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Current Biology
Journal Prestige (SJR): 4.296
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ISSN (Print) 0960-9822
Published by Elsevier Homepage  [3162 journals]
  • Modulation of DNA Repair Systems in Blind Cavefish during Evolution in
           Constant Darkness
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Haiyu Zhao, Giuseppe Di Mauro, Sebastian Lungu-Mitea, Pietro Negrini, Andrea Maria Guarino, Elena Frigato, Thomas Braunbeck, Hongju Ma, Tilman Lamparter, Daniela Vallone, Cristiano Bertolucci, Nicholas S. FoulkesSummaryHow the environment shapes the function and evolution of DNA repair systems is poorly understood. In a comparative study using zebrafish and the Somalian blind cavefish, Phreatichthys andruzzii, we reveal that during evolution for millions of years in continuous darkness, photoreactivation DNA repair function has been lost in P. andruzzii. We demonstrate that this loss results in part from loss-of-function mutations in pivotal DNA-repair genes. Specifically, C-terminal truncations in P. andruzzii DASH and 6-4 photolyase render these proteins predominantly cytoplasmic, with consequent loss in their functionality. In addition, we reveal a general absence of light-, UV-, and ROS-induced expression of P. andruzzii DNA-repair genes. This results from a loss of function of the D-box enhancer element, which coordinates and enhances DNA repair in response to sunlight. Our results point to P. andruzzii being the only species described, apart from placental mammals, that lacks the highly evolutionary conserved photoreactivation function. We predict that in the DNA repair systems of P. andruzzii, we may be witnessing the first stages in a process that previously occurred in the ancestors of placental mammals during the Mesozoic era.
  • Hexadirectional Modulation of Theta Power in Human Entorhinal Cortex
           during Spatial Navigation
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Dong Chen, Lukas Kunz, Wenjing Wang, Hui Zhang, Wen-Xu Wang, Andreas Schulze-Bonhage, Peter C. Reinacher, Wenjing Zhou, Shuli Liang, Nikolai Axmacher, Liang WangSummaryGrid cells and theta oscillations are fundamental components of the brain’s navigation system. Grid cells provide animals [1, 2] and humans [3, 4] with a spatial map of the environment by exhibiting multiple firing fields arranged in a regular grid of equilateral triangles. This unique firing pattern presumably constitutes the neural basis for path integration [5, 6, 7, 8] and may also enable navigation in visual and conceptual spaces [9, 10, 11, 12]. Theta frequency oscillations are a prominent mesoscopic network phenomenon during navigation in both rodents and humans [13, 14] and encode movement speed [15, 16, 17], distance traveled [18], and proximity to spatial boundaries [19]. Whether theta oscillations may also carry a grid-like signal remains elusive, however. Capitalizing on previous fMRI studies revealing a macroscopic proxy of sum grid cell activity in human entorhinal cortex (EC) [20, 21, 22], we examined intracranial EEG recordings from the EC of epilepsy patients (n = 9) performing a virtual navigation task. We found that the power of theta oscillations (4–8 Hz) exhibits 6-fold rotational modulation by movement direction, reminiscent of grid cell-like representations detected using fMRI. Modulation of theta power was specific to 6-fold rotational symmetry and to the EC. Hexadirectional modulation of theta power by movement direction only emerged during fast movements, stabilized over the course of the experiment, and showed sensitivity to the environmental boundary. Our results suggest that oscillatory power in the theta frequency range carries an imprint of sum grid cell activity potentially enabled by a common grid orientation of neighboring grid cells [23].
  • Collective Infection of Cells by Viral Aggregates Promotes Early Viral
           Proliferation and Reveals a Cellular-Level Allee Effect
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Iván Andreu-Moreno, Rafael SanjuánSummaryIn addition to the conventional release of free, individual virions, virus dispersal can involve multi-virion assemblies that collectively infect cells. However, the implications of collective infection for viral fitness remain largely unexplored. Using vesicular stomatitis virus, here, we compare the fitness of free versus saliva-aggregated viral particles. We find that aggregation has a positive effect on early progeny production, conferring a fitness advantage relative to equal numbers of free particles in most cell types. The advantage of aggregation resides, at least partially, in increasing the cellular multiplicity of infection. In mouse embryonic fibroblasts, the per capita, short-term viral progeny production peaked for a dose of ca. three infectious particles per cell. This reveals an Allee effect restricting early viral proliferation at the cellular level, which should select for dispersal in groups. We find that genetic complementation between deleterious mutants is probably not the mechanism underlying the fitness advantage of collective infection. Instead, this advantage is cell type dependent and correlates with cellular permissivity to the virus, as well as with the ability of host cells to mount an antiviral innate immune response.Graphical Graphical abstract for this article
  • Quantitative Matching of Clutch Size in Reciprocating Hermaphroditic Worms
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Laura Picchi, Guénaël Cabanes, Claire Ricci-Bonot, Maria Cristina LorenziSummaryReciprocity [1] is one of the most controversial evolutionary explanations of cooperation among non-kin [2, 3]. For some authors, cognitive capacity of non-human organisms is limiting, and more parsimonious mechanisms should apply [3, 4, 5]; for others, the debate is mainly semantic [2, 6], and empirical evidence can be found in a wide range of taxa [7]. However, while the ability to alternate cooperative behaviors does not settle the reciprocity controversy, the capacity to adjust cooperative behavior to the value of received help could prove decisive. Marine polychaete worms Ophryotrocha diadema, as several simultaneous hermaphrodites, do not self-fertilize and have unilateral mating (i.e., they behave either as females or as males during each mating event). They are also external fertilizers and thus cannot store allosperm, which contribute to make them ideal model organisms to investigate reciprocity, since partners usually alternate sexual roles with each other, repeatedly exchanging egg clutch of variable size [8, 9, 10, 11, 12]. However, whether the alternation of sexual roles is the result of conditional reciprocity rather than by-product reciprocity has never been tested [13]. Here, we show that O. diadema worms reciprocate eggs conditionally to the partner’s behavior and adjust the quality of cooperation according to that of their partners. Moreover, only egg reciprocation offers similar fitness returns via both the female and the male function with respect to non-reciprocating laying strategies. These results document that fine-tuned forms of conditional reciprocity can emerge in cognitively unsophisticated animals, broadening the criteria to recognize conditional reciprocity among animals.
  • Hexadirectional Modulation of High-Frequency Electrophysiological Activity
           in the Human Anterior Medial Temporal Lobe Maps Visual Space
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Tobias Staudigl, Marcin Leszczynski, Joshua Jacobs, Sameer A. Sheth, Charles E. Schroeder, Ole Jensen, Christian F. DoellerSummaryGrid cells are one of the core building blocks of spatial navigation [1]. Single-cell recordings of grid cells in the rodent entorhinal cortex revealed hexagonal coding of the local environment during spatial navigation [1]. Grid-like activity has also been identified in human single-cell recordings during virtual navigation [2]. Human fMRI studies further provide evidence that grid-like signals are also accessible on a macroscopic level [3, 4, 5, 6, 7]. Studies in both non-human primates [8] and humans [9, 10] suggest that grid-like coding in the entorhinal cortex generalizes beyond spatial navigation during locomotion, providing evidence for grid-like mapping of visual space during visual exploration—akin to the grid cell positional code in rodents during spatial navigation. However, electrophysiological correlates of the grid code in humans remain unknown. Here, we provide evidence for grid-like, hexadirectional coding of visual space by human high-frequency activity, based on two independent datasets: non-invasive magnetoencephalography (MEG) in healthy subjects and entorhinal intracranial electroencephalography (EEG) recordings in an epileptic patient. Both datasets consistently show a hexadirectional modulation of broadband high-frequency activity (60–120 Hz). Our findings provide first evidence for a grid-like MEG signal, indicating that the human entorhinal cortex codes visual space in a grid-like manner [8, 9, 10], and support the view that grid coding generalizes beyond environmental mapping during locomotion [4, 5, 6, 11]. Due to their millisecond accuracy, MEG recordings allow linking of grid-like activity to epochs during relevant behavior, thereby opening up the possibility for new MEG-based investigations of grid coding at high temporal resolution.
  • Selective Inhibition of Volitional Hand Movements after Stimulation of the
           Dorsoposterior Parietal Cortex in Humans
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Michel Desmurget, Nathalie Richard, Pierre-Aurélien Beuriat, Alexandru Szathmari, Carmine Mottolese, Jean-René Duhamel, Angela SiriguSummaryInhibition is a central component of motor control. Although current models emphasize the involvement of frontal networks [1, 2], indirect evidence suggests a potential contribution of the posterior parietal cortex (PPC). This region is active during inhibition of upper-limb movements to undesired targets [3], and its stimulation with single magnetic pulses can depress motor-evoked potentials [4, 5]. Also, it has been speculated that alien hand movements caused by focal parietal lesions reflect a release of inhibition from PPC to M1 [6]. Considering these observations, we instructed 16 patients undergoing awake brain surgery to perform continuous hand movements while electrical stimulation was applied over PPC. Within a restricted dorsoposterior area, we identified focal sites where stimulation prevented movement initiation and instantly inhibited ongoing responses (which restarted promptly at stimulation offset). Inhibition was selective of the instructed response. It did not affect speech, hand movements passively generated through muscle electrical stimulation, or the ability to initiate spontaneous actions with other body segments (e.g., the feet). When a patient inadvertently performed a bilateral movement, a bilateral inhibition was found. When asked to produce unilateral movements, this patient presented a contralesional but not ipsilateral inhibition. This selectivity contrasted sharply with the unspecific inhibitions reported by previous studies within frontal regions, where speech and all limbs are typically affected (as we here confirm in a subset of patients) [7, 8, 9, 10]. These results provide direct evidence that a specific area in the dorsoposterior parietal cortex can inhibit volitional upper-limb responses with high selectivity.
  • A Positive Feedback between Growth and Polarity Provides Directional
           Persistency and Flexibility to the Process of Tip Growth
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Armin Haupt, Dmitry Ershov, Nicolas MincSummaryPolar cell growth is a conserved morphogenetic process needed for survival, mating, and infection [1, 2]. It typically implicates the assembly and spatial stabilization of a cortical polar domain of the active form of a small GTPase of the Rho family, such as Cdc42, which promotes cytoskeleton assembly and secretion needed for local surface expansion [3, 4, 5, 6]. In multiple physiological instances, polarity domains may switch from being spatially unstable, exhibiting a wandering behavior around the cell surface, to being stable at a fixed cellular location [7, 8, 9, 10, 11]. Here, we show that the rate of surface growth may be a key determinant in controlling the spatial stability of active Cdc42 domains. Reducing the growth rate of single rod-shaped fission yeast cells using chemical, genetic, and mechanical means systematically causes polar domains to detach from cell tips and oscillate around the cell surface within minutes. Conversely, an abrupt increase in growth rate improves domain stabilization. A candidate screen identifies vesicular transport along actin cables as an important module mediating this process. Similar behavior observed in distant filamentous fungi suggests that this positive feedback between growth and polarity could represent a basal property of eukaryotic polarization, promoting persistent polar growth as well as growth redirection with respect to the mechanical environment of cells.Graphical Graphical abstract for this article
  • Unicellular Origin of the Animal MicroRNA Machinery
    • Abstract: Publication date: Available online 11 October 2018Source: Current BiologyAuthor(s): Jon Bråte, Ralf S. Neumann, Bastian Fromm, Arthur A.B. Haraldsen, James E. Tarver, Hiroshi Suga, Philip C.J. Donoghue, Kevin J. Peterson, Iñaki Ruiz-Trillo, Paul E. Grini, Kamran Shalchian-TabriziSummaryThe emergence of multicellular animals was associated with an increase in phenotypic complexity and with the acquisition of spatial cell differentiation and embryonic development. Paradoxically, this phenotypic transition was not paralleled by major changes in the underlying developmental toolkit and regulatory networks. In fact, most of these systems are ancient, established already in the unicellular ancestors of animals [1, 2, 3, 4, 5]. In contrast, the Microprocessor protein machinery, which is essential for microRNA (miRNA) biogenesis in animals, as well as the miRNA genes themselves produced by this Microprocessor, have not been identified outside of the animal kingdom [6]. Hence, the Microprocessor, with the key proteins Pasha and Drosha, is regarded as an animal innovation [7, 8, 9]. Here, we challenge this evolutionary scenario by investigating unicellular sister lineages of animals through genomic and transcriptomic analyses. We identify in Ichthyosporea both Drosha and Pasha (DGCR8 in vertebrates), indicating that the Microprocessor complex evolved long before the last common ancestor of animals, consistent with a pre-metazoan origin of most of the animal developmental gene elements. Through small RNA sequencing, we also discovered expressed bona fide miRNA genes in several species of the ichthyosporeans harboring the Microprocessor. A deep, pre-metazoan origin of the Microprocessor and miRNAs comply with a view that the origin of multicellular animals was not directly linked to the innovation of these key regulatory components.
  • Mutation Rates: Simpler Than We Thought'
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): John F.Y. BrookfieldSummaryMutation rate variation is often explained by varying optimal rates, or through effective population sizes determining the effectiveness of selection. But a rate difference between humans and owl monkeys is now explained mechanistically as a consequence of differing reproductive longevities.
