Hot off the presses! Jun 21 Curr Bio

The Jun 21 issue of the Curr Bio is now up on Pubget (About Curr Bio): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

• Boom time for neuroscience in China
  - Curr Bio 21(12):R441-R444 (2011)
  A decade after the foundation of the Institute of Neuroscience in Shanghai, the field enjoys rapid growth and can attract young investigators back from abroad. Michael Gross reports.
• Fang Fang
  - Curr Bio 21(12):R444-R446 (2011)
  
• Argonaute proteins
  - Curr Bio 21(12):R446-R449 (2011)
  
• Reproductive interference
  - Curr Bio 21(12):R450-R451 (2011)
  
• Antarctic marine biology
  - Curr Bio 21(12):R451-R457 (2011)
  Antarctica is a continent of extremes: on average it is the highest, windiest, coldest and driest land mass on Earth. It also has the largest ice-mass, with less than 1% of its surface offering ice-free space for biology. Biology in the Southern Ocean surrounding Antarctica is also extreme in its isolation, light climate, water temperature and viscosity, continental shelf depth and, in the shallows, intense disturbance from scouring by icebergs. Being isolated and difficult of access, there are large areas which have never been sampled or even visited, and much of the biology is very poorly known away from the proximity of research stations.
• Could Scott have survived with today's physiological knowledge?
  - Curr Bio 21(12):R457-R461 (2011)
  In 1911, members of a British expedition walked across the Antarctic to the South Pole, but in the punishingly hostile environment, retracing their steps back to the edge of the continent proved fatal. Over the last 100 years, knowledge about human physiology has greatly increased and, on the centenary of this most extreme of all journeys, this essay explores the true extent of the physiological stress experienced by the men involved and whether their fate was inevitable.
• Rocking synchronizes brain waves during a short nap
  - Curr Bio 21(12):R461-R462 (2011)
  Why do we cradle babies or irresistibly fall asleep in a hammock? Although such simple behaviors are common across cultures and generations, the nature of the link between rocking and sleep is poorly understood [1] and [2]. Here we aimed to demonstrate that swinging can modulate physiological parameters of human sleep. To this end, we chose to study sleep during an afternoon nap using polysomnography and EEG spectral analyses. We show that lying on a slowly rocking bed (0.25 Hz) facilitates the transition from waking to sleep, and increases the duration of stage N2 sleep. Rocking also induces a sustained boosting of slow oscillations and spindle activity. It is proposed that sensory stimulation associated with a swinging motion exerts a synchronizing action in the brain that reinforces endogenous sleep rhythms. These results thus provide scientific support to the traditional belief that rocking can soothe our sleep.
• Animal Behaviour: Emotion in Invertebrates?
  - Curr Bio 21(12):R463-R465 (2011)
  Bees exposed to vigorous shaking designed to simulate a dangerous event judge ambiguous stimuli as predicting a negative outcome — a 'pessimistic' cognitive bias that is characteristic of anxious or depressed humans and other vertebrates in putative negative emotional states.
• Thermal Robustness: Lessons from Bacterial Chemotaxis
  - Curr Bio 21(12):R465-R468 (2011)
  Temperature changes affect reaction kinetics. How do signaling pathways cope with such global perturbation? A recent study dissects the solution found by bacterial chemotaxis.
• Conservation Biology: The Many Ways to Protect Biodiversity
  - Curr Bio 21(12):R468-R470 (2011)
  Protecting hotspots of marine species richness may not be an effective strategy to conserve biodiversity because these sites do not coincide with hotspots of functional and phylogenetic diversity.
• Behavioral Neurobiology: The Bitter Life of Male Flies
  - Curr Bio 21(12):R470-R472 (2011)
  Male fruit flies demonstrate aggression and even courtship towards other male flies. A new study reveals that these behaviors are induced via a bitter gustatory receptor.
• Tendon Homeostasis: The Right Pull
  - Curr Bio 21(12):R472-R474 (2011)
  Mechanotransduction, the conversion of a biophysical force into a cellular response, allows cells and tissues to respond to their mechanical milieu. How muscle force is translated through TGF-β signaling to regulate tendon homeostasis offers an interesting in vivo example of mechanotransduction.
