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Current Biology
Journal Prestige (SJR): 4.296
Citation Impact (citeScore): 5
Number of Followers: 250  
 
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ISSN (Print) 0960-9822
Published by Elsevier Homepage  [3163 journals]
  • Megaherbivores Modify Trophic Cascades Triggered by Fear of Predation in
           an African Savanna Ecosystem
    • Abstract: Publication date: Available online 19 July 2018Source: Current BiologyAuthor(s): Elizabeth le Roux, Graham I.H. Kerley, Joris P.G.M. CromsigtSummaryThe loss of apex consumers (large mammals at the top of their food chain) is a major driver of global change [1]. Yet, research on the two main apex consumer guilds, large carnivores [2] and megaherbivores [3], has developed independently, overlooking any potential interactions. Large carnivores provoke behavioral responses in prey [1, 4], driving prey to distribute themselves within a “landscape of fear” [5] and intensify their impacts on lower trophic levels in low-risk areas [6], where they may concentrate nutrients through localized dung deposition [7, 8]. We suggest, however, that megaherbivores modify carnivore-induced trophic cascades. Megaherbivores (>1,000 kg [9]) are largely invulnerable to predation and should respond less to the landscape of fear, thereby counteracting the effects of fear-triggered trophic cascades. By experimentally clearing plots to increase visibility and reduce predation risk, we tested the collective role of both apex consumer guilds in influencing nutrient dynamics in African savanna. We evaluated whether megaherbivores could counteract a behaviorally mediated trophic cascade by redistributing nutrients that accumulate through fear-driven prey aggregations. Our experiment showed that mesoherbivores concentrated fecal nutrients in more open habitat, but that megaherbivores moved nutrients against this fear-driven nutrient accumulation by feeding within the open habitat, yet defecating more evenly across the risk gradient. This work adds to the growing recognition of functional losses that are likely to have accompanied megafaunal extinctions by contributing empirical evidence from one of the last systems with a functionally complete megaherbivore assemblage. Our results suggest that carnivore-induced trophic cascades work differently in a world of giants.
       
  • Microtubule-Dependent Confinement of a Cell Signaling and Actin
           Polymerization Control Module Regulates Polarized Cell Growth
    • Abstract: Publication date: Available online 19 July 2018Source: Current BiologyAuthor(s): Makoto Yanagisawa, Jose M. Alonso, Daniel B. SzymanskiSummaryCell types with wildly varying shapes use many of the same signaling and cytoskeletal proteins to dynamically pattern their geometry [1, 2, 3]. Plant cells are encased in a tough outer cell wall, and growth patterns are indirectly controlled by the cytoskeleton and its ability to locally specify the material properties of the wall [4, 5]. Broad and non-overlapping domains of actin and microtubules are predicted to create sharp cell-wall boundaries with distinct mechanical properties [6] that are often proposed to direct growth patterns and cell shape [1, 6, 7]. However, mechanisms by which the cytoskeleton is patterned at the spatial and temporal scales that dictate cell morphology are not known. Here, we used combinations of live-cell imaging probes and unique morphology mutants in Arabidopsis to discover how the microtubule and actin systems are spatially coordinated to pattern polarized growth in leaf epidermal cells. The DOCK family guanine nucleotide exchange factor (GEF) SPIKE1 [8, 9] clusters and activates conserved heteromeric WAVE/SCAR and ARP2/3 complexes at the cell apex to generate organized actin networks that define general cytoplasmic flow patterns. Cortical microtubules corral punctate SPIKE1 signaling nodules and restrict actin polymerization within a broad microtubule-depletion zone at the cell apex. Our data provide a useful model for cell-shape control, in which a GEF, actin filament nucleation complexes, microtubules, and the cell wall function as interacting systems that dynamically pattern polarized growth.Graphical Graphical abstract for this article
       
  • Pan-genome Analysis of Ancient and Modern Salmonella enterica Demonstrates
           Genomic Stability of the Invasive Para C Lineage for Millennia
    • Abstract: Publication date: Available online 19 July 2018Source: Current BiologyAuthor(s): Zhemin Zhou, Inge Lundstrøm, Alicia Tran-Dien, Sebastián Duchêne, Nabil-Fareed Alikhan, Martin J. Sergeant, Gemma Langridge, Anna K. Fotakis, Satheesh Nair, Hans K. Stenøien, Stian S. Hamre, Sherwood Casjens, Axel Christophersen, Christopher Quince, Nicholas R. Thomson, François-Xavier Weill, Simon Y.W. Ho, M. Thomas P. Gilbert, Mark AchtmanSummarySalmonella enterica serovar Paratyphi C causes enteric (paratyphoid) fever in humans. Its presentation can range from asymptomatic infections of the blood stream to gastrointestinal or urinary tract infection or even a fatal septicemia [1]. Paratyphi C is very rare in Europe and North America except for occasional travelers from South and East Asia or Africa, where the disease is more common [2, 3]. However, early 20th-century observations in Eastern Europe [3, 4] suggest that Paratyphi C enteric fever may once have had a wide-ranging impact on human societies. Here, we describe a draft Paratyphi C genome (Ragna) recovered from the 800-year-old skeleton (SK152) of a young woman in Trondheim, Norway. Paratyphi C sequences were recovered from her teeth and bones, suggesting that she died of enteric fever and demonstrating that these bacteria have long caused invasive salmonellosis in Europeans. Comparative analyses against modern Salmonella genome sequences revealed that Paratyphi C is a clade within the Para C lineage, which also includes serovars Choleraesuis, Typhisuis, and Lomita. Although Paratyphi C only infects humans, Choleraesuis causes septicemia in pigs and boar [5] (and occasionally humans), and Typhisuis causes epidemic swine salmonellosis (chronic paratyphoid) in domestic pigs [2, 3]. These different host specificities likely evolved in Europe over the last ∼4,000 years since the time of their most recent common ancestor (tMRCA) and are possibly associated with the differential acquisitions of two genomic islands, SPI-6 and SPI-7. The tMRCAs of these bacterial clades coincide with the timing of pig domestication in Europe [6].
       
  • CLAVATA Was a Genetic Novelty for the Morphological Innovation of
           3D Growth in Land Plants
    • Abstract: Publication date: Available online 19 July 2018Source: Current BiologyAuthor(s): Chris D. Whitewoods, Joseph Cammarata, Zoe Nemec Venza, Stephanie Sang, Ashley D. Crook, Tsuyoshi Aoyama, Xiao Y. Wang, Manuel Waller, Yasuko Kamisugi, Andrew C. Cuming, Péter Szövényi, Zachary L. Nimchuk, Adrienne H.K. Roeder, Michael J. Scanlon, C. Jill HarrisonSummaryHow genes shape diverse plant and animal body forms is a key question in biology. Unlike animal cells, plant cells are confined by rigid cell walls, and cell division plane orientation and growth rather than cell movement determine overall body form. The emergence of plants on land coincided with a new capacity to rotate stem cell divisions through multiple planes, and this enabled three-dimensional (3D) forms to arise from ancestral forms constrained to 2D growth. The genes involved in this evolutionary innovation are largely unknown. The evolution of 3D growth is recapitulated during the development of modern mosses when leafy shoots arise from a filamentous (2D) precursor tissue. Here, we show that a conserved, CLAVATA peptide and receptor-like kinase pathway originated with land plants and orients stem cell division planes during the transition from 2D to 3D growth in a moss, Physcomitrella. We find that this newly identified role for CLAVATA in regulating cell division plane orientation is shared between Physcomitrella and Arabidopsis. We report that roles for CLAVATA in regulating cell proliferation and cell fate are also shared and that CLAVATA-like peptides act via conserved receptor components in Physcomitrella. Our results suggest that CLAVATA was a genetic novelty enabling the morphological innovation of 3D growth in land plants.
       
  • Prolific Origination of Eyes in Cnidaria with Co-option of Non-visual
           Opsins
    • Abstract: Publication date: Available online 19 July 2018Source: Current BiologyAuthor(s): Natasha Picciani, Jamie R. Kerlin, Noemie Sierra, Andrew J.M. Swafford, M. Desmond Ramirez, Nickellaus G. Roberts, Johanna T. Cannon, Marymegan Daly, Todd H. OakleySummaryAnimal eyes vary considerably in morphology and complexity and are thus ideal for understanding the evolution of complex biological traits [1]. While eyes evolved many times in bilaterian animals with elaborate nervous systems, image-forming and simpler eyes also exist in cnidarians, which are ancient non-bilaterians with neural nets and regions with condensed neurons to process information. How often eyes of varying complexity, including image-forming eyes, arose in animals with such simple neural circuitry remains obscure. Here, we produced large-scale phylogenies of Cnidaria and their photosensitive proteins and coupled them with an extensive literature search on eyes and light-sensing behavior to show that cnidarian eyes originated at least eight times, with complex, lensed-eyes having a history separate from other eye types. Compiled data show widespread light-sensing behavior in eyeless cnidarians, and comparative analyses support ancestors without eyes that already sensed light with dispersed photoreceptor cells. The history of expression of photoreceptive opsin proteins supports the inference of distinct eye origins via separate co-option of different non-visual opsin paralogs into eyes. Overall, our results show eyes evolved repeatedly from ancestral photoreceptor cells in non-bilaterian animals with simple nervous systems, co-opting existing precursors, similar to what occurred in Bilateria. Our study underscores the potential for multiple, evolutionarily distinct visual systems even in animals with simple nervous systems.Graphical Graphical abstract for this article
       
  • Arctic Geese Tune Migration to a Warming Climate but Still Suffer from a
           Phenological Mismatch
    • Abstract: Publication date: Available online 19 July 2018Source: Current BiologyAuthor(s): Thomas K. Lameris, Henk P. van der Jeugd, Götz Eichhorn, Adriaan M. Dokter, Willem Bouten, Michiel P. Boom, Konstantin E. Litvin, Bruno J. Ens, Bart A. NoletSummaryClimate warming challenges animals to advance their timing of reproduction [1], but many animals appear to be unable to advance at the same rate as their food species [2, 3]. As a result, mismatches can arise between the moment of largest food requirements for their offspring and peak food availability [4, 5, 6], with important fitness consequences [7]. For long-distance migrants, adjustment of phenology to climate warming may be hampered by their inability to predict the optimal timing of arrival at the breeding grounds from their wintering grounds [8]. Arrival can be advanced if birds accelerate migration by reducing time on stopover sites [9, 10], but a recent study suggests that most long-distance migrants are on too tight a schedule to do so [11]. This may be different for capital-breeding migrants, which use stopovers not only to fuel migration but also to acquire body stores needed for reproduction [12, 13, 14]. By combining multiple years of tracking and reproduction data, we show that a long-distance migratory bird (the barnacle goose, Branta leucopsis) accelerates its 3,000 km spring migration to advance arrival on its rapidly warming Arctic breeding grounds. As egg laying has advanced much less than arrival, they still encounter a phenological mismatch that reduces offspring survival. A shift toward using more local resources for reproduction suggests that geese first need to refuel body stores at the breeding grounds after accelerated migration. Although flexibility in body store use allows migrants to accelerate migration, this cannot solve the time constraint they are facing under climate warming.Graphical Graphical abstract for this article
       
  • A Neuronal Hub Binding Sleep Initiation and Body Cooling in Response to a
           Warm External Stimulus
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Edward C. Harding, Xiao Yu, Andawei Miao, Nathanael Andrews, Ying Ma, Zhiwen Ye, Leda Lignos, Giulia Miracca, Wei Ba, Raquel Yustos, Alexei L. Vyssotski, William Wisden, Nicholas P. FranksSummaryMammals, including humans, prepare for sleep by nesting and/or curling up, creating microclimates of skin warmth. To address whether external warmth induces sleep through defined circuitry, we used c-Fos-dependent activity tagging, which captures populations of activated cells and allows them to be reactivated to test their physiological role. External warming tagged two principal groups of neurons in the median preoptic (MnPO)/medial preoptic (MPO) hypothalamic area. GABA neurons located mainly in MPO produced non-rapid eye movement (NREM) sleep but no body temperature decrease. Nitrergic-glutamatergic neurons in MnPO-MPO induced both body cooling and NREM sleep. This circuitry explains how skin warming induces sleep and why the maximal rate of core body cooling positively correlates with sleep onset. Thus, the pathways that promote NREM sleep, reduced energy expenditure, and body cooling are inextricably linked, commanded by the same neurons. This implies that one function of NREM sleep is to lower brain temperature and/or conserve energy.Graphical Graphical abstract for this article
       
  • A Critical Role for Thermosensation in Host Seeking by Skin-Penetrating
           Nematodes
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Astra S. Bryant, Felicitas Ruiz, Spencer S. Gang, Michelle L. Castelletto, Jacqueline B. Lopez, Elissa A. HallemSummarySkin-penetrating parasitic nematodes infect approximately one billion people worldwide and are a major source of neglected tropical disease [1, 2, 3, 4, 5, 6]. Their life cycle includes an infective third-larval (iL3) stage that searches for hosts to infect in a poorly understood process that involves both thermal and olfactory cues. Here, we investigate the temperature-driven behaviors of skin-penetrating iL3s, including the human-parasitic threadworm Strongyloides stercoralis and the human-parasitic hookworm Ancylostoma ceylanicum. We show that human-parasitic iL3s respond robustly to thermal gradients. Like the free-living nematode Caenorhabditis elegans, human-parasitic iL3s show both positive and negative thermotaxis, and the switch between them is regulated by recent cultivation temperature [7]. When engaging in positive thermotaxis, iL3s migrate toward temperatures approximating mammalian body temperature. Exposing iL3s to a new cultivation temperature alters the thermal switch point between positive and negative thermotaxis within hours, similar to the timescale of thermal plasticity in C. elegans [7]. Thermal plasticity in iL3s may enable them to optimize host finding on a diurnal temperature cycle. We show that temperature-driven responses can be dominant in multisensory contexts such that, when thermal drive is strong, iL3s preferentially engage in temperature-driven behaviors despite the presence of an attractive host odorant. Finally, targeted mutagenesis of the S. stercoralis tax-4 homolog abolishes heat seeking, providing the first evidence that parasitic host-seeking behaviors are generated through an adaptation of sensory cascades that drive environmental navigation in C. elegans [7, 8, 9, 10]. Together, our results provide insight into the behavioral strategies and molecular mechanisms that allow skin-penetrating nematodes to target humans.
       