  • Neuroethology of bat navigation
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Daria Genzel, Yossi Yovel, Michael M. Yartsev
  • Lingering Effects of Herbivory and Plant Defenses on Pollinators
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Deidra J. Jacobsen, Robert A. RagusoIn order to survive and reproduce, flowering plants must balance the conflicting selective pressures of herbivore avoidance and pollinator attraction. Links between herbivory and reproduction are often attributed to indirect effects of leaf damage on pollination via reductions in floral allocation, or increases in chemical defenses on herbivore-damaged plants. However, the impacts of herbivory on pollinators have the potential to extend beyond initial floral visits when plant defenses impact pollinator health, foraging behavior, and reproductive success. Here, we examine important but underexplored ways in which herbivory may alter floral phenotype and thus impact pollinators. First, we outline genetic and biochemical mechanisms predicted to underlie floral changes following herbivory, as they impact the floral resources (nectar and pollen) sought by pollinators. Next, we discuss how the consumption of secondary compounds might impact pollinator fitness, including carryover effects on subsequent foraging, mating success, and transgenerational effects on offspring. We consider how pollinator health, life history, and coevolutionary history might result in context-dependent impacts of plant defensive chemistry on pollinator fitness. Finally, we call for studies that measure the impact of herbivore-induced plant defenses on the full spectrum of flower visitors, and contrast case studies on conventional pollinators (for example, generalized bees) versus insects whose larvae are herbivores on the same plants that adults pollinate (such as several butterflies and moths). By linking these consequences of herbivory to fitness effects on both herbivores and pollinators, we will better understand how coevolution between plants, herbivores, and pollinators shapes both defensive and reproductive plant traits.
  • Dinosaurs: Four Legs Good, Two Legs Bad
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): P. Martin Sander, Jens N. LallensackSummaryThe quadrupedal Sauropods — the biggest dinosaurs to walk the Earth — evolved from bipedal ancestors. Two new early sauropodomorphs from South Africa and Argentina indicate that very large, flexed-limbed sauropodomorphs coexisted with early columnar-limbed sauropods for 20 million years.
  • Neuroscience: Modeling the Brain on Acid
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Johan van der Meer, Michael BreakspearSummaryA receptor map of serotonin distribution is integrated into a model of the dynamic activity of the brain under the effects of LSD. The approach opens new avenues to understand experimental manipulations of healthy brain activity and offers a novel drug-discovery platform.
  • Nervous System Development: Flies and Worms Converging on Neuron Identity
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Paschalis Kratsios, Oliver HobertSummaryDistinct neuronal cell types display phenotypic similarities such as their neurotransmitter identity. Studies in worms and flies have revealed that this phenotypic convergence can be brought about by distinct transcription factors regulating the same effector genes in different neuron types.
  • Selective Attention: A Plausible Mechanism Underlying Confirmation Bias
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Genís Prat-Ortega, Jaime de la RochaSummaryOur perception is strongly influenced by our experience of past stimuli and choices. A new study suggests that our attention is selectively deployed to those aspects of the sensory evidence which are consistent with our previous decisions, thus introducing a confirmation bias.
  • Animal Behavior: Socializing Octopus
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Tamar Gutnick, Michael J. KubaSummaryBuilding on the recently published Octopus bimaculoides genome, a new study identifies an evolutionarily conserved neural mechanism for serotonergic regulation of social behaviors.
  • Plant Physiology: One Way to Dump Salt
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Colin BrownleeSummarySoil salinization is a major challenge to global food security. The quinoa plant tolerates saline conditions by dumping excess salt into specialised bladder cells on the leaves. The pathways and transporters underlying this one-way accumulation system are now becoming clearer.
  • Human Cooperation: The Hunter-Gatherer Puzzle
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Joseph HenrichSummaryIn tracing the roots of human cooperation, researchers have gleaned insights from the sociality of contemporary hunter-gatherers. A new study among the Hadza, one of the few surviving foraging populations, challenges popular approaches to cooperation while suggesting a central role for cultural transmission.
  • Roads threaten Asiatic cheetahs in Iran
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Jamshid Parchizadeh, Fraser Shilling, Maria Gatta, Roberta Bencini, Ali Turk Qashqaei, Mohammad Ali Adibi, Samual T. WilliamsSummaryWildlife–vehicle collisions are an important cause of mortality for many animal species. They also prove extremely detrimental to the critically endangered Asiatic cheetah (Acinonyx jubatus venaticus) 1, 2. One to two Asiatic cheetahs are killed by vehicles on Iran’s roads annually 3, 4. As such, the Asiatic cheetah could be the next charismatic felid subspecies to go extinct in the near future [5]. We identified one statistically-significant cluster of cheetah–vehicle collisions on the Shahroud-Sabzevar Highway (SSH), in Semnan Province. Because of the extremely small population of cheetahs and the corresponding difficulty of finding statistically-significant clusters, we propose that every single cheetah–vehicle collision should be considered important. We further recommend that wildlife underpasses and associated fencing be constructed in areas of previous cheetah–vehicle collisions.
  • Protection against the lethal side effects of social immunity in ants
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Christopher D. Pull, Sina Metzler, Elisabeth Naderlinger, Sylvia CremerSummaryMany animals use antimicrobials to prevent or cure disease 1, 2. For example, some animals will ingest plants with medicinal properties, both prophylactically to prevent infection and therapeutically to self-medicate when sick. Antimicrobial substances are also used as topical disinfectants, to prevent infection, protect offspring and to sanitise their surroundings 1, 2. Social insects (ants, bees, wasps and termites) build nests in environments with a high abundance and diversity of pathogenic microorganisms — such as soil and rotting wood — and colonies are often densely crowded, creating conditions that favour disease outbreaks. Consequently, social insects have evolved collective disease defences to protect their colonies from epidemics. These traits can be seen as functionally analogous to the immune system of individual organisms 3, 4. This ‘social immunity’ utilises antimicrobials to prevent and eradicate infections, and to keep the brood and nest clean. However, these antimicrobial compounds can be harmful to the insects themselves, and it is unknown how colonies prevent collateral damage when using them. Here, we demonstrate that antimicrobial acids, produced by workers to disinfect the colony, are harmful to the delicate pupal brood stage, but that the pupae are protected from the acids by the presence of a silk cocoon.
  • Marine plastics threaten giant Atlantic Marine Protected Areas
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): D.K.A. Barnes, S.A. Morley, J. Bell, P. Brewin, K. Brigden, M. Collins, T. Glass, W.P. Goodall-Copestake, L. Henry, V. Laptikhovsky, N. Piechaud, A. Richardson, P. Rose, C.J. Sands, A. Schofield, R. Shreeve, A. Small, T. Stamford, B. TaylorSummaryThere has been a recent shift in global perception of plastics in the environment, resulting in a call for greater action. Science and the popular media have highlighted plastic as an increasing stressor 1, 2. Efforts have been made to confer protected status to some remote locations, forming some of the world’s largest Marine Protected Areas, including several UK overseas territories. We assessed plastic at these remote Atlantic Marine Protected Areas, surveying the shore, sea surface, water column and seabed, and found drastic changes from 2013–2018. Working from the RRS James Clark Ross at Ascension, St. Helena, Tristan da Cunha, Gough and the Falkland Islands (Figure 1A), we showed that marine debris on beaches has increased more than 10 fold in the past decade. Sea surface plastics have also increased, with in-water plastics occurring at densities of 0.1 items m–3; plastics on seabeds were observed at ≤ 0.01 items m–2. For the first time, beach densities of plastics at remote South Atlantic sites approached those at industrialised North Atlantic sites. This increase even occurs hundreds of meters down on seamounts. We also investigated plastic incidence in 2,243 animals (comprising 26 species) across remote South Atlantic oceanic food webs, ranging from plankton to seabirds. We found that plastics had been ingested by primary consumers (zooplankton) to top predators (seabirds) at high rates. These findings suggest that MPA status will not mitigate the threat of plastic proliferation to this rich, unique and threatened biodiversity.
  • Avoiding death by feigning death
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): John SkelhornSummaryThanatosis is a common phenomenon in which prey appear to feign death when attacked by predators. It was once widely believed that thanatosis exploited predators’ tendencies to avoid dead prey. However, this hypothesis has never been tested, and its feasibility has been questioned to the point that it has been largely abandoned 1, 2. Here, I show that naive birds quickly learned that dead Indian stick insects Carausius morosus were unpalatable, and subsequently rejected live insects that displayed thanatosis, but not those that failed to show thanatosis. Thanatosis had no effect on the behavior of birds that had never experienced dead insects, or those that had experienced dead insects whose resemblance to thanatosic insects had been destroyed. Therefore, thanatosis clearly caused predators to avoid prey that they mistakenly perceived to be dead.
  • Chromokinesins
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Ana C. Almeida, Helder MaiatoSummaryDuring the cell cycle it is critical that the duplicated DNA faithfully segregates to give rise to two genetically identical daughter cells. An even distribution of the genome during mitosis is mediated by mitotic spindle microtubules, assisted by, among others, motor proteins of the kinesin superfamily. Chromokinesins are members of the kinesin superfamily that harbour a specific DNA-binding domain. The best characterized chromokinesins belong to the kinesin-4/Kif4 and kinesin-10/Kif22 families, respectively. Functional analysis of chromokinesins in several model systems revealed their involvement in chromosome arm orientation and oscillations. This is consistent with their originally proposed role in the generation of polar ejection forces that assist chromosome congression to the spindle equator. Kinesin-12/Kif15 members comprise a third family of chromokinesins, but their role remains less understood. Noteworthy, all chromokinesins exhibit chromosome-independent localization on spindle microtubules, and recent works have significantly extended the portfolio of mitotic processes in which chromokinesins play a role, from error correction and DNA compaction, to the regulation of spindle microtubule dynamics.
  • Sleep spindles
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Monika Schönauer, Dorothee Pöhlchen
  • Cryo-EM
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Eva Nogales
  • Animal aesthetics
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): D.J. Hosken
  • Jakob Vinther
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Jakob Vinther
  • Bee worries beyond neonicotinoids
    • Abstract: Publication date: 8 October 2018Source: Current Biology, Volume 28, Issue 19Author(s): Michael GrossSummaryAs the EU ban on the outdoor use of three neonicotinoids is about to come into force, a study shows a new alternative pesticide has similar sublethal but harmful effects. A good solution to the dilemma of distinguishing between useful insects and pests may not exist, but at least the amounts of pesticides released can be reduced. Michael Gross reports.
  • The Genomic Basis of Color Pattern Polymorphism in the Harlequin Ladybird
    • Abstract: Publication date: Available online 23 August 2018Source: Current BiologyAuthor(s): Mathieu Gautier, Junichi Yamaguchi, Julien Foucaud, Anne Loiseau, Aurélien Ausset, Benoit Facon, Bernhard Gschloessl, Jacques Lagnel, Etienne Loire, Hugues Parrinello, Dany Severac, Celine Lopez-Roques, Cecile Donnadieu, Maxime Manno, Helene Berges, Karim Gharbi, Lori Lawson-Handley, Lian-Sheng Zang, Heiko Vogel, Arnaud EstoupSummaryMany animal species comprise discrete phenotypic forms. A common example in natural populations of insects is the occurrence of different color patterns, which has motivated a rich body of ecological and genetic research [1, 2, 3, 4, 5, 6]. The occurrence of dark, i.e., melanic, forms displaying discrete color patterns is found across multiple taxa, but the underlying genomic basis remains poorly characterized. In numerous ladybird species (Coccinellidae), the spatial arrangement of black and red patches on adult elytra varies wildly within species, forming strikingly different complex color patterns [7, 8]. In the harlequin ladybird, Harmonia axyridis, more than 200 distinct color forms have been described, which classic genetic studies suggest result from allelic variation at a single, unknown, locus [9, 10]. Here, we combined whole-genome sequencing, population-based genome-wide association studies, gene expression, and functional analyses to establish that the transcription factor Pannier controls melanic pattern polymorphism in H. axyridis. We show that pannier is necessary for the formation of melanic elements on the elytra. Allelic variation in pannier leads to protein expression in distinct domains on the elytra and thus determines the distinct color patterns in H. axyridis. Recombination between pannier alleles may be reduced by a highly divergent sequence of ∼170 kb in the cis-regulatory regions of pannier, with a 50 kb inversion between color forms. This most likely helps maintain the distinct alleles found in natural populations. Thus, we propose that highly variable discrete color forms can arise in natural populations through cis-regulatory allelic variation of a single gene.Graphical Graphical abstract for this article
  • Warburg Effect Metabolism Drives Neoplasia in a Drosophila Genetic Model
           of Epithelial Cancer
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Teresa Eichenlaub, René Villadsen, Flávia C.P. Freitas, Diana Andrejeva, Blanca I. Aldana, Hung Than Nguyen, Ole William Petersen, Jan Gorodkin, Héctor Herranz, Stephen M. CohenSummaryCancers develop in a complex mutational landscape. Genetic models of tumor formation have been used to explore how combinations of mutations cooperate to promote tumor formation in vivo. Here, we identify lactate dehydrogenase (LDH), a key enzyme in Warburg effect metabolism, as a cooperating factor that is both necessary and sufficient for epidermal growth factor receptor (EGFR)-driven epithelial neoplasia and metastasis in a Drosophila model. LDH is upregulated during the transition from hyperplasia to neoplasia, and neoplasia is prevented by LDH depletion. Elevated LDH is sufficient to drive this transition. Notably, genetic alterations that increase glucose flux, or a high-sugar diet, are also sufficient to promote EGFR-driven neoplasia, and this depends on LDH activity. We provide evidence that increased LDHA expression promotes a transformed phenotype in a human primary breast cell culture model. Furthermore, analysis of publically available cancer data showed evidence of synergy between elevated EGFR and LDHA activity linked to poor clinical outcome in a number of human cancers. Altered metabolism has generally been assumed to be an enabling feature that accelerates cancer cell proliferation. Our findings provide evidence that sugar metabolism may have a more profound role in driving neoplasia than previously appreciated.
