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Current Biology
Journal Prestige (SJR): 4.296
Citation Impact (citeScore): 5
Number of Followers: 251  
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ISSN (Print) 0960-9822
Published by Elsevier Homepage  [3159 journals]
  • Systematic Revision of Symbiodiniaceae Highlights the Antiquity and
           Diversity of Coral Endosymbionts
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Todd C. LaJeunesse, John Everett Parkinson, Paul W. Gabrielson, Hae Jin Jeong, James Davis Reimer, Christian R. Voolstra, Scott R. SantosSummaryThe advent of molecular data has transformed the science of organizing and studying life on Earth. Genetics-based evidence provides fundamental insights into the diversity, ecology, and origins of many biological systems, including the mutualisms between metazoan hosts and their micro-algal partners. A well-known example is the dinoflagellate endosymbionts (“zooxanthellae”) that power the growth of stony corals and coral reef ecosystems. Once assumed to encompass a single panmictic species, genetic evidence has revealed a divergent and rich diversity within the zooxanthella genus Symbiodinium. Despite decades of reporting on the significance of this diversity, the formal systematics of these eukaryotic microbes have not kept pace, and a major revision is long overdue. With the consideration of molecular, morphological, physiological, and ecological data, we propose that evolutionarily divergent Symbiodinium “clades” are equivalent to genera in the family Symbiodiniaceae, and we provide formal descriptions for seven of them. Additionally, we recalibrate the molecular clock for the group and amend the date for the earliest diversification of this family to the middle of the Mesozoic Era (∼160 mya). This timing corresponds with the adaptive radiation of analogs to modern shallow-water stony corals during the Jurassic Period and connects the rise of these symbiotic dinoflagellates with the emergence and evolutionary success of reef-building corals. This improved framework acknowledges the Symbiodiniaceae’s long evolutionary history while filling a pronounced taxonomic gap. Its adoption will facilitate scientific dialog and future research on the physiology, ecology, and evolution of these important micro-algae.
  • Actin-Network Architecture Regulates Microtubule Dynamics
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Alexandra Colin, Pavithra Singaravelu, Manuel Théry, Laurent Blanchoin, Zoher GuerouiSummaryCoordination between actin filaments and microtubules is critical to complete important steps during cell division. For instance, cytoplasmic actin filament dynamics play an active role in the off-center positioning of the spindle during metaphase I in mouse oocytes [1, 2, 3] or in gathering the chromosomes to ensure proper spindle formation in starfish oocytes [4, 5], whereas cortical actin filaments control spindle rotation and positioning in adherent cells or in mouse oocytes [6, 7, 8, 9]. Several molecular effectors have been found to facilitate anchoring between the meiotic spindle and the cortical actin [10, 11, 12, 13, 14]. In vitro reconstitutions have provided detailed insights in the biochemical and physical interactions between microtubules and actin filaments [15, 16, 17, 18, 19, 20]. Yet how actin meshwork architecture affects microtubule dynamics is still unclear. Here, we reconstituted microtubule aster in the presence of a meshwork of actin filaments using confined actin-intact Xenopus egg extracts. We found that actin filament branching reduces the lengths and growth rates of microtubules and constrains the mobility of microtubule asters. By reconstituting the interaction between dynamic actin filaments and microtubules in a minimal system based on purified proteins, we found that the branching of actin filaments is sufficient to block microtubule growth and trigger microtubule disassembly. In a further exploration of Xenopus egg extracts, we found that dense and static branched actin meshwork perturbs monopolar spindle assembly by constraining the motion of the spindle pole. Interestingly, monopolar spindle assembly was not constrained in conditions supporting dynamic meshwork rearrangements. We propose that branched actin filament meshwork provides physical barriers that limit microtubule growth.
  • Basal Forebrain and Brainstem Cholinergic Neurons Differentially Impact
           Amygdala Circuits and Learning-Related Behavior
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Teemu Aitta-aho, Y. Audrey Hay, Benjamin U. Phillips, Lisa M. Saksida, Tim J. Bussey, Ole Paulsen, John Apergis-SchouteSummaryThe central cholinergic system and the amygdala are important for motivation and mnemonic processes. Different cholinergic populations innervate the amygdala, but it is unclear how these projections impact amygdala processes. Using optogenetic circuit-mapping strategies in choline acetyltransferase (ChAT)-cre mice, we demonstrate that amygdala-projecting basal forebrain and brainstem ChAT-containing neurons can differentially affect amygdala circuits and behavior. Photo-activating ChAT terminals in vitro revealed the underlying synaptic impact of brainstem inputs to the central lateral division to be excitatory, mediated via the synergistic glutamatergic activation of AMPA and NMDA receptors. In contrast, stimulating basal forebrain inputs to the basal nucleus resulted in endogenous acetylcholine (ACh) release, resulting in biphasic inhibition-excitation responses onto principal neurons. Such response profiles are physiological hallmarks of neural oscillations and could thus form the basis of ACh-mediated rhythmicity in amygdala networks. Consistent with this, in vivo basal forebrain ChAT+ activation strengthened amygdala basal nucleus theta and gamma frequency rhythmicity, both of which continued for seconds after stimulation and were dependent on local muscarinic and nicotinic receptor activation, respectively. Activation of brainstem ChAT-containing neurons, however, resulted in a transient increase in central lateral amygdala activity that was independent of cholinergic receptors. In addition, driving these respective inputs in behaving animals induced opposing appetitive and defensive learning-related behavioral changes. Because learning and memory are supported by both cellular and network-level processes in central cholinergic and amygdala networks, these results provide a route by which distinct cholinergic inputs can convey salient information to the amygdala and promote associative biophysical changes that underlie emotional memories.
  • C. elegans Eats Its Own Intestine to Make Yolk Leading to Multiple
           Senescent Pathologies
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Marina Ezcurra, Alexandre Benedetto, Thanet Sornda, Ann F. Gilliat, Catherine Au, Qifeng Zhang, Sophie van Schelt, Alexandra L. Petrache, Hongyuan Wang, Yila de la Guardia, Shoshana Bar-Nun, Eleanor Tyler, Michael J. Wakelam, David GemsSummaryAging (senescence) is characterized by the development of numerous pathologies, some of which limit lifespan. Key to understanding aging is discovery of the mechanisms (etiologies) that cause senescent pathology. In C. elegans, a major senescent pathology of unknown etiology is atrophy of its principal metabolic organ, the intestine. Here we identify a cause of not only this pathology but also of yolky lipid accumulation and redistribution (a form of senescent obesity): autophagy-mediated conversion of intestinal biomass into yolk. Inhibiting intestinal autophagy or vitellogenesis rescues both visceral pathologies and can also extend lifespan. This defines a disease syndrome leading to multimorbidity and contributing to late-life mortality. Activation of gut-to-yolk biomass conversion by insulin/IGF-1 signaling (IIS) promotes reproduction and senescence. This illustrates how major, IIS-promoted senescent pathologies in C. elegans can originate not from damage accumulation but from direct effects of futile, continued action of a wild-type biological program (vitellogenesis).Graphical Graphical abstract for this article
  • Temporal Regulation of ESCO2 Degradation by the MCM Complex, the
           CUL4-DDB1-VPRBP Complex, and the Anaphase-Promoting Complex
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Masashi Minamino, Shoin Tei, Lumi Negishi, Masato T. Kanemaki, Atsunori Yoshimura, Takashi Sutani, Masashige Bando, Katsuhiko ShirahigeSummarySister chromatid cohesion, mediated by cohesin, is required for accurate chromosome segregation [1, 2]. This process requires acetylation of cohesin subunit SMC3 by evolutionarily conserved cohesin acetyltransferases: Eco1 in budding yeast; XEco1 and XEco2 in Xenopus; and ESCO1 and ESCO2 in human [3, 4, 5, 6, 7, 8, 9, 10]. Eco1 is recruited to chromatin through physical interaction with PCNA [11] and is degraded by the Skp1/Cul1/F-box protein complex after DNA replication to prevent ectopic cohesion formation [12]. In contrast, XEco2 recruitment to chromatin requires prereplication complex formation [13] and is degraded by the anaphase-promoting complex (APC) [14]. In human, whereas ESCO1 is expressed throughout the cell cycle, ESCO2 is detectable in S phase and is degraded after DNA replication [6, 15]. Although PDS5, a cohesin regulator, preferentially promotes ESCO1-dependent SMC3 acetylation [16], little is known about the molecular basis of the temporal regulation of ESCO2. Here, we show that ESCO2 is recruited to chromatin before PCNA accumulation. Whereas no interaction between PCNA and ESCO proteins is observed, ESCO2, but not ESCO1, interacts with the MCM complex through a unique ESCO2 domain. Interestingly, the interaction is required to protect ESCO2 from proteasomal degradation and is attenuated in late S phase. We also found that ESCO2 physically interacts with the CUL4-DDB1-VPRBP E3 ubiquitin ligase complex in late S phase and that post-replicative ESCO2 degradation requires the complex as well as APC. Thus, we propose that the MCM complex couples ESCO2 with DNA replication and that the CUL4-DDB1-VPRBP complex promotes post-replicative ESCO2 degradation, presumably to suppress cohesion formation during mitosis.