  • The Iceman’s Last Meal Consisted of Fat, Wild Meat, and Cereals
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Frank Maixner, Dmitrij Turaev, Amaury Cazenave-Gassiot, Marek Janko, Ben Krause-Kyora, Michael R. Hoopmann, Ulrike Kusebauch, Mark Sartain, Gea Guerriero, Niall O’Sullivan, Matthew Teasdale, Giovanna Cipollini, Alice Paladin, Valeria Mattiangeli, Marco Samadelli, Umberto Tecchiati, Andreas Putzer, Mine Palazoglu, John Meissen, Sandra LöschSummaryThe history of humankind is marked by the constant adoption of new dietary habits affecting human physiology, metabolism, and even the development of nutrition-related disorders. Despite clear archaeological evidence for the shift from hunter-gatherer lifestyle to agriculture in Neolithic Europe [1], very little information exists on the daily dietary habits of our ancestors. By undertaking a complementary -omics approach combined with microscopy, we analyzed the stomach content of the Iceman, a 5,300-year-old European glacier mummy [2, 3]. He seems to have had a remarkably high proportion of fat in his diet, supplemented with fresh or dried wild meat, cereals, and traces of toxic bracken. Our multipronged approach provides unprecedented analytical depth, deciphering the nutritional habit, meal composition, and food-processing methods of this Copper Age individual.
       
  • Theta Rhythmic Neuronal Activity and Reaction Times Arising from Cortical
           Receptive Field Interactions during Distributed Attention
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Ricardo Kienitz, Joscha T. Schmiedt, Katharine A. Shapcott, Kleopatra Kouroupaki, Richard C. Saunders, Michael Christoph SchmidSummaryGrowing evidence suggests that distributed spatial attention may invoke theta (3–9 Hz) rhythmic sampling processes. The neuronal basis of such attentional sampling is, however, not fully understood. Here we show using array recordings in visual cortical area V4 of two awake macaques that presenting separate visual stimuli to the excitatory center and suppressive surround of neuronal receptive fields (RFs) elicits rhythmic multi-unit activity (MUA) at 3–6 Hz. This neuronal rhythm did not depend on small fixational eye movements. In the context of a distributed spatial attention task, during which the monkeys detected a spatially and temporally uncertain target, reaction times (RTs) exhibited similar rhythmic fluctuations. RTs were fast or slow depending on the target occurrence during high or low MUA, resulting in rhythmic MUA-RT cross-correlations at theta frequencies. These findings show that theta rhythmic neuronal activity can arise from competitive RF interactions and that this rhythm may result in rhythmic RTs potentially subserving attentional sampling.
       
  • A Glutamatergic Hypothalamomedullary Circuit Mediates Thermogenesis, but
           Not Heat Conservation, during Stress-Induced Hyperthermia
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Natalia L.S. Machado, Stephen B.G. Abbott, Jon M. Resch, Lin Zhu, Elda Arrigoni, Bradford B. Lowell, Patrick M. Fuller, Marco A.P. Fontes, Clifford B. SaperSummaryStress elicits a variety of autonomic responses, including hyperthermia (stress fever) in humans and animals. In this present study, we investigated the circuit basis for thermogenesis and heat conservation during this response. We first demonstrated the glutamatergic identity of the dorsal hypothalamic area (DHAVglut2) neurons that innervate the raphe pallidus nucleus (RPa) to regulate core temperature (Tc) and mediate stress-induced hyperthermia. Then, using chemogenetic and optogenetic methods to manipulate this hypothalamomedullary circuit, we found that activation of DHAVglut2 neurons potently drove an increase in Tc, but surprisingly, stress-induced hyperthermia was only reduced by about one-third when they were inhibited. Further investigation showed that DHAVglut2 neurons activate brown adipose tissue (BAT) but do not cause vasoconstriction, instead allowing reflex tail artery vasodilation as a response to BAT-induced hyperthermia. Retrograde rabies virus tracing revealed projections from DHAVglut2 neurons to RPaVglut3, but not to RPaGABA neurons, and identified a set of inputs to DHAVglut2 → RPa neurons that are likely to mediate BAT activation. The dissociation of the DHAVglut2 thermogenic pathway from the thermoregulatory vasoconstriction (heat-conserving) pathway may explain stress flushing (skin vasodilation but a feeling of being too hot) during stressful times.Graphical Graphical abstract for this article
       
  • Processive Kinesin-14 HSET Exhibits Directional Flexibility Depending on
           Motor Traffic
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Dana N. Reinemann, Stephen R. Norris, Ryoma Ohi, Matthew J. LangSummaryA common mitotic defect observed in cancer cells that possess supernumerary (more than two) centrosomes is multipolar spindle formation [1, 2]. Such structures are resolved into a bipolar geometry by minus-end-directed motor proteins, such as cytoplasmic dynein and the kinesin-14 HSET [3, 4, 5, 6, 7, 8]. HSET is also thought to antagonize plus-end-directed kinesin-5 Eg5 to balance spindle forces [4, 5, 7, 9]. However, the biomechanics of this force opposition are unclear, as HSET has previously been defined as a non-processive motor [10, 11, 12, 13, 14, 15, 16]. Here, we use optical trapping to elucidate the mechanism of force generation by HSET. We show that a single HSET motor has a processive nature with the ability to complete multiple steps while trapped along a microtubule and when unloaded can move in both directions for microns. Compared to other kinesins, HSET has a relatively weak stall force of 1.1 pN [17, 18]. Moreover, HSET’s tail domain and its interaction with the E-hook of tubulin are necessary for long-range motility. In vitro polarity-marked bundle assays revealed that HSET selectively generates force in anti-parallel bundles on the order of its stall force. When combined with varied ratios of Eg5, HSET adopts Eg5’s directionality while acting as an antagonizing force brake, requiring at least a 10-fold higher Eg5 concentration to surpass HSET’s sliding force. These results reveal HSET’s ability to change roles within the spindle from acting as an adjustable microtubule slider and force regulator to a processive motor that aids in minus end focusing.
       
  • The Central Stalk Determines the Motility of Mitotic Kinesin-14 Homodimers
    • Abstract: Publication date: Available online 12 July 2018Source: Current BiologyAuthor(s): Pan Wang, Kuo-Fu Tseng, Yuan Gao, Michael Cianfrocco, Lijun Guo, Weihong QiuSummaryMitotic kinesin-14 homodimers that contain an N-terminal nonmotor microtubule-binding tail contribute to spindle organization by preferentially crosslinking two different spindle microtubules rather than interacting with a single microtubule to generate processive motility. However, the mechanism underlying such selective motility behavior remains poorly understood. Here, we show that when a flexible polypeptide linker is inserted into the coiled-coil central stalk, two homodimeric mitotic kinesin-14s of distinct motility—the processive plus-end-directed KlpA from Aspergillus nidulans [1] and the nonprocessive minus-end-directed Ncd from Drosophila melanogaster [2]—both switch to become processive minus-end-directed motors. Our results demonstrate that the polypeptide linker introduces greater conformational flexibility into the central stalk. Importantly, we find that the linker insertion significantly weakens the ability of Ncd to preferentially localize between and interact with two microtubules. Collectively, our results reveal that besides the canonical role of enabling dimerization, the central stalk also functions as a mechanical component to determine the motility of homodimeric mitotic kinesin-14 motors. We suggest that the central stalk is an evolutionary design that primes these kinesin-14 motors for nontransport roles within the mitotic spindle.
       
  • Neuroscience: The Key to Consciousness May Not Be under the Streetlight
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): J.D. Knotts, Brian Odegaard, Hakwan LauSummaryKey theories of consciousness predict that the prefrontal cortex (PFC) plays important roles, but there has been relatively little causal evidence showing that manipulation of activity in the region can broadly affect conscious experiences. A new study provides crucial findings to help resolve this issue, showing that direct pharmacological stimulation of PFC restores wakefulness in anesthetized rats.
       
  • Widespread vulnerability of Malagasy predators to the toxins of an
           introduced toad
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Benjamin Michael Marshall, Nicholas R. Casewell, Miguel Vences, Frank Glaw, Franco Andreone, Andolalao Rakotoarison, Giulia Zancolli, Friederike Woog, Wolfgang Wüster
       
  • The Value of Ecosystem Services from Giant Panda Reserves
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Fuwen Wei, Robert Costanza, Qiang Dai, Natalie Stoeckl, Xiaodong Gu, Stephen Farber, Yonggang Nie, Ida Kubiszewski, Yibo Hu, Ronald Swaisgood, Xuyu Yang, Michael Bruford, Youping Chen, Alexey Voinov, Dunwu Qi, Megan Owen, Li Yan, Daniel C. Kenny, Zejun Zhang, Rong HouSummaryEcosystem services (the benefits to humans from ecosystems) are estimated globally at $125 trillion/year [1, 2]. Similar assessments at national and regional scales show how these services support our lives [3]. All valuations recognize the role of biodiversity, which continues to decrease around the world in maintaining these services [4, 5]. The giant panda epitomizes the flagship species [6]. Its unrivalled public appeal translates into support for conservation funding and policy, including a tax on foreign visitors to support its conservation [7]. The Chinese government has established a panda reserve system, which today numbers 67 reserves [8, 9]. The biodiversity of these reserves is among the highest in the temperate world [10], covering many of China’s endemic species [11]. The panda is thus also an umbrella species [12]—protecting panda habitat also protects other species. Despite the benefits derived from pandas, some journalists have suggested that it would be best to let the panda go extinct. With the recent downlisting of the panda from Endangered to Vulnerable, it is clear that society’s investment has started to pay off in terms of panda population recovery [13, 14]. Here, we estimate the value of ecosystem services of the panda and its reserves at between US$2.6 and US$6.9 billion/year in 2010. Protecting the panda as an umbrella species and the habitat that supports it yields roughly 10–27 times the cost of maintaining the current reserves, potentially further motivating expansion of the reserves and other investments in natural capital in China.
       
  • Early African Fossils Elucidate the Origin of Embrithopod Mammals
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Emmanuel Gheerbrant, Arnaud Schmitt, László KocsisSummaryModern mammals rapidly evolved in the early Cenozoic in all continental provinces, including in Africa, with one of the first placental branches, the Afrotheria [1, 2]. Afrotherian evolution is at the origin of the major radiation of African ungulate-like mammals, including extant hyrax, elephant, and sea cow orders, which all belong to the Paenungulata. The paenungulate radiation also includes the extinct order Embrithopoda of uncertain interordinal relationships, which is best known for the giant and strangely specialized Oligocene genus Arsinoitherium. The Ouled Abdoun basin, Morocco, yielded exceptional Paleocene-Eocene fossils documenting the early paenungulate evolution [3, 4, 5, 6, 7, 8]. Here we report two new small Ypresian species, Stylolophus minor n.g., n.sp. and cf. Stylolophus sp., which are the earliest and most primitive embrithopods. The cladistic analysis relates the Embrithopoda to crown paenungulates as the stem-group of the Tethytheria, which makes crown tethytherians restricted to extant elephant and sea cow orders. The Embrithopoda is therefore an early tethytherian offshoot predating the elephant and sea cow divergence. The resulting phylogeny supports a strictly African early radiation of the paenungulates excluding the Phenacolophidae and Anthracobunia. It sustains an at least early Paleocene African origin of the Embrithopoda. The unique tooth pattern of the embrithopods (hyperdilambdodont and pseudolophodont molars) is resolved as evolving early and directly from the dilambdodont (W-shaped labial molar crests) ancestral paenungulate morphotype. The specialized upper molar morphology with two transverse crests is convergent and non-homologous in embrithopods and crown Tethytheria. These convergences for specialized folivorous diet were driven by free herbivorous African niches in the early Paleogene.
       