  • Modularity and Overcompensatory Growth in Ediacaran Rangeomorphs
           Demonstrate Early Adaptations for Coping with Environmental Pressures
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Charlotte G. Kenchington, Frances S. Dunn, Philip R. WilbySummaryThe first known diverse, complex, macroscopic benthic marine ecosystems (late Ediacaran, ca. 571–541 Ma) were dominated by the Rangeomorpha, an enigmatic group of extinct frondose eukaryotes that are candidate early metazoans [1, 2]. The group is characterized by a self-similar branching architecture that was most likely optimized for exchange, but nearly every other aspect of their biology is contentious [2, 3, 4]. We report locally enhanced, aberrant growth (“eccentric branching”) in a stalked, multifoliate rangeomorph—Hylaecullulus fordi n. gen., n. sp.—from Charnwood Forest (UK), confirming the presence of true biological modularity within the group. Random branches achieve unusually large proportions and mimic the architecture of their parent branch, rather than that of their neighbors (the norm). Their locations indicate exceptional growth at existing loci, rather than insertion at new sites. Analogous overcompensatory branching in extant modular organisms requires the capacity to orchestrate growth at specific sites and occurs most frequently in response to damage or environmental stress, allowing regeneration toward optimum morphology (e.g., [5, 6, 7]). Its presence in rangeomorphs indicates a hitherto unappreciated level of control to their growth plan, a previously unrecognized form of morphological plasticity within the group, and an ability to actively respond to external physical stimuli. The trait would have afforded rangeomorphs resilience to fouling and abrasion, partially accounting for their wide environmental tolerance, and may have pre-adapted them to withstand predation, weakening this argument for their extinction. Our findings highlight that multiple, phylogenetically disparate clades first achieved large size through modularity.
  • A Human Polymorphism in CHRNA5 Is Linked to Relapse to Nicotine Seeking in
           Transgenic Rats
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Benoit Forget, Petra Scholze, Francina Langa, Carole Morel, Stephanie Pons, Sarah Mondoloni, Morgane Besson, Romain Durand-de Cuttoli, Audrey Hay, Ludovic Tricoire, Bertrand Lambolez, Alexandre Mourot, Philippe Faure, Uwe MaskosSummaryTobacco addiction is a chronic and relapsing disorder with an important genetic component that represents a major public health issue. Meta-analysis of large-scale human genome-wide association studies (GWASs) identified a frequent non-synonymous SNP in the gene coding for the α5 subunit of nicotinic acetylcholine receptors (α5SNP), which significantly increases the risk for tobacco dependence and delays smoking cessation. To dissect the neuronal mechanisms underlying the vulnerability to nicotine addiction in carriers of the α5SNP, we created rats expressing this polymorphism using zinc finger nuclease technology and evaluated their behavior under the intravenous nicotine-self-administration paradigm. The electrophysiological responses of their neurons to nicotine were also evaluated. α5SNP rats self-administered more nicotine at high doses and exhibited higher nicotine-induced reinstatement of nicotine seeking than wild-type rats. Higher reinstatement was associated with altered neuronal activity in several discrete areas that are interconnected, including in the interpeduncular nucleus (IPN), a GABAergic structure that strongly expresses α5-containing nicotinic receptors. The altered reactivity of IPN neurons of α5SNP rats to nicotine was confirmed electrophysiologically. In conclusion, the α5SNP polymorphism is a major risk factor for nicotine intake at high doses and for relapse to nicotine seeking in rats, a dual effect that reflects the human condition. Our results also suggest an important role for the IPN in the higher relapse to nicotine seeking observed in α5SNP rats.
  • Distinct Predatory Behaviors in Scimitar- and Dirk-Toothed Sabertooth Cats
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Borja Figueirido, Stephan Lautenschlager, Alejandro Pérez-Ramos, Blaire Van ValkenburghSummaryOver the Cenozoic, large cat-like forms have convergently evolved into specialized killers of “megaherbivores” that relied on their large, and laterally compressed (saber-like) canines to rapidly subdue their prey [1, 2, 3, 4, 5]. Scimitar- and dirk-toothed sabertooths are distinct ecomorphs that differ in canine tooth length, degree of serration, and postcranial features indicative of dissimilar predatory behavior [6, 7, 8, 9, 10, 11, 12, 13]. Despite these differences, it is assumed that they used a similar “canine-shear” bite to kill their prey [14, 15]. We investigated the killing behavior of the scimitar-toothed Homotherium serum and the dirk-toothed Smilodon fatalis using a comparative sample of living carnivores and a new quantitative approach to the analysis of skull function. For the first time, we quantified differences in the relative amount and distribution of cortical and trabecular bone in coronal sections of skulls to assess relative skull stiffness and flexibility [16, 17, 18, 19]. We also use finite element analysis to simulate various killing scenarios that load skulls in ways that likely favor distinct proportions of cortical versus trabecular bone across the skull. Our data reveal that S. fatalis had an extremely thick skull and relatively little trabecular bone, consistent with a large investment in cranial strength for a stabbing canine-shear bite. However, H. serum had more trabecular bone and most likely deployed an unusual predatory behavior more similar to the clamp-and-hold technique of the lion than S. fatalis. These data broaden the killing repertoire of sabertooths and highlight the degree of ecological specialization among members of the large carnivore guild during the Late Pleistocene of North America.
  • Prevalence of Mutation-Prone Microhomology-Mediated End Joining in a
           Chordate Lacking the c-NHEJ DNA Repair Pathway
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Wei Deng, Simon Henriet, Daniel ChourroutSummaryClassical non-homologous end joining (c-NHEJ), a fundamental pathway that repairs double-strand breaks in DNA, is almost universal in eukaryotes and involves multiple proteins highly conserved from yeast to human [1]. The genes encoding these proteins were not detected in the genome of Oikopleura dioica, a new model system of tunicate larvaceans known for its very compact and highly rearranged genome [2, 3, 4]. After showing their absence in the genomes of six other larvacean species, the present study examined how O. dioica oocytes and embryos repair double-strand DNA breaks (DSBs), using two approaches: the injection of linearized plasmids, which resulted in their rapid end joining, and a newly established CRISPR Cas9 technique. In both cases, end joining merged short microhomologous sequences surrounding the break (mainly 4 bp long), thus inducing deletions larger than for the tunicate ascidian Ciona intestinalis and human cells. A relatively high frequency of nucleotide insertions was also observed. Finally, a survey of genomic indels supports the involvement of microhomology-mediated repair in natural conditions. Overall, O. dioica repairs DSBs as other organisms do when their c-NHEJ pathway is experimentally rendered deficient, using another mode of end joining with the same effect as alternative NHEJ (a-NHEJ) or microhomology-mediated end joining (MMEJ) [5, 6, 7]. We discuss how the exceptional loss of c-NHEJ and its replacement by a more mutation-prone mechanism may have contributed to reshaping this genome and even been advantageous under pressure for genome compaction.
  • Wild Birds Learn Songs from Experimental Vocal Tutors
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Daniel J. Mennill, Stéphanie M. Doucet, Amy E.M. Newman, Heather Williams, Ines G. Moran, Ian P. Thomas, Bradley K. Woodworth, D. Ryan NorrisSummaryIn eight groups of animals, including humans and songbirds, juveniles are understood to learn vocalizations by listening to adults [1, 2, 3, 4]. Experimental studies of laboratory-reared animals support this hypothesis for vocal learning [5, 6, 7], yet we lack experimental evidence of vocal learning in wild animals. We developed an innovative playback technology involving automated loudspeakers that broadcast songs with distinctive acoustic signatures. We used this technology to simulate vocal tutors in the wild and conducted year-long tutoring sessions to five cohorts of free-living migratory Savannah Sparrows in eastern Canada. We confirm that wild birds learn songs by listening to adult conspecific animals, and we show that they pass these songs on to subsequent generations. Further, we provide the first experimental evidence in the wild that the timing of exposure to tutor song influences vocal learning: wild Savannah Sparrows preferentially learn songs heard during both their natal summer and at the outset of their first breeding season. This research provides direct experimental evidence of song learning by wild animals and shows that wild birds learn songs during two critical stages of development early in life.Graphical Graphical abstract for this article
  • Shugoshin Is Essential for Meiotic Prophase Checkpoints in
           C. elegans
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Tisha Bohr, Christian R. Nelson, Stefani Giacopazzi, Piero Lamelza, Needhi BhallaSummaryThe conserved factor Shugoshin is dispensable in C. elegans for the two-step loss of sister chromatid cohesion that directs the proper segregation of meiotic chromosomes. We show that the C. elegans ortholog of Shugoshin, SGO-1, is required for checkpoint activity in meiotic prophase. This role in checkpoint function is similar to that of conserved proteins that structure meiotic chromosome axes. Indeed, null sgo-1 mutants exhibit additional phenotypes similar to that of a partial loss-of-function allele of the axis component, HTP-3: premature synaptonemal complex disassembly, the activation of alternate DNA repair pathways, and an inability to recruit a conserved effector of the DNA damage pathway, HUS-1. SGO-1 localizes to pre-meiotic nuclei when HTP-3 is present but not yet loaded onto chromosome axes and genetically interacts with a central component of the cohesin complex, SMC-3, suggesting that it contributes to meiotic chromosome metabolism early in meiosis by regulating cohesin. We propose that SGO-1 acts during pre-meiotic replication to ensure fully functional meiotic chromosome architecture, rendering these chromosomes competent for checkpoint activity and normal progression of meiotic recombination. Given that most research on Shugoshin has focused on its regulation of sister chromatid cohesion during chromosome segregation, this novel role may be conserved but previously uncharacterized in other organisms. Further, our findings expand the repertoire of Shugoshin’s functions beyond coordinating regulatory activities at the centromere.Graphical Graphical abstract for this article
  • Intraflagellar Transport Complex A Genes Differentially Regulate Cilium
           Formation and Transition Zone Gating
    • Abstract: Publication date: Available online 4 October 2018Source: Current BiologyAuthor(s): Noémie Scheidel, Oliver E. BlacqueSummaryCilia are found on most eukaryotic cell types, serving motility, environment sensing, and signaling (cell-cell) functions, and defects cause genetic diseases (ciliopathies), affecting the development of many tissues [1]. Cilia are built by intraflagellar transport (IFT), a bidirectional microtubule-based motility driven by kinesin-2 anterograde (toward ciliary tip) and IFT-dynein retrograde (toward ciliary base) motors together with IFT-A and IFT-B cargo adaptor complexes that control retrograde and anterograde IFT, respectively [2]. Ciliary composition is also facilitated by the transition zone (TZ) at the ciliary base and the associated Meckel-Gruber syndrome (MKS) and nephronophthisis (NPHP) modules that establish protein diffusion barriers and regulate cilium structure [3]. Although the molecular architecture of the IFT machine is emerging [2], how individual components contribute to cilium subtype formation and IFT remains relatively unexplored, especially in vivo. In addition, little is known about functional interactions between IFT and TZ modules. Here, in Caenorhabditis elegans (roundworms), we identify cell-type-specific mechanisms by which IFT-A sculpts the structures of discrete ciliary subtypes and regulates IFT. We also uncover differential roles for IFT-A subunits in controlling the TZ restriction of MKS module components and ciliary exclusion (gating) of periciliary membrane proteins, with IFT-140 controlling their ciliary entry and IFT-43/121/139 controlling their ciliary removal. Furthermore, we determine that IFT-A and MKS module components synergistically interact to determine cilium structure. Overall, this work provides insight into the functional architecture of a metazoan IFT-A complex in different cell types and uncovers new relationships between ciliopathy-associated IFT-A and TZ modules.
  • Whole-Brain Multimodal Neuroimaging Model Using Serotonin Receptor Maps
           Explains Non-linear Functional Effects of LSD
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Gustavo Deco, Josephine Cruzat, Joana Cabral, Gitte M. Knudsen, Robin L. Carhart-Harris, Peter C. Whybrow, Nikos K. Logothetis, Morten L. KringelbachSummaryUnderstanding the underlying mechanisms of the human brain in health and disease will require models with necessary and sufficient details to explain how function emerges from the underlying anatomy and is shaped by neuromodulation. Here, we provide such a detailed causal explanation using a whole-brain model integrating multimodal imaging in healthy human participants undergoing manipulation of the serotonin system. Specifically, we combined anatomical data from diffusion magnetic resonance imaging (dMRI) and functional magnetic resonance imaging (fMRI) with neurotransmitter data obtained with positron emission tomography (PET) of the detailed serotonin 2A receptor (5-HT2AR) density map. This allowed us to model the resting state (with and without concurrent music listening) and mechanistically explain the functional effects of 5-HT2AR stimulation with lysergic acid diethylamide (LSD) on healthy participants. The whole-brain model used a dynamical mean-field quantitative description of populations of excitatory and inhibitory neurons as well as the associated synaptic dynamics, where the neuronal gain function of the model is modulated by the 5-HT2AR density. The model identified the causative mechanisms for the non-linear interactions between the neuronal and neurotransmitter system, which are uniquely linked to (1) the underlying anatomical connectivity, (2) the modulation by the specific brainwide distribution of neurotransmitter receptor density, and (3) the non-linear interactions between the two. Taking neuromodulatory activity into account when modeling global brain dynamics will lead to novel insights into human brain function in health and disease and opens exciting possibilities for drug discovery and design in neuropsychiatric disorders.