  • Global Determinants of Navigation Ability
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Antoine Coutrot, Ricardo Silva, Ed Manley, Will de Cothi, Saber Sami, Véronique D. Bohbot, Jan M. Wiener, Christoph Hölscher, Ruth C. Dalton, Michael Hornberger, Hugo J. SpiersSummaryHuman spatial ability is modulated by a number of factors, including age [1, 2, 3] and gender [4, 5]. Although a few studies showed that culture influences cognitive strategies [6, 7, 8, 9, 10, 11, 12, 13], the interaction between these factors has never been globally assessed as this requires testing millions of people of all ages across many different countries in the world. Since countries vary in their geographical and cultural properties, we predicted that these variations give rise to an organized spatial distribution of cognition at a planetary-wide scale. To test this hypothesis, we developed a mobile-app-based cognitive task, measuring non-verbal spatial navigation ability in more than 2.5 million people and sampling populations in every nation state. We focused on spatial navigation due to its universal requirement across cultures. Using a clustering approach, we find that navigation ability is clustered into five distinct, yet geographically related, groups of countries. Specifically, the economic wealth of a nation was predictive of the average navigation ability of its inhabitants, and gender inequality was predictive of the size of performance difference between males and females. Thus, cognitive abilities, at least for spatial navigation, are clustered according to economic wealth and gender inequalities globally, which has significant implications for cross-cultural studies and multi-center clinical trials using cognitive testing.
  • Ectopic BASL Reveals Tissue Cell Polarity throughout Leaf Development in
           Arabidopsis thaliana
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Catherine Mansfield, Jacob L. Newman, Tjelvar S.G. Olsson, Matthew Hartley, Jordi Chan, Enrico CoenSummaryTissue-wide polarity fields, in which cell polarity is coordinated across the tissue, have been described for planar organs such as the Drosophila wing and are considered important for coordinating growth and differentiation [1]. In planar plant organs, such as leaves, polarity fields have been identified for subgroups of cells, such as stomatal lineages [2], trichomes [3, 4], serrations [5], or early developmental stages [6]. Here, we show that ectopic induction of the stomatal protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) reveals a tissue-wide epidermal polarity field in leaves throughout development. Ectopic GFP-BASL is typically localized toward the proximal end of cells and to one lobe of mature pavement cells, revealing a polarity field that aligns with the proximodistal axis of the leaf (base to tip). The polarity field is largely parallel to the midline of the leaf but diverges in more lateral positions, particularly at later stages in development, suggesting it may be deformed during growth. The polarity field is observed in the speechless mutant, showing that it is independent of stomatal lineages, and is observed in isotropic cells, showing that cell shape anisotropy is not required for orienting polarity. Ectopic BASL forms convergence and divergence points at serrations, mirroring epidermal PIN polarity patterns, suggesting a common underlying polarity mechanism. Thus, we show that similar to the situation in animals, planar plant organs have a tissue-wide cell polarity field, and this may provide a general cellular mechanism for guiding growth and differentiation.Graphical Graphical abstract for this article
  • Phase-Locked Stimulation during Cortical Beta Oscillations Produces
           Bidirectional Synaptic Plasticity in Awake Monkeys
    • Abstract: Publication date: Available online 9 August 2018Source: Current BiologyAuthor(s): Stavros Zanos, Irene Rembado, Daofen Chen, Eberhard E. FetzSummaryThe functional role of cortical beta oscillations, if any, remains unresolved. During oscillations, the periodic fluctuation in excitability of entrained cells modulates transmission of neural impulses and periodically enhances synaptic interactions. The extent to which oscillatory episodes affect activity-dependent synaptic plasticity remains to be determined. In nonhuman primates, we delivered single-pulse electrical cortical stimulation to a “stimulated” site in sensorimotor cortex triggered on a specific phase of ongoing beta (12–25 Hz) field potential oscillations recorded at a separate “triggering” site. Corticocortical connectivity from the stimulated to the triggering site as well as to other (non-triggering) sites was assessed by cortically evoked potentials elicited by test stimuli to the stimulated site, delivered outside of oscillatory episodes. In separate experiments, connectivity was assessed by intracellular recordings of evoked excitatory postsynaptic potentials. The conditioning paradigm produced transient (1–2 s long) changes in connectivity between the stimulated and the triggering site that outlasted the duration of the oscillatory episodes. The direction of the plasticity effect depended on the phase from which stimulation was triggered: potentiation in depolarizing phases, depression in hyperpolarizing phases. Plasticity effects were also seen at non-triggering sites that exhibited oscillations synchronized with those at the triggering site. These findings indicate that cortical beta oscillations provide a spatial and temporal substrate for short-term, activity-dependent synaptic plasticity in primate neocortex and may help explain the role of oscillations in attention, learning, and cortical reorganization.
  • Neuroscience: A Mechanism for Rhythmic Sampling in Vision
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Ayelet N. LandauSummaryOngoing perception ebbs and flows rhythmically. Understanding the source and scope of this phenomenon is an important step in unraveling the foundations of sensory processing. A new study demonstrates that local neuronal interactions generate rhythmic brain activity and correspond to rhythmic performance patterns on a visual-detection task.
  • Phosphorylation of p38 by GRK2 at the Docking Groove Unveils a Novel
           Mechanism for Inactivating p38MAPK
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Sandra Peregrin, Maria Jurado-Pueyo, Pedro M. Campos, Victoria Sanz-Moreno, Ana Ruiz-Gomez, Piero Crespo, Federico Mayor, Cristina Murga
  • Organelle Turnover: A USP30 Safety Catch Restrains the Trigger for
           Mitophagy and Pexophagy
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Ian G. GanleySummaryIt is crucial to remove dysfunctional mitochondria and peroxisomes to prevent cellular damage. Recent work suggests that under basal conditions USP30, a deubiquitinating enzyme, works to ensure that both of these organelles are only turned over at the right time.
  • Drosophila Courtship: Love Is Not Blind
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Tetsuya Nojima, Annika Rings, Stephen F. GoodwinSummaryAnimals rely on sensory cues to help them find suitable mates. Visual cues are particularly useful for locating mates during the day. A new study has revealed key visual neurons in male Drosophila used to identify and pursue potential mates.
  • 3D Body Evolution: Adding a New Dimension to Colonize the Land
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Chihiro Furumizu, Yuki Hirakawa, John L. Bowman, Shinichiro SawaSummaryComplex multicellular plant bodies evolved in both generations of land plants. A new study demonstrates that CLAVATA3-like peptides function via conserved receptors in Physcomitrella patens as key molecules for morphological innovation of 3D growth in land plants.
  • Ecology: Megaherbivores Homogenize the Landscape of Fear
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Robert M. PringleSummaryWhen herbivores avoid areas with high predation risk, the intensity of plant consumption and nutrient deposition is distributed unevenly across landscapes. Experimental work in African savanna ecosystems shows that the biggest herbivores, virtually immune to predators, smooth out these imbalances.