  • The Earth’s Magnetic Field and Visual Landmarks Steer Migratory Flight
           Behavior in the Nocturnal Australian Bogong Moth
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): David Dreyer, Barrie Frost, Henrik Mouritsen, Anja Günther, Ken Green, Mary Whitehouse, Sönke Johnsen, Stanley Heinze, Eric WarrantSummaryLike many birds [1], numerous species of nocturnal moths undertake spectacular long-distance migrations at night [2]. Each spring, billions of Bogong moths (Agrotis infusa) escape hot conditions in different regions of southeast Australia by making a highly directed migration of over 1,000 km to a limited number of cool caves in the Australian Alps, historically used for aestivating over the summer [3, 4]. How moths determine the direction of inherited migratory trajectories at night and locate their destination (i.e., navigate) is currently unknown [5, 6, 7]. Here we show that Bogong moths can sense the Earth’s magnetic field and use it in conjunction with visual landmarks to steer migratory flight behavior. By tethering migrating moths in an outdoor flight simulator [8], we found that their flight direction turned predictably when dominant visual landmarks and a natural Earth-strength magnetic field were turned together, but that the moths became disoriented within a few minutes when these cues were set in conflict. We thus conclude that Bogong moths, like nocturnally migrating birds [9], can use a magnetic sense. Our results represent the first reliable demonstration of the use of the Earth’s magnetic field to steer flight behavior in a nocturnal migratory insect.Graphical Graphical abstract for this article
       
  • Baculovirus Actin-Based Motility Drives Nuclear Envelope Disruption and
           Nuclear Egress
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Taro Ohkawa, Matthew D. WelchSummaryViruses that replicate in the host cell nucleus face challenges in usurping cellular pathways to enable passage through the nuclear envelope [1]. Baculoviruses are enveloped, double-stranded DNA viruses that infect lepidopteran insects and are tools for protein expression, cell transduction, and pest management [2, 3, 4]. The type species Autographa californica M nucleopolyhedrovirus (AcMNPV) shares with other pathogens an ability to assemble host actin monomers (G-actin) into actin filaments (F-actin) to drive motility [5]. During early infection, actin-based motility in the cytoplasm speeds AcMNPV transit to the nucleus and passage through nuclear pores, enabling nuclear ingress [6, 7]. During late infection, AcMNPV assembles F-actin within the nucleus [8], which is essential for virus production [9, 10]. However, the function of nuclear F-actin is poorly understood [11], and its mechanistic role in AcMNPV infection was unknown. We show that AcMNPV mobilizes actin within the nucleus to promote egress. AcMNPV nucleocapsids exhibit intranuclear actin-based motility, mediated by the viral protein P78/83 and the host Arp2/3 complex. Viral motility drives transit to the nuclear periphery and is required for viruses to enter protrusions of the nuclear envelope. Moreover, actin polymerization is necessary for viral disruption of nuclear envelope integrity during egress. In the cytoplasm, viruses use actin-based motility to reach the plasma membrane to enable budding. Our results demonstrate that pathogens can harness actin polymerization to disrupt the nuclear envelope. Employing actin for nuclear envelope disruption may reflect viral appropriation of normal functions of nuclear actin in nuclear envelope integrity, stability, and remodeling.Graphical Graphical abstract for this article
       
  • Differential Role of Prefrontal and Parietal Cortices in Controlling Level
           of Consciousness
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Dinesh Pal, Jon G. Dean, Tiecheng Liu, Duan Li, Christopher J. Watson, Anthony G. Hudetz, George A. MashourSummaryConsciousness is determined both by level (e.g., being awake versus being anesthetized) and content (i.e., the qualitative aspects of experience). Subcortical areas are known to play a causal role in regulating the level of consciousness [1, 2, 3, 4, 5, 6, 7, 8, 9], but the role of the cortex is less well understood. Clinical and correlative data have been used both to support and refute a role for prefrontal and posterior cortices in the level of consciousness [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]. The prefrontal cortex has extensive reciprocal connections to wake-promoting centers in the brainstem and diencephalon [23, 24], and hence is in a unique position to modulate level of consciousness. Furthermore, a recent study suggested that the prefrontal cortex might be important in regulating level of consciousness [25] but causal evidence, and a comparison with more posterior cortical sites, is lacking. Therefore, to test the hypothesis that prefrontal cortex plays a role in regulating level of consciousness, we attempted to reverse sevoflurane anesthesia by cholinergic or noradrenergic stimulation of the prefrontal prelimbic cortex and two areas of parietal cortex in rat. General anesthesia was defined by loss of the righting reflex, a widely used surrogate measure in rodents. We demonstrate that cholinergic stimulation of prefrontal cortex, but not parietal cortex, restored wake-like behavior, despite continuous exposure to clinically relevant concentrations of sevoflurane anesthesia. Noradrenergic stimulation of the prefrontal and parietal areas resulted in electroencephalographic activation but failed to produce any signs of wake-like behavior. We conclude that cholinergic mechanisms in prefrontal cortex can regulate the level of consciousness.
       
  • An Immune-Responsive Cytoskeletal-Plasma Membrane Feedback Loop in Plants
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Stefan Sassmann, Cecilia Rodrigues, Stephen W. Milne, Anja Nenninger, Ellen Allwood, George R. Littlejohn, Nicholas J. Talbot, Christian Soeller, Brendan Davies, Patrick J. Hussey, Michael J. DeeksSummaryCell wall appositions (CWAs) are produced reactively by the plant immune system to arrest microbial invasion through the local inversion of plant cell growth. This process requires the controlled invagination of the plasma membrane (PM) in coordination with the export of barrier material to the volume between the plant PM and cell wall. Plant actin dynamics are essential to this response, but it remains unclear how exocytosis and the cytoskeleton are linked in space and time to form functional CWAs. Here, we show that actin-dependent trafficking to immune response sites of Arabidopsis thaliana delivers membrane-integrated FORMIN4, which in turn contributes to local cytoskeletal dynamics. Total internal reflection fluorescence (TIRF) microscopy combined with controlled induction of FORMIN4-GFP expression reveals a dynamic population of vesicular bodies that accumulate to form clusters at the PM through an actin-dependent process. Deactivation of FORMIN4 and its close homologs partially compromises subsequent defense and alters filamentous actin (F-actin) distribution at mature CWAs. The localization of FORMIN4 is stable and segregated from the dynamic traffic of the endosomal network. Moreover, the tessellation of FORMIN4 at the PM with meso-domains of PEN3 reveals a fine spatial segregation of destinations for actin-dependent immunity cargo. Together, our data suggest a model where FORMIN4 is a spatial feedback element in a multi-layered, temporally defined sequence of cytoskeletal response. This positional feedback makes a significant contribution to the distribution of actin filaments at the dynamic CWA boundary and to the outcomes of pre-invasion defense.Graphical Graphical abstract for this article
       
  • Multiple Scales of Representation along the Hippocampal Anteroposterior
           Axis in Humans
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Iva K. Brunec, Buddhika Bellana, Jason D. Ozubko, Vincent Man, Jessica Robin, Zhong-Xu Liu, Cheryl Grady, R. Shayna Rosenbaum, Gordon Winocur, Morgan D. Barense, Morris MoscovitchSummaryThe ability to represent the world accurately relies on simultaneous coarse and fine-grained neural information coding, capturing both gist and detail of an experience. The longitudinal axis of the hippocampus may provide a gradient of representational granularity in spatial and episodic memory in rodents and humans [1, 2, 3, 4, 5, 6, 7, 8]. Rodent place cells in the ventral hippocampus exhibit significantly larger place fields and greater autocorrelation than those in the dorsal hippocampus [1, 9, 10, 11], which may underlie a coarser and slower changing representation of space [10, 12]. Recent evidence suggests that properties of cellular dynamics in rodents can be captured with fMRI in humans during spatial navigation [13] and conceptual learning [14]. Similarly, mechanisms supporting granularity along the long axis may also be extrapolated to the scale of fMRI signal. Here, we provide the first evidence for separable scales of representation along the human hippocampal anteroposterior axis during navigation and rest by showing (1) greater similarity among voxel time courses and (2) higher temporal autocorrelation in anterior hippocampus (aHPC), relative to posterior hippocampus (pHPC), the human homologs of ventral and dorsal rodent hippocampus. aHPC voxels exhibited more similar activity at each time point and slower signal change over time than voxels in pHPC, consistent with place field organization in rodents. Importantly, similarity between voxels was related to navigational strategy and episodic memory. These findings provide evidence that the human hippocampus supports an anterior-to-posterior gradient of coarse-to-fine spatiotemporal representations, suggesting the existence of a cross-species mechanism, whereby lower neural similarity supports more complex coding of experience.
       
  • Competition for Space Is Controlled by Apoptosis-Induced Change of Local
           Epithelial Topology
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Alice Tsuboi, Shizue Ohsawa, Daiki Umetsu, Yukari Sando, Erina Kuranaga, Tatsushi Igaki, Koichi FujimotoSummaryDuring the initial stage of tumor progression, oncogenic cells spread despite spatial confinement imposed by surrounding normal tissue. This spread of oncogenic cells (winners) is thought to be governed by selective killing of surrounding normal cells (losers) through a phenomenon called “cell competition” (i.e., supercompetition). Although the mechanisms underlying loser elimination are increasingly apparent, it is not clear how winner cells selectively occupy the space made available following loser apoptosis. Here, we combined live imaging analyses of two different oncogenic clones (Yki/YAP activation and Ras activation) in the Drosophila epithelium with computer simulation of tissue mechanics to elucidate such a mechanism. Contrary to the previous expectation that cell volume loss after apoptosis of loser cells was simply compensated for by the faster proliferation of winner cells, we found that the lost volume was compensated for by rapid cell expansion of winners. Mechanistically, the rapid winner-dominated cell expansion was driven by apoptosis-induced epithelial junction remodeling, which causes re-connection of local cellular connectivity (cell topology) in a manner that selectively increases winner apical surface area. In silico experiments further confirmed that repetition of loser elimination accelerates tissue-scale winner expansion through topological changes over time. Our proposed mechanism for linking loser death and winner expansion provides a new perspective on how tissue homeostasis disruption can initiate from an oncogenic mutation.Graphical Graphical abstract for this article
       
  • Marked Diversity of Unique Cortical Enhancers Enables Neuron-Specific
           Tools by Enhancer-Driven Gene Expression
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Stefan Blankvoort, Menno P. Witter, James Noonan, Justin Cotney, Cliff KentrosSummaryUnderstanding neural circuit function requires individually addressing their component parts: specific neuronal cell types. However, not only do the precise genetic mechanisms specifying neuronal cell types remain obscure, access to these neuronal cell types by transgenic techniques also remains elusive. Whereas most genes are expressed in the brain, the vast majority are expressed in many different kinds of neurons, suggesting that promoters alone are not sufficiently specific to distinguish cell types. However, there are orders of magnitude more distal genetic cis-regulatory elements controlling transcription (i.e., enhancers), so we screened for enhancer activity in microdissected samples of mouse cortical subregions. This identified thousands of novel putative enhancers, many unique to particular cortical subregions. Pronuclear injection of expression constructs containing such region-specific enhancers resulted in transgenic lines driving expression in distinct sets of cells specifically in the targeted cortical subregions, even though the parent gene’s promoter was relatively non-specific. These data showcase the promise of utilizing the genetic mechanisms underlying the specification of diverse neuronal cell types for the development of genetic tools potentially capable of targeting any neuronal circuit of interest, an approach we call enhancer-driven gene expression (EDGE).
       
  • Electrostatic Tuning of a Potassium Channel in Electric Fish
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Immani Swapna, Alfredo Ghezzi, Julia M. York, Michael R. Markham, D. Brent Halling, Ying Lu, Jason R. Gallant, Harold H. ZakonSummaryMolecular variation contributes to the evolution of adaptive phenotypes, though it is often difficult to understand precisely how. The adaptively significant electric organ discharge behavior of weakly electric fish is the direct result of biophysical membrane properties set by ion channels. Here, we describe a voltage-gated potassium-channel gene in African electric fishes that is under positive selection and highly expressed in the electric organ. The channel produced by this gene shortens electric organ action potentials by activating quickly and at hyperpolarized membrane potentials. The source of these properties is a derived patch of negatively charged amino acids in an extracellular loop near the voltage sensor. We demonstrate that this negative patch acts by contributing to the global surface charge rather than by local interactions with specific amino acids in the channel’s extracellular face. We suggest a more widespread role for this loop in the evolutionary tuning of voltage-dependent channels.Graphical Graphical abstract for this article
       
  • Activity-Dependent Actin Remodeling at the Base of Dendritic Spines
           Promotes Microtubule Entry
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Philipp Schätzle, Marta Esteves da Silva, Roderick P. Tas, Eugene A. Katrukha, Hai Yin Hu, Corette J. Wierenga, Lukas C. Kapitein, Casper C. HoogenraadSummaryIn neurons, microtubules form dense bundles and run along the length of axons and dendrites. Occasionally, dendritic microtubules can grow from the shaft directly into dendritic spines. Microtubules target dendritic spines that are undergoing activity-dependent changes, but the mechanism by which microtubules enter spines has remained poorly understood. Using live-cell imaging, high-resolution microscopy, and local glutamate uncaging, we show that local actin remodeling at the base of a spine promotes microtubule spine targeting. Microtubule spine entry is triggered by activation of N-Methyl-D-aspartic acid (NMDA) receptors and calcium influx and requires dynamic actin remodeling. Activity-dependent translocation of the actin remodeling protein cortactin out of the spine correlates with increased microtubule targeting at a single spine level. Our data show that the structural changes in the actin cytoskeleton at the base of the spine are directly involved in microtubule entry and emphasize the importance of actin-microtubule crosstalk in orchestrating synapse function and plasticity.Graphical Graphical abstract for this article
       