  • Autophagy Promotes Tumor-like Stem Cell Niche Occupancy
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Shaowei Zhao, Tina M. Fortier, Eric H. BaehreckeSummaryAdult stem cells usually reside in specialized niche microenvironments. Accumulating evidence indicates that competitive niche occupancy favors stem cells with oncogenic mutations, also known as tumor-like stem cells. However, the mechanisms that regulate tumor-like stem cell niche occupancy are largely unknown. Here, we use Drosophila ovarian germline stem cells as a model and use bam mutant cells as tumor-like stem cells. Interestingly, we find that autophagy is low in wild-type stem cells but elevated in bam mutant stem cells. Significantly, autophagy is required for niche occupancy by bam mutant stem cells. Although loss of either atg6 or Fip200 alone in stem cells does not impact their competitiveness, loss of these conserved regulators of autophagy decreases bam mutant stem cell niche occupancy. In addition, starvation enhances the competition of bam mutant stem cells for niche occupancy in an autophagy-dependent manner. Of note, loss of autophagy slows the cell cycle of bam mutant stem cells and does not influence stem cell death. In contrast to canonical epithelial cell competition, loss of regulators of tissue growth, either the insulin receptor or cyclin-dependent kinase 2 function, influences the competition of bam mutant stem cells for niche occupancy. Additionally, autophagy promotes the tumor-like growth of bam mutant ovaries. Autophagy is known to be induced in a wide variety of tumors. Therefore, these results suggest that specifically targeting autophagy in tumor-like stem cells has potential as a therapeutic strategy.Graphical Graphical abstract for this article
  • Visual Detection and Avoidance of Pathogenic Bacteria by Aphids
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Tory A. Hendry, Russell A. Ligon, Kevin R. Besler, Rachel L. Fay, Melanie R. SmeeSummaryAphids are diverse sap-sucking insects [1] that can be serious agricultural pests and vectors of plant disease [2]. Some species, including pea aphids (Acyrthosiphon pisum), are susceptible to infection by epiphytic bacteria that are commonly found on plant surfaces [3, 4, 5]. Pea aphids appear unable to recover from these infections, possibly because pea aphids are missing apparent orthologs of some immune response genes [6], and these aphids exhibit relatively low immune responses after pathogen exposure [7]. We therefore tested the ability of pea aphids to use avoidance as a non-immunological defense against Pseudomonas syringae, a widespread plant epiphyte and aphid pathogen [8, 9]. Pea aphids avoided highly virulent strains of P. syringae, but not all strains, and avoidance led to a significant reduction in infection among aphids. We found that aphids can use visual cues to detect the ultraviolet (UV)-based fluorescence of the bacterial siderophore pyoverdine [10] produced by virulent strains. Avoided epiphytic bacteria caused light leaving the surface of leaves to be richer in wavelengths that were tightly linked to both aphid visual sensitivities and the fluorescent emission spectra of pyoverdine, suggesting that pyoverdine fluorescence mediates avoidance and may be a visual cue used by aphids to detect epiphytic pathogens. Although pyoverdine production in Pseudomonas species may be a broadly reliable indicator of bacterial virulence within the phyllosphere, it was not directly responsible for virulence to aphids. Aphids may be under selection to avoid fluorescence on leaves, a phenomenon with potential use for the control of agricultural pest insects.
  • Reproductive Longevity Predicts Mutation Rates in Primates
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Gregg W.C. Thomas, Richard J. Wang, Arthi Puri, R. Alan Harris, Muthuswamy Raveendran, Daniel S.T. Hughes, Shwetha C. Murali, Lawrence E. Williams, Harsha Doddapaneni, Donna M. Muzny, Richard A. Gibbs, Christian R. Abee, Mary R. Galinski, Kim C. Worley, Jeffrey Rogers, Predrag Radivojac, Matthew W. HahnSummaryMutation rates vary between species across several orders of magnitude, with larger organisms having the highest per-generation mutation rates. Hypotheses for this pattern typically invoke physiological or population-genetic constraints imposed on the molecular machinery preventing mutations [1]. However, continuing germline cell division in multicellular eukaryotes means that organisms with longer generation times and of larger size will leave more mutations to their offspring simply as a byproduct of their increased lifespan [2, 3]. Here, we deeply sequence the genomes of 30 owl monkeys (Aotus nancymaae) from six multi-generation pedigrees to demonstrate that paternal age is the major factor determining the number of de novo mutations in this species. We find that owl monkeys have an average mutation rate of 0.81 × 10−8 per site per generation, roughly 32% lower than the estimate in humans. Based on a simple model of reproductive longevity that does not require any changes to the mutational machinery, we show that this is the expected mutation rate in owl monkeys. We further demonstrate that our model predicts species-specific mutation rates in other primates, including study-specific mutation rates in humans based on the average paternal age. Our results suggest that variation in life history traits alone can explain variation in the per-generation mutation rate among primates, and perhaps among a wide range of multicellular organisms.
  • Latrunculin A Accelerates Actin Filament Depolymerization in Addition to
           Sequestering Actin Monomers
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Ikuko Fujiwara, Mark E. Zweifel, Naomi Courtemanche, Thomas D. PollardSummaryLatrunculin A (LatA), a toxin from the red sea sponge Latrunculia magnifica, is the most widely used reagent to depolymerize actin filaments in experiments on live cells. LatA binds actin monomers and sequesters them from polymerization [1, 2]. Low concentrations of LatA result in rapid (tens of seconds) disassembly of actin filaments in animal [3] and yeast cells [2]. Depolymerization is usually assumed to result from sequestration of actin monomers. Our observations of single-muscle actin filaments by TIRF microscopy showed that LatA bound ATP-actin monomers with a higher affinity (Kd = 0.1 μM) than ADP-Pi-actin (Kd = 0.4 μM) or ADP-actin (Kd = 4.7 μM). LatA also slowly severed filaments and increased the depolymerization rate at both ends of filaments freshly assembled from ATP-actin to the rates of ADP-actin. This rate plateaued at LatA concentrations>60 μM. LatA did not change the depolymerization rates of ADP- actin filaments or ADP-Pi-actin filaments generated with 160 mM phosphate in the buffer. LatA did not increase the rate of phosphate release from bulk samples of filaments assembled from ATP-actin. Thermodynamic analysis showed that LatA binds weakly to actin filaments with a Kd>100 μM. We propose that concentrations of LatA much lower than this Kd promote phosphate dissociation only from both ends of filaments, resulting in depolymerization limited by the rate of ADP-actin dissociation. Thus, one must consider both rapid actin depolymerization and severing in addition to sequestering actin monomers when interpreting the effects of LatA on cells.Graphical Graphical abstract for this article
  • The Xerobranching Response Represses Lateral Root Formation When Roots Are
           Not in Contact with Water
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Beata Orman-Ligeza, Emily C. Morris, Boris Parizot, Tristan Lavigne, Aurelie Babé, Aleksander Ligeza, Stephanie Klein, Craig Sturrock, Wei Xuan, Ondřey Novák, Karin Ljung, Maria A. Fernandez, Pedro L. Rodriguez, Ian C. Dodd, Ive De Smet, Francois Chaumont, Henri Batoko, Claire Périlleux, Jonathan P. Lynch, Malcolm J. BennettSummaryEfficient soil exploration by roots represents an important target for crop improvement and food security [1, 2]. Lateral root (LR) formation is a key trait for optimizing soil foraging for crucial resources such as water and nutrients. Here, we report an adaptive response termed xerobranching, exhibited by cereal roots, that represses branching when root tips are not in contact with wet soil. Non-invasive X-ray microCT imaging revealed that cereal roots rapidly repress LR formation as they enter an air space within a soil profile and are no longer in contact with water. Transcript profiling of cereal root tips revealed that transient water deficit triggers the abscisic acid (ABA) response pathway. In agreement with this, exogenous ABA treatment can mimic repression of LR formation under transient water deficit. Genetic analysis in Arabidopsis revealed that ABA repression of LR formation requires the PYR/PYL/RCAR-dependent signaling pathway. Our findings suggest that ABA acts as the key signal regulating xerobranching. We conclude that this new ABA-dependent adaptive mechanism allows roots to rapidly respond to changes in water availability in their local micro-environment and to use internal resources efficiently.Graphical Graphical abstract for this article
  • A Wake-Promoting Circadian Output Circuit in Drosophila
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Angélique Lamaze, Patrick Krätschmer, Ko-Fan Chen, Simon Lowe, James E.C. JepsonSummaryCircadian clocks play conserved roles in gating sleep and wake states throughout the day-night cycle [1, 2, 3, 4, 5]. In the fruit fly Drosophila melanogaster, DN1p clock neurons have been reported to play both wake- and sleep-promoting roles [6, 7, 8, 9, 10, 11], suggesting a complex coupling of DN1p neurons to downstream sleep and arousal centers. However, the circuit logic by which DN1p neurons modulate sleep remains poorly understood. Here, we show that DN1p neurons can be divided into two morphologically distinct subsets. Projections from one subset surround the pars intercerebralis, a previously defined circadian output region [12]. In contrast, the second subset also sends presynaptic termini to a visual processing center, the anterior optic tubercle (AOTU) [13]. Within the AOTU, we find that DN1p neurons inhibit a class of tubercular-bulbar (TuBu) neurons that act to promote consolidated sleep. These TuBu neurons in turn form synaptic connections with R neurons of the ellipsoid body, a region linked to visual feature detection, locomotion, spatial memory, and sleep homeostasis [14, 15, 16, 17]. Our results define a second output arm from DN1p neurons and suggest a role for TuBu neurons as regulators of sleep drive.Graphical Graphical abstract for this article
  • A Giant Dinosaur from the Earliest Jurassic of South Africa and the
           Transition to Quadrupedality in Early Sauropodomorphs
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Blair W. McPhee, Roger B.J. Benson, Jennifer Botha-Brink, Emese M. Bordy, Jonah N. ChoiniereSummarySauropod dinosaurs were dominant, bulk-browsing herbivores for 130 million years of the Mesozoic, attaining gigantic body masses in excess of 60 metric tons [1, 2]. A columnar-limbed, quadrupedal posture enabled these giant body sizes [3], but the nature of the transition from bipedal sauropodomorph ancestors to derived quadrupeds remains contentious [4, 5, 6]. We describe a gigantic, new sauropodomorph from the earliest Jurassic of South Africa weighing 12 metric tons and representing a phylogenetically independent origin of sauropod-like body size in a non-sauropod. Osteohistological evidence shows that this specimen was an adult of maximum size and approximately 14 years old at death. Ledumahadi mafube gen. et sp. nov. shows that gigantic body sizes were possible in early sauropodomorphs, which were habitual quadrupeds but lacked the derived, columnar limb postures of sauropods. We use data from this new taxon and a discriminant analysis of tetrapod limb measurements to study postural evolution in sauropodomorphs. Our results show that quadrupedality appeared by the mid-Late Triassic (Norian), well outside of Sauropoda. Secondary reversion to bipedality occurred in some lineages phylogenetically close to Sauropoda, indicating early experimentation in locomotory styles. Morphofunctional observations support the hypothesis that partially flexed (rather than columnar) limbs characterized Ledumahadi and other early-branching quadrupedal sauropodomorphs. Patterns of locomotory and body-size evolution show that quadrupedality allowed Triassic sauropodomorphs to achieve body sizes of at least 3.8 metric tons. Ledumahadi’s Early Jurassic age shows that maximum body mass in sauropodomorph dinosaurs was either unaffected or rapidly rebounded after the end-Triassic extinction event.Graphical Graphical abstract for this article
  • No Discrete Start/Stop Signals in the Dorsal Striatum of Mice Performing a
           Learned Action
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Carola Sales-Carbonell, Wahiba Taouali, Loubna Khalki, Matthieu O. Pasquet, Ludovic F. Petit, Typhaine Moreau, Pavel E. Rueda-Orozco, David RobbeSummaryA popular hypothesis is that the dorsal striatum generates discrete “traffic light” signals that initiate, maintain, and terminate the execution of learned actions. Alternatively, the striatum may continuously monitor the dynamics of movements associated with action execution by processing inputs from somatosensory and motor cortices. Here, we recorded the activity of striatal neurons in mice performing a run-and-stop task and characterized the diversity of firing rate modulations relative to run performance (tuning curves) across neurons. We found that the tuning curves could not be statistically clustered in discrete functional groups (start or stop neurons). Rather, their shape varied continuously according to the movement dynamics of the task. Moreover, striatal spiking activity correlated with running speed on a run-by-run basis and was modulated by task-related non-locomotor movements, such as licking. We hypothesize that such moment-to-moment movement monitoring by the dorsal striatum contributes to the learning of adaptive actions and/or updating their kinematics.
  • FERONIA Receptor Kinase Contributes to Plant Immunity by Suppressing
           Jasmonic Acid Signaling in Arabidopsis thaliana
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Hongqing Guo, Trevor M. Nolan, Gaoyuan Song, Sanzhen Liu, Zhouli Xie, Jiani Chen, Patrick S. Schnable, Justin W. Walley, Yanhai YinSummaryBacterial pathogens use effectors and phytotoxins to facilitate infection of host plants. Coronatine (COR) is one of the phytotoxins produced in bacterial pathogens, such as Pseudomonas syringae pv. tomato DC3000 (pst DC3000). COR structurally and functionally mimics the active form of the plant hormone jasmonic acid (JA), JA-isoleucine (JA-Ile), and can hijack the host JA-signaling pathway to achieve host disease susceptibility [1]. COR utilizes the transcription factor MYC2, a master regulator of JA signaling, to activate NAC transcription factors, which functions to inhibit accumulation of salicylic acid (SA) and thus compromise host immunity [2]. It has been demonstrated that SA can antagonize JA signaling through NONEXPRESSOR of PATHOGENESIS-RELATED GENE1 (NPR1) [3] and downstream transcription factors TGAs [4] and WRKYs [5, 6]. However, the detailed mechanism by which host plants counteract COR-mediated susceptibility is largely unknown. Here, we show that the receptor kinase FERONIA (FER) functions to inhibit JA and COR signaling by phosphorylating and destabilizing MYC2, thereby positively regulating immunity. Conversely, the peptide ligand RALF23 acts through FER to stabilize MYC2 and elevate JA signaling, negatively contributing to plant immunity. Our results establish the RALF23-FER-MYC2 signaling module and provide a previously unknown mechanism by which host plants utilize FER signaling to counteract COR-mediated host disease susceptibility.