  • Developmental Biology: Reissner’s Fiber and Straightening of
           the Body Axis
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Wolfgang DrieverSummaryA straight longitudinal body axis supports efficient directed locomotion of fish and other vertebrates. New research demonstrates that Reissner’s fiber, an enigmatic structure within the spinal central canal, is essential for development of an extended trunk to tail axis.
  • Social Behavior: A Neural Circuit for Social Behavior in Zebrafish
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Gonzalo G. de Polavieja, Michael B. OrgerSummaryA new study on the zebrafish has discovered a population of forebrain neurons necessary for social orienting, providing a foundation for dissecting social brain networks in this powerful vertebrate model.
  • Courtship Behavior: Hearing New Notes in Classic Songs
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Benjamin de BivortSummaryCourtship depends on communication between partners; for example, male flies sing to entice females. New research, deploying modern statistical techniques, has identified a previously unrecognized note in the song repertoire, expanding the richness of this model system of communication and sexual reproduction.
  • The cephalo-thoracic apparatus of Caputoraptor elegans may have been used
           to squeeze prey
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Petr KočárekSummaryAlienoptera is an insect order recently described from mid-Cretaceous amber [1] and is phylogenetically nested in the Dictyoptera lineage. Alienoptera currently comprises three species: Alienopterus brachyelytrus[1], Alienopterella stigmatica[2] and Caputoraptor elegans[3]. The most interesting is Caputoraptor elegans, which was recently described in Current Biology by Bai and colleagues [3] and which has an unusual cephalo-thoracic device formed by wing-like extensions of the genae and the corresponding edges of the pronotum. Bai and colleagues [3] suggested that the cephalo-thoracic apparatus may have been used to hold the female and male together during copulation. According to this possible function, the cephalo-thoracic apparatus of the female would fit together with the spread forewings of the male while the female was on the back of the male during copulation. This function was proposed based on examination of females and nymphs, and the authors stated that it could be falsified if a male with a similar apparatus were discovered. After examining a male nymph of this species (Figure 1), I here suggest that the cephalo-thoracic apparatus was not used for copulation but was instead used for predation and feeding.
  • Extremely rapid maturation of a wild African annual fish
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Milan Vrtílek, Jakub Žák, Martin Pšenička, Martin ReichardSummaryEphemeral habitats can impose challenging conditions for population persistence. Survival strategies in these environments can range from high dispersal capacity to the evolution of dormant stages able to tolerate a harsh environment outside the temporal window of favourable conditions [1]. Annual killifish have evolved to live in seasonal pools on the African savannah and display a range of adaptations to cope with an unpredictable environment 2, 3. For most of the year, killifish populations survive as diapausing embryos buried in dry sediment. When savannah depressions fill with rainwater, the fish hatch, grow rapidly and, after attaining sexual maturity, reproduce daily 2, 4. Nothobranchius furzeri, a model species in ageing research 2, 3, is distributed in a region where the climate is particularly dry and rains are unpredictable [5]. Here, we demonstrate that the fast juvenile growth and rapid sexual maturation shown by N. furzeri in captivity is actually an underestimate of their natural developmental rate. We estimated the age of N. furzeri in natural populations by counting daily-deposited increments in the otoliths and performing histological analysis of gonads. We found that N. furzeri are capable of reaching sexual maturity within 14 days after hatching, which to our knowledge is the fastest rate of sexual maturation recorded for a vertebrate. We also demonstrate that N. furzeri can grow from an initial length of 5 mm up to 54 mm over the course of a two-week period. Such rapid juvenile development is likely to be adaptive since some pools were entirely desiccated 3–5 weeks after filling, but retained a viable killifish population that reproduced before the adults succumbed to the disappearance of their pool.
  • The suprachiasmatic nucleus
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Andrew P. Patton, Michael H. HastingsSummaryLike it or not, your two suprachiasmatic nuclei (SCN) govern your life: from when you wake up and fall asleep, to when you feel hungry or can best concentrate. Each is composed of approximately 10,000 tightly interconnected neurons, and the pair sit astride the mid-line third ventricle of the hypothalamus, immediately dorsal to the optic chiasm (Figure 1A). Together, they constitute the master circadian clock of the mammalian brain. They generate an internal representation of solar time that is conveyed to every cell in our body and in this way they co-ordinate the daily cycles of physiology and behaviour that adapt us to the twenty-four hour world. The temporary discomfort associated with jetlag is a reminder of the importance of this daily programme, but there is growing recognition that its chronic disruption carries a cost for health of far greater scale. In this primer, we shall briefly review the historical identification of the SCN as the master circadian clock, and then discuss it on three different levels: the cell-autonomous SCN, the SCN as a cellular network and, finally, the SCN as circadian orchestrator. We shall focus on the intrinsic electrical and transcriptional properties of the SCN and how these properties are thought to form an input to, and an output from, its intrinsic cellular clockwork. Second, we shall describe the anatomical arrangement of the SCN, how its sub-regions are delineated by different neuropeptides, and how SCN neurons communicate with each other via these neuropeptides and the neurotransmitter γ-aminobutyric acid (GABA). Finally, we shall discuss how the SCN functions as a circadian oscillator that dictates behaviour, and how intersectional genetic approaches are being used to try to unravel the specific contributions to pacemaking of specific SCN cell populations.
  • Grass stomata
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Katelyn H. McKown, Dominique C. Bergmann
  • Oomycetes
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Marco Thines
  • Dominique Bergmann
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Dominique Bergmann
  • Biological invasions and the homogenization of life on Earth
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Ruth A. Hufbauer
  • Oceans: going deep into their past to understand their future
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Roberto Danovaro
  • Arctic shipping threatens wildlife
    • Abstract: Publication date: 6 August 2018Source: Current Biology, Volume 28, Issue 15Author(s): Michael GrossSummaryThe dramatic decline of sea ice in the Arctic is opening up new shipping routes and other commercial opportunities from resource extraction to tourism. This expansion of human activities into higher latitudes will have serious effects on the Arctic wildlife already impacted by the regional climate changing more rapidly than the global average. Michael Gross reports.