  • Cheating on Cheaters Stabilizes Cooperation in Pseudomonas
           aeruginosa
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Özhan Özkaya, Roberto Balbontín, Isabel Gordo, Karina B. XavierSummaryBacterial cooperation can be disrupted by non-producers that can profit from public goods without paying their production cost. A cheater can increase in frequency, exhausting the public good and causing a population collapse. Here, we investigate how interactions among two cheaters for distinct social traits influence the short- and long-term dynamics of polymorphic populations. Using as a model Pseudomonas aeruginosa and its extensively studied social traits, production of the siderophore pyoverdine, and the quorum-sensing regulated elastase, we analyzed the social dynamics of polymorphic populations under conditions where the two traits are required for optimal growth. We show that cheaters for either trait compete with both the wild-type and each other and that mutants for pyoverdine production can prevent a drastic population collapse caused by quorum-sensing cheaters. A simple mathematical model suggests that the observed social dynamics are determined by the ratio of the costs of each social trait, such that the mutant, which avoids paying the highest cost, dominates the population; in contrast, mean fitness of the population is determined by the difference between the benefits and the costs of the social traits. Finally, we demonstrate how quorum-sensing regulation can avoid the full loss of cooperation.Graphical Graphical abstract for this article
       
  • Encoding of Target Detection during Visual Search by Single Neurons in the
           Human Brain
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Shuo Wang, Adam N. Mamelak, Ralph Adolphs, Ueli RutishauserSummaryNeurons in the primate medial temporal lobe (MTL) respond selectively to visual categories such as faces, contributing to how the brain represents stimulus meaning. However, it remains unknown whether MTL neurons continue to encode stimulus meaning when it changes flexibly as a function of variable task demands imposed by goal-directed behavior. While classically associated with long-term memory, recent lesion and neuroimaging studies show that the MTL also contributes critically to the online guidance of goal-directed behaviors such as visual search. Do such tasks modulate responses of neurons in the MTL, and if so, do their responses mirror bottom-up input from visual cortices or do they reflect more abstract goal-directed properties' To answer these questions, we performed concurrent recordings of eye movements and single neurons in the MTL and medial frontal cortex (MFC) in human neurosurgical patients performing a memory-guided visual search task. We identified a distinct population of target-selective neurons in both the MTL and MFC whose response signaled whether the currently fixated stimulus was a target or distractor. This target-selective response was invariant to visual category and predicted whether a target was detected or missed behaviorally during a given fixation. The response latencies, relative to fixation onset, of MFC target-selective neurons preceded those in the MTL by ∼200 ms, suggesting a frontal origin for the target signal. The human MTL thus represents not only fixed stimulus identity, but also task-specified stimulus relevance due to top-down goal relevance.
       
  • Endogenous Stochastic Decoding of the CUG Codon by Competing Ser- and
           Leu-tRNAs in Ascoidea asiatica
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Stefanie Mühlhausen, Hans Dieter Schmitt, Kuan-Ting Pan, Uwe Plessmann, Henning Urlaub, Laurence D. Hurst, Martin KollmarSummaryAlthough the “universal” genetic code is now known not to be universal, and stop codons can have multiple meanings, one regularity remains, namely that for a given sense codon there is a unique translation. Examining CUG usage in yeasts that have transferred CUG away from leucine, we here report the first example of dual coding: Ascoidea asiatica stochastically encodes CUG as both serine and leucine in approximately equal proportions. This is deleterious, as evidenced by CUG codons being rare, never at conserved serine or leucine residues, and predominantly in lowly expressed genes. Related yeasts solve the problem by loss of function of one of the two tRNAs. This dual coding is consistent with the tRNA-loss-driven codon reassignment hypothesis, and provides a unique example of a proteome that cannot be deterministically predicted.Video Graphical Graphical abstract for this article
       
  • Focal Adhesions Undergo Longitudinal Splitting into Fixed-Width Units
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Lorna E. Young, Henry N. HiggsSummaryFocal adhesions (FAs) and stress fibers (SFs) act in concert during cell motility and in response to the extracellular environment. Although the structures of mature FAs and SFs are well studied, less is known about how they assemble and mature de novo during initial cell spreading. In this study using live-cell Airyscan microscopy, we find that FAs undergo “splitting” during their assembly, in which the FA divides along its longitudinal axis. Before splitting, FAs initially appear as assemblies of multiple linear units (FAUs) of 0.3-μm width. Splitting occurs between FAUs, resulting in mature FAs of either a single FAU or of a small number of FAUs that remain attached at their distal tips. Variations in splitting occur based on cell type and extracellular matrix. Depletion of adenomatous polyposis coli (APC) or vasodilator-stimulated phosphoprotein (VASP) results in reduced splitting. FA-associated tension increases progressively during splitting. Early in cell spreading, ventral SFs are detected first, with other SF sub-types (transverse arcs and dorsal SFs) being detected later. Our findings suggest that the fundamental unit of FAs is the fixed-width FAU, and that dynamic interactions between FAUs control adhesion morphology.Graphical Graphical abstract for this article
       
  • Zebrafish Differentially Process Color across Visual Space to Match
           Natural Scenes
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Maxime J.Y. Zimmermann, Noora E. Nevala, Takeshi Yoshimatsu, Daniel Osorio, Dan-Eric Nilsson, Philipp Berens, Tom BadenSummaryAnimal eyes have evolved to process behaviorally important visual information, but how retinas deal with statistical asymmetries in visual space remains poorly understood. Using hyperspectral imaging in the field, in vivo 2-photon imaging of retinal neurons, and anatomy, here we show that larval zebrafish use a highly anisotropic retina to asymmetrically survey their natural visual world. First, different neurons dominate different parts of the eye and are linked to a systematic shift in inner retinal function: above the animal, there is little color in nature, and retinal circuits are largely achromatic. Conversely, the lower visual field and horizon are color rich and are predominately surveyed by chromatic and color-opponent circuits that are spectrally matched to the dominant chromatic axes in nature. Second, in the horizontal and lower visual field, bipolar cell terminals encoding achromatic and color-opponent visual features are systematically arranged into distinct layers of the inner retina. Third, above the frontal horizon, a high-gain UV system piggybacks onto retinal circuits, likely to support prey capture.Graphical Graphical abstract for this article
       
  • Reconfiguration of a Multi-oscillator Network by Light in the
           Drosophila Circadian Clock
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Abhishek Chatterjee, Angélique Lamaze, Joydeep De, Wilson Mena, Elisabeth Chélot, Béatrice Martin, Paul Hardin, Sebastian Kadener, Patrick Emery, François RouyerSummaryThe brain clock that drives circadian rhythms of locomotor activity relies on a multi-oscillator neuronal network. In addition to synchronizing the clock with day-night cycles, light also reformats the clock-driven daily activity pattern. How changes in lighting conditions modify the contribution of the different oscillators to remodel the daily activity pattern remains largely unknown. Our data in Drosophila indicate that light readjusts the interactions between oscillators through two different modes. We show that a morning s-LNv> DN1p circuit works in series, whereas two parallel evening circuits are contributed by LNds and other DN1ps. Based on the photic context, the master pacemaker in the s-LNv neurons swaps its enslaved partner-oscillator—LNd in the presence of light or DN1p in the absence of light—to always link up with the most influential phase-determining oscillator. When exposure to light further increases, the light-activated LNd pacemaker becomes independent by decoupling from the s-LNvs. The calibration of coupling by light is layered on a clock-independent network interaction wherein light upregulates the expression of the PDF neuropeptide in the s-LNvs, which inhibits the behavioral output of the DN1p evening oscillator. Thus, light modifies inter-oscillator coupling and clock-independent output-gating to achieve flexibility in the network. It is likely that the light-induced changes in the Drosophila brain circadian network could reveal general principles of adapting to varying environmental cues in any neuronal multi-oscillator system.Graphical Graphical abstract for this article
       
  • Decision Making: How Fruit Flies Integrate Olfactory Evidence
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Yu-Shan Hung, Mark StopferSummaryNew studies show that, as in mammals, perceptual decision-making behavior in fruit flies involves the integration of sensory information that accumulates over time; this involves a process of dendritic integration that depends on the transcription factor FoxP.
       
  • Developmental Biology: Morphogen in a Dish
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Kristina S. Stapornwongkul, Guillaume Salbreux, Jean-Paul VincentSummaryReconstitution of a Hedgehog morphogen gradient in vitro and in silico reveals the architectural features of the signal transduction pathway that ensure rapid formation of a robust signalling gradient.
       
  • Social Evolution: Selection on Multiple Cooperative Traits Optimizes
           Cost–Benefit Relationships
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Kyle L. Asfahl, Ajai A. DandekarSummaryCooperation is potentially risky in a population where non-producing cheats can reap benefits from and gain a fitness advantage over cooperators. A new study shows that cooperation can be safeguarded by selection on multiple traits.
       
  • Tau Does Not Stabilize Axonal Microtubules but Rather Enables Them to Have
           Long Labile Domains
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Liang Qiang, Xiaohuan Sun, Timothy O. Austin, Hemalatha Muralidharan, Daphney C. Jean, Mei Liu, Wenqian Yu, Peter W. BaasSummaryIt is widely believed that tau stabilizes microtubules in the axon [1, 2, 3] and, hence, that disease-induced loss of tau from axonal microtubules leads to their destabilization [3, 4, 5]. An individual microtubule in the axon has a stable domain and a labile domain [6, 7, 8]. We found that tau is more abundant on the labile domain, which is inconsistent with tau’s proposed role as a microtubule stabilizer. When tau is experimentally depleted from cultured rat neurons, the labile microtubule mass of the axon drops considerably, the remaining labile microtubule mass becomes less labile, and the stable microtubule mass increases. MAP6 (also called stable tubule-only polypeptide), which is normally enriched on the stable domain [9], acquires a broader distribution across the microtubule when tau is depleted, providing a potential explanation for the increase in stable microtubule mass. When MAP6 is depleted, the labile microtubule mass becomes even more labile, indicating that, unlike tau, MAP6 is a genuine stabilizer of axonal microtubules. We conclude that tau is not a stabilizer of axonal microtubules but is enriched on the labile domain of the microtubule to promote its assembly while limiting the binding to it of genuine stabilizers, such as MAP6. This enables the labile domain to achieve great lengths without being stabilized. These conclusions are contrary to tau dogma.Graphical Graphical abstract for this article
       
  • Social Behavior: How the Brain Thinks like a Mom
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Sourish Mukhopadhyay, Lisa StowersSummaryBecoming a parent changes our choices and actions. Identifying the underlying neural circuits is necessary to understand the transformation of an animal’s behavior post-parenthood. Multiple nodes of the ‘parenting circuit’ have now been identified to reveal the workings of a single brain region key to the orchestration of parent-specific behaviors.
       
  • Communication: Potassium Channels Define the Dialect
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Elena O. Gracheva, Sviatoslav N. BagriantsevSummaryWeakly electric fishes use electric pulses to interact with conspecifics, but the molecular origin of species-specific communication is unknown. A new study shows that some properties of the electric fish ‘language’ are dictated by the activity of a voltage-gated potassium channel in electrocytes.
       
  • Cell Competition: How to Take Over the Space Left by Your Neighbours
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Romain LevayerSummaryFast-growing cells can expand in a tissue by eliminating and replacing the neighbouring wild-type cells. A new study provides an elegant explanation for how cell elimination contributes to the preferential expansion of the invading population.
       
  • Auditory Perception: Laurel and Yanny Together at Last
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): D. Pressnitzer, J. Graves, C. Chambers, V. de Gardelle, P. EgréSummaryAn auditory illusion caught the world’s attention recently. For the same noisy speech utterance, different people reported hearing either ‘Laurel’ or ‘Yanny’. The dichotomy highlights how perceptions are inferences from inherently ambiguous sensory information, even though ambiguity is often unnoticed.
       
  • Sensory Biology: How to Structure a Tailor-Made Retina
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Stephan C.F. NeuhaussSummaryA new study of the zebrafish retina using sophisticated imaging has revealed how anisotropic properties of the retina are closely matched to the statistics of the natural visual world that the fish experiences.
       
  • Strengthening functionally specific neural pathways with transcranial
           brain stimulation
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Emilio Chiappini, Juha Silvanto, Paul B. Hibbard, Alessio Avenanti, Vincenzo RomeiSummaryCortico-cortical paired associative stimulation (ccPAS) is a recently established offline dual-coil transcranial magnetic stimulation (TMS) protocol 1, 2, 3 based on the Hebbian principle of associative plasticity and designed to transiently enhance synaptic efficiency in neural pathways linking two interconnected (targeted) brain regions 4, 5. Here, we present a new ‘function-tuning ccPAS’ paradigm in which, by pairing ccPAS with the presentation of a specific visual feature, for example a specific motion direction, we can selectively target and enhance the synaptic efficiency of functionally specific, but spatially overlapping, pathways. We report that ccPAS applied in a state-dependent manner and at a low intensity selectively enhanced detection of the specific motion direction primed during the combined visual-TMS manipulations. This paradigm significantly enhances the specificity of TMS-induced plasticity, by allowing the targeting of cortico-cortical pathways associated with specific functions.
       
  • How does the insect central complex use mushroom body output for
           steering'
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Matthew Collett, Thomas S. CollettSummaryResearch on central brain areas in Drosophila and other insects is revealing the highly conserved neural circuitries in the central complex that are responsible for course control using visual, ideothetic and compass cues 1, 2, and in the mushroom bodies that hold long-term visual and olfactory memories 3, 4. Interactions between these areas are likely to be particularly important for navigation in which long-term memories determine an insect’s course. Many ants, for example, use long-term visual memories for guidance along routes between their nest and food sites. But the interactions remain a puzzle: both because there are no known direct connections between mushroom body and central complex, and because the output from the mushroom body, where the route memories are probably stored [5], may simply signal whether a sensory input is attractive or aversive [4]. Extrapolating from a recent behavioural finding [6], we propose one way that the long-term memories in the mushroom body may be transformed into central complex steering commands. This answer, if correct, may reconcile two apparently conflicting ways of thinking about route following — suggesting how steering along a route can use a feedback controller based on a few prominent features [7], while the route memories themselves are holistic memories of the entire panorama [5]. It also suggests how visual navigation is related to (and possibly evolved from) visual targeting and olfactory-based guidance.
       