  • Crozier’s Effect and the Acceptance of Intraspecific Brood Parasites
    • Abstract: Publication date: Available online 27 September 2018Source: Current BiologyAuthor(s): Jeremy Field, Chris Accleton, William A. FosterSummaryOrganisms can often benefit by distinguishing between different classes of individuals. An example is kin recognition, whereby individuals preferentially associate with or aid genetic relatives that bear matching recognition cues but reject others. Despite its potential benefits, however, kin recognition using genetically based cues is often weak or absent [1, 2, 3, 4]. A general explanation, termed “Crozier’s effect,” is that when individuals interact randomly, rarer cue alleles less often match cues of other individuals, and so are involved predominantly in “reject”-type interactions. If such interactions are more costly, positive frequency-dependent selection will erode the cue diversity upon which discrimination depends [4, 5]. Although widely cited [1, 2, 4, 6, 7, 8, 9], this idea lacks rigorous testing in the field. Here, we show how Crozier’s effect applies to interactions between hosts and conspecific parasites, and measure it using field data. In the wasp we studied, conspecific parasitism fits a key assumption of Crozier’s model: the same females act as both hosts and parasites. By exchanging offspring between nests experimentally, we find no evidence that females respond to genetically based cues associated with foreign offspring. Through measuring costs and benefits, however, we demonstrate a strong Crozier effect: because more parental investment is wasted when foreign offspring are rejected, interactions involving rejection have substantially lower payoffs than interactions involving acceptance. Costly rejection can thus eliminate cue diversity by causing selection against rare cue alleles, consistent with the absence of genetically based recognition that we observe. Females instead appear to rely on non-genetic cues that enable them to detect less than half of parasitic offspring.
  • Evolution: Plasticity versus Selection, or Plasticity and Selection'
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Blair W. Perry, Drew R. Schield, Todd A. CastoeSummaryWhether phenotypic plasticity enables or hinders genetic adaptation has been debated for over a century. A study of lizard coloration uncovers the means by which plasticity can facilitate colonization of novel environments and enable eventual adaptation by natural selection.
  • Gut Microbiota: IgA Protects the Pioneers
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Whitman B. Schofield, Noah W. PalmSummaryThe secretory antibody immunoglobulin A counteracts pathogenic infections at mucosal surfaces. Recent work now reveals that IgA responses can also stabilize intestinal colonization by symbiotic microorganisms and confer resistance to future invasion by exogenous competitors.
  • Vision: Microcircuits Rage against the Dimming of the Light
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Benjamin Sivyer, Henrique von GersdorffSummaryAt sundown when light levels fall, rod photoreceptors take the night shift from the daylight-sensitive cones and a specialized mammalian microcircuit ‘wires’ the rods into the ancestral cone pathway. A recent study combines serial electron microscopy and simultaneous patch clamp recordings to shed light on this microcircuit in unprecedented detail.
  • Superior Colliculus: A Vision for Orienting
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Ziad M. HafedSummaryThe superior colliculus contains neurons sensitive to motion direction. New research shows that these neurons are anatomically clustered: those representing the region of visual space ‘seen’ by both eyes preferentially respond to nasal motion directions and others to opposite directions.
  • Corvid Technologies: How Do New Caledonian Crows Get Their Tool
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Christian Rutz, Gavin R. Hunt, James J.H. St ClairSummaryRecent research shows that New Caledonian crows can incorporate information from researcher-made objects into objects they subsequently manufacture. This ‘mental template matching’ is one of several possible — mutually compatible — mechanisms for the cultural transmission of tool designs among wild crows.
  • Neuroscience: Intracranial Recordings of Value
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Paula Kaanders, Laurence T. HuntSummaryThe role of orbitofrontal cortex in value-based choice is well-established from animal research, but there are challenges in relating neurophysiological recordings from animals to equivalent data from humans: a new study bridges this gap.
  • Speech Entrainment: Rhythmic Predictions Carried by Neural Oscillations
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Benedikt ZoefelSummaryIt has been hypothesized that stimulus-aligned brain rhythms reflect predictions about upcoming input. New research shows that these rhythms bias subsequent speech perception, in line with a mechanism of prediction.
  • Plant Genetics: Two Steps on the Path to Maize Adaptation
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): James B. HollandSummaryTwo distinct variations in the promoter of a key flowering time gene were selected during the spread of maize from its tropical origin to northern North America.
  • Cognitive Neuroscience: Exciting Developments in Schematic Learning
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Frances Xia, Paul W. FranklandSummaryLearning, in context of prior knowledge, engages NMDAR-independent mechanisms. However, which aspects of previous learning are responsible for this phenomenon remain unclear. New evidence shows that procedural similarity between learning events is the key determinant for engaging NMDAR-independent mechanisms.
  • Medial prefrontal cortex supports perceptual memory
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Caspar M. Schwiedrzik, Sandrin S. Sudmann, Thomas Thesen, Xiuyuan Wang, David M. Groppe, Pierre Mégevand, Werner Doyle, Ashesh D. Mehta, Orrin Devinsky, Lucia MelloniSummaryOur visual environment constantly changes, yet we experience the world as a stable, unified whole. How is this stability achieved' It has been proposed that the brain preserves an implicit perceptual memory in sensory cortices [1] which stabilizes perception towards previously experienced states 2, 3. The role of higher-order areas, especially prefrontal cortex (PFC), in perceptual memory is less explored. Because PFC exhibits long neural time constants, invariance properties, and large receptive fields which may stabilize perception against time-varying inputs, it seems particularly suited to implement perceptual memory [4]. Support for this idea comes from a neuroimaging study reporting that dorsomedial PFC (dmPFC) correlates with perceptual memory [5]. But dmPFC also participates in decision making [6], so its contribution to perceptual memory could arise on a post-perceptual, decisional level [7]. To determine which role, if any, PFC plays in perceptual memory, we obtained direct intracranial recordings in six epilepsy patients while they performed sequential orientation judgements on ambiguous stimuli known to elicit perceptual memory [8]. We found that dmPFC activity in the high gamma frequency band (HGB, 70–150 Hz) correlates with perceptual memory. This effect is anatomically specific to dmPFC and functionally specific for memories of preceding percepts. Further, dmPFC appears to play a causal role, as a patient with a lesion in this area showed impaired perceptual memory. Thus, dmPFC integrates current sensory information with prior percepts, stabilizing visual experience against the perpetual variability of our surroundings.
  • Lateral eyes direct principal eyes as jumping spiders track objects
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Elizabeth M. Jakob, Skye M. Long, Duane P. Harland, Robert R. Jackson, Ashley Carey, Mary Emma Searles, Adam H. Porter, Cristina Canavesi, Jannick P. RollandSummaryOne way of circumventing the functional tradeoffs on eye design 1, 2 is to have different eyes for different tasks. For example, jumping spiders (Salticidae), known for elaborate, visually guided courtship and predatory behavior [3], view the same object simultaneously with two of their four pairs of eyes: the antero-lateral eyes (ALEs) and the principal eyes (reviewed in [2]; Figure 1A). The ALEs, with immobile lenses and retinas, wide fields of view, and hyperacute sensitivity to moving stimuli [4], are structurally distinct from the principal eyes, which have the best spatial acuity known for terrestrial invertebrates and can discern fine details of stationary objects [5]. Behind the immobile corneal lenses of the principal eyes are miniature, boomerang-shaped retinas with correspondingly small fields of view (Figure 1B). The principal-eye visual fields are greatly expanded and overlap because of eye movements: these retinas are at the proximal ends of long, moveable tubes within the spider’s cephalothorax [6]. By designing and using a specialized eyetracker, we tested whether principal-eye gaze direction is influenced by what the ALEs see. The principal eyes scanned stationary objects regardless of whether the ALEs were masked, but only when the ALEs were unmasked did the principal eyes smoothly track moving disks. The principal eyes, with high acuity but a narrow field of view, can thus precisely target moving stimuli, but only with the guidance of the secondary eyes.
  • Heterosis in plants
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Frank Hochholdinger, Jutta A. Baldauf
  • Orbitofrontal cortex
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Peter H. Rudebeck, Erin L. Rich
  • Mobbing
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Nora V. Carlson, Susan D. Healy, Christopher N. Templeton
  • Sabrina Sabatini
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Sabrina Sabatini
  • Science careers — improve your effectiveness but keep your passion
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Robert Insall
  • Can botanic gardens save all plants'
    • Abstract: Publication date: 24 September 2018Source: Current Biology, Volume 28, Issue 18Author(s): Michael GrossSummaryEarly botanic gardens served medicine, and then they became important for biological research as well as for the transfer of crop species around the globe. Today, they are important sites for outreach and education, but globally their most crucial role may be in conservation. Will they be able to save every plant known to science' Michael Gross reports.
  • A Conserved Role for Serotonergic Neurotransmission in Mediating Social
           Behavior in Octopus
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Eric Edsinger, Gül DölenSummaryHuman and octopus lineages are separated by over 500 million years of evolution [1, 2] and show divergent anatomical patterns of brain organization [3, 4]. Despite these differences, growing evidence suggests that ancient neurotransmitter systems are shared across vertebrate and invertebrate species and in many cases enable overlapping functions [5]. Sociality is widespread across the animal kingdom, with numerous examples in both invertebrate (e.g., bees, ants, termites, and shrimps) and vertebrate (e.g., fishes, birds, rodents, and primates) lineages [6]. Serotonin is an evolutionarily ancient molecule [7] that has been implicated in regulating both invertebrate [8] and vertebrate [9] social behaviors, raising the possibility that this neurotransmitter’s prosocial functions may be conserved across evolution. Members of the order Octopoda are predominantly asocial and solitary [10]. Although at this time it is unknown whether serotonergic signaling systems are functionally conserved in octopuses, ethological studies indicate that agonistic behaviors are suspended during mating [11, 12, 13], suggesting that neural mechanisms subserving social behaviors exist in octopuses but are suppressed outside the reproductive period. Here we provide evidence that, as in humans, the phenethylamine (+/−)-3,4-methylendioxymethamphetamine (MDMA) enhances acute prosocial behaviors in Octopus bimaculoides. This finding is paralleled by the evolutionary conservation of the serotonin transporter (SERT, encoded by the Slc6A4 gene) binding site of MDMA in the O. bimaculoides genome. Taken together, these data provide evidence that the neural mechanisms subserving social behaviors exist in O. bimaculoides and indicate that the role of serotonergic neurotransmission in regulating social behaviors is evolutionarily conserved.
  • SHOU4 Proteins Regulate Trafficking of Cellulose Synthase Complexes to the
           Plasma Membrane
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Joanna K. Polko, William J. Barnes, Cătălin Voiniciuc, Stephanie Doctor, Blaire Steinwand, Joseph L. Hill, Ming Tien, Markus Pauly, Charles T. Anderson, Joseph J. KieberSummaryCell walls play critical roles in plants, regulating tissue mechanics, defining the extent and orientation of cell expansion, and providing a physical barrier against pathogen attack [1]. Cellulose microfibrils, which are synthesized by plasma membrane-localized cellulose synthase (CESA) complexes, are the primary load-bearing elements of plant cell walls [2]. Cell walls are dynamic structures that are regulated in part by cell wall integrity (CWI)-monitoring systems that feed back to modulate wall properties and the synthesis of new wall components [3]. Several receptor-like kinases have been implicated as sensors of CWI [3, 4, 5], including the FEI1/FEI2 receptor-like kinases [4]. Here, we characterize two genes encoding novel plant-specific plasma membrane proteins (SHOU4 and SHOU4L) that were identified in a suppressor screen of the cellulose-deficient fei1 fei2 mutant. shou4 shou4l double mutants display phenotypes consistent with elevated levels of cellulose, and elevated levels of non-crystalline cellulose are present in this mutant. Disruption of SHOU4 and SHOU4L increases the abundance of CESA proteins at the plasma membrane as a result of enhanced exocytosis. The SHOU4/4L N-terminal cytosolic domains directly interact with CESAs. Our results suggest that the SHOU4 proteins regulate cellulose synthesis in plants by influencing the trafficking of CESA complexes to the cell surface.Graphical Graphical abstract for this article
  • Understanding the Molecular Basis of Salt Sequestration in Epidermal
           Bladder Cells of Chenopodium quinoa
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Jennifer Böhm, Maxim Messerer, Heike M. Müller, Joachim Scholz-Starke, Antonella Gradogna, Sönke Scherzer, Tobias Maierhofer, Nadia Bazihizina, Heng Zhang, Christian Stigloher, Peter Ache, Khaled A.S. Al-Rasheid, Klaus F.X. Mayer, Sergey Shabala, Armando Carpaneto, Georg Haberer, Jian-Kang Zhu, Rainer HedrichSummarySoil salinity is destroying arable land and is considered to be one of the major threats to global food security in the 21st century. Therefore, the ability of naturally salt-tolerant halophyte plants to sequester large quantities of salt in external structures, such as epidermal bladder cells (EBCs), is of great interest. Using Chenopodium quinoa, a pseudo-cereal halophyte of great economic potential, we have shown previously that, upon removal of salt bladders, quinoa becomes salt sensitive. In this work, we analyzed the molecular mechanism underlying the unique salt dumping capabilities of bladder cells in quinoa. The transporters differentially expressed in the EBC transcriptome and functional electrophysiological testing of key EBC transporters in Xenopus oocytes revealed that loading of Na+ and Cl− into EBCs is mediated by a set of tailored plasma and vacuole membrane-based sodium-selective channel and chloride-permeable transporter.