• Innate Immunity: Unfolding the Neuro-Immuno Connections
  - Curr Bio 21(12):R474-R476 (2011)
  The innate immune system maintains health and fitness during infection by eliminating infectious agents and by limiting damage caused by pathogens or immune activation. The nervous system contributes to innate immunity by modulating the expression of antimicrobial peptides and by regulating the unfolded protein response.
• Development: A Pathway to Plant Female Germ Cells
  - Curr Bio 21(12):R476-R478 (2011)
  Plant germ cells form late in development, but little is known about the molecular basis for germline specification in plants. Recent results have identified components of a regulatory pathway controlling female germ cell determination, including a key transcription factor and some putative signaling proteins.
• Mitochondrial Dynamics: A Strategy for Avoiding Autophagy
  - Curr Bio 21(12):R478-R480 (2011)
  Cells normally respond to a lack of nutrients by activating autophagy, a prominent pro-survival pathway that involves the catabolism and recycling of cytoplasmic material. Recent results indicate that mitochondria actively elongate during autophagy, thereby avoiding their degradation and sustaining cell viability.
• A Molecular Switch for Initiating Cell Differentiation in Arabidopsis
  - Curr Bio 21(12):999-1008 (2011)
  Background The onset of differentiation entails modifying the gene expression state of cells, to allow activation of developmental programs that are maintained repressed in the undifferentiated precursor cells [[1] and [2]]. This requires a mechanism to change gene expression on a genome-scale. Recent evidence suggests that in mammalian stem cells, derepression of developmental regulators during differentiation involves a shift from stalled to productive elongation of their transcripts [[3], [4] and [5]], but factors mediating this shift have not been identified and the evidence remains correlative. Results We report the identification of the MINIYO (IYO) gene, a positive regulator of transcriptional elongation that is essential for cells to initiate differentiation in Arabidopsis. IYO interacts with RNA polymerase II and the Elongator complex and is required to sustain global levels of transcriptional elongation activity, specifically in differentiating tissues. Accordingly, IYO is expressed in embryos, meristems, and organ primordia and not in mature tissues. Moreover, differential subcellular protein distribution further refines the domain of IYO function by directing nuclear accumulation, and thus its transcriptional activity, to cells initiating differentiation. Importantly, IYO overexpression induces premature cell differentiation and leads to meristem termination phenotypes. Conclusions These findings identify IYO as a necessary and sufficient factor for initiating differentiation in Arabidopsis and suggest that the targeted nuclear accumulation of IYO functions as a transcriptional switch for this fate transition.
• Arabidopsis WIH1 and WIH2 Genes Act in the Transition from Somatic to Reproductive Cell Fate
  - Curr Bio 21(12):1009-1017 (2011)
  Background Unlike animals, higher plants do not establish a germ line in embryo development but form haploid germ cells from diploid somatic cells late in their life cycle. However, despite its prime importance, little is known about how this transition is regulated. Results Here, we show that the WUSCHEL (WUS) gene, initially identified as a stem cell regulator in the shoot meristem, is required for megasporogenesis and thus ultimately for the formation of female generative cells. WUS functions in this process by indirectly activating the expression of the WINDHOSE1 (WIH1) and WIH2 genes that encode small peptides found in plants and fungi, but not in animals. WIH genes function together with the tetraspanin-type protein TORNADO2 (TRN2)/EKEKO in promoting megasporogenesis. Conclusions Together, our studies identify a pathway promoting germ cell formation from somatic precursor cells.
• Cohesion Fatigue Induces Chromatid Separation in Cells Delayed at Metaphase
  - Curr Bio 21(12):1018-1024 (2011)
  Background Chromosome instability is thought to be a major contributor to cancer malignancy and birth defects. For balanced chromosome segregation in mitosis, kinetochores on sister chromatids bind and pull on microtubules emanating from opposite spindle poles. This tension contributes to the correction of improper kinetochore attachments and is opposed by the cohesin complex that holds the sister chromatids together. Normally, within minutes of alignment at the metaphase plate, chromatid cohesion is released, allowing each cohort of chromatids to move synchronously to opposite poles in anaphase, an event closely coordinated with mitotic exit. Results Here we show that during experimentally induced metaphase delay, spindle pulling forces can cause asynchronous chromatid separation, a phenomenon we term "cohesion fatigue." Cohesion fatigue is not blocked by inhibition of Plk1, a kinase essential for the "prophase pathway" of cohesin release from chromosomes, or by depletion of separase, the protease that normally drives chromatid separation at anaphase. Cohesion fatigue is inhibited by drug-induced depolymerization of mitotic spindle microtubules and by experimentally increasing the levels of cohesin on mitotic chromosomes. In cells undergoing cohesion fatigue, cohesin proteins remain associated with the separated chromatids. Conclusion In cells arrested at metaphase, pulling forces originating from kinetochore-microtubule interactions can, with time, rupture normal sister chromatid cohesion. This cohesion fatigue, resulting in unscheduled chromatid separation in cells delayed at metaphase, constitutes a previously overlooked source for chromosome instability in mitosis and meiosis.