  • Methanogenesis
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Zhe Lyu, Nana Shao, Taiwo Akinyemi, William B. WhitmanSummaryMethanogenesis is an anaerobic respiration that generates methane as the final product of metabolism. In aerobic respiration, organic matter such as glucose is oxidized to CO2, and O2 is reduced to H2O. In contrast, during hydrogenotrophic methanogenesis, H2 is oxidized to H+, and CO2 is reduced to CH4. Although similar in principle to other types of respiration, methanogenesis has some distinctive features: the energy yield is very low, ≤1 ATP per methane generated, and only methanogens — organisms capable of this specialized metabolism — carry out biological methane production. Methanogens, like the process they catalyze, are similarly distinctive. Methanogens are comprised exclusively of archaea. They are obligate methane producers, that is, they do not grow using fermentation or alternative electron acceptors for respiration. Finally, methanogens are strict anaerobes and do not grow in the presence of O2. Historically, methanogenesis has been viewed as a highly specialized metabolism restricted to a narrow group of prokaryotes. However, recent developments have revealed enormous diversity within the methanogens and suggest that this metabolism is one of the most ancient on earth.
       
  • Ashleigh Griffin
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Ashleigh Griffin
       
  • Fuxianhuiids
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Javier Ortega-Hernández, Jie Yang, Xi-guang Zhang
       
  • The past, present and future of the beasts that may have made our brains
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Lars Chittka
       
  • The genome sequence of everything
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Michael GrossSummaryA group of genome researchers is making the case for sequencing the genomes of all eukaryotic species within ten years, predicting that it would benefit fundamental biology, conservation, and applied sciences, while not costing more than the first sequencing of the human genome. Michael Gross reports.
       
  • Phylogenomics, Diversification Dynamics, and Comparative Transcriptomics
           across the Spider Tree of Life
    • Abstract: Publication date: 9 July 2018Source: Current Biology, Volume 28, Issue 13Author(s): Rosa Fernández, Robert J. Kallal, Dimitar Dimitrov, Jesús A. Ballesteros, Miquel A. Arnedo, Gonzalo Giribet, Gustavo Hormiga
       
  • γ-TuRC Heterogeneity Revealed by Analysis of Mozart1
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Corinne A. Tovey, Chloe E. Tubman, Eva Hamrud, Zihan Zhu, Anna E. Dyas, Andrew N. Butterfield, Alex Fyfe, Errin Johnson, Paul T. ConduitSummaryMicrotubules are essential for various cell processes [1] and are nucleated by multi-protein γ-tubulin ring complexes (γ-TuRCs) at various microtubule organizing centers (MTOCs), including centrosomes [2, 3, 4, 5, 6]. Recruitment of γ-TuRCs to different MTOCs at different times influences microtubule array formation, but how this is regulated remains an open question. It also remains unclear whether all γ-TuRCs within the same organism have the same composition and how any potential heterogeneity might influence γ-TuRC recruitment. MOZART1 (Mzt1) was recently identified as a γ-TuRC component [7, 8] and is conserved in nearly all eukaryotes [6, 9]. Mzt1 has so far been studied in cultured human cells, yeast, and plants; its absence leads to failures in γ-TuRC recruitment and cell division, resulting in cell death [7, 9, 10, 11, 12, 13, 14, 15]. Mzt1 is small (∼8.5 kDa), binds directly to core γ-TuRC components [9, 10, 14, 15], and appears to mediate the interaction between γ-TuRCs and proteins that tether γ-TuRCs to MTOCs [9, 15]. Here, we use Drosophila to investigate the function of Mzt1 in a multicellular animal for the first time. Surprisingly, we find that Drosophila Mzt1 is expressed only in the testes and is present in γ-TuRCs recruited to basal bodies, but not to mitochondria, in developing sperm cells. mzt1 mutants are viable but have defects in basal body positioning and γ-TuRC recruitment to centriole adjuncts; sperm formation is affected and mutants display a rapid age-dependent decline in sperm motility and male fertility. Our results reveal that tissue-specific and MTOC-specific γ-TuRC heterogeneity exist in Drosophila and highlight the complexity of γ-TuRC recruitment in a multicellular animal.Graphical Graphical abstract for this article
       
  • Co-polymers of Actin and Tropomyosin Account for a Major Fraction of the
           Human Actin Cytoskeleton
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Joyce C.M. Meiring, Nicole S. Bryce, Yao Wang, Manuel H. Taft, Dietmar J. Manstein, Sydney Liu Lau, Jeffrey Stear, Edna C. Hardeman, Peter W. GunningSummaryTropomyosin proteins form stable coiled-coil dimers that polymerize along the α-helical groove of actin filaments [1]. The actin cytoskeleton consists of both co-polymers of actin and tropomyosin and polymers of tropomyosin-free actin [2]. The fundamental distinction between these two types of filaments is that tropomyosin determines the functional capability of actin filaments in an isoform-dependent manner [3, 4, 5, 6, 7, 8, 9]. However, it is unknown what portion of actin filaments are associated with tropomyosin. To address this deficit, we have measured the relative distribution between these two filament populations by quantifying tropomyosin and actin levels in a variety of human cell types, including bone (U2OS); breast epithelial (MCF-10A); transformed breast epithelial (MCF-7); and primary (BJpar), immortalized (BJeH), and Ras-transformed (BJeLR) BJ fibroblasts [10]. Our measurements of tropomyosin and actin predict the saturation of the actin cytoskeleton, implying that tropomyosin binding must be inhibited in order to generate tropomyosin-free actin filaments. We find the majority of actin filaments to be associated with tropomyosin in four of the six cell lines tested and the portion of actin filaments associated with tropomyosin to decrease with transformation. We also discover that high-molecular-weight (HMW), unlike low-molecular-weight (LMW), tropomyosin isoforms are primarily co-polymerized with actin in untransformed cells. This differential partitioning of tropomyosins is not due to a lack of N-terminal acetylation of LMW tropomyosins, but it is, in part, explained by the susceptibility of soluble HMW tropomyosins to proteasomal degradation. We conclude that actin-tropomyosin co-polymers make up a major fraction of the human actin cytoskeleton.Graphical Graphical abstract for this article
       
  • Motor Error in Parietal Area 5 and Target Error in Area 7 Drive
           Distinctive Adaptation in Reaching
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Masato Inoue, Shigeru KitazawaSummaryErrors in reaching drive trial-by-trial adaptation to compensate for the error. Parietal association areas are implicated in error coding, but whether the parietal error signals directly drive adaptation remains unknown. We first examined the activity of neurons in areas 5 and 7 while two monkeys performed rapid target reaching to clarify whether and how the parietal error signals drive adaptation in reaching. We introduced random errors using a motor-driven prism device to augment random motor errors in reaching. Neurons in both regions encoded information on the target position prior to reaching and information on the motor error after reaching. However, post-movement microstimulation caused trial-by-trial adaptation to cancel the motor error only when it was delivered to area 5. By contrast, stimulation to area 7 caused trial-by-trial adaptation so that the reaching endpoint was adjusted toward the target position. We further hypothesized that area 7 would encode target error that is caused by a target jump during the reach, and our results support this hypothesis. Area 7 neurons encoded target error information, but area 5 neurons did not encode this information. These results suggest that area 5 provides signals for adapting to motor errors and that area 7 provides signals to adapt to target errors.
       
  • Ion Channels Regulate Nyctinastic Leaf Opening in Samanea saman
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Takaya Oikawa, Yasuhiro Ishimaru, Shintaro Munemasa, Yusuke Takeuchi, Kento Washiyama, Shin Hamamoto, Nobuyuki Yoshikawa, Yoshiyuki Mutara, Nobuyuki Uozumi, Minoru UedaSummaryThe circadian leaf opening and closing (nyctinasty) of Fabaceae has attracted scientists’ attention since the era of Charles Darwin. Nyctinastic movement is triggered by the alternate swelling and shrinking of motor cells at the base of the leaf. This, in turn, is facilitated by changing osmotic pressures brought about by ion flow through anion and potassium ion channels. However, key regulatory ion channels and molecular mechanisms remain largely unknown. Here, we identify three key ion channels in mimosoid tree Samanea saman: the slow-type anion channels, SsSLAH1 and SsSLAH3, and the Shaker-type potassium channel, SPORK2. We show that cell-specific circadian expression of SsSLAH1 plays a key role in nyctinastic leaf opening. In addition, SsSLAH1 co-expressed with SsSLAH3 in flexor (abaxial) motor cells promoted leaf opening. We confirm the importance of SLAH1 in leaf movement using SLAH1-impaired Glycine max. Identification of this “master player” advances our molecular understanding of nyctinasty.
       
  • Recovery of “Lost” Infant Memories in Mice
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Axel Guskjolen, Justin W. Kenney, Juan de la Parra, Bi-ru Amy Yeung, Sheena A. Josselyn, Paul W. FranklandSummaryHippocampus-dependent, event-related memories formed in early infancy in human and non-human animals are rapidly forgotten. Recently we found that high levels of hippocampal neurogenesis contribute to accelerated rates of forgetting during infancy. Here, we ask whether these memories formed in infancy are permanently erased (i.e., storage failure) or become progressively inaccessible with time (i.e., retrieval failure). To do this, we developed an optogenetic strategy that allowed us to permanently express channelrhodopsin-2 (ChR2) in neuronal ensembles that were activated during contextual fear encoding in infant mice. We then asked whether reactivation of ChR2-tagged ensembles in the dentate gyrus was sufficient for memory recovery in adulthood. We found that optogenetic stimulation of tagged dentate gyrus neurons recovered “lost” infant memories up to 3 months following training and that memory recovery was associated with broader reactivation of tagged hippocampal and cortical neuronal ensembles.
       
  • Noradrenaline Modulates Visual Perception and Late Visually Evoked
           Activity
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Hagar Gelbard-Sagiv, Efrat Magidov, Haggai Sharon, Talma Hendler, Yuval NirSummaryAn identical sensory stimulus may or may not be incorporated into perceptual experience, depending on the behavioral and cognitive state of the organism. What determines whether a sensory stimulus will be perceived? While different behavioral and cognitive states may share a similar profile of electrophysiology, metabolism, and early sensory responses, neuromodulation is often different and therefore may constitute a key mechanism enabling perceptual awareness. Specifically, noradrenaline improves sensory responses, correlates with orienting toward behaviorally relevant stimuli, and is markedly reduced during sleep, while experience is largely “disconnected” from external events. Despite correlative evidence hinting at a relationship between noradrenaline and perception, causal evidence remains absent. Here, we pharmacologically down- and upregulated noradrenaline signaling in healthy volunteers using clonidine and reboxetine in double-blind placebo-controlled experiments, testing the effects on perceptual abilities and visually evoked electroencephalography (EEG) and fMRI responses. We found that detection sensitivity, discrimination accuracy, and subjective visibility change in accordance with noradrenaline (NE) levels, whereas decision bias (criterion) is not affected. Similarly, noradrenaline increases the consistency of EEG visually evoked potentials, while lower noradrenaline levels delay response components around 200 ms. Furthermore, blood-oxygen-level-dependent (BOLD) fMRI activations in high-order visual cortex selectively vary along with noradrenaline signaling. Taken together, these results point to noradrenaline as a key factor causally linking visual awareness to external world events.Video Graphical Graphical abstract for this article
       
  • The Rise and Fall of African Rice Cultivation Revealed by Analysis of 246
           New Genomes
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Philippe Cubry, Christine Tranchant-Dubreuil, Anne-Céline Thuillet, Cécile Monat, Marie-Noelle Ndjiondjop, Karine Labadie, Corinne Cruaud, Stefan Engelen, Nora Scarcelli, Bénédicte Rhoné, Concetta Burgarella, Christian Dupuy, Pierre Larmande, Patrick Wincker, Olivier François, François Sabot, Yves VigourouxSummaryAfrican rice (Oryza glaberrima) was domesticated independently from Asian rice. The geographical origin of its domestication remains elusive. Using 246 new whole-genome sequences, we inferred the cradle of its domestication to be in the Inner Niger Delta. Domestication was preceded by a sharp decline of most wild populations that started more than 10,000 years ago. The wild population collapse occurred during the drying of the Sahara. This finding supports the hypothesis that depletion of wild resources in the Sahara triggered African rice domestication. African rice cultivation strongly expanded 2,000 years ago. During the last 5 centuries, a sharp decline of its cultivation coincided with the introduction of Asian rice in Africa. A gene, PROG1, associated with an erect plant architecture phenotype, showed convergent selection in two rice cultivated species, Oryza glaberrima from Africa and Oryza sativa from Asia. In contrast, a shattering gene, SH5, showed selection signature during African rice domestication, but not during Asian rice domestication. Overall, our genomic data revealed a complex history of African rice domestication influenced by important climatic changes in the Saharan area, by the expansion of African agricultural society, and by recent replacement by another domesticated species.
       