  • A Plausible Microtubule-Based Mechanism for Cell Division Orientation in
           Plant Embryogenesis
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Bandan Chakrabortty, Viola Willemsen, Thijs de Zeeuw, Che-Yang Liao, Dolf Weijers, Bela Mulder, Ben ScheresSummaryOriented cell divisions are significant in plant morphogenesis because plant cells are embedded in cell walls and cannot relocate. Cell divisions follow various regular orientations, but the underlying mechanisms have not been clarified. We propose that cell-shape-dependent self-organization of cortical microtubule arrays is able to provide a mechanism for determining planes of early tissue-generating divisions and may form the basis for robust control of cell division orientation in the embryo. To show this, we simulate microtubules on actual cell surface shapes, from which we derive a minimal set of three rules for proper array orientation. The first rule captures the effects of cell shape alone on microtubule organization, the second rule describes the regulation of microtubule stability at cell edges, and the third rule includes the differential effect of auxin on local microtubule stability. These rules generate early embryonic division plane orientations and potentially offer a framework for understanding patterned cell divisions in plant morphogenesis.Graphical Graphical abstract for this article
  • Inactivation of Medial Frontal Cortex Changes Risk Preference
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Xiaomo Chen, Veit StuphornSummaryHumans and other animals need to make decisions under varying degrees of uncertainty. These decisions are strongly influenced by an individual’s risk preference; however, the neuronal circuitry by which risk preference shapes choice is still unclear [1]. Supplementary eye field (SEF), an oculomotor area within primate medial frontal cortex, is thought to be an essential part of the neuronal circuit underlying oculomotor decision making, including decisions under risk [2, 3, 4, 5]. Consistent with this view, risk-related action value and monitoring signals have been observed in SEF [6, 7, 8]. However, such activity has also been observed in other frontal areas, including orbitofrontal [9, 10, 11], cingulate [12, 13, 14], and dorsal-lateral frontal cortex [15]. It is thus unknown whether the activity in SEF causally contributes to risky decisions, or whether it is merely a reflection of neural processes in other cortical regions. Here, we tested a causal role of SEF in risky oculomotor choices. We found that SEF inactivation strongly reduced the frequency of risky choices. This reduction was largely due to a reduced attraction to reward uncertainty and high reward gain, but not due to changes in the subjective estimation of reward probability or average expected reward. Moreover, SEF inactivation also led to increased sensitivity to differences between expected and actual reward during free choice. Nevertheless, it did not affect adjustments of decisions based on reward history.
  • Conserved SUN-KASH Interfaces Mediate LINC Complex-Dependent Nuclear
           Movement and Positioning
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Natalie E. Cain, Zeinab Jahed, Amy Schoenhofen, Venecia A. Valdez, Baila Elkin, Hongyan Hao, Nathan J. Harris, Leslie A. Herrera, Brian M. Woolums, Mohammad R.K. Mofrad, G.W. Gant Luxton, Daniel A. StarrSummaryMany nuclear positioning events involve linker of nucleoskeleton and cytoskeleton (LINC) complexes, which transmit forces generated by the cytoskeleton across the nuclear envelope. LINC complexes are formed by trans-luminal interactions between inner nuclear membrane SUN proteins and outer nuclear membrane KASH proteins, but how these interactions are regulated is poorly understood. We combine in vivo C. elegans genetics, in vitro wounded fibroblast polarization, and in silico molecular dynamics simulations to elucidate mechanisms of LINC complexes. The extension of the KASH domain by a single alanine residue or the mutation of the conserved tyrosine at −7 completely blocked the nuclear migration function of C. elegans UNC-83. Analogous mutations at −7 of mouse nesprin-2 disrupted rearward nuclear movements in NIH 3T3 cells, but did not disrupt ANC-1 in nuclear anchorage. Furthermore, conserved cysteines predicted to form a disulfide bond between SUN and KASH proteins are important for the function of certain LINC complexes, and might promote a developmental switch between nuclear migration and nuclear anchorage. Mutations of conserved cysteines in SUN or KASH disrupted ANC-1-dependent nuclear anchorage in C. elegans and Nesprin-2G-dependent nuclear movements in polarizing fibroblasts. However, the SUN cysteine mutation did not disrupt nuclear migration. Moreover, molecular dynamics simulations showed that a disulfide bond is necessary for the maximal transmission of cytoskeleton-generated forces by LINC complexes in silico. Thus, we have demonstrated functions for SUN-KASH binding interfaces, including a predicted intermolecular disulfide bond, as mechanistic determinants of nuclear positioning that may represent targets for regulation.Graphical Graphical abstract for this article
  • Robust Sensorimotor Learning during Variable Sentence-Level Speech
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Daniel R. Lametti, Harriet J. Smith, Kate E. Watkins, Douglas M. ShillerSummarySensorimotor learning has been studied by altering the sound of the voice in real time as speech is produced. In response to voice alterations, learned changes in production reduce the perceived auditory error and persist for some time after the alteration is removed [1, 2, 3, 4, 5]. The results of such experiments have led to the development of prominent models of speech production. This work proposes that the control of speech relies on forward models to predict sensory outcomes of movements, and errors in these predictions drive sensorimotor learning [5, 6, 7]. However, sensorimotor learning in speech has only been observed following intensive training on a handful of discrete words or perceptually similar sentences. Stereotyped production does not capture the complex sensorimotor demands of fluid, real-world speech [8, 9, 10, 11]. It remains unknown whether talkers predict the sensory consequences of variable sentence production to allow rapid and precise updating of speech motor plans when sensory prediction errors are encountered. Here, we used real-time alterations of speech feedback to test for sensorimotor learning during the production of 50 sentences that varied markedly in length, vocabulary, and grammar. Following baseline production, all vowels were simultaneously altered and played back through headphones in near real time. Robust feedforward changes in sentence production were observed that, on average, precisely countered the direction of the alteration. These changes occurred in every participant and transferred to the production of single words with varying vowel sounds. The results show that to maintain accurate sentence production, the brain actively predicts the auditory consequences of variable sentence-level speech.
  • Phylotranscriptomics of Pristionchus Nematodes Reveals Parallel Gene Loss
           in Six Hermaphroditic Lineages
    • Abstract: Publication date: Available online 20 September 2018Source: Current BiologyAuthor(s): Christian Rödelsperger, Waltraud Röseler, Neel Prabh, Kohta Yoshida, Christian Weiler, Matthias Herrmann, Ralf J. SommerSummaryMutation and recombination are main drivers of phenotypic diversity, but the ability to create new allelic combinations is strongly dependent on the mode of reproduction. While most animals are dioecious (i.e., separated male and female sexes), in a number of evolutionary lineages females have gained the ability to self-fertilize [1, 2], with drastic consequences on effective recombination rate, genetic diversity, and the efficacy of selection [3]. In the genus Caenorhabditis, such hermaphroditic or androdioecious lineages, including C. briggsae and C. tropicalis, display a genome shrinkage relative to their dioecious sister species C. nigoni and C. brenneri, respectively [4, 5]. However, common consequences of reproductive modes on nematode genomes remain unknown, because most taxa contain single or few androdioecious species. One exception is the genus Pristionchus, with seven androdioecious species. Pristionchus worms are found in association with scarab beetles in worldwide samplings, resulting in deep taxon sampling and currently 39 culturable and available species. Here, we use phylotranscriptomics of all 39 Pristionchus species to provide a robust phylogeny based on an alignment of more than 2,000 orthologous clusters, which indicates that the seven androdioecious species represent six independent lineages. We show that gene loss is more prevalent in all hermaphroditic lineages than in dioecious relatives and that the majority of lost genes evolved recently in the Pristionchus genus. Further, we provide evidence that genes with male-biased expression are preferentially lost in hermaphroditic lineages. This supports a contribution of adaptive gene loss to shaping nematode genomes following the evolution of hermaphroditism.Graphical Graphical abstract for this article
  • Stepwise cis-Regulatory Changes in ZCN8 Contribute to Maize Flowering-Time
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Li Guo, Xuehan Wang, Min Zhao, Cheng Huang, Cong Li, Dan Li, Chin Jian Yang, Alessandra M. York, Wei Xue, Guanghui Xu, Yameng Liang, Qiuyue Chen, John F. Doebley, Feng TianSummaryMaize (Zea mays ssp. mays) was domesticated in southwestern Mexico ∼9,000 years ago from its wild ancestor, teosinte (Zea mays ssp. parviglumis) [1]. From its center of origin, maize experienced a rapid range expansion and spread over 90° of latitude in the Americas [2, 3, 4], which required a novel flowering-time adaptation. ZEA CENTRORADIALIS 8 (ZCN8) is the maize florigen gene and has a central role in mediating flowering [5, 6]. Here, we show that ZCN8 underlies a major quantitative trait locus (QTL) (qDTA8) for flowering time that was consistently detected in multiple maize-teosinte experimental populations. Through association analysis in a large diverse panel of maize inbred lines, we identified a SNP (SNP-1245) in the ZCN8 promoter that showed the strongest association with flowering time. SNP-1245 co-segregated with qDTA8 in maize-teosinte mapping populations. We demonstrate that SNP-1245 is associated with differential binding by the flowering activator ZmMADS1. SNP-1245 was a target of selection during early domestication, which drove the pre-existing early flowering allele to near fixation in maize. Interestingly, we detected an independent association block upstream of SNP-1245, wherein the early flowering allele that most likely originated from Zea mays ssp. mexicana introgressed into the early flowering haplotype of SNP-1245 and contributed to maize adaptation to northern high latitudes. Our study demonstrates how independent cis-regulatory variants at a gene can be selected at different evolutionary times for local adaptation, highlighting how complex cis-regulatory control mechanisms evolve. Finally, we propose a polygenic map for the pre-Columbian spread of maize throughout the Americas.
  • Suppression of Plant Immunity by Fungal Chitinase-like Effectors
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Gabriel Lorencini Fiorin, Andrea Sanchéz-Vallet, Daniela Paula de Toledo Thomazella, Paula Favoretti Vital do Prado, Leandro Costa do Nascimento, Antonio Vargas de Oliveira Figueira, Bart P.H.J. Thomma, Gonçalo Amarante Guimarães Pereira, Paulo José Pereira Lima TeixeiraSummaryCrop diseases caused by fungi constitute one of the most important problems in agriculture, posing a serious threat to food security [1]. To establish infection, phytopathogens interfere with plant immune responses [2, 3]. However, strategies to promote virulence employed by fungal pathogens, especially non-model organisms, remain elusive [4], mainly because fungi are more complex and difficult to study when compared to the better-characterized bacterial pathogens. Equally incomplete is our understanding of the birth of microbial virulence effectors. Here, we show that the cacao pathogen Moniliophthora perniciosa evolved an enzymatically inactive chitinase (MpChi) that functions as a putative pathogenicity factor. MpChi is among the most highly expressed fungal genes during the biotrophic interaction with cacao and encodes a chitinase with mutations that abolish its enzymatic activity. Despite the lack of chitinolytic activity, MpChi retains substrate binding specificity and prevents chitin-triggered immunity by sequestering immunogenic chitin fragments. Remarkably, its sister species M. roreri encodes a second non-orthologous catalytically impaired chitinase with equivalent function. Thus, a class of conserved enzymes independently evolved as putative virulence factors in these fungi. In addition to unveiling a strategy of host immune suppression by fungal pathogens, our results demonstrate that the neofunctionalization of enzymes may be an evolutionary pathway for the rise of new virulence factors in fungi. We anticipate that analogous strategies are likely employed by other pathogens.Graphical Graphical abstract for this article
  • Confirmation Bias through Selective Overweighting of Choice-Consistent
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Bharath Chandra Talluri, Anne E. Urai, Konstantinos Tsetsos, Marius Usher, Tobias H. DonnerSummaryPeople’s assessments of the state of the world often deviate systematically from the information available to them [1]. Such biases can originate from people’s own decisions: committing to a categorical proposition, or a course of action, biases subsequent judgment and decision-making. This phenomenon, called confirmation bias [2], has been explained as suppression of post-decisional dissonance [3, 4]. Here, we provide insights into the underlying mechanism. It is commonly held that decisions result from the accumulation of samples of evidence informing about the state of the world [5, 6, 7, 8]. We hypothesized that choices bias the accumulation process by selectively altering the weighting (gain) of subsequent evidence, akin to selective attention. We developed a novel psychophysical task to test this idea. Participants viewed two successive random dot motion stimuli and made two motion-direction judgments: a categorical discrimination after the first stimulus and a continuous estimation of the overall direction across both stimuli after the second stimulus. Participants’ sensitivity for the second stimulus was selectively enhanced when that stimulus was consistent with the initial choice (compared to both, first stimuli and choice-inconsistent second stimuli). A model entailing choice-dependent selective gain modulation explained this effect better than several alternative mechanisms. Choice-dependent gain modulation was also established in another task entailing averaging of numerical values instead of motion directions. We conclude that intermittent choices direct selective attention during the evaluation of subsequent evidence, possibly due to decision-related feedback in the brain [9]. Our results point to a recurrent interplay between decision-making and selective attention.
