    • Abstract: Publication date: Available online 8 August 2019Source: Current BiologyAuthor(s): Michelle A. Attner, Wolfgang Keil, Justin M. Benavidez, Iva GreenwaldSummaryStochastic mechanisms diversify cell fate in organisms ranging from bacteria to humans [1, 2, 3, 4]. In the anchor cell/ventral uterine precursor cell (AC/VU) fate decision during C. elegans gonadogenesis, two “α cells,” each with equal potential to be an AC or a VU, interact via LIN-12/Notch and its ligand LAG-2/DSL [5, 6]. This LIN-12/Notch-mediated interaction engages feedback mechanisms that amplify a stochastic initial difference between the two α cells, ensuring that the cell with higher lin-12 activity becomes the VU while the other becomes the AC [7, 8, 9]. The initial difference between the α cells was originally envisaged as a random imbalance from “noise” in lin-12 expression/activity [6]. However, subsequent evidence that the relative birth order of the α cells biases their fates suggested other factors may be operating [7]. Here, we investigate the nature of the initial difference using high-throughput lineage analysis [10]; GFP-tagged endogenous LIN-12, LAG-2, and HLH-2, a conserved transcription factor that orchestrates AC/VU development [7, 11]; and tissue-specific hlh-2 null alleles. We identify two stochastic elements: relative birth order, which largely originates at the beginning of the somatic gonad lineage three generations earlier, and onset of HLH-2 expression, such that the α cell whose parent expressed HLH-2 first is biased toward the VU fate. We find that these elements are interrelated, because initiation of HLH-2 expression is linked to the birth of the parent cell. Finally, we provide a potential deterministic mechanism for the HLH-2 expression bias by showing that hlh-2 is required for LIN-12 expression in the α cells.Graphical Graphical abstract for this article
       
 
 
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