Declining oxygen in the global ocean and coastal waters

<p>Oxygen is fundamental to life. Not only is it essential for the survival of individual animals, but it regulates global cycles of major nutrients and carbon. The oxygen content of the open ocean and coastal waters has been declining for at least the past half-century, largely because of human activities that have increased global temperatures and nutrients discharged to coastal waters. These changes have accelerated consumption of oxygen by microbial respiration, reduced solubility of oxygen in water, and reduced the rate of oxygen resupply from the atmosphere to the ocean interior, with a wide range of biological and ecological consequences. Further research is needed to understand and predict long-term, global- and regional-scale oxygen changes and their effects on marine and estuarine fisheries and ecosystems.</p>

Transferrin receptor 1 is a reticulocyte-specific receptor for Plasmodium vivax

<p><I>Plasmodium vivax</I> shows a strict host tropism for reticulocytes. We identified transferrin receptor 1 (TfR1) as the receptor for <I>P. vivax</I> reticulocyte-binding protein 2b (PvRBP2b). We determined the structure of the N-terminal domain of PvRBP2b involved in red blood cell binding, elucidating the molecular basis for TfR1 recognition. We validated TfR1 as the biological target of PvRBP2b engagement by means of TfR1 expression knockdown analysis. TfR1 mutant cells deficient in PvRBP2b binding were refractory to invasion of <I>P. vivax</I> but not to invasion of <I>P. falciparum</I>. Using Brazilian and Thai clinical isolates, we show that PvRBP2b monoclonal antibodies that inhibit reticulocyte binding also block <I>P. vivax</I> entry into reticulocytes. These data show that TfR1-PvRBP2b invasion pathway is critical for the recognition of reticulocytes during <I>P. vivax</I> invasion.</p>

Rapid genome shrinkage in a self-fertile nematode reveals sperm competition proteins

<p>To reveal impacts of sexual mode on genome content, we compared chromosome-scale assemblies of the outcrossing nematode <I>Caenorhabditis nigoni</I> to its self-fertile sibling species, <I>C. briggsae</I>. <I>C. nigoni</I>&rsquo;s genome resembles that of outcrossing relatives but encodes 31% more protein-coding genes than <I>C. briggsae</I>. <I>C. nigoni</I> genes lacking <I>C. briggsae</I> orthologs were disproportionately small and male-biased in expression. These include the <I>male secreted short </I>(<I>mss</I>) gene family, which encodes sperm surface glycoproteins conserved only in outcrossing species. Sperm from <I>mss</I>-null males of outcrossing <I>C. remanei</I> failed to compete with wild-type sperm, despite normal fertility in noncompetitive mating. Restoring <I>mss</I> to <I>C. briggsae</I> males was sufficient to enhance sperm competitiveness. Thus, sex has a pervasive influence on genome content that can be used to identify sperm competition factors.</p>

Hydraulically amplified self-healing electrostatic actuators with muscle-like performance

<p>Existing soft actuators have persistent challenges that restrain the potential of soft robotics, highlighting a need for soft transducers that are powerful, high-speed, efficient, and robust. We describe a class of soft actuators, termed hydraulically amplified self-healing electrostatic (HASEL) actuators, which harness a mechanism that couples electrostatic and hydraulic forces to achieve a variety of actuation modes. We introduce prototypical designs of HASEL actuators and demonstrate their robust, muscle-like performance as well as their ability to repeatedly self-heal after dielectric breakdown&mdash;all using widely available materials and common fabrication techniques. A soft gripper handling delicate objects and a self-sensing artificial muscle powering a robotic arm illustrate the wide potential of HASEL actuators for next-generation soft robotic devices.</p>

In situ measurements of Saturns ionosphere show that it is dynamic and interacts with the rings

<p>The ionized upper layer of Saturn&rsquo;s atmosphere, its ionosphere, provides a closure of currents mediated by the magnetic field to other electrically charged regions (for example, rings) and hosts ion-molecule chemistry. In 2017, the Cassini spacecraft passed inside the planet&rsquo;s rings, allowing in situ measurements of the ionosphere. The Radio and Plasma Wave Science instrument detected a cold, dense, and dynamic ionosphere at Saturn that interacts with the rings. Plasma densities reached up to 1000 cubic centimeters, and electron temperatures were below 1160 kelvin near closest approach. The density varied between orbits by up to two orders of magnitude. Saturn&rsquo;s A- and B-rings cast a shadow on the planet that reduced ionization in the upper atmosphere, causing a north-south asymmetry.</p>