  • Natural Genetic Variation in a Multigenerational Phenotype in
           C. elegans
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Lise Frézal, Emilie Demoinet, Christian Braendle, Eric Miska, Marie-Anne FélixSummaryAlthough heredity mostly relies on the transmission of DNA sequence, additional molecular and cellular features are heritable across several generations. In the nematode Caenorhabditis elegans, insights into such unconventional inheritance result from two lines of work. First, the mortal germline (Mrt) phenotype was defined as a multigenerational phenotype whereby a selfing lineage becomes sterile after several generations, implying multigenerational memory [1, 2]. Second, certain RNAi effects are heritable over several generations in the absence of the initial trigger [3, 4, 5]. Both lines of work converged when the subset of Mrt mutants that are heat sensitive were found to closely correspond to mutants defective in the RNAi-inheritance machinery, including histone modifiers [6, 7, 8, 9]. Here, we report the surprising finding that several C. elegans wild isolates display a heat-sensitive mortal germline phenotype in laboratory conditions: upon chronic exposure to higher temperatures, such as 25°C, lines reproducibly become sterile after several generations. This phenomenon is reversible, as it can be suppressed by temperature alternations at each generation, suggesting a non-genetic basis for the sterility. We tested whether natural variation in the temperature-induced Mrt phenotype was of genetic nature by building recombinant inbred lines between the isolates MY10 (Mrt) and JU1395 (non-Mrt). Using bulk segregant analysis, we detected two quantitative trait loci. After further recombinant mapping and genome editing, we identified the major causal locus as a polymorphism in the set-24 gene, encoding a SET- and SPK-domain protein. We conclude that C. elegans natural populations may harbor natural genetic variation in epigenetic inheritance phenomena.Graphical Graphical abstract for this article
  • Static Dental Disparity and Morphological Turnover in Sharks across the
           End-Cretaceous Mass Extinction
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Mohamad Bazzi, Benjamin P. Kear, Henning Blom, Per E. Ahlberg, Nicolás E. CampioneSummaryThe Cretaceous–Palaeogene (K–Pg) mass extinction profoundly altered vertebrate ecosystems and prompted the radiation of many extant clades [1, 2]. Sharks (Selachimorpha) were one of the few larger-bodied marine predators that survived the K–Pg event and are represented by an almost-continuous dental fossil record. However, the precise dynamics of their transition through this interval remain uncertain [3]. Here, we apply 2D geometric morphometrics to reconstruct global and regional dental morphospace variation among Lamniformes (Mackerel sharks) and Carcharhiniformes (Ground sharks). These clades are prevalent predators in today’s oceans, and were geographically widespread during the late Cretaceous–early Palaeogene. Our results reveal a decoupling of morphological disparity and taxonomic richness. Indeed, shark disparity was nearly static across the K–Pg extinction, in contrast to abrupt declines among other higher-trophic-level marine predators [4, 5]. Nevertheless, specific patterns indicate that an asymmetric extinction occurred among lamniforms possessing low-crowned/triangular teeth and that a subsequent proliferation of carcharhiniforms with similar tooth morphologies took place during the early Paleocene. This compositional shift in post-Mesozoic shark lineages hints at a profound and persistent K–Pg signature evident in the heterogeneity of modern shark communities. Moreover, such wholesale lineage turnover coincided with the loss of many cephalopod [6] and pelagic amniote [5] groups, as well as the explosive radiation of middle trophic-level teleost fishes [1]. We hypothesize that a combination of prey availability and post-extinction trophic cascades favored extant shark antecedents and laid the foundation for their extensive diversification later in the Cenozoic [7, 8, 9, 10].Graphical Graphical abstract for this article
  • Decoupling Yeast Cell Division and Stress Defense Implicates mRNA
           Repression in Translational Reallocation during Stress
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Yi-Hsuan Ho, Evgenia Shishkova, James Hose, Joshua J. Coon, Audrey P. GaschSummaryStress tolerance and rapid growth are often competing interests in cells. Upon severe environmental stress, many organisms activate defense systems concurrent with growth arrest. There has been debate as to whether aspects of the stress-activated transcriptome are regulated by stress or an indirect byproduct of reduced proliferation. For example, stressed Saccharomyces cerevisiae cells mount a common gene expression program called the environmental stress response (ESR) [1] comprised of ∼300 induced (iESR) transcripts involved in stress defense and ∼600 reduced (rESR) mRNAs encoding ribosomal proteins (RPs) and ribosome biogenesis factors (RiBi) important for division. Because ESR activation also correlates with reduced growth rate in nutrient-restricted chemostats and prolonged G1 in slow-growing mutants, an alternate proposal is that the ESR is simply a consequence of reduced division [2, 3, 4, 5]. A major challenge is that past studies did not separate effects of division arrest and stress defense; thus, the true responsiveness of the ESR—and the purpose of stress-dependent rESR repression in particular—remains unclear. Here, we decoupled cell division from the stress response by following transcriptome, proteome, and polysome changes in arrested cells responding to acute stress. We show that the ESR cannot be explained by changes in growth rate or cell-cycle phase during stress acclimation. Instead, failure to repress rESR transcripts reduces polysome association of induced transcripts, delaying production of their proteins. Our results suggest that stressed cells alleviate competition for translation factors by removing mRNAs and ribosomes from the translating pool, directing translational capacity toward induced transcripts to accelerate protein production.Graphical Graphical abstract for this article
  • Impact of Yeast Pigmentation on Heat Capture and Latitudinal Distribution
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Radames J.B. Cordero, Vincent Robert, Gianluigi Cardinali, Ebuka S. Arinze, Susanna M. Thon, Arturo CasadevallSummaryPigmentation is a fundamental characteristic of living organisms that is used to absorb radiation energy and to regulate temperature. Since darker pigments absorb more radiation than lighter ones, they stream more heat, which can provide an adaptive advantage at higher latitudes and a disadvantage near the Tropics, because of the risk of overheating. This intuitive process of color-mediated thermoregulation, also known as the theory of thermal melanism (TTM), has been only tested in ectothermic animal models [1, 2, 3, 4, 5, 6, 7, 8]. Here, we report an association between yeast pigmentation and their latitude of isolation, with dark-pigmented isolates being more frequent away from the Tropics. To measure the impact of microbial pigmentation in energy capture from radiation, we generated 20 pigmented variants of Cryptococcus neoformans and Candida spp. Infrared thermography revealed that dark-pigmented yeasts heated up faster and reached higher temperatures (up to 2-fold) than lighter ones following irradiation. Melanin-pigmented C. neoformans exhibited a growth advantage relative to non-melanized yeasts when incubated under the light at 4°C but increased thermal susceptibility at 25°C ambient temperatures. Our results extend the TTM to microbiology and suggest pigmentation as an ancient adaptation mechanism for gaining thermal energy from radiation. The contribution of microbial pigmentation in heat absorption is relevant to microbial ecology and for estimating global temperatures. The color variations available in yeasts provide new opportunities in chromatology to quantify radiative heat transfer and validate biophysical models of heat flow [9] that are not possible with plants or animals.
  • Circadian Entrainment in Arabidopsis by the Sugar-Responsive
           Transcription Factor bZIP63
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Alexander Frank, Cleverson C. Matiolli, Américo J.C. Viana, Timothy J. Hearn, Jelena Kusakina, Fiona E. Belbin, David Wells Newman, Aline Yochikawa, Dora L. Cano-Ramirez, Anupama Chembath, Kester Cragg-Barber, Michael J. Haydon, Carlos T. Hotta, Michel Vincentz, Alex A.R. Webb, Antony N. DoddSummarySynchronization of circadian clocks to the day-night cycle ensures the correct timing of biological events. This entrainment process is essential to ensure that the phase of the circadian oscillator is synchronized with daily events within the environment [1], to permit accurate anticipation of environmental changes [2, 3]. Entrainment in plants requires phase changes in the circadian oscillator, through unidentified pathways, which alter circadian oscillator gene expression in response to light, temperature, and sugars [4, 5, 6]. To determine how circadian clocks respond to metabolic rhythms, we investigated the mechanisms by which sugars adjust the circadian phase in Arabidopsis [5]. We focused upon metabolic regulation because interactions occur between circadian oscillators and metabolism in several experimental systems [5, 7, 8, 9], but the molecular mechanisms are unidentified. Here, we demonstrate that the transcription factor BASIC LEUCINE ZIPPER63 (bZIP63) regulates the circadian oscillator gene PSEUDO RESPONSE REGULATOR7 (PRR7) to change the circadian phase in response to sugars. We find that SnRK1, a sugar-sensing kinase that regulates bZIP63 activity and circadian period [10, 11, 12, 13, 14] is required for sucrose-induced changes in circadian phase. Furthermore, TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1), which synthesizes the signaling sugar trehalose-6-phosphate, is required for circadian phase adjustment in response to sucrose. We demonstrate that daily rhythms of energy availability can entrain the circadian oscillator through the function of bZIP63, TPS1, and the KIN10 subunit of the SnRK1 energy sensor. This identifies a molecular mechanism that adjusts the circadian phase in response to sugars.Graphical Graphical abstract for this article
  • A Novel Eukaryotic Denitrification Pathway in Foraminifera
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Christian Woehle, Alexandra-Sophie Roy, Nicolaas Glock, Tanita Wein, Julia Weissenbach, Philip Rosenstiel, Claas Hiebenthal, Jan Michels, Joachim Schönfeld, Tal DaganSummaryBenthic foraminifera are unicellular eukaryotes inhabiting sediments of aquatic environments. Several species were shown to store and use nitrate for complete denitrification, a unique energy metabolism among eukaryotes. The population of benthic foraminifera reaches high densities in oxygen-depleted marine habitats, where they play a key role in the marine nitrogen cycle. However, the mechanisms of denitrification in foraminifera are still unknown, and the possibility of a contribution of associated bacteria is debated. Here, we present evidence for a novel eukaryotic denitrification pathway that is encoded in foraminiferal genomes. Large-scale genome and transcriptomes analyses reveal the presence of a denitrification pathway in foraminifera species of the genus Globobulimina. This includes the enzymes nitrite reductase (NirK) and nitric oxide reductase (Nor) as well as a wide range of nitrate transporters (Nrt). A phylogenetic reconstruction of the enzymes’ evolutionary history uncovers evidence for an ancient acquisition of the foraminiferal denitrification pathway from prokaryotes. We propose a model for denitrification in foraminifera, where a common electron transport chain is used for anaerobic and aerobic respiration. The evolution of hybrid respiration in foraminifera likely contributed to their ecological success, which is well documented in palaeontological records since the Cambrian period.