  • Electric Fields Elicit Ballooning in Spiders
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Erica L. Morley, Daniel RobertSummaryWhen one thinks of airborne organisms, spiders do not usually come to mind. However, these wingless arthropods have been found 4 km up in the sky [1], dispersing hundreds of kilometers [2]. To disperse, spiders “balloon,” whereby they climb to the top of a prominence, let out silk, and float away. The prevailing view is that drag forces from light wind allow spiders to become airborne [3], yet ballooning mechanisms are not fully explained by current aerodynamic models [4, 5]. The global atmospheric electric circuit and the resulting atmospheric potential gradient (APG) [6] provide an additional force that has been proposed to explain ballooning [7]. Here, we test the hypothesis that electric fields (e-fields) commensurate with the APG can be detected by spiders and are sufficient to stimulate ballooning. We find that the presence of a vertical e-field elicits ballooning behavior and takeoff in spiders. We also investigate the mechanical response of putative sensory receivers in response to both e-field and air-flow stimuli, showing that spider mechanosensory hairs are mechanically activated by weak e-fields. Altogether, the evidence gathered reveals an electric driving force that is sufficient for ballooning. These results also suggest that the APG, as additional meteorological information, can reveal the auspicious time to engage in ballooning. We propose that atmospheric electricity adds key information to our understanding and predictive capability of the ecologically important mass migration patterns of arthropod fauna [8].Video
       
  • The Role of Association in Pre-schoolers’ Solutions to “Spoon Tests”
           of Future Planning
    • Abstract: Publication date: Available online 5 July 2018Source: Current BiologyAuthor(s): Katherine L. Dickerson, James A. Ainge, Amanda M. SeedSummaryImagining the future is a powerful tool for making plans and solving problems. It is thought to rely on the episodic system which also underpins remembering a specific past event [1, 2, 3]. However, the emergence of episodic future thinking over development and evolution is debated [4, 5, 6, 7, 8, 9]. One key source of positive evidence in pre-schoolers and animals is the “spoon test” or item choice test [4, 10], in which participants encounter a problem in one context and then a choice of items in another context, one of which is the solution to the problem. A majority of studies report that most children choose the right item by age 4 [10, 11, 12, 13, 14, 15, cf.16]. Apes and corvids have also been shown to pass versions of the test [17, 18, 19]. However, it has been suggested that a simpler mechanism could be driving choice: the participant simply chooses the item that has been assigned salience or value, without necessarily imagining the future event [16, 20, 21, 22, 23]. We developed a new test in which two of the items offered to children were associated with positive outcomes, but only one was still useful. We found that older children (5-, 6-, and 7-year-olds) chose the correct item at above chance levels, but younger children (3- and 4-year-olds) did not. In further tests, 4-year-olds showed an intact memory for the encoding event. We conclude that positive association substantially impacts performance on item choice tests in 4-year-olds and that future planning may have a more protracted developmental trajectory than episodic memory.
       
  • Selective Attention Controls Olfactory Decisions and the Neural Encoding
           of Odors
    • Abstract: Publication date: Available online 28 June 2018Source: Current BiologyAuthor(s): Kaitlin S. Carlson, Marie A. Gadziola, Emma S. Dauster, Daniel W. WessonSummaryCritical animal behaviors, especially among rodents, are guided by odors in remarkably well-coordinated manners, yet many extramodal sensory cues compete for cognitive resources in these ecological contexts. That rodents can engage in such odor-guided behaviors suggests that they can selectively attend to odors. Indeed, higher-order cognitive processes—such as learning, memory, decision making, and action selection—rely on the proper filtering of sensory cues based on their relative salience. We developed a behavioral paradigm to reveal that rats are capable of selectively attending to odors in the presence of competing extramodal stimuli. We found that this selective attention facilitates accurate odor-guided decisions, which become further strengthened with experience. Further, we uncovered that selective attention to odors adaptively sharpens their representation among neurons in the olfactory tubercle, an olfactory cortex region of the ventral striatum that is considered integral for evaluating sensory information in the context of motivated behaviors. Odor-directed selective attention exerts influences during moments of heightened odor anticipation and enhances odorant representation by increasing stimulus contrast in a signal-to-noise-type coding scheme. Together, these results reveal that rats engage selective attention to optimize olfactory outcomes. Further, our finding of attention-dependent coding in the olfactory tubercle challenges the notion that a thalamic relay is integral for the attentional control of sensory coding.
       
  • The Bilateral Prefronto-striatal Pathway Is Necessary for Learning New
           Goal-Directed Actions
    • Abstract: Publication date: Available online 28 June 2018Source: Current BiologyAuthor(s): Genevra Hart, Laura A. Bradfield, Sandra Y. Fok, Billy Chieng, Bernard W. BalleineSummaryThe acquisition of new goal-directed actions requires the encoding of action-outcome associations. At a neural level, this encoding has been hypothesized to involve a prefronto-striatal circuit extending between the prelimbic cortex (PL) and the posterior dorsomedial striatum (pDMS); however, no research identifying this pathway with any precision has been reported. We started by mapping the prelimbic input to the dorsal and ventral striatum using a combination of retrograde and anterograde tracing with CLARITY and established that PL-pDMS projections share some overlap with projections to the nucleus accumbens core (NAc) in rats. We then tested whether each of these pathways were functionally required for goal-directed learning; we used a pathway-specific dual-virus chemogenetic approach to selectively silence pDMS-projecting or NAc-projecting PL neurons during instrumental training and tested rats for goal-directed action. We found that silencing PL-pDMS projections abolished goal-directed learning, whereas silencing PL-NAc projections left goal-directed learning intact. Finally, we used a three-virus approach to silence bilateral and contralateral pDMS-projecting PL neurons and again blocked goal-directed learning. These results establish that the acquisition of new goal-directed actions depends on the bilateral PL-pDMS pathway driven by intratelencephalic cortical neurons.
       
  • Prefrontal Cortex Represents Long-Term Memory of Object Values for Months
    • Abstract: Publication date: Available online 28 June 2018Source: Current BiologyAuthor(s): Ali Ghazizadeh, Simon Hong, Okihide HikosakaSummaryAs a central hub for cognitive control, prefrontal cortex (PFC) is thought to utilize memories. However, unlike working or short-term memory, the neuronal representation of long-term memory in PFC has not been systematically investigated. Using single-unit recordings in macaques, we show that PFC neurons rapidly update and maintain responses to objects based on short-term reward history. Interestingly, after repeated object-reward association, PFC neurons continue to show value-biased responses to objects even in the absence of reward. This value-biased response is retained for several months after training and is resistant to extinction and to interference from new object-reward learning for many complex objects (>90). Accordingly, the monkeys remember the values of the learned objects for several months in separate testing. These findings reveal that in addition to flexible short-term and low-capacity memories, primate PFC represents stable long-term and high-capacity memories, which could prioritize valuable objects far into the future.
       
  • Cohesin and chromosome segregation
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Vasso Makrantoni, Adele L. MarstonSummaryCohesin is a ring-shaped protein complex that organises the genome, enabling its condensation, expression, repair and transmission. Cohesin is best known for its role in chromosome segregation, where it provides the cohesion that is established between the two newly duplicated sister chromatids during S phase. This cohesion enables the proper attachment of sister chromatids to microtubules of the spindle by resisting their opposing pulling forces. Once all chromosomes are correctly attached, cohesin is abruptly destroyed, triggering the equal segregation of sister chromatids to opposite poles in anaphase. Here we summarise the molecular functions and regulation of cohesin that underlie its central role in chromosome segregation during mitosis.
       
  • Division of Labor during Biofilm Matrix Production
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Anna Dragoš, Heiko Kiesewalter, Marivic Martin, Chih-Yu Hsu, Raimo Hartmann, Tobias Wechsler, Carsten Eriksen, Susanne Brix, Knut Drescher, Nicola Stanley-Wall, Rolf Kümmerli, Ákos T. KovácsSummaryOrganisms as simple as bacteria can engage in complex collective actions, such as group motility and fruiting body formation. Some of these actions involve a division of labor, where phenotypically specialized clonal subpopulations or genetically distinct lineages cooperate with each other by performing complementary tasks. Here, we combine experimental and computational approaches to investigate potential benefits arising from division of labor during biofilm matrix production. We show that both phenotypic and genetic strategies for a division of labor can promote collective biofilm formation in the soil bacterium Bacillus subtilis. In this species, biofilm matrix consists of two major components, exopolysaccharides (EPSs) and TasA. We observed that clonal groups of B. subtilis phenotypically segregate into three subpopulations composed of matrix non-producers, EPS producers, and generalists, which produce both EPSs and TasA. This incomplete phenotypic specialization was outperformed by a genetic division of labor, where two mutants, engineered as specialists, complemented each other by exchanging EPSs and TasA. The relative fitness of the two mutants displayed a negative frequency dependence both in vitro and on plant roots, with strain frequency reaching a stable equilibrium at 30% TasA producers, corresponding exactly to the population composition where group productivity is maximized. Using individual-based modeling, we show that asymmetries in strain ratio can arise due to differences in the relative benefits that matrix compounds generate for the collective and that genetic division of labor can be favored when it breaks metabolic constraints associated with the simultaneous production of two matrix components.Graphical Graphical abstract for this article
       
  • Profilin Negatively Regulates Formin-Mediated Actin Assembly to Modulate
           PAMP-Triggered Plant Immunity
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): He Sun, Zhu Qiao, Khi Pin Chua, Alma Tursic, Xu Liu, Yong-Gui Gao, Yuguang Mu, Xingliang Hou, Yansong MiaoSummaryProfilin functions with formin in actin assembly, a process that regulates multiple aspects of plant development and immune responses. High-level eukaryotes contain multiple isoforms of profilin, formin, and actin, whose partner-specific interactions in actin assembly are not completely understood in plant development and defense responses. To examine the functionally distinct interactions between profilin and formin, we studied all five Arabidopsis profilins and their interactions with formin by using both in vitro biochemical and in vivo cell biology approaches. Unexpectedly, we found a previously undescribed negative regulatory function of AtPRF3 in AtFH1-mediated actin polymerization. The N-terminal 37 residues of AtPRF3 were identified to play a predominant role in inhibiting formin-mediated actin nucleation via their high affinity for the formin polyproline region and their triggering of the oligomerization of AtPRF3. Both in vivo and in vitro mechanistic studies of AtPRF3 revealed a universal mechanism in which the weak interaction between profilin and formin positively regulates actin assembly by ensuring rapid recycling of profilin, whereas profilin oligomerization negatively regulates actin polymerization. Upon recognition of the pathogen-associated molecular pattern, the gene transcription and protein degradation of AtPRF3 are modulated for actin assembly during plant innate immunity. The prf3 Arabidopsis plants show higher sensitivity to the bacterial flagellum peptide in both the plant growth and ROS responses. These findings demonstrate a profilin-mediated actin assembly mechanism underlying the plant immune responses.Graphical Graphical abstract for this article
       
  • Stochastic Seeding Coupled with mRNA Self-Recruitment Generates
           Heterogeneous Drosophila Germ Granules
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Matthew G. Niepielko, Whitby V.I. Eagle, Elizabeth R. GavisSummaryThe formation of ribonucleoprotein assemblies called germ granules is a conserved feature of germline development. In Drosophila, germ granules form at the posterior of the oocyte in a specialized cytoplasm called the germ plasm, which specifies germline fate during embryogenesis. mRNAs, including nanos (nos) and polar granule component (pgc), that function in germline development are localized to the germ plasm through their incorporation into germ granules, which deliver them to the primordial germ cells. Germ granules are nucleated by Oskar (Osk) protein and contain varying combinations and quantities of their constituent mRNAs, which are organized as spatially distinct, multi-copy homotypic clusters. The process that gives rise to such heterogeneous yet organized granules remains unknown. Here, we show that individual nos and pgc transcripts can populate the same nascent granule, and these first transcripts then act as seeds, recruiting additional like transcripts to form homotypic clusters. Within a granule, homotypic clusters grow independently of each other but depend on the simultaneous acquisition of additional Osk. Although granules can contain multiple clusters of a particular mRNA, granule mRNA content is dominated by cluster size. These results suggest that the accumulation of mRNAs in the germ plasm is controlled by the mRNAs themselves through their ability to form homotypic clusters; thus, RNA self-association drives germ granule mRNA localization. We propose that a stochastic seeding and self-recruitment mechanism enables granules to simultaneously incorporate many different mRNAs while ensuring that each becomes enriched to a functional threshold.Graphical Graphical abstract for this article
       
  • A Spatial Map of Onset and Sustained Responses to Speech in the Human
           Superior Temporal Gyrus
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Liberty S. Hamilton, Erik Edwards, Edward F. ChangSummaryTo derive meaning from speech, we must extract multiple dimensions of concurrent information from incoming speech signals. That is, equally important to processing phonetic features is the detection of acoustic cues that give structure and context to the information we hear. How the brain organizes this information is unknown. Using data-driven computational methods on high-density intracranial recordings from 27 human participants, we reveal the functional distinction of neural responses to speech in the posterior superior temporal gyrus according to either onset or sustained response profiles. Though similar response types have been observed throughout the auditory system, we found novel evidence for a major spatial parcellation in which a distinct caudal zone detects acoustic onsets and a rostral-surround zone shows sustained, relatively delayed responses to ongoing speech stimuli. While posterior onset and anterior sustained responses are used substantially during natural speech perception, they are not limited to speech stimuli and are seen even for reversed or spectrally rotated speech. Single-electrode encoding of phonetic features in each zone depended upon whether the sound occurred at sentence onset, suggesting joint encoding of phonetic features and their temporal context. Onset responses in the caudal zone could accurately decode sentence and phrase onset boundaries, providing a potentially important internal mechanism for detecting temporal landmarks in speech and other natural sounds. These findings suggest that onset and sustained responses not only define the basic spatial organization of high-order auditory cortex but also have direct implications for how speech information is parsed in the cortex.Video Graphical Graphical abstract for this article
       
  • Production of Supra-regular Spatial Sequences by Macaque Monkeys
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Xinjian Jiang, Tenghai Long, Weicong Cao, Junru Li, Stanislas Dehaene, Liping WangSummaryUnderstanding and producing embedded sequences in language, music, or mathematics, is a central characteristic of our species. These domains are hypothesized to involve a human-specific competence for supra-regular grammars, which can generate embedded sequences that go beyond the regular sequences engendered by finite-state automata. However, is this capacity truly unique to humans' Using a production task, we show that macaque monkeys can be trained to produce time-symmetrical embedded spatial sequences whose formal description requires supra-regular grammars or, equivalently, a push-down stack automaton. Monkeys spontaneously generalized the learned grammar to novel sequences, including longer ones, and could generate hierarchical sequences formed by an embedding of two levels of abstract rules. Compared to monkeys, however, preschool children learned the grammars much faster using a chunking strategy. While supra-regular grammars are accessible to nonhuman primates through extensive training, human uniqueness may lie in the speed and learning strategy with which they are acquired.
       