• Regulatory Mechanism Controlling Stomatal Behavior Conserved across 400 Million Years of Land Plant Evolution
  - Curr Bio 21(12):1025-1029 (2011)
  Stomatal pores evolved more than 410 million years ago [[1] and [2]] and allowed vascular plants to regulate transpirational water loss during the uptake of CO2 for photosynthesis [3]. Here, we show that stomata on the sporophytes of the moss Physcomitrella patens [2] respond to environmental signals in a similar way to those of flowering plants [4] and that a homolog of a key signaling component in the vascular plant drought hormone abscisic acid (ABA) response [5] is involved in stomatal control in mosses. Cross-species complementation experiments reveal that the stomatal ABA response of a flowering plant (Arabidopsis thaliana) mutant, lacking the ABA-regulatory protein kinase OPEN STOMATA 1 (OST1) [6], is rescued by substitution with the moss P. patens homolog, PpOST1-1, which evolved more than 400 million years earlier. We further demonstrate through the targeted knockout of the PpOST1-1 gene in P. patens that its role in guard cell closure is conserved, with stoma! ta of mutant mosses exhibiting a significantly attenuated ABA response. Our analyses indicate that core regulatory components involved in guard cell ABA signaling of flowering plants are operational in mosses and likely originated in the last common ancestor of these lineages more than 400 million years ago [7], prior to the evolution of ferns [[8] and [9]].
• Land Plants Acquired Active Stomatal Control Early in Their Evolutionary History
  - Curr Bio 21(12):1030-1035 (2011)
  Stomata are pores that regulate plant gas exchange [1]. They evolved more than 400 million years ago [[2] and [3]], but the origin of their active physiological responses to endogenous and environmental cues is unclear [[2], [3], [4], [5] and [6]]. Recent research suggests that the stomata of lycophytes and ferns lack pore closure responses to abscisic acid (ABA) and CO2. This evidence led to the hypothesis that a fundamental transition from passive to active control of plant water balance occurred after the divergence of ferns 360 million years ago [[7] and [8]]. Here we show that stomatal responses of the lycophyte Selaginella [9] to ABA and CO2 are directly comparable to those of the flowering plant Arabidopsis [10]. Furthermore, we show that the underlying intracellular signaling pathways responsible for stomatal aperture control are similar in both basal and modern vascular plant lineages. Our evidence challenges the hypothesis that acquisition of active stomatal ! control of plant carbon and water balance represents a critical turning point in land plant evolution [[7] and [8]]. Instead, we suggest that the critical evolutionary development is represented by the innovation of stomata themselves and that physiologically active stomatal control originated at least as far back as the emergence of the lycophytes (circa 420 million years ago) [11].
• Different Roles for Homologous Interneurons in Species Exhibiting Similar Rhythmic Behaviors
  - Curr Bio 21(12):1036-1043 (2011)
  It is often assumed that similar behaviors in related species are produced by similar neural mechanisms. To test this, we examined the neuronal basis of a simple swimming behavior in two nudibranchs (Mollusca, Opisthobranchia), Melibe leonina and Dendronotus iris. The side-to-side swimming movements of Dendronotus [1] strongly resemble those of Melibe [[2] and [3]]. In Melibe, it was previously shown that the central pattern generator (CPG) for swimming is composed of two bilaterally symmetric pairs of identified interneurons, swim interneuron 1 (Si1) and swim interneuron 2 (Si2), which are electrically coupled ipsilaterally and mutually inhibit both contralateral counterparts [[2] and [4]]. We identified homologs of Si1 and Si2 in Dendronotus. (Henceforth, homologous neurons in each species will be distinguished by the subscripts Den and Mel.) We found that Si2Den and Si2Mel play similar roles in generating the swim motor pattern. However, unlike Si1Mel, Si1Den was no! t part of the swim CPG, was not strongly coupled to the ipsilateral Si2Den, and did not inhibit the contralateral neurons. Thus, species differences exist in the neuronal organization of the swim CPGs despite the similarity of the behaviors. Therefore, similarity in species-typical behavior is not necessarily predictive of common neural mechanisms, even for homologous neurons in closely related species.