  • Olfactory Landmark-Based Communication in Interacting Drosophila
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Damien Mercier, Yoshiko Tsuchimoto, Kazumi Ohta, Hokto KazamaSummaryTo communicate with conspecifics, animals deploy various strategies to release pheromones, chemical signals modulating social and sexual behaviors [1, 2, 3, 4, 5]. Importantly, a single pheromone induces different behaviors depending on the context and exposure dynamics [6, 7, 8]. Therefore, to comprehend the ethological role of pheromones, it is essential to characterize how neurons in the recipients respond to temporally and spatially fluctuating chemical signals emitted by donors during natural interactions. In Drosophila melanogaster, the male pheromone 11-cis-vaccenyl acetate (cVA) [9] activates specific olfactory receptor neurons (ORNs) [10, 11] to regulate diverse social and sexual behaviors in recipients [12, 13, 14, 15]. Physicochemical analyses have identified this chemical on an animal’s body [16, 17] and in its local environment [18, 19]. However, because these methods are imprecise in capturing spatiotemporal dynamics, it is poorly understood how individual pheromone cues are released, detected, and interpreted by recipients. Here, we developed a system based on bioluminescence to monitor neural activity in freely interacting Drosophila, and investigated the active detection and perception of the naturally emitted cVA. Unexpectedly, neurons specifically tuned to cVA did not exhibit significant activity during physical interactions between males, and instead responded strongly to olfactory landmarks deposited by males. These landmarks mediated attraction through Or67d receptors and allured both sexes to the marked region. Importantly, the landmarks remained attractive even when a pair of flies was engaged in courtship behavior. In contrast, female deposits did not affect the exploration pattern of either sex. Thus, Drosophila use pheromone marking to remotely signal their sexual identity and to enhance social interactions.
  • Presynaptic Inhibition Selectively Gates Auditory Transmission to the
           Brainstem Startle Circuit
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Kathryn M. Tabor, Trevor S. Smith, Mary Brown, Sadie A. Bergeron, Kevin L. Briggman, Harold A. BurgessSummaryFiltering mechanisms prevent a continuous stream of sensory information from swamping perception, leading to diminished focal attention and cognitive processing. Mechanisms for sensory gating are commonly studied using prepulse inhibition, a paradigm that measures the regulated transmission of auditory information to the startle circuit; however, the underlying neuronal pathways are unresolved. Using large-scale calcium imaging, optogenetics, and laser ablations, we reveal a cluster of 30 morphologically identified neurons in zebrafish that suppress the transmission of auditory signals during prepulse inhibition. These neurons project to a key sensorimotor interface in the startle circuit—the termination zone of auditory afferents on the dendrite of a startle command neuron. Direct measurement of auditory nerve neurotransmitter release revealed selective presynaptic inhibition of sensory transmission to the startle circuit, sparing signaling to other brain regions. Our results provide the first cellular resolution circuit for prepulse inhibition in a vertebrate, revealing a central role for presynaptic gating of sensory information to a brainstem motor circuit.
  • A Local Auxin Gradient Regulates Root Cap Self-Renewal and Size
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Carole Dubreuil, Xu Jin, Andreas Grönlund, Urs FischerSummaryOrgan size homeostasis, compensatory growth to replace lost tissue, requires constant measurement of size and adjustment of growth rates. Morphogen gradients control organ and tissue sizes by regulating stem cell activity, cell differentiation, and removal in animals [1, 2, 3]. In plants, control of tissue size is of specific importance in root caps to protect the growing root tip from mechanical damage [4]. New root cap tissue is formed by the columella and lateral root-cap-epidermal stem cells, whose activity is regulated through non-dividing niche-like cells, the quiescent center (QC) [4, 5]. Columella daughter cells in contact with the QC retain the potency to divide, while derivatives oriented toward the mature cap undergo differentiation. The outermost columella layers are sequentially separated from the root body, involving remodeling of cell walls [6]. Factors regulating the balance between cell division, elongation, and separation to keep root cap size constant are currently unknown [4]. Here, we report that stem cell proliferation induced cell separation at the periphery of the root cap, resulting in tissue size homeostasis. An auxin response gradient with a maximum in the QC and a minimum in the detaching layer was established prior to the onset of cell separation. In agreement with a mathematical model, tissue size was positively regulated by the amount of auxin released from the source. Auxin transporters localized non-polarly to plasma membranes of the inner cap, partly isolating separating layers from the auxin source. Together, these results are in support of an auxin gradient measuring and regulating tissue size.Graphical Graphical abstract for this article
  • Birds Learn Socially to Recognize Heterospecific Alarm Calls by Acoustic
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Dominique A. Potvin, Chaminda P. Ratnayake, Andrew N. Radford, Robert D. MagrathSummaryAnimals in natural communities gain information from members of other species facing similar ecological challenges [1, 2, 3, 4, 5], including many vertebrates that recognize the alarm calls of heterospecifics vulnerable to the same predators [6]. Learning is critical in explaining this widespread recognition [7, 8, 9, 10, 11, 12, 13], but there has been no test of the role of social learning in alarm-call recognition, despite the fact that it is predicted to be important in this context [14, 15]. We show experimentally that wild superb fairy-wrens, Malurus cyaneus, learn socially to recognize new alarm calls and can do so through the previously undemonstrated mechanism of acoustic-acoustic association of unfamiliar with known alarm calls. Birds were trained in the absence of any predator by broadcasting unfamiliar sounds, to which they did not originally flee, in combination with a chorus of conspecific and heterospecific aerial alarm calls (typically given to hawks in flight). The fairy-wrens responded to the new sounds after training, usually by fleeing to cover, and responded equally as strongly in repeated tests over a week. Control playbacks showed that the response was not due simply to greater wariness. Fairy-wrens therefore learnt to associate new calls with known alarm calls, without having to see the callers or a predator. This acoustic-acoustic association mechanism of social learning could result in the rapid spread of alarm-call recognition in natural communities, even when callers or predators are difficult to observe. Moreover, this mechanism offers potential for use in conservation by enhancing training of captive-bred individuals before release into the wild.Graphical Graphical abstract for this article
  • Chloroplast Biogenesis Controlled by DELLA-TOC159 Interaction in Early
           Plant Development
    • Abstract: Publication date: Available online 2 August 2018Source: Current BiologyAuthor(s): Venkatasalam Shanmugabalaji, Hicham Chahtane, Sonia Accossato, Michèle Rahire, Guillaume Gouzerh, Luis Lopez-Molina, Felix KesslerSummaryChloroplast biogenesis, visible as greening, is the key to photoautotrophic growth in plants. At the organelle level, it requires the development of non-photosynthetic, color-less proplastids to photosynthetically active, green chloroplasts at early stages of plant development, i.e., in germinating seeds. This depends on the import of thousands of different preproteins into the developing organelle by the chloroplast protein import machinery [1]. The preprotein import receptor TOC159 is essential in the process, its mutation blocking chloroplast biogenesis and resulting in albino plants [2]. The molecular mechanisms controlling the onset of chloroplast biogenesis during germination are largely unknown. Germination depends on the plant hormone gibberellic acid (GA) and is repressed by DELLA when GA concentrations are low [3, 4]. Here, we show that DELLA negatively regulates TOC159 protein abundance under low GA. The direct DELLA-TOC159 interaction promotes TOC159 degradation by the ubiquitin/proteasome system (UPS). Moreover, the accumulation of photosynthesis-associated proteins destined for the chloroplast is downregulated posttranscriptionally. Analysis of a model import substrate indicates that it is targeted for removal by the UPS prior to import. Thus, under low GA, the UPS represses chloroplast biogenesis by a dual mechanism comprising the DELLA-dependent destruction of the import receptor TOC159, as well as that of its protein cargo. In conclusion, our data provide a molecular framework for the GA hormonal control of proplastid to chloroplast transition during early plant development.Graphical Graphical abstract for this article
  • Forebrain Control of Behaviorally Driven Social Orienting in Zebrafish