An excess of massive stars in the local 30 Doradus starburst

<p>The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large star-formation events in the distant universe. We determined the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic observations of 247 stars more massive than 15 solar masses (<f>M</f>). The main episode of massive star formation began about 8 million years (My) ago, and the star-formation rate seems to have declined in the last 1 My. The IMF is densely sampled up to 200 <f>M</f> and contains 32 &plusmn; 12% more stars above 30 <f>M</f> than predicted by a standard Salpeter IMF. In the mass range of 15 to 200 <f>M</f>, the IMF power-law exponent is <f>1.90&ndash;0.26+0.37</f>, shallower than the Salpeter value of 2.35.</p>

Mechanically robust, readily repairable polymers via tailored noncovalent cross-linking

<p>Expanding the range of healable materials is an important challenge for sustainable societies. Noncrystalline, high-molecular-weight polymers generally form mechanically robust materials, which, however, are difficult to repair once they are fractured. This is because their polymer chains are heavily entangled and diffuse too sluggishly to unite fractured surfaces within reasonable time scales. Here we report that low-molecular-weight polymers, when cross-linked by dense hydrogen bonds, yield mechanically robust yet readily repairable materials, despite their extremely slow diffusion dynamics. A key was to use thiourea, which anomalously forms a zigzag hydrogen-bonded array that does not induce unfavorable crystallization. Another key was to incorporate a structural element for activating the exchange of hydrogen-bonded pairs, which enables the fractured portions to rejoin readily upon compression.</p>

Observation of the quantum spin Hall effect up to 100 kelvin in a monolayer crystal

<p>A variety of monolayer crystals have been proposed to be two-dimensional topological insulators exhibiting the quantum spin Hall effect (QSHE), possibly even at high temperatures. Here we report the observation of the QSHE in monolayer tungsten ditelluride (WTe<SUB>2</SUB>) at temperatures up to 100 kelvin. In the short-edge limit, the monolayer exhibits the hallmark transport conductance, ~<I>e</I><sup>2</sup>/<I>h</I> per edge, where <I>e</I> is the electron charge and <I>h</I> is Planck&rsquo;s constant. Moreover, a magnetic field suppresses the conductance, and the observed Zeeman-type gap indicates the existence of a Kramers degenerate point and the importance of time-reversal symmetry for protection from elastic backscattering. Our results establish the QSHE at temperatures much higher than in semiconductor heterostructures and allow for exploring topological phases in atomically thin crystals.</p>

Spatial and temporal patterns of mass bleaching of corals in the Anthropocene

<p>Tropical reef systems are transitioning to a new era in which the interval between recurrent bouts of coral bleaching is too short for a full recovery of mature assemblages. We analyzed bleaching records at 100 globally distributed reef locations from 1980 to 2016. The median return time between pairs of severe bleaching events has diminished steadily since 1980 and is now only 6 years. As global warming has progressed, tropical sea surface temperatures are warmer now during current La Ni&ntilde;a conditions than they were during El Ni&ntilde;o events three decades ago. Consequently, as we transition to the Anthropocene, coral bleaching is occurring more frequently in all El Ni&ntilde;o&ndash;Southern Oscillation phases, increasing the likelihood of annual bleaching in the coming decades.</p>

Genomic signals of selection predict climate-driven population declines in a migratory bird

<p>The ongoing loss of biodiversity caused by rapid climatic shifts requires accurate models for predicting species&rsquo; responses. Despite evidence that evolutionary adaptation could mitigate climate change impacts, evolution is rarely integrated into predictive models. Integrating population genomics and environmental data, we identified genomic variation associated with climate across the breeding range of the migratory songbird, yellow warbler (<I>Setophaga petechia</I>). Populations requiring the greatest shifts in allele frequencies to keep pace with future climate change have experienced the largest population declines, suggesting that failure to adapt may have already negatively affected populations. Broadly, our study suggests that the integration of genomic adaptation can increase the accuracy of future species distribution models and ultimately guide more effective mitigation efforts.</p>

Elevated HLA-A expression impairs HIV control through inhibition of NKG2A-expressing cells

<p>The highly polymorphic human leukocyte antigen (<I>HLA</I>) locus encodes cell surface proteins that are critical for immunity. <I>HLA-A</I> expression levels vary in an allele-dependent manner, diversifying allele-specific effects beyond peptide-binding preference. Analysis of 9763 HIV-infected individuals from 21 cohorts shows that higher <I>HLA-A</I> levels confer poorer control of HIV. Elevated <I>HLA-A</I> expression provides enhanced levels of an HLA-A&ndash;derived signal peptide that specifically binds and determines expression levels of HLA-E, the ligand for the inhibitory NKG2A natural killer (NK) cell receptor. <I>HLA-B</I> haplotypes that favor NKG2A-mediated NK cell licensing (i.e., education) exacerbate the deleterious effect of high <I>HLA-A</I> on HIV control, consistent with NKG2A-mediated inhibition impairing NK cell clearance of HIV-infected targets. Therapeutic blockade of HLA-E:NKG2A interaction may yield benefit in HIV disease.</p>