• Protected and Threatened Components of Fish Biodiversity in the Mediterranean Sea
  - Curr Bio 21(12):1044-1050 (2011)
  The Mediterranean Sea (0.82% of the global oceanic surface) holds 4%–18% of all known marine species (17,000), with a high proportion of endemism [[1] and [2]]. This exceptional biodiversity is under severe threats [1] but benefits from a system of 100 marine protected areas (MPAs). Surprisingly, the spatial congruence of fish biodiversity hot spots with this MPA system and the areas of high fishing pressure has not been assessed. Moreover, evolutionary and functional breadth of species assemblages [3] has been largely overlooked in marine systems. Here we adopted a multifaceted approach to biodiversity by considering the species richness of total, endemic, and threatened coastal fish assemblages as well as their functional and phylogenetic diversity. We show that these fish biodiversity components are spatially mismatched. The MPA system covers a small surface of the Mediterranean (0.4%) and is spatially congruent with the hot spots of all taxonomic components of fi! sh diversity. However, it misses hot spots of functional and phylogenetic diversity. In addition, hot spots of endemic species richness and phylogenetic diversity are spatially congruent with hot spots of fishery impact. Our results highlight that future conservation strategies and assessment efficiency of current reserve systems will need to be revisited after deconstructing the different components of biodiversity.
• Pervasive Multinucleotide Mutational Events in Eukaryotes
  - Curr Bio 21(12):1051-1054 (2011)
  Many aspects of mutational processes are nonrandom, from the preponderance of transitions relative to transversions to the higher rate of mutation at CpG dinucleotides [1]. However, it is still often assumed that single-nucleotide mutations are independent of one another, each being caused by separate mutational events. The occurrence of multiple, closely spaced substitutions appears to violate assumptions of independence and is often interpreted as evidence for the action of adaptive natural selection [[2] and [3]], balancing selection [4], or compensatory evolution [[5] and [6]]. Here we provide evidence of a frequent, widespread multinucleotide mutational process active throughout eukaryotes. Genomic data from mutation-accumulation experiments, parent-offspring trios, and human polymorphisms all show that simultaneous nucleotide substitutions occur within short stretches of DNA. Regardless of species, such multinucleotide mutations (MNMs) consistently comprise 3% of! the total number of nucleotide substitutions. These results imply that previous adaptive interpretations of multiple, closely spaced substitutions may have been unwarranted and that MNMs must be considered when interpreting sequence data.
• Cell Plate Restricted Association of DRP1A and PIN Proteins Is Required for Cell Polarity Establishment in Arabidopsis
  - Curr Bio 21(12):1055-1060 (2011)
  The polarized transport of the phytohormone auxin [1], which is crucial for the regulation of different stages of plant development [[2] and [3]], depends on the asymmetric plasma membrane distribution of the PIN-FORMED (PIN) auxin efflux carriers [[4] and [5]]. The PIN polar localization results from clathrin-mediated endocytosis (CME) from the plasma membrane and subsequent polar recycling [6]. The Arabidopsis genome encodes two groups of dynamin-related proteins (DRPs) that show homology to mammalian dynamin—a protein required for fission of endocytic vesicles during CME [[7] and [8]]. Here we show by coimmunoprecipitation (coIP), bimolecular fluorescence complementation (BiFC), and Förster resonance energy transfer (FRET) that members of the DRP1 group closely associate with PIN proteins at the cell plate. Localization and phenotypic analysis of novel drp1 mutants revealed a requirement for DRP1 function in correct PIN distribution and in auxin-mediated developm! ent. We propose that rapid and specific internalization of PIN proteins mediated by the DRP1 proteins and the associated CME machinery from the cell plate membranes during cytokinesis is an important mechanism for proper polar PIN positioning in interphase cells.