  • Developmental Biology: Neurons That Divide Together Wire Together
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Michelle M. Pang, Thomas R. ClandininSummaryRetinotopic maps represent a fundamental organizing principle of visual system wiring. A recent study illustrates how careful coordination of developmental strategies can simultaneously create a diverse array of cell types and establish a complex wiring diagram.
       
  • Microsporidia: A Single Horizontal Gene Transfer Drives a Great Leap
           Forward
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Julius Lukeš, Filip HusníkSummaryHorizontal gene transfer from bacteria to eukaryotes is the subject of much debate. A recent study reveals the instrumental role that the acquisition of bacterial nucleotide transporters played in the evolution of the ubiquitous, intracellular eukaryotic parasites, the microsporidia.
       
  • Amblyopia: The Thalamus Is a No-Go Area for Visual Acuity
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Koen Seignette, Christiaan N. LeveltSummaryWhen one eye does not function well during development, the visual cortex becomes less responsive to it and visual acuity declines. New research suggests that reduced response strength and deteriorating acuity occur in separate circuits.
       
  • Membrane Trafficking: A Little Flexibility Helps Vesicles Get into Shape
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Catherine L. JacksonSummaryFormation of a transport vesicle in membrane trafficking pathways requires deformation of the membrane to form a highly curved structure. A recent study reveals a crucial function for the conical lipid lysophosphatidylinositol in reducing the bending rigidity of the membrane during COPII vesicle budding in the early secretory pathway.
       
  • Animal Cognition: Chimps Use Human Knowledge When Reasoning Statistically
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): William A. RobertsSummaryA recent study found that chimpanzees chose hidden rewards selected by humans from two populations containing different proportions of favoured and non-favoured items; their choice was based on statistical reasoning about random sampling, human preferences, and inferences about humans' knowledge of their own choices.
       
  • Transgenerational Inheritance: Parental Guidance Suggested
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Douglas L. ChalkerSummaryRNAs have been attractive candidates to transmit epigenetic information over multiple generations. In Tetrahymena, a new study demonstrates that the selective degradation of small RNAs that occurs by interaction with the parental genome can communicate altered patterns of heterochromatin formation and DNA elimination in offspring.
       
  • Neuroethology: Fur Seals Don’t Lose Sleep over REM Lost at Sea
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Gianina Ungurean, Niels C. RattenborgSummaryNorthern fur seals forego large amounts of rapid eye movement (REM) sleep when sleeping in water, but remain healthy and do not recover this loss once back on land, challenging current theories for the function of REM sleep.
       
  • Division of Labor: How Microbes Split Their Responsibility
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Babak MomeniSummaryWithin a biofilm, individual cells might perform only a subset of activities required for overall success of the biofilm. A new study examining matrix production, a task necessary for biofilm formation, shows possible mechanisms of genetic or phenotypic division of labor.
       
  • Bio-Linguistics: Monkeys Break Through the Syntax Barrier
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): W. Tecumseh FitchSummaryMacaque monkeys can be trained to produce complex spatial sequences beyond the simplest levels of grammar previously known from animal studies. This indicates cognitive capabilities in the spatial-motor domain that approach the computational complexity level of human syntax.
       
  • Mitochondrial genome of a 22,000-year-old giant panda from southern China
           reveals a new panda lineage
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Albert Min-Shan Ko, Yingqi Zhang, Melinda A. Yang, Yibo Hu, Peng Cao, Xiaotian Feng, Lizhao Zhang, Fuwen Wei, Qiaomei FuSummaryPresent-day giant pandas (Ailuropoda melanoleuca) are estimated to have diverged from their closest relatives, all other bears, ∼20 million years ago, based on molecular data [1]. With fewer than 2,500 individuals living today [2], it is unclear how well genetic data from extant and historical giant pandas [3] reflect the past [3]. To date, there has been no complete mitochondrial DNA (mtDNA) sequenced from an ancient giant panda. Here, we use ancient DNA capture techniques [4] to sequence the complete mitochondrial genome of a ∼22,000-year-old giant panda specimen (radiocarbon date of 21,910–21,495 cal BP with ± 2σ at 95.4% probability; Lab.no Beta-473743) from the Cizhutuo Cave, in Leye County, Guangxi Province, China (Figure 1A). Its date and location in Guangxi, where no wild giant pandas live today, as well as the difficulty of DNA preservation in a hot and humid region, place it as a unique specimen to learn about ancient giant pandas from the last glacial maximum. We find that the mtDNA lineage of the Cizhutuo panda coalesced with present-day pandas ∼183 thousand years ago (kya, 95% HPD, 227–144 kya), earlier than the time to the most recent common ancestor (TMRCA) of mtDNA lineages shared by present-day pandas (∼72 kya, 95% HPD, 94–55 kya, Supplemental Information). Furthermore, the Cizhutuo panda possessed 18 non-synonymous mutations across six mitochondrial genes. Our results show that the Cizhutuo mtDNA lineage underwent a distinct history from that of present-day populations.
       
  • Tick-Bacteria Mutualism Depends on B Vitamin Synthesis Pathways
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Olivier Duron, Olivier Morel, Valérie Noël, Marie Buysse, Florian Binetruy, Renaud Lancelot, Etienne Loire, Claudine Ménard, Olivier Bouchez, Fabrice Vavre, Laurence VialSummaryMutualistic interactions with microbes have facilitated the radiation of major eukaryotic lineages [1, 2]. Microbes can notably provide biochemical abilities, allowing eukaryotes to adapt to novel habitats or to specialize on particular feeding niches [2, 3, 4]. To investigate the importance of mutualisms for the exclusive blood feeding habits of ticks, we focused on a bacterial genus of medical interest, Francisella, which is known to include both virulent intracellular pathogens of vertebrates [5, 6] and maternally inherited symbionts of ticks [7, 8, 9]. Through a series of physiological experiments, we identified a Francisella type, F-Om, as an obligate nutritional mutualist in the life cycle of the African soft tick Ornithodoros moubata. Francisella F-Om mutualism synthesizes B vitamins that are deficient in the blood meal of ticks. Indeed, experimental elimination of Francisella F-Om resulted in alteration of tick life history traits and physical abnormalities, deficiencies which were fully restored with an oral supplement of B vitamins. We also show that Francisella F-Om is maternally transmitted to all maturing tick oocytes, suggesting that this heritable symbiont is an essential adaptive element in the life cycle of O. moubata. The Francisella F-Om genome further revealed a recent origin from a Francisella pathogenic life style, as observed in other Francisella symbionts [6, 7, 10]. Though half of its protein-coding sequences are now pseudogenized or lost, Francisella F-Om has kept several B vitamin synthesis pathways intact, confirming the importance of these genes in evolution of its nutritional mutualism with ticks.
       
  • Perceptual grouping
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Michael H. Herzog
       
  • Claus Schwechheimer
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Claus Schwechheimer
       
  • Darwin meets Waddington
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Steven Henikoff
       
  • The Indo-European ancestors’ tale
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Michael GrossSummaryAncient DNA from populations linked to the common origin and subsequent spread of Indo-European languages offers the unique opportunity to match up a highly detailed linguistic phylogeny with substantial genetic data as well as with the archaeological record. Michael Gross reports.
       
  • Distinct Circuits for Recovery of Eye Dominance and Acuity in Murine
           Amblyopia
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Céleste-Élise Stephany, Xiaokuang Ma, Hilary M. Dorton, Jie Wu, Alexander M. Solomon, Michael G. Frantz, Shenfeng Qiu, Aaron W. McGeeSummaryDegrading vision by one eye during a developmental critical period yields enduring deficits in both eye dominance and visual acuity. A predominant model is that “reactivating” ocular dominance (OD) plasticity after the critical period is required to improve acuity in amblyopic adults. However, here we demonstrate that plasticity of eye dominance and acuity are independent and restricted by the nogo-66 receptor (ngr1) in distinct neuronal populations. Ngr1 mutant mice display greater excitatory synaptic input onto both inhibitory and excitatory neurons with restoration of normal vision. Deleting ngr1 in excitatory cortical neurons permits recovery of eye dominance but not acuity. Reciprocally, deleting ngr1 in thalamus is insufficient to rectify eye dominance but yields improvement of acuity to normal. Abolishing ngr1 expression in adult mice also promotes recovery of acuity. Together, these findings challenge the notion that mechanisms for OD plasticity contribute to the alterations in circuitry that restore acuity in amblyopia.
       
  • Non-canonical mTOR-Independent Role of DEPDC5 in Regulating GABAergic
           Network Development
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Amrutha Swaminathan, Rahma Hassan-Abdi, Solène Renault, Aleksandra Siekierska, Raphaëlle Riché, Meijiang Liao, Peter A.M. de Witte, Constantin Yanicostas, Nadia Soussi-Yanicostas, Pierre Drapeau, Éric SamarutSummaryMutations in DEPDC5 are causal factors for a broad spectrum of focal epilepsies, but the underlying pathogenic mechanisms are still largely unknown. To address this question, a zebrafish depdc5 knockout model showing spontaneous epileptiform events in the brain, increased drug-induced seizure susceptibility, general hypoactivity, premature death at 2–3 weeks post-fertilization, as well as the expected hyperactivation of mTOR signaling was developed. Using this model, the role of DEPDC5 in brain development was investigated using an unbiased whole-transcriptomic approach. Surprisingly, in addition to mTOR-associated genes, many genes involved in synaptic function, neurogenesis, axonogenesis, and GABA network activity were found to be dysregulated in larval brains. Although no gross defects in brain morphology or neuron loss were observed, immunostaining of depdc5−/− brains for several GABAergic markers revealed specific defects in the fine branching of the GABAergic network. Consistently, some defects in depdc5−/− could be compensated for by treatment with GABA, corroborating that GABA signaling is indeed involved in DEPDC5 pathogenicity. Further, the mTOR-independent nature of these neurodevelopmental defects was demonstrated by the inability of rapamycin to rescue the GABAergic network defects observed in depdc5−/− brains and, conversely, the inability of GABA to rescue the hypoactivity in another genetic model showing mTOR hyperactivation. This study hence provides the first in vivo evidence that DEPDC5 plays previously unknown roles apart from its canonical function as an mTOR inhibitor. Moreover, these results propose that defective neurodevelopment of GABAergic networks could be a key factor in epileptogenesis when DEPDC5 is mutated.Graphical Graphical abstract for this article
       
  • Small RNA-Mediated trans-Nuclear and trans-Element Communications in
           Tetrahymena DNA Elimination
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Tomoko Noto, Kazufumi MochizukiSummaryEpigenetic inheritance of acquired traits is widespread among eukaryotes, but how and to what extent such information is transgenerationally inherited is still unclear. The patterns of programmed DNA elimination in ciliates are epigenetically and transgenerationally inherited, and it has been proposed that small RNAs, which shuttle between the germline and the soma, regulate this epigenetic inheritance. In this study, we test the existence and role of such small-RNA-mediated communication by epigenetically disturbing the pattern of DNA elimination in Tetrahymena. We show that the pattern of DNA elimination is, indeed, determined by the selective turnover of small RNAs, which is induced by the interaction between germline-derived small RNAs and the somatic genome. In addition, we show that DNA elimination of an element is regulated by small-RNA-mediated communication with other eliminated elements. By contrast, no evidence obtained thus far supports the notion that transfer of epigenetic information from the soma to the germline, if any, regulates DNA elimination. Our results indicate that small-RNA-mediated trans-nuclear and trans-element communication, in addition to unknown information in the germline genome, contributes to determining the pattern of DNA elimination.Graphical Graphical abstract for this article
       