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Sarah J. Stednitz, Erin M. McDermott, Denver Ncube, Alexandra Tallafuss, Judith S. Eisen, Philip WashbourneSummaryDeficits in social engagement are diagnostic of multiple neurodevelopmental disorders, including autism and schizophrenia [1]. Genetically tractable animal models like zebrafish (Danio rerio) could provide valuable insight into developmental factors underlying these social impairments, but this approach is predicated on the ability to accurately and reliably quantify subtle behavioral changes. Similarly, characterizing local molecular and morphological phenotypes requires knowledge of the neuroanatomical correlates of social behavior. We leveraged behavioral and genetic tools in zebrafish to both refine our understanding of social behavior and identify brain regions important for driving it. We characterized visual social interactions between pairs of adult zebrafish and discovered that they perform a stereotyped orienting behavior that reflects social attention [2]. Furthermore, in pairs of fish, the orienting behavior of one individual is the primary factor driving the same behavior in the other individual. We used manual and genetic lesions to investigate the forebrain contribution to this behavior and identified a population of neurons in the ventral telencephalon whose ablation suppresses social interactions, while sparing other locomotor and visual behaviors. These neurons are cholinergic and express the gene encoding the transcription factor Lhx8a, which is required for development of cholinergic neurons in the mouse forebrain [3]. The neuronal population identified in zebrafish lies in a region homologous to mammalian forebrain regions implicated in social behavior such as the lateral septum [4]. Our data suggest that an evolutionarily conserved population of neurons controls social orienting in zebrafish.Graphical Graphical abstract for this article
  • Low Levels of Artificial Light at Night Strengthen Top-Down Control in
           Insect Food Web
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Dirk Sanders, Rachel Kehoe, Dave Cruse, F.J. Frank van Veen, Kevin J. GastonSummaryArtificial light has transformed the nighttime environment of large areas of the earth, with 88% of Europe and almost 50% of the United States experiencing light-polluted night skies [1]. The consequences for ecosystems range from exposure to high light intensities in the vicinity of direct light sources to the very widespread but lower lighting levels further away [2]. While it is known that species exhibit a range of physiological and behavioral responses to artificial nighttime lighting [e.g., 3, 4, 5], there is a need to gain a mechanistic understanding of whole ecological community impacts [6, 7], especially to different light intensities. Using a mesocosm field experiment with insect communities, we determined the impact of intensities of artificial light ranging from 0.1 to 100 lux on different trophic levels and interactions between species. Strikingly, we found the strongest impact at low levels of artificial lighting (0.1 to 5 lux), which led to a 1.8 times overall reduction in aphid densities. Mechanistically, artificial light at night increased the efficiency of parasitoid wasps in attacking aphids, with twice the parasitism rate under low light levels compared to unlit controls. However, at higher light levels, parasitoid wasps spent longer away from the aphid host plants, diminishing this increased efficiency. Therefore, aphids reached higher densities under increased light intensity as compared to low levels of lighting, where they were limited by higher parasitoid efficiency. Our study highlights the importance of different intensities of artificial light in driving the strength of species interactions and ecosystem functions.
  • Discovery of a New Song Mode in Drosophila Reveals Hidden Structure in the
           Sensory and Neural Drivers of Behavior
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Jan Clemens, Philip Coen, Frederic A. Roemschied, Talmo D. Pereira, David Mazumder, Diego E. Aldarondo, Diego A. Pacheco, Mala MurthySummaryDeciphering how brains generate behavior depends critically on an accurate description of behavior. If distinct behaviors are lumped together, separate modes of brain activity can be wrongly attributed to the same behavior. Alternatively, if a single behavior is split into two, the same neural activity can appear to produce different behaviors. Here, we address this issue in the context of acoustic communication in Drosophila. During courtship, males vibrate their wings to generate time-varying songs, and females evaluate songs to inform mating decisions. For 50 years, Drosophila melanogaster song was thought to consist of only two modes, sine and pulse, but using unsupervised classification methods on large datasets of song recordings, we now establish the existence of at least three song modes: two distinct pulse types, along with a single sine mode. We show how this seemingly subtle distinction affects our interpretation of the mechanisms underlying song production and perception. Specifically, we show that visual feedback influences the probability of producing each song mode and that male song mode choice affects female responses and contributes to modulating his song amplitude with distance. At the neural level, we demonstrate how the activity of four separate neuron types within the fly’s song pathway differentially affects the probability of producing each song mode. Our results highlight the importance of carefully segmenting behavior to map the underlying sensory, neural, and genetic mechanisms.
  • AMPK-Mediated BECN1 Phosphorylation Promotes Ferroptosis by Directly
           Blocking System Xc – Activity
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Xinxin Song, Shan Zhu, Pan Chen, Wen Hou, Qirong Wen, Jiao Liu, Yangchun Xie, Jinbao Liu, Daniel J. Klionsky, Guido Kroemer, Michael T. Lotze, Herbert J. Zeh, Rui Kang, Daolin TangSummaryFerroptosis is a form of regulated cell death triggered by lipid peroxidation after inhibition of the cystine/glutamate antiporter system Xc–. However, key regulators of system Xc– activity in ferroptosis remain undefined. Here, we show that BECN1 plays a hitherto unsuspected role in promoting ferroptosis through directly blocking system Xc– activity via binding to its core component, SLC7A11 (solute carrier family 7 member 11). Knockdown of BECN1 by shRNA inhibits ferroptosis induced by system Xc– inhibitors (e.g., erastin, sulfasalazine, and sorafenib), but not other ferroptosis inducers including RSL3, FIN56, and buthionine sulfoximine. Mechanistically, AMP-activated protein kinase (AMPK)-mediated phosphorylation of BECN1 at Ser90/93/96 is required for BECN1-SLC7A11 complex formation and lipid peroxidation. Inhibition of PRKAA/AMPKα by siRNA or compound C diminishes erastin-induced BECN1 phosphorylation at S93/96, BECN1-SLC7A11 complex formation, and subsequent ferroptosis. Accordingly, a BECN1 phosphorylation-defective mutant (S90,93,96A) reverses BECN1-induced lipid peroxidation and ferroptosis. Importantly, genetic and pharmacological activation of the BECN1 pathway by overexpression of the protein in tumor cells or by administration of the BECN1 activator peptide Tat-beclin 1, respectively, increases ferroptotic cancer cell death (but not apoptosis and necroptosis) in vitro and in vivo in subcutaneous and orthotopic tumor mouse models. Collectively, our work reveals that BECN1 plays a novel role in lipid peroxidation that could be exploited to improve anticancer therapy by the induction of ferroptosis.Graphical Graphical abstract for this article
  • Carbon Storage and Land-Use Strategies in Agricultural Landscapes across
           Three Continents
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): David R. Williams, Ben Phalan, Claire Feniuk, Rhys E. Green, Andrew BalmfordSummaryThe loss of carbon stocks through agricultural land-use change is a key driver of greenhouse gas emissions [1, 2, 3, 4], and the methods used to manage agricultural land will have major impacts on the global climate in the 21st century [4, 5, 6, 7, 8, 9]. It remains unresolved whether carbon losses would be minimized by increasing farm yields and limiting the conversion of natural habitats (“land sparing”), or maximizing on-farm carbon stocks, even at the cost of reduced yields and therefore greater habitat clearance (“land sharing”). In this paper, we use field surveys of over 11,000 trees, in-depth interviews with farmers, and existing agricultural data, to evaluate the potential impacts of these contrasting approaches, and plausible intermediate strategies, on above-ground carbon stocks across a diverse range of agricultural and natural systems. Our analyses include agroforestry and oil palm plantations in the humid tropics of Ghana; cattle ranching in dry tropical forest in Mexico; and arable cropping in temperate wetlands and forests in Poland. Strikingly, despite the range of systems investigated, land sparing consistently had a higher potential to sustain regional above-ground carbon stocks than any other strategy. This was the case in all three regions and at all plausible levels of food production, including falls in demand. However, if agricultural production increases to meet likely future demand levels, we project large decreases in above-ground carbon stocks, regardless of land-use strategy. Our results strongly suggest that maintaining above-ground carbon stocks will depend on both limiting future food demand and minimizing agricultural expansion through linking high-yield farming with conserving or restoring natural habitats.