  • Encoding of Multiple Reward-Related Computations in Transient and
           Sustained High-Frequency Activity in Human OFC
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Ignacio Saez, Jack Lin, Arjen Stolk, Edward Chang, Josef Parvizi, Gerwin Schalk, Robert T. Knight, Ming HsuSummaryHuman orbitofrontal cortex (OFC) has long been implicated in value-based decision making. In recent years, convergent evidence from human and model organisms has further elucidated its role in representing reward-related computations underlying decision making. However, a detailed description of these processes remains elusive due in part to (1) limitations in our ability to observe human OFC neural dynamics at the timescale of decision processes and (2) methodological and interspecies differences that make it challenging to connect human and animal findings or to resolve discrepancies when they arise. Here, we sought to address these challenges by conducting multi-electrode electrocorticography (ECoG) recordings in neurosurgical patients during economic decision making to elucidate the electrophysiological signature, sub-second temporal profile, and anatomical distribution of reward-related computations within human OFC. We found that high-frequency activity (HFA) (70–200 Hz) reflected multiple valuation components grouped in two classes of valuation signals that were dissociable in temporal profile and information content: (1) fast, transient responses reflecting signals associated with choice and outcome processing, including anticipated risk and outcome regret, and (2) sustained responses explicitly encoding what happened in the immediately preceding trial. Anatomically, these responses were widely distributed in partially overlapping networks, including regions in the central OFC (Brodmann areas 11 and 13), which have been consistently implicated in reward processing in animal single-unit studies. Together, these results integrate insights drawn from human and animal studies and provide evidence for a role of human OFC in representing multiple reward computations.
  • A Single-Cell Transcriptional Atlas of the Developing Murine Cerebellum
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Robert A. Carter, Laure Bihannic, Celeste Rosencrance, Jennifer L. Hadley, Yiai Tong, Timothy N. Phoenix, Sivaraman Natarajan, John Easton, Paul A. Northcott, Charles GawadSummaryThe cerebellum develops from a restricted number of cell types that precisely organize to form the circuitry that controls sensory-motor coordination and some higher-order cognitive processes. To acquire an enhanced understanding of the molecular processes that mediate cerebellar development, we performed single-cell RNA-sequencing of 39,245 murine cerebellar cells at twelve critical developmental time points. Using recognized lineage markers, we confirmed that the single-cell data accurately recapitulate cerebellar development. We then followed distinct populations from emergence through migration and differentiation, and determined the associated transcriptional cascades. After identifying key lineage commitment decisions, focused analyses uncovered waves of transcription factor expression at those branching points. Finally, we created Cell Seek, a flexible online interface that facilitates exploration of the dataset. Our study provides a transcriptional summarization of cerebellar development at single-cell resolution that will serve as a valuable resource for future investigations of cerebellar development, neurobiology, and disease.
  • Insights into the Evolution of Multicellularity from the Sea Lettuce
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Olivier De Clerck, Shu-Min Kao, Kenny A. Bogaert, Jonas Blomme, Fatima Foflonker, Michiel Kwantes, Emmelien Vancaester, Lisa Vanderstraeten, Eylem Aydogdu, Jens Boesger, Gianmaria Califano, Benedicte Charrier, Rachel Clewes, Andrea Del Cortona, Sofie D’Hondt, Noe Fernandez-Pozo, Claire M. Gachon, Marc Hanikenne, Linda Lattermann, Frederik LeliaertSummaryWe report here the 98.5 Mbp haploid genome (12,924 protein coding genes) of Ulva mutabilis, a ubiquitous and iconic representative of the Ulvophyceae or green seaweeds. Ulva’s rapid and abundant growth makes it a key contributor to coastal biogeochemical cycles; its role in marine sulfur cycles is particularly important because it produces high levels of dimethylsulfoniopropionate (DMSP), the main precursor of volatile dimethyl sulfide (DMS). Rapid growth makes Ulva attractive biomass feedstock but also increasingly a driver of nuisance “green tides.” Ulvophytes are key to understanding the evolution of multicellularity in the green lineage, and Ulva morphogenesis is dependent on bacterial signals, making it an important species with which to study cross-kingdom communication. Our sequenced genome informs these aspects of ulvophyte cell biology, physiology, and ecology. Gene family expansions associated with multicellularity are distinct from those of freshwater algae. Candidate genes, including some that arose following horizontal gene transfer from chromalveolates, are present for the transport and metabolism of DMSP. The Ulva genome offers, therefore, new opportunities to understand coastal and marine ecosystems and the fundamental evolution of the green lineage.
  • Replacement Bisphenols Adversely Affect Mouse Gametogenesis with
           Consequences for Subsequent Generations
    • Abstract: Publication date: Available online 13 September 2018Source: Current BiologyAuthor(s): Tegan S. Horan, Hannah Pulcastro, Crystal Lawson, Roy Gerona, Spencer Martin, Mary C. Gieske, Caroline V. Sartain, Patricia A. HuntSummary20 years ago, accidental bisphenol A (BPA) exposure caused a sudden increase in chromosomally abnormal eggs from our control mice [1]. Subsequent rodent studies demonstrated developmental effects of exposure with repercussions on adult health and fertility (e.g., [2, 3, 4, 5, 6, 7, 8, 9]; reviewed in [10, 11, 12, 13, 14, 15, 16, 17]). Studies in monkeys, humans, fish, and worms suggest BPA effects extend across species (e.g., [18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30]; reviewed in [31, 32, 33]). Widespread use has resulted in ubiquitous environmental contamination and human BPA exposure. Consumer concern resulted in “BPA-free” products produced using structurally similar bisphenols that are now detectable environmental and human contaminants (e.g., [34, 35, 36, 37, 38, 39, 40, 41]). We report here studies initiated by meiotic changes mirroring our previous BPA experience and implicating exposure to BPS (a common BPA replacement) from damaged polysulfone cages. Like with BPA [1, 2, 5], our data show that exposure to common replacement bisphenols induces germline effects in both sexes that may affect multiple generations. These findings add to growing evidence of the biological risks posed by this class of chemicals. Rapid production of structural variants of BPA and other EDCs circumvents efforts to eliminate dangerous chemicals, exacerbates the regulatory burden of safety assessment, and increases environmental contamination. Our experience suggests that these environmental contaminants pose a risk not only to reproductive health but also to the integrity of the research environment. EDCs, like endogenous hormones, can affect diverse processes. The sensitivity of the germline allows us to detect effects that, although not immediately apparent in other systems, may induce variability that undermines experimental reproducibility and impedes scientific advancement.
  • Cortico-hippocampal Schemas Enable NMDAR-Independent Fear Conditioning in
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Peter S.B. Finnie, Karine Gamache, Maria Protopoulos, Elizabeth Sinclair, Andrew G. Baker, Szu-Han Wang, Karim NaderSummaryThe neurobiology of memory formation has been studied primarily in experimentally naive animals, but the majority of learning unfolds on a background of prior experience. Considerable evidence now indicates that the brain processes initial and subsequent learning differently. In rodents, a first instance of contextual fear conditioning requires NMDA receptor (NMDAR) activation in the dorsal hippocampus, but subsequent conditioning to another context does not. This shift may result from a change in molecular plasticity mechanisms or in the information required to learn the second task. To clarify how related events are encoded, it is critical to identify which aspect of a first task engages NMDAR-independent learning and the brain regions that maintain this state. Here, we show in rats that the requirement for NMDARs in hippocampus depends neither on prior exposure to context nor footshock alone but rather on the procedural similarity between two conditioning tasks. Importantly, NMDAR-independent learning requires the memory of the first task to remain hippocampus dependent. Furthermore, disrupting memory maintenance in the anterior cingulate cortex after the first task also reinstates NMDAR dependency. These results reveal cortico-hippocampal interactions supporting experience-dependent learning.
  • The Genetic Basis of Adaptation following Plastic Changes in Coloration in
           a Novel Environment
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Ammon Corl, Ke Bi, Claudia Luke, Akshara Sree Challa, Aaron James Stern, Barry Sinervo, Rasmus NielsenSummaryPhenotypic plasticity has been hypothesized to precede and facilitate adaptation to novel environments [1, 2, 3, 4, 5, 6, 7, 8], but examples of plasticity preceding adaptation in wild populations are rare (but see [9, 10]). We studied a population of side-blotched lizards, Uta stansburiana, living on a lava flow that formed 22,500 years ago [11] to understand the origin of their novel melanic phenotype that makes them cryptic on the black lava. We found that lizards living on and off of the lava flow exhibited phenotypic plasticity in coloration but also appeared to have heritable differences in pigmentation. We sequenced the exomes of 104 individuals and identified two known regulators of melanin production, PREP and PRKAR1A, which had markedly increased levels of divergence between lizards living on and off the lava flow. The derived variants in PREP and PRKAR1A were only found in the lava population and were associated with increased pigmentation levels in an experimental cohort of hatchling lizards. Simulations suggest that the derived variants in the PREP and PRKAR1A genes arose recently and were under strong positive selection in the lava population. Overall, our results suggest that ancestral plasticity for coloration facilitated initial survival in the lava environment and was followed by genetic changes that modified the phenotype in the direction of the induced plastic response, possibly through de novo mutations. These observations provide a detailed example supporting the hypothesis that plasticity aids in the initial colonization of a novel habitat, with natural selection subsequently refining the phenotype with genetic adaptations to the new environment.Video Graphical Graphical abstract for this article
  • Direct Electrophysiological Evidence for Prefrontal Control of Hippocampal
           Processing during Voluntary Forgetting
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Carina R. Oehrn, Juergen Fell, Conrad Baumann, Timm Rosburg, Eva Ludowig, Henrik Kessler, Simon Hanslmayr, Nikolai AxmacherSummaryForgetting does not necessarily reflect failure to encode information but can, to some extent, also be voluntarily controlled. Previous studies have suggested that voluntary forgetting relies on active inhibition of encoding processes in the hippocampus by the dorsolateral prefrontal cortex (DLPFC) [1, 2, 3, 4]. During attentional and sensorimotor processing, enhanced DLPFC theta power alongside increased alpha/beta oscillations are a neural signature of an inhibitory top-down mechanism, with theta oscillations reflecting prefrontal control and alpha/beta oscillations occurring in areas targeted by inhibition [5, 6, 7, 8, 9, 10, 11, 12]. Here, we used intracranial EEG recordings in presurgical epilepsy patients implanted in DLPFC (n = 13) and hippocampus (n = 15) during an item-method directed forgetting paradigm. We found that voluntary forgetting is associated with increased neural oscillations in the low theta band (3–5 Hz) in DLPFC and in a broad theta/alpha/beta (6–18 Hz) frequency range in hippocampus. Combining time-lagged correlation analysis, phase synchronization, and Granger causality in 6 patients with electrodes in both DLPFC and hippocampus, we obtained converging evidence for a top-down control of hippocampal activity by the DLPFC. Together, our results provide strong support for a model in which voluntary forgetting relies on enhanced inhibition of the hippocampus by the DLPFC.
  • Neural Entrainment Determines the Words We Hear
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Anne Kösem, Hans Rutger Bosker, Atsuko Takashima, Antje Meyer, Ole Jensen, Peter HagoortSummaryLow-frequency neural entrainment to rhythmic input has been hypothesized as a canonical mechanism that shapes sensory perception in time. Neural entrainment is deemed particularly relevant for speech analysis, as it would contribute to the extraction of discrete linguistic elements from continuous acoustic signals. However, its causal influence in speech perception has been difficult to establish. Here, we provide evidence that oscillations build temporal predictions about the duration of speech tokens that affect perception. Using magnetoencephalography (MEG), we studied neural dynamics during listening to sentences that changed in speech rate. We observed neural entrainment to preceding speech rhythms persisting for several cycles after the change in rate. The sustained entrainment was associated with changes in the perceived duration of the last word’s vowel, resulting in the perception of words with different meanings. These findings support oscillatory models of speech processing, suggesting that neural oscillations actively shape speech perception.