• A Positive Feedback Loop Involving Haspin and Aurora B Promotes CPC Accumulation at Centromeres in Mitosis
  - Curr Bio 21(12):1061-1069 (2011)
  Haspin phosphorylates histone H3 at Thr3 (H3T3ph) during mitosis [[1] and [2]], providing a chromatin binding site for the chromosomal passenger complex (CPC) at centromeres to regulate chromosome segregation [[3], [4] and [5]]. H3T3ph becomes increasingly focused at inner centromeres during prometaphase [[1] and [2]], but little is known about how its level or location and the consequent chromosomal localization of the CPC are regulated. In addition, CPC binding to shugoshin proteins contributes to centromeric Aurora B localization [[5] and [6]]. Recruitment of the shugoshins to centromeres requires the phosphorylation of histone H2A at Thr120 (H2AT120ph) by the kinetochore kinase Bub1 [7], but the molecular basis for the collaboration of this pathway with H3T3ph has been unclear. Here, we show that Aurora B phosphorylates Haspin to promote generation of H3T3ph and that Aurora B kinase activity is required for normal chromosomal localization of the CPC, indicating an ! intimate linkage between Aurora B and Haspin functions in mitosis. We propose that Aurora B activity triggers a CPC-Haspin-H3T3ph feedback loop that promotes generation of H3T3ph on chromatin. We also provide evidence that the Bub1-shugoshin-CPC pathway supplies a signal that boosts the CPC-Haspin-H3T3ph feedback loop specifically at centromeres to produce the well-known accumulation of the CPC in these regions.
• Agitated Honeybees Exhibit Pessimistic Cognitive Biases
  - Curr Bio 21(12):1070-1073 (2011)
  Whether animals experience human-like emotions is controversial and of immense societal concern [[1], [2] and [3]]. Because animals cannot provide subjective reports of how they feel, emotional state can only be inferred using physiological, cognitive, and behavioral measures [[4], [5], [6], [7] and [8]]. In humans, negative feelings are reliably correlated with pessimistic cognitive biases, defined as the increased expectation of bad outcomes [[9], [10] and [11]]. Recently, mammals [[12], [13], [14], [15] and [16]] and birds [[17], [18], [19] and [20]] with poor welfare have also been found to display pessimistic-like decision making, but cognitive biases have not thus far been explored in invertebrates. Here, we ask whether honeybees display a pessimistic cognitive bias when they are subjected to an anxiety-like state induced by vigorous shaking designed to simulate a predatory attack. We show for the first time that agitated bees are more likely to classify ambiguou! s stimuli as predicting punishment. Shaken bees also have lower levels of hemolymph dopamine, octopamine, and serotonin. In demonstrating state-dependent modulation of categorization in bees, and thereby a cognitive component of emotion, we show that the bees' response to a negatively valenced event has more in common with that of vertebrates than previously thought. This finding reinforces the use of cognitive bias as a measure of negative emotional states across species and suggests that honeybees could be regarded as exhibiting emotions. Video Abstract To view the video inline, enable JavaScript on your browser. However, you can download and view the video by clicking on the icon below Download this Video (12116 K)
• The Inositol 5-Phosphatase dOCRL Controls PI(4,5)P2 Homeostasis and Is Necessary for Cytokinesis
  - Curr Bio 21(12):1074-1079 (2011)
  During cytokinesis, constriction of an equatorial actomyosin ring physically separates the two daughter cells. At the cleavage furrow, the phosphoinositide PI(4,5)P2 plays an important role by recruiting and regulating essential proteins of the cytokinesis machinery [1]. Accordingly, perturbation of PI(4,5)P2 regulation leads to abortive furrowing and binucleation [[2], [3] and [4]]. To determine how PI(4,5)P2 is regulated during cytokinesis, we individually knocked down each of the enzymes controlling the phosphoinositide (PIP) cycle in Drosophila. We show that depletion of the Drosophila ortholog of human oculocerebrorenal syndrome of Lowe 1 (OCRL1), an inositol 5-phosphatase mutated in the X-linked disorder oculocerebrorenal Lowe syndrome, triggers a high rate of cytokinesis failure. In absence of dOCRL, several essential components of the cleavage furrow were found to be incorrectly localized on giant cytoplasmic vacuoles rich in PI(4,5)P2 and in endocytic markers.! We demonstrate that dOCRL is associated with endosomes and that it dephosphorylates PI(4,5)P2 on internal membranes to restrict this phosphoinositide at the plasma membrane and thereby regulates cleavage furrow formation and ingression. Identification of dOCRL as essential for cell division may be important to understand the molecular basis of the phenotypic manifestations of Lowe syndrome.