Gut microbiome influences efficacy of PD-1-based immunotherapy against epithelial tumors

<p>Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 axis induce sustained clinical responses in a sizable minority of cancer patients. We found that primary resistance to ICIs can be attributed to abnormal gut microbiome composition. Antibiotics inhibited the clinical benefit of ICIs in patients with advanced cancer. Fecal microbiota transplantation (FMT) from cancer patients who responded to ICIs into germ-free or antibiotic-treated mice ameliorated the antitumor effects of PD-1 blockade, whereas FMT from nonresponding patients failed to do so. Metagenomics of patient stool samples at diagnosis revealed correlations between clinical responses to ICIs and the relative abundance of <I>Akkermansia muciniphila</I>. Oral supplementation with <I>A. muciniphila</I> after FMT with nonresponder feces restored the efficacy of PD-1 blockade in an interleukin-12&ndash;dependent manner by increasing the recruitment of CCR9<sup>+</sup>CXCR3<sup>+</sup>CD4<sup>+</sup> T lymphocytes into mouse tumor beds.</p>

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients

<p>Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti&ndash;programmed cell death 1 protein (PD-1) immunotherapy (<I>n</I> = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (<I>n </I>= 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (<I>P </I>&lt; 0.01) and relative abundance of bacteria of the Ruminococcaceae family (<I>P </I>&lt; 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.</p>

The commensal microbiome is associated with anti-PD-1 efficacy in metastatic melanoma patients

<p>Anti&ndash;PD-1&ndash;based immunotherapy has had a major impact on cancer treatment but has only benefited a subset of patients. Among the variables that could contribute to interpatient heterogeneity is differential composition of the patients&rsquo; microbiome, which has been shown to affect antitumor immunity and immunotherapy efficacy in preclinical mouse models. We analyzed baseline stool samples from metastatic melanoma patients before immunotherapy treatment, through an integration of 16<I>S</I> ribosomal RNA gene sequencing, metagenomic shotgun sequencing, and quantitative polymerase chain reaction for selected bacteria. A significant association was observed between commensal microbial composition and clinical response. Bacterial species more abundant in responders included <I>Bifidobacterium longum</I>, <I>Collinsella aerofaciens</I>, and <I>Enterococcus faecium.</I> Reconstitution of germ-free mice with fecal material from responding patients could lead to improved tumor control, augmented T cell responses, and greater efficacy of anti&ndash;PD-L1 therapy. Our results suggest that the commensal microbiome may have a mechanistic impact on antitumor immunity in human cancer patients.</p>

A mitosis-specific and R loop-driven ATR pathway promotes faithful chromosome segregation

<p>The ataxia telangiectasia mutated and Rad3-related (ATR) kinase is crucial for DNA damage and replication stress responses. Here, we describe an unexpected role of ATR in mitosis. Acute inhibition or degradation of ATR in mitosis induces whole-chromosome missegregation. The effect of ATR ablation is not due to altered cyclin-dependent kinase 1 (CDK1) activity, DNA damage responses, or unscheduled DNA synthesis but to loss of an ATR function at centromeres. In mitosis, ATR localizes to centromeres through Aurora A&ndash;regulated association with centromere protein F (CENP-F), allowing ATR to engage replication protein A (RPA)&ndash;coated centromeric R loops. As ATR is activated at centromeres, it stimulates Aurora B through Chk1, preventing formation of lagging chromosomes. Thus, a mitosis-specific and R loop&ndash;driven ATR pathway acts at centromeres to promote faithful chromosome segregation, revealing functions of R loops and ATR in suppressing chromosome instability.</p>

S1P-dependent interorgan trafficking of group 2 innate lymphoid cells supports host defense

<p>Innate lymphoid cells (ILCs) are innate counterparts of adaptive T lymphocytes, contributing to host defense, tissue repair, metabolic homeostasis, and inflammatory diseases. ILCs have been considered to be tissue-resident cells, but whether ILCs move between tissue sites during infection has been unclear. We show here that interleukin-25&ndash; or helminth-induced inflammatory ILC2s are circulating cells that arise from resting ILC2s residing in intestinal lamina propria. They migrate to diverse tissues based on sphingosine 1-phosphate (S1P)&ndash;mediated chemotaxis that promotes lymphatic entry, blood circulation, and accumulation in peripheral sites, including the lung, where they contribute to anti-helminth defense and tissue repair. This ILC2 expansion and migration is a behavioral parallel to the antigen-driven proliferation and migration of adaptive lymphocytes to effector sites and indicates that ILCs complement adaptive immunity by providing both local and distant tissue protection during infection.</p>

Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source

<p>On 17 August 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer detected gravitational waves (GWs) emanating from a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) telescopes detected a gamma-ray transient, GRB 170817A. At 10.9 hours after the GW trigger, we discovered a transient and fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40 megaparsecs. The precise location of GW170817 provides an opportunity to probe the nature of these cataclysmic events by combining electromagnetic and GW observations.</p>