  • Construction of a Functional Casparian Strip in Non-endodermal Lineages Is
           Orchestrated by Two Parallel Signaling Systems in Arabidopsis thaliana
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Pengxue Li, Qiaozhi Yu, Xu Gu, Chunmiao Xu, Shilian Qi, Hong Wang, Fenglin Zhong, Tobias I. Baskin, Abidur Rahman, Shuang WuSummaryThe Casparian strip in the root endodermis forms an apoplastic barrier between vascular tissues and outer ground tissues to enforce selective absorption of water and nutrients. Because of its cell-type specificity, the presence of a Casparian strip is used as a marker for a functional endodermis. Here, we examine the minimal regulators required for reprograming non-endodermal cells to build a functional Casparian strip. We demonstrate that the transcription factor SHORT-ROOT (SHR) serves as a master regulator and promotes Casparian strip formation through two independent activities: inducing the expression of essential Casparian strip enzymes via MYB36 and directing the subcellular localization of Casparian strip formation via SCARECROW (SCR). However, this hierarchical signaling cascade still needs SHR-independent small peptides, derived from the stele, to eventually build a functional Casparian strip in non-endodermal cells. Our study provides a synthetic approach to induce Casparian-strip-containing endodermis using a minimal network of regulators and reveals the deployment of both apoplastic and symplastic communication in the promotion of a specific cell fate.
  • Receptor Kinase THESEUS1 Is a Rapid Alkalinization Factor 34 Receptor in
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Martine Gonneau, Thierry Desprez, Marjolaine Martin, Verónica G. Doblas, Laura Bacete, Fabien Miart, Rodnay Sormani, Kian Hématy, Julien Renou, Benoit Landrein, Evan Murphy, Brigitte Van De Cotte, Samantha Vernhettes, Ive De Smet, Herman HöfteSummaryThe growth of plants, like that of other walled organisms, depends on the ability of the cell wall to yield without losing its integrity. In this context, plant cells can sense the perturbation of their walls and trigger adaptive modifications in cell wall polymer interactions. Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) THESEUS1 (THE1) was previously shown in Arabidopsis to trigger growth inhibition and defense responses upon perturbation of the cell wall, but so far, neither the ligand nor the role of the receptor in normal development was known. Here, we report that THE1 is a receptor for the peptide rapid alkalinization factor (RALF) 34 and that this signaling module has a role in the fine-tuning of lateral root initiation. We also show that RALF34-THE1 signaling depends, at least for some responses, on FERONIA (FER), another RALF receptor involved in a variety of processes, including immune signaling, mechanosensing, and reproduction [1]. Together, the results show that RALF34 and THE1 are part of a signaling network that integrates information on the integrity of the cell wall with the coordination of normal morphogenesis.Graphical Graphical abstract for this article
  • Nutrient- and Dose-Dependent Microbiome-Mediated Protection against a
           Plant Pathogen
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Maureen Berg, Britt KoskellaSummaryPlant-associated microbial communities can promote plant nutrient uptake, growth, and resistance to pathogens [1, 2, 3]. Host resistance to infection can increase directly through commensal-pathogen interactions or indirectly through modulation of host defenses [4, 5, 6], the mechanisms of which are best described for rhizosphere-associated bacteria. For example, Arabidopsis plants infected with the foliar pathogen, Pseudomonas syringae pathovar tomato (Pst), increase their root secretion of malate, which attracts Bacillus subtillis to the roots and leads to a stronger host response against Pst [7]. Although there are numerous examples of individual defensive symbionts (e.g., [8]), it is less clear whether this type of protection is an emergent property of whole microbial communities. In particular, relatively little is known about whether and how the presence of phyllosphere (above-ground) microbial communities can increase host resistance against pathogens. In this study, we examined the ability of augmented tomato phyllosphere microbiomes to confer resistance against the causal agent of bacterial speck, Pst. Across five independent experiments, the augmented phyllosphere microbiome was found to decrease pathogen colonization. Furthermore, the dose of commensal bacteria applied affected the degree of protection conferred, and although the effect is dependent on microbial composition, it is not clearly related to overall bacterial diversity. Finally, our results suggest that resources available to the phyllosphere microbial community may play an important role in protection, as the addition of fertilizer abolished the observed microbiome-mediated protection. Together, these results have clear relevance to microbiome-mediated protection within agricultural settings and the use of plant probiotics to increase disease resistance.
  • The Location and Protection Status of Earth’s Diminishing Marine
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Kendall R. Jones, Carissa J. Klein, Benjamin S. Halpern, Oscar Venter, Hedley Grantham, Caitlin D. Kuempel, Nicole Shumway, Alan M. Friedlander, Hugh P. Possingham, James E.M. WatsonSummaryAs human activities increasingly threaten biodiversity [1, 2], areas devoid of intense human impacts are vital refugia [3]. These wilderness areas contain high genetic diversity, unique functional traits, and endemic species [4, 5, 6, 7]; maintain high levels of ecological and evolutionary connectivity [8, 9, 10]; and may be well placed to resist and recover from the impacts of climate change [11, 12, 13]. On land, rapid declines in wilderness [3] have led to urgent calls for its protection [3, 14]. In contrast, little is known about the extent and protection of marine wilderness [4, 5]. Here we systematically map marine wilderness globally by identifying areas that have both very little impact (lowest 10%) from 15 anthropogenic stressors and also a very low combined cumulative impact from these stressors. We discover that ∼13% of the ocean meets this definition of global wilderness, with most being located in the high seas. Recognizing that human influence differs across ocean regions, we repeat the analysis within each of the 16 ocean realms [15]. Realm-specific wilderness extent varies considerably, with>16 million km2 (8.6%) in the Warm Indo-Pacific, down to
  • The Reissner Fiber in the Cerebrospinal Fluid Controls Morphogenesis of
           the Body Axis
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Yasmine Cantaut-Belarif, Jenna R. Sternberg, Olivier Thouvenin, Claire Wyart, Pierre-Luc BardetSummaryOrgan development depends on the integration of coordinated long-range communication between cells. The cerebrospinal fluid composition and flow properties regulate several aspects of central nervous system development, including progenitor proliferation, neurogenesis, and migration [1, 2, 3]. One understudied component of the cerebrospinal fluid, described over a century ago in vertebrates, is the Reissner fiber. This extracellular thread forming early in development results from the assembly of the SCO-spondin protein in the third and fourth brain ventricles and central canal of the spinal cord [4]. Up to now, the function of the Reissner fiber has remained elusive, partly due to the lack of genetic invalidation models [4]. Here, by mutating the scospondin gene, we demonstrate that the Reissner fiber is critical for the morphogenesis of a straight posterior body axis. In zebrafish mutants where the Reissner fiber is lost, ciliogenesis and cerebrospinal fluid flow are intact but body axis morphogenesis is impaired. Our results also explain the frequently observed phenotype that mutant embryos with defective cilia exhibit defects in body axis curvature. Here, we reveal that these mutants systematically fail to assemble the Reissner fiber. We show that cilia promote the formation of the Reissner fiber and that the fiber is necessary for proper body axis morphogenesis. Our study sets the stage for future investigations of the mechanisms linking the Reissner fiber to the control of body axis curvature during vertebrate development.Graphical Graphical abstract for this article
  • Ciliary Length Sensing Regulates IFT Entry via Changes in FLA8/KIF3B
           Phosphorylation to Control Ciliary Assembly
    • Abstract: Publication date: Available online 26 July 2018Source: Current BiologyAuthor(s): Yinwen Liang, Xin Zhu, Qiong Wu, Junmin PanSummaryThe length of cilia is robustly regulated [1]. Previous data suggest that cells possess a sensing system to control ciliary length [2, 3, 4, 5]. However, the details of the mechanism are currently not known [6, 7]. Such a system requires a mechanism that responds to ciliary length, and consequently, disruption of that response system should alter ciliary length [1]. The assembly rate of cilium mediated by intraflagellar transport (IFT) gradually decreases as the cilium elongates and eventually is balanced by the constant rate of disassembly, at which point cilium elongation stops [8, 9]. Because the rate of IFT entry into the cilium also decreases as the cilium elongates [10], regulation of IFT entry could provide the mechanism for length control. Previously, we showed that phosphorylation of the FLA8/KIF3B subunit of the anterograde kinesin-II IFT motor blocks IFT entry and flagellar assembly in Chlamydomonas [11]. Here, we show in Chlamydomonas that cellular signaling in response to alteration of flagellar length regulates phosphorylation of FLA8/KIF3B, which restricts IFT entry and, thus, flagellar assembly to control flagellar length. Cellular levels of phosphorylated FLA8 (pFLA8) are tightly linked to flagellar length: FLA8 phosphorylation is reduced in cells with short flagella and elevated in cells with long flagella. Depletion of the phosphatases CrPP1 and CrPP6 increases the level of cellular pFLA8, leading to short flagella due to decreased IFT entry. The results demonstrate that ciliary length control is achieved by a cellular sensing system that controls IFT entry through phosphorylation of the anterograde IFT motor.Graphical Graphical abstract for this article
  • Motor Learning: A Cortical System for Adaptive Motor Control
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Reza ShadmehrSummaryNeurons in various areas of the frontal and parietal lobes can be distinguished based on their preference for the direction of reach errors. Stimulation of these neurons corrects for those errors, uncovering a cortical system for adaptive motor control.