  • Lysophospholipids Facilitate COPII Vesicle Formation
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Alejandro Melero, Nicolas Chiaruttini, Takefumi Karashima, Isabelle Riezman, Kouichi Funato, Charles Barlowe, Howard Riezman, Aurélien RouxSummaryCoat protein complex II (COPII) proteins form vesicles from the endoplasmic reticulum to export cargo molecules to the Golgi apparatus. Among the many proteins involved in this process, Sec12 is a key regulator, functioning as the guanosine diphosphate (GDP) exchange factor for Sar1p, the small guanosine triphosphatase (GTPase) that initiates COPII assembly. Here we show that overexpression of phospholipase B3 in the thermosensitive sec12-4 mutant partially restores growth and protein transport at non-permissive temperatures. Lipidomics analyses of these cells show a higher content of lysophosphatidylinositol (lysoPI), consistent with the lipid specificity of PLB3. Furthermore, we show that lysoPI is specifically enriched in COPII vesicles isolated from in vitro budding assays. As these results suggested that lysophospholipids could facilitate budding under conditions of defective COPII coat dynamics, we reconstituted COPII binding onto giant liposomes with purified proteins and showed that lysoPI decreases membrane rigidity and enhances COPII recruitment to liposomes. Our results support a mechanical facilitation of COPII budding by lysophospholipids.Graphical Graphical abstract for this article
       
  • Chimpanzees Consider Humans’ Psychological States when Drawing
           Statistical Inferences
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Johanna Eckert, Hannes Rakoczy, Josep Call, Esther Herrmann, Daniel HanusSummaryGreat apes have been shown to be intuitive statisticians: they can use proportional information within a population to make intuitive probability judgments about randomly drawn samples [1, J.E., J.C., J.H., E.H., and H.R., unpublished data]. Humans, from early infancy onward, functionally integrate intuitive statistics with other cognitive domains to judge the randomness of an event [2, 3, 4, 5, 6]. To date, nothing is known about such cross-domain integration in any nonhuman animal, leaving uncertainty about the origins of human statistical abilities. We investigated whether chimpanzees take into account information about psychological states of experimenters (their biases and visual access) when drawing statistical inferences. We tested 21 sanctuary-living chimpanzees in a previously established paradigm that required subjects to infer which of two mixed populations of preferred and non-preferred food items was more likely to lead to a desired outcome for the subject. In a series of three experiments, we found that chimpanzees chose based on proportional information alone when they had no information about experimenters’ preferences and (to a lesser extent) when experimenters had biases for certain food types but drew blindly. By contrast, when biased experimenters had visual access, subjects ignored statistical information and instead chose based on experimenters’ biases. Lastly, chimpanzees intuitively used a violation of statistical likelihoods as indication for biased sampling. Our results suggest that chimpanzees have a random sampling assumption that can be overridden under the appropriate circumstances and that they are able to use mental state information to judge whether this is necessary. This provides further evidence for a shared statistical inference mechanism in apes and humans.
       
  • Decoupling of Nuclear Division Cycles and Cell Size during the Coenocytic
           Growth of the Ichthyosporean Sphaeroforma arctica
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Andrej Ondracka, Omaya Dudin, Iñaki Ruiz-TrilloSummaryCoordination of the cell division cycle with the growth of the cell is critical to achieve cell size homeostasis [1]. Mechanisms coupling the cell division cycle with cell growth have been described across diverse eukaryotic taxa [2, 3, 4], but little is known about how these processes are coordinated in organisms that undergo more complex life cycles, such as coenocytic growth. Coenocytes (multinucleate cells formed by sequential nuclear divisions without cytokinesis) are commonly found across the eukaryotic kingdom, including in animal and plant tissues and several lineages of unicellular eukaryotes [5]. Among the organisms that form coenocytes are ichthyosporeans, a lineage of unicellular holozoans that are of significant interest due to their phylogenetic placement as one of the closest relatives of animals [6]. Here, we characterize the coenocytic cell division cycle in the ichthyosporean Sphaeroforma arctica. We observe that, in laboratory conditions, S. arctica cells undergo a uniform and easily synchronizable coenocytic cell cycle, reaching up to 128 nuclei per cell before cellularization and release of daughter cells. Cycles of nuclear division occur synchronously within the coenocyte and in regular time intervals (11–12 hr). We find that the growth of cell volume is dependent on concentration of nutrients in the media; in contrast, the rate of nuclear division cycles is constant over a range of nutrient concentrations. Together, the results suggest that nuclear division cycles in the coenocytic growth of S. arctica are driven by a timer, which ensures periodic and synchronous nuclear cycles independent of the cell size and growth.Graphical Graphical abstract for this article
       
  • Orthonectids Are Highly Degenerate Annelid Worms
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Philipp H. Schiffer, Helen E. Robertson, Maximilian J. TelfordSummaryThe animal groups of Orthonectida and Dicyemida are tiny, extremely simple, vermiform endoparasites of various marine animals and have been linked in the Mesozoa (Figure 1). The Orthonectida (Figures 1A and 1B) have a few hundred cells, including a nervous system of just ten cells [2], and the Dicyemida (Figure 1C) are even simpler, with ∼40 cells [3]. They are classic “Problematica” [4]—the name Mesozoa suggests an evolutionary position intermediate between Protozoa and Metazoa (animals) [5] and implies that their simplicity is a primitive state, but molecular data have shown they are members of Lophotrochozoa within Bilateria [6, 7, 8, 9], which means that they derive from a more complex ancestor. Their precise affinities remain uncertain, however, and it is disputed whether they even constitute a clade. Ascertaining their affinities is complicated by the very fast evolution observed in their genes, potentially leading to the common systematic error of long-branch attraction (LBA) [10]. Here, we use mitochondrial and nuclear gene sequence data and show that both dicyemids and orthonectids are members of the Lophotrochozoa. Carefully addressing the effects of unequal rates of evolution, we show that the Mesozoa is polyphyletic. While the precise position of dicyemids remains unresolved within Lophotrochozoa, we identify orthonectids as members of the phylum Annelida. This result reveals one of the most extreme cases of body-plan simplification in the animal kingdom; our finding makes sense of an annelid-like cuticle in orthonectids [2] and suggests that the circular muscle cells repeated along their body [11] may be segmental in origin.
       
  • Variation in Plant Defense Suppresses Herbivore Performance
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Ian S. Pearse, Ryan Paul, Paul J. OdeSummaryDefensive variability of crops and natural systems can alter herbivore communities and reduce herbivory [1, 2]. However, it is still unknown how defense variability translates into herbivore suppression. Nonlinear averaging and constraints in physiological tracking (also more generally called time-dependent effects) are the two mechanisms by which defense variability might impact herbivores [3, 4]. We conducted a set of experiments manipulating the mean and variability of a plant defense, showing that defense variability does suppress herbivore performance and that it does so through physiological tracking effects that cannot be explained by nonlinear averaging. While nonlinear averaging predicted higher or the same herbivore performance on a variable defense than on an invariable defense, we show that variability actually decreased herbivore performance and population growth rate. Defense variability reduces herbivore performance in a way that is more than the average of its parts. This is consistent with constraints in physiological matching of detoxification systems for herbivores experiencing variable toxin levels in their diet and represents a more generalizable way of understanding the impacts of variability on herbivory [5]. Increasing defense variability in croplands at a scale encountered by individual herbivores can suppress herbivory, even if that is not anticipated by nonlinear averaging.
       
  • no blokes Is Essential for Male Viability and X Chromosome Gene
           Expression in the Australian Sheep Blowfly
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Rebecca J. Davis, Esther J. Belikoff, Elizabeth H. Scholl, Fang Li, Maxwell J. ScottSummaryIt has been hypothesized that the Drosophila 4th chromosome is derived from an ancient X chromosome [1]. In the Australian sheep blowfly, Lucilia cuprina, the heterochromatic X chromosome contains few active genes and orthologs of Drosophila X-linked genes are autosomal. Of 8 X-linked genes identified previously in L. cuprina, 6 were orthologs of Drosophila 4th-chromosome genes [2]. The X-linked genes were expressed equally in males and females. Here we identify an additional 51 X-linked genes and show that most are dosage compensated. Orthologs of 49 of the 59 X-linked genes are on the 4th chromosome in D. melanogaster. Because painting of fourth (Pof) is important for expression of Drosophila 4th-chromosome genes [3], we used Cas9 to make a loss-of-function knockin mutation in an L. cuprina Pof ortholog we call no blokes (nbl). Homozygous nbl males derived from homozygous nbl mothers die at the late pupal stage. Homozygous nbl females are viable, fertile, and live longer than heterozygous nbl females. RNA expression of most X-linked genes was reduced in homozygous nbl male pupae and to a lesser extent in nbl females compared to heterozygous siblings. The results suggest that NBL could be important for X chromosome dosage compensation in L. cuprina. NBL may also facilitate gene expression in the heterochromatic environment of the X chromosome in both sexes. This study supports the hypothesis on the origin of the Drosophila 4th chromosome and that a POF-like protein was required for normal gene expression on the ancient X chromosome.Graphical Graphical abstract for this article
       
  • Bottlenose Dolphins Retain Individual Vocal Labels in Multi-level
           Alliances
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Stephanie L. King, Whitney R. Friedman, Simon J. Allen, Livia Gerber, Frants H. Jensen, Samuel Wittwer, Richard C. Connor, Michael KrützenSummaryCooperation between allied individuals and groups is ubiquitous in human societies, and vocal communication is known to play a key role in facilitating such complex human behaviors [1, 2]. In fact, complex communication may be a feature of the kind of social cognition required for the formation of social alliances, facilitating both partner choice and the execution of coordinated behaviors [3]. As such, a compelling avenue for investigation is what role flexible communication systems play in the formation and maintenance of cooperative partnerships in other alliance-forming animals. Male bottlenose dolphins in some populations form complex multi-level alliances, where individuals cooperate in the pursuit and defense of an important resource: access to females [4]. These strong relationships can last for decades and are critical to each male’s reproductive success [4]. Convergent vocal accommodation is used to signal social proximity to a partner or social group in many taxa [5, 6], and it has long been thought that allied male dolphins also converge onto a shared signal to broadcast alliance identity [5, 6, 7, 8]. Here, we combine a decade of data on social interactions with dyadic relatedness estimates to show that male dolphins that form multi-level alliances in an open social network retain individual vocal labels that are distinct from those of their allies. Our results differ from earlier reports of signature whistle convergence among males that form stable alliance pairs. Instead, they suggest that individual vocal labels play a central role in the maintenance of differentiated relationships within complex nested alliances.
       
  • Fur Seals Suppress REM Sleep for Very Long Periods without Subsequent
           Rebound
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Oleg I. Lyamin, Peter O. Kosenko, Svetlana M. Korneva, Alexei L. Vyssotski, Lev M. Mukhametov, Jerome M. SiegelSummaryVirtually all land mammals and birds have two sleep states: slow-wave sleep (SWS) and rapid eye movement (REM) sleep [1, 2]. After deprivation of REM sleep by repeated awakenings, mammals increase REM sleep time [3], supporting the idea that REM sleep is homeostatically regulated. Some evidence suggests that periods of REM sleep deprivation for a week or more cause physiological dysfunction and eventual death [4, 5]. However, separating the effects of REM sleep loss from the stress of repeated awakening is difficult [2, 6]. The northern fur seal (Callorhinus ursinus) is a semiaquatic mammal [7]. It can sleep on land and in seawater. The fur seal is unique in showing both the bilateral SWS seen in most mammals and the asymmetric sleep previously reported in cetaceans [8]. Here we show that when the fur seal stays in seawater, where it spends most of its life [7], it goes without or greatly reduces REM sleep for days or weeks. After this nearly complete elimination of REM, it displays minimal or no REM rebound upon returning to baseline conditions. Our data are consistent with the hypothesis that REM sleep may serve to reverse the reduced brain temperature and metabolism effects of bilateral nonREM sleep, a state that is greatly reduced when the fur seal is in the seawater, rather than REM sleep being directly homeostatically regulated. This can explain the absence of REM sleep in the dolphin and other cetaceans and its increasing proportion as the end of the sleep period approaches in humans and other mammals.
       
  • Spatial Memory Engram in the Mouse Retrosplenial Cortex
    • Abstract: Publication date: 18 June 2018Source: Current Biology, Volume 28, Issue 12Author(s): Michal M. Milczarek, Seralynne D. Vann, Frank SengpielSummaryMemory relies on lasting adaptations of neuronal properties elicited by stimulus-driven plastic changes [1]. The strengthening (and weakening) of synapses results in the establishment of functional ensembles. It is presumed that such ensembles (or engrams) are activated during memory acquisition and re-activated upon memory retrieval. The retrosplenial cortex (RSC) has emerged as a key brain area supporting memory [2], including episodic and topographical memory in humans [3, 4, 5], as well as spatial memory in rodents [6, 7]. Dysgranular RSC is densely connected with dorsal stream visual areas [8] and contains place-like and head-direction cells, making it a prime candidate for integrating navigational information [9]. While previous reports [6, 10] describe the recruitment of RSC ensembles during navigational tasks, such ensembles have never been tracked long enough to provide evidence of stable engrams and have not been related to the retention of long-term memory. Here, we used in vivo 2-photon imaging to analyze patterns of activity of over 6,000 neurons within dysgranular RSC. Eight mice were trained on a spatial memory task. Learning was accompanied by the gradual emergence of a context-specific pattern of neuronal activity over a 3-week period, which was re-instated upon retrieval more than 3 weeks later. The stability of this memory engram was predictive of the degree of forgetting; more stable engrams were associated with better performance. This provides direct evidence for the interdependence of spatial memory consolidation and RSC engram formation. Our results demonstrate the participation of RSC in spatial memory storage at the level of neuronal ensembles.
       
 
 
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