  • IRTKS (BAIAP2L1) Elongates Epithelial Microvilli Using EPS8-Dependent and
           Independent Mechanisms
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Meagan M. Postema, Nathan E. Grega-Larson, Abigail C. Neininger, Matthew J. TyskaSummaryTransporting epithelial cells like those that line the gut build large arrays of actin-supported protrusions called microvilli, which extend from the apical surface into luminal spaces to increase functional surface area. Although critical for maintaining physiological homeostasis, mechanisms controlling the formation of microvilli remain poorly understood. Here, we report that the inverse-bin-amphiphysin-Rvs (I-BAR)-domain-containing protein insulin receptor tyrosine kinase substrate (IRTKS) (also known as BAIAP2L1) promotes the growth of epithelial microvilli. Super-resolution microscopy and live imaging of differentiating epithelial cells revealed that IRTKS localizes to the distal tips of actively growing microvilli via a mechanism that requires its N-terminal I-BAR domain. At microvillar tips, IRTKS promotes elongation through a mechanism involving its C-terminal actin-binding WH2 domain. IRTKS can also drive microvillar elongation using its SH3 domain to recruit the bundling protein EPS8 to microvillar tips. These results provide new insight on mechanisms that control microvillar growth during the differentiation of transporting epithelial cells and help explain why IRTKS is targeted by enteric pathogens that disrupt microvillar structure during infection of the intestinal epithelium.Graphical Graphical abstract for this article
  • A Switch in Microtubule Orientation during C. elegans
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Stefanie Redemann, Ina Lantzsch, Norbert Lindow, Steffen Prohaska, Martin Srayko, Thomas Müller-ReichertSummaryIn oocytes of many organisms, meiotic spindles form in the absence of centrosomes [1, 2, 3, 4, 5]. Such female meiotic spindles have a pointed appearance in metaphase with microtubules focused at acentrosomal spindle poles. At anaphase, the microtubules of acentrosomal spindles then transition to an inter-chromosomal array, while the spindle poles disappear. This transition is currently not understood. Previous studies have focused on this inter-chromosomal microtubule array and proposed a pushing model to drive chromosome segregation [6, 7]. This model includes an end-on orientation of microtubules with chromosomes. Alternatively, chromosomes were thought to associate along bundles of microtubules [8, 9]. Starting with metaphase, this second model proposed a pure lateral chromosome-to-microtubule association up to the final meiotic stages of anaphase. Here, we applied large-scale electron tomography [10] of staged C. elegans oocytes in meiosis to analyze the orientation of microtubules in respect to chromosomes. We show that microtubules at metaphase I are primarily oriented laterally to the chromosomes and that microtubules switch to an end-on orientation during progression through anaphase. We further show that this switch in microtubule orientation involves a kinesin-13 microtubule depolymerase, KLP-7, which removes laterally associated microtubules around chromosomes. From this, we conclude that both lateral and end-on modes of microtubule-to-chromosome orientations are successively used in C. elegans oocytes to segregate meiotic chromosomes.Graphical Graphical abstract for this article
  • Exaptation as a Mechanism for Functional Reinforcement of an Animal
           Pheromone System
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Margo Maex, Dag Treer, Henri De Greve, Paul Proost, Ines Van Bocxlaer, Franky BossuytSummaryAnimal sex pheromone systems often exist as multicomponent signals [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] to which chemical cues have been added over evolutionary time. Little is known on why and how additional molecules become recruited and conserved in an already functional pheromone system. Here, we investigated the evolutionary trajectory of a series of 15 kDa proteins—termed persuasins—that were co-opted more recently alongside the ancient sodefrin precursor-like factor (SPF) courtship pheromone system in salamanders [9, 12]. Expression, genomic, and molecular phylogenetic analyses show that persuasins originated from a gene that is expressed as a multi-domain protein in internal organs where it has no pheromone function but underwent gene duplication and neofunctionalization. The subsequent evolution combined domain loss and the introduction of a proteolytic cleavage site in the duplicated gene to give rise to two-domain cysteine rich proteins with structural properties similar to SPF pheromones [12]. An expression shift to the pheromone-producing glands, where expression of persuasins was immediately spatiotemporally synchronized with the already available pheromone system, completed the birth of a new pheromone. Electrostatic forces between members of both protein families likely enhance co-localization and simultaneous activation of different female olfactory neurons, explaining why persuasins immediately had a selective advantage. In line with this, behavioral assays show that persuasins increase female receptivity on their own but also exert a cumulative or synergistic effect in combination with SPF, clearly reinforcing the pheromone system as a whole. Our study reveals molecular remodeling of an existing protein architecture as an evolutionary mechanism for functional reinforcement of animal pheromone systems.
  • Rapid Antagonistic Coevolution in an Emerging Pathogen and Its Vertebrate
    • Abstract: Publication date: Available online 6 September 2018Source: Current BiologyAuthor(s): Camille Bonneaud, Mathieu Giraudeau, Luc Tardy, Molly Staley, Geoffrey E. Hill, Kevin J. McGrawSummaryHost-pathogen coevolution is assumed to play a key role in eco-evolutionary processes, including epidemiological dynamics and the evolution of sexual reproduction [1, 2, 3, 4]. Despite this, direct evidence for host-pathogen coevolution is exceptional [5, 6, 7], particularly in vertebrate hosts. Indeed, although vertebrate hosts have been shown to evolve in response to pathogens or vice versa [8, 9, 10, 11, 12], there is little evidence for the necessary reciprocal changes in the success of both antagonists over time [13]. Here, we generate a time-shift experiment to demonstrate adaptive, reciprocal changes in North American house finches (Haemorhous mexicanus) and their emerging bacterial pathogen, Mycoplasma gallisepticum [14, 15, 16]. Our experimental design is made possible by the existence of disease-exposed and unexposed finch populations, which were known to exhibit equivalent responses to experimental inoculation until the recent spread of genetic resistance in the former [14, 17]. Whereas inoculations with pathogen isolates from epidemic outbreak caused comparable sub-lethal eye swelling in hosts from exposed (hereafter adapted) and unexposed (hereafter ancestral) populations, inoculations with isolates sampled after the spread of resistance were threefold more likely to cause lethal symptoms in hosts from ancestral populations. Similarly, the probability that pathogens successfully established an infection in the primary host and, before inducing death, transmitted to an uninfected sentinel was highest when recent isolates were inoculated in hosts from ancestral populations and lowest when early isolates were inoculated in hosts from adapted populations. Our results demonstrate antagonistic host-pathogen coevolution, with hosts and pathogens displaying increased resistance and virulence in response to each other over time.
  • Local Inversion Heterozygosity Alters Recombination throughout the Genome
    • Abstract: Publication date: Available online 30 August 2018Source: Current BiologyAuthor(s): K. Nicole Crown, Danny E. Miller, Jeff Sekelsky, R. Scott HawleySummaryCrossovers (COs) are formed during meiosis by the repair of programmed DNA double-strand breaks (DSBs) and are required for the proper segregation of chromosomes. More DSBs are made than COs, and the remaining DSBs are repaired as noncrossovers (NCOs). The distribution of recombination events along a chromosome occurs in a stereotyped pattern that is shaped by CO-promoting and CO-suppressing forces, collectively referred to as crossover patterning mechanisms. Chromosome inversions are structural aberrations that, when heterozygous, disrupt the recombination landscape by suppressing crossing over. In Drosophila species, the local suppression of COs by heterozygous inversions triggers an increase in crossing over on freely recombining chromosomes termed the interchromosomal (IC) effect [1, 2]. The molecular mechanism(s) by which heterozygous inversions suppress COs, whether noncrossover gene conversions (NCOGCs) are similarly affected, and what mediates the increase in COs in the rest of the genome remain open questions. By sequencing whole genomes of individual offspring from mothers containing heterozygous inversions, we show that, although COs are suppressed by inversions, NCOGCs occur throughout inversions at higher than wild-type frequencies. We confirm that CO frequency increases on the freely recombining chromosomes, yet CO interference remains intact. Intriguingly, NCOGCs do not increase in frequency on the freely recombining chromosomes and the total number of DSBs is approximately the same per genome. Together, our data show that heterozygous inversions change the recombination landscape by altering the relative proportions of COs and NCOGCs and suggest that DSB fate may be plastic until a CO assurance checkpoint has been satisfied.
  • Retinotopic Separation of Nasal and Temporal Motion Selectivity in the
           Mouse Superior Colliculus
    • Abstract: Publication date: Available online 30 August 2018Source: Current BiologyAuthor(s): Daniel de Malmazet, Norma K. Kühn, Karl FarrowSummarySensory neurons often display an ordered spatial arrangement that enhances the encoding of specific features on different sides of natural borders in the visual field (for example, [1, 2, 3]). In central visual areas, one prominent natural border is formed by the confluence of information from the two eyes, the monocular-binocular border [4]. Here, we investigate whether receptive field properties of neurons in the mouse superior colliculus show any systematic organization about the monocular-binocular border. The superior colliculus is a layered midbrain structure that plays a significant role in the orienting responses of the eye, head, and body [5]. Its superficial layers receive direct input from the majority of retinal ganglion cells and are retinotopically organized [6, 7]. Using two-photon calcium imaging, we recorded the activity of collicular neurons from the superficial layers of awake mice and determined their direction selectivity, orientation selectivity, and retinotopic location. This revealed that nearby direction-selective neurons have a strong tendency to prefer the same motion direction. In retinotopic space, the local preference of direction-selective neurons shows a sharp transition in the preference for nasal versus temporal motion at the monocular-binocular border. The maps representing orientation and direction appear to be independent. These results illustrate the important coherence between the spatial organization of inputs and response properties within the visual system and suggest a re-analysis of the receptive field organization within the superior colliculus from an ecological perspective.
  • Rank-Related Contrasts in Longevity Arise from Extra-Group Excursions Not
           Delayed Senescence in a Cooperative Mammal
    • Abstract: Publication date: Available online 30 August 2018Source: Current BiologyAuthor(s): Dominic L. Cram, Pat Monaghan, Robert Gillespie, Ben Dantzer, Christopher Duncan, Helen Spence-Jones, Tim Clutton-BrockSummaryIn many cooperatively breeding animal societies, breeders outlive non-breeding subordinates, despite investing heavily in reproduction [1, 2, 3]. In eusocial insects, the extended lifespans of breeders arise from specialized slowed aging profiles [1], prompting suggestions that reproduction and dominance similarly defer aging in cooperatively breeding vertebrates, too [4, 5, 6]. Although lacking the permanent castes of eusocial insects, breeders of vertebrate societies could delay aging via phenotypic plasticity (similar rank-related changes occur in growth, neuroendocrinology, and behavior [7, 8, 9, 10]), and such plastic deferment of aging may reveal novel targets for preventing aging-related diseases [11]. Here, we investigate whether breeding dominants exhibit extended longevity and delayed age-related physiological declines in wild cooperatively breeding meerkats. We show that dominants outlive subordinates but exhibit faster telomere attrition (a marker of cellular senescence and hallmark of aging [12]) and that in dominants (but not subordinates), rapid telomere attrition is associated with mortality. Our findings further suggest that, rather than resulting from specialized aging profiles, differences in longevity between dominants and subordinates are driven by subordinate dispersal forays, which become exponentially more frequent with age and increase subordinate mortality. These results highlight the need to critically examine the causes of rank-related longevity contrasts in other cooperatively breeding vertebrates, including social mole-rats, where they are currently attributed to specialized aging profiles in dominants [4].Graphical Graphical abstract for this article
  • Somatosensory Neurons Enter a State of Altered Excitability during
    • Abstract: Publication date: Available online 30 August 2018Source: Current BiologyAuthor(s): Lydia J. Hoffstaetter, Marco Mastrotto, Dana K. Merriman, Sulayman D. Dib-Hajj, Stephen G. Waxman, Sviatoslav N. Bagriantsev, Elena O. GrachevaSummaryHibernation in mammals involves prolonged periods of inactivity, hypothermia, hypometabolism, and decreased somatosensation. Peripheral somatosensory neurons play an essential role in the detection and transmission of sensory information to CNS and in the generation of adaptive responses. During hibernation, when body temperature drops to as low as 2°C, animals dramatically reduce their sensitivity to physical cues [1, 2]. It is well established that, in non-hibernators, cold exposure suppresses energy production, leading to dissipation of the ionic and electrical gradients across the plasma membrane and, in the case of neurons, inhibiting the generation of action potentials [3]. Conceivably, such cold-induced elimination of electrogenesis could be part of a general mechanism that inhibits sensory abilities in hibernators. However, when hibernators become active, the bodily functions—including the ability to sense environmental cues—return to normal within hours, suggesting the existence of mechanisms supporting basal functionality of cells during torpor and rapid restoration of activity upon arousal. We tested this by comparing properties of somatosensory neurons from active and torpid thirteen-lined ground squirrels (Ictidomys tridecemlineatus). We found that torpid neurons can compensate for cold-induced functional deficits, resulting in unaltered resting potential, input resistance, and rheobase. Torpid neurons can generate action potentials but manifest markedly altered firing patterns, partially due to decreased activity of voltage-gated sodium channels. Our results provide insights into the mechanism that preserves somatosensory neurons in a semi-active state, enabling fast restoration of sensory function upon arousal. These findings contribute to the development of strategies enabling therapeutic hypothermia and hypometabolism.
  • A Maladaptive Combination of Traits Contributes to the Maintenance of a
           Drosophila Hybrid Zone
    • Abstract: Publication date: Available online 30 August 2018Source: Current BiologyAuthor(s): Brandon S. Cooper, Alisa Sedghifar, W. Thurston Nash, Aaron A. Comeault, Daniel R. MatuteSummaryDrosophila teissieri and D. yakuba diverged approximately 3 mya and are thought to share a large, ancestral, African range [1, 2, 3]. These species now co-occur in parts of continental Africa and in west Africa on the island of Bioko [1, 4]. While D. yakuba is a human commensal, D. teissieri seems to be associated with Parinari fruits, restricting its range to forests [4, 5, 6]. Genome data indicate introgression, despite no evidence of contemporary hybridization. Here we report the discovery of D. yakuba-D. teissieri hybrids at the interface of secondary forests and disturbed, open habitats on Bioko. We demonstrate that hybrids are the F1 progeny of D. yakuba females and D. teissieri males. At high temperatures like those found on Bioko, D. teissieri females are generally less receptive to mating, and in combination with temperature effects on egg lay and egg-to-adult viability, this decreases the potential for gene flow between female D. teissieri and male D. yakuba relative to the reciprocal cross. Field and laboratory experiments demonstrate that F1 hybrids have a maladaptive combination of D. yakuba behavior and D. teissieri physiology, generating additional barriers to gene flow. Nevertheless, analysis of introgressed and non-introgressed regions of the genome indicate that, while rare, gene flow is relatively recent. Our observations identify precise intrinsic and extrinsic factors that, along with hybrid male sterility, limit gene flow and maintain these species. These data contribute to a growing body of literature that suggests the Gulf of Guinea may be a hotspot for hybridization.
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