  • Retraction Notice to: Vergence eye movements direct others’ attention
           in three-dimensional space
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): A.T.T. Nguyen, C.J. Palmer, C.W.G. Clifford
  • Neuroscience: A ‘Skin Warming’ Circuit that Promotes Sleep and
           Body Cooling
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): John PeeverSummarySkin and body warming help initiate sleep, but the underlying neural mechanisms remain unclear. New research in mice shows that skin warming recruits a previously unidentified hypothalamic circuit that functions to promote sleep and body cooling.
  • Evolutionary Biology: A New Home for the Powerhouse'
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Ryan M.R. GawrylukSummaryMetagenomic assemblies of oceanic datasets have unearthed novel and diverse alphaproteobacterial groups. Sophisticated phylogenetic analyses based on these metagenomes suggest that mitochondria do not descend from within Alphaproteobacteria, as typically thought, but from a still undiscovered sister lineage.
  • Thermosensation: Human Parasitic Nematodes Use Heat to Hunt Hosts
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Michael P. O’Donnell, Munzareen Khan, Piali SenguptaSummaryTemperature is a critical host-emitted cue for many parasitic species. A recent study shows that skin-penetrating human parasitic hookworms and threadworms exhibit adaptive host-seeking behaviors that are based on their temperature experience, opening up possibilities for new intervention strategies.
  • Neuroscience: Brain Mechanisms of Blushing
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Victor Mathis, Paul J. KennySummaryThe dorsal hypothalamic area regulates increases in body temperature in response to stress, but precise mechanisms are unclear. A new study suggests that glutamatergic neurons in this brain area regulate this action and, surprisingly, may also be involved in blushing.
  • Hominin Brain Evolution: The Only Way Is Up'
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Stephen MontgomerySummaryTraditional views of human brain evolution focus on increases in brain size. However, the brain endocast of Homo naledi adds evidence that brain re-organisation played a significant role in hominin evolution.
  • Domestication Genomics: Untangling the Complex History of African Rice
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Samantha J. Snodgrass, Matthew B. HuffordSummaryStudy of domestication is complex but essential to our understanding of evolutionary processes and for crop breeding. A new study analyzes genomic data from 163 lines of domesticated African rice and 83 lines of its wild relative, clarifying the history of African rice domestication.
  • Memory: The Majestic Case of an Amnestic Trace
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Anahita B. Hamidi, Steve RamirezSummaryMemories formed during infancy are forgotten in adulthood, a phenomenon called ‘infantile amnesia’. New research suggests that these memories can be artificially recovered in adulthood, suggesting that they were never completely lost in the first place.
  • Auditory smiles trigger unconscious facial imitation
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Pablo Arias, Pascal Belin, Jean-Julien AucouturierSummarySmiles, produced by the bilateral contraction of the zygomatic major muscles, are one of the most powerful expressions of positive affect and affiliation and also one of the earliest to develop [1]. The perception–action loop responsible for the fast and spontaneous imitation of a smile is considered a core component of social cognition [2]. In humans, social interaction is overwhelmingly vocal, and the visual cues of a smiling face co-occur with audible articulatory changes on the speaking voice [3]. Yet remarkably little is known about how such ‘auditory smiles’ are processed and reacted to. We have developed a voice transformation technique that selectively simulates the spectral signature of phonation with stretched lips and report here how we have used this technique to study facial reactions to smiled and non-smiled spoken sentences, finding that listeners’ zygomatic muscles tracked auditory smile gestures even when they did not consciously detect them.
  • Prey mistake masquerading predators for the innocuous items they resemble
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): John SkelhornSummaryUnderstanding how natural selection has shaped animals’ visual appearance to aid predator avoidance and prey capture has been an ongoing challenge since the conception of evolutionary theory 1, 2. Masquerade — animals resembling inedible objects common in the local environment (e.g. twigs, leaves, stones) — is one of a handful of strategies that has been suggested to serve both protective and aggressive functions (i.e. to work for both prey and predators) [3]. There is now good evidence for protective masquerade: predators detect masquerading prey but ignore them because they mistake them for the inedible objects they resemble [4]. However, there is no direct evidence that predators can benefit from aggressive masquerade 3, 5. Here, I tested the idea that prey detect masquerading predators but mistake them for the innocuous items that they resemble, making them less wary and easier for predators to catch. Because prey can only mistake masquerading predators for the objects they resemble if they have previous experience of those items, I manipulated house crickets’ (Acheta domesticus) experience with dead leaves, before placing them in tanks with dead-leaf-resembling Ghost mantises (Phyllocrania paradoxa). I found that mantises given crickets with experience of unmanipulated dead leaves caught crickets faster and after fewer attempts than mantises given crickets without experience of dead leaves, or crickets with experience of manipulated dead leaves that no longer resembled mantises. These findings demonstrate that predators can indeed benefit from aggressive masquerade.
  • African bush elephants respond to a honeybee alarm pheromone blend
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Mark G. Wright, Craig Spencer, Robin M. Cook, Michelle D. Henley, Warren North, Agenor Mafra-NetoSummaryWe here report the responses of African bush elephants (Loxodonta africana) to a crude approximation of the honeybee alarm pheromone blend. We show that the elephants had an avoidance response to the semiochemical blend. The use of honeybee alarm pheromones to manage elephant movements in a non-invasive manner, using natural cues to which elephants may have an evolved response, holds potential for development of new options for an integrated system for elephant movement management and protection.
  • Chelicerates
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Prashant P. SharmaSummaryCompared to other arthropods, such as crustaceans or insects, the term ‘chelicerate’ often does not evoke a similar sense of recognition or familiarity. Yet the subphylum Chelicerata has been encountered by every living person today, frequently to the effect of fear, awe, or outright revulsion. Chelicerates include such familiar groups as spiders, scorpions, mites, and ticks, as well as an array of bizarre and unfamiliar forms, such as vinegaroons, camel spiders, and hooded tick spiders (Figure 1).
  • Neonicotinoids
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Chris Bass, Linda M. Field
  • Toxoplasma gondii
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Joshua A. Kochanowsky, Anita A. Koshy
  • Karen Vousden
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Karen Vousden
  • The (nearly) complete dog
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Kurt Kotrschal
  • The meaning of life
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Jonathan Flint
  • Building blocks for bottom-up biology
    • Abstract: Publication date: 23 July 2018Source: Current Biology, Volume 28, Issue 14Author(s): Michael GrossSummaryScience has made great progress in understanding the machinery of life, but the ultimate test of our understanding is whether we are able to build something that functions the same way. Researchers have identified building blocks and modular principles in protein evolution and in self-organising patterns, enabling them to create new functional units. Michael Gross reports.
  • 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
    • 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
    • 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.
  • 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
    • 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.
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