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

<p>Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.</p>

Swift and NuSTAR observations of GW170817: Detection of a blue kilonova

<p>With the first direct detection of merging black holes in 2015, the era of gravitational wave (GW) astrophysics began. A complete picture of compact object mergers, however, requires the detection of an electromagnetic (EM) counterpart. We report ultraviolet (UV) and x-ray observations by <I>Swift</I> and the <I>Nuclear Spectroscopic Telescope Array</I> of the EM counterpart of the binary neutron star merger GW170817. The bright, rapidly fading UV emission indicates a high mass (0.03 solar masses) wind-driven outflow with moderate electron fraction (<I>Y</I><SUB>e</SUB> 0.27). Combined with the x-ray limits, we favor an observer viewing angle of 30&deg; away from the orbital rotation axis, which avoids both obscuration from the heaviest elements in the orbital plane and a direct view of any ultrarelativistic, highly collimated ejecta (a -ray burst afterglow).</p>

Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis

<p>On 17 August 2017, gravitational waves (GWs) were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB 170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.9 hours to 18 days postmerger. We constrain the radioactively powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in rapid neutron capture (r-process) nucleosynthesis in the universe.</p>

Early spectra of the gravitational wave source GW170817: Evolution of a neutron star merger

<p>On 17 August 2017, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of the binary neutron star gravitational wave event GW170817. We report time-series spectroscopy of SSS17a from 11.75 hours until 8.5 days after the merger. Over the first hour of observations, the ejecta rapidly expanded and cooled. Applying blackbody fits to the spectra, we measured the photosphere cooling from <f>11,000&ndash;900+3400</f> to <f>9300&ndash;300+300</f> kelvin, and determined a photospheric velocity of roughly 30% of the speed of light. The spectra of SSS17a began displaying broad features after 1.46 days and evolved qualitatively over each subsequent day, with distinct blue (early-time) and red (late-time) components. The late-time component is consistent with theoretical models of r-process&ndash;enriched neutron star ejecta, whereas the blue component requires high-velocity, lanthanide-free material.</p>

A radio counterpart to a neutron star merger

<p>Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry.</p>

Electromagnetic evidence that SSS17a is the result of a binary neutron star merger

<p>Eleven hours after the detection of gravitational wave source GW170817 by the Laser Interferometer Gravitational-Wave Observatory and Virgo Interferometers, an associated optical transient, SSS17a, was identified in the galaxy NGC 4993. Although the gravitational wave data indicate that GW170817 is consistent with the merger of two compact objects, the electromagnetic observations provide independent constraints on the nature of that system. We synthesize the optical to near-infrared photometry and spectroscopy of SSS17a collected by the One-Meter Two-Hemisphere collaboration, finding that SSS17a is unlike other known transients. The source is best described by theoretical models of a kilonova consisting of radioactive elements produced by rapid neutron capture (the r-process). We conclude that SSS17a was the result of a binary neutron star merger, reinforcing the gravitational wave result.</p>

Maxima in the thermodynamic response and correlation functions of deeply supercooled water

<p>Femtosecond x-ray laser pulses were used to probe micrometer-sized water droplets that were cooled down to 227 kelvin in vacuum. Isothermal compressibility and correlation length were extracted from x-ray scattering at the low&ndash;momentum transfer region. The temperature dependence of these thermodynamic response and correlation functions shows maxima at 229 kelvin for water and 233 kelvin for heavy water. In addition, we observed that the liquids undergo the fastest growth of tetrahedral structures at similar temperatures. These observations point to the existence of a Widom line, defined as the locus of maximum correlation length emanating from a critical point at positive pressures in the deeply supercooled regime. The difference in the maximum value of the isothermal compressibility between the two isotopes shows the importance of nuclear quantum effects.</p>

Determination of intrinsic attenuation in the oceanic lithosphere-asthenosphere system

<p>We recorded <I>P</I> and <I>S</I> waves traveling through the oceanic lithosphere-asthenosphere system (LAS) using broadband ocean-bottom seismometers in the northwest Pacific, and we quantitatively separated the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic LAS. The strong intrinsic attenuation in the asthenosphere obtained at higher frequency (~3 hertz) is comparable to that constrained at lower frequency (~100 seconds) by surface waves and suggests frequency-independent anelasticity, whereas the intrinsic attenuation in the lithosphere is frequency dependent. This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere.</p>

Arabidopsis pollen tube integrity and sperm release are regulated by RALF-mediated signaling

<p>In flowering plants, fertilization requires complex cell-to-cell communication events between the pollen tube and the female reproductive tissues, which are controlled by extracellular signaling molecules interacting with receptors at the pollen tube surface. We found that two such receptors in <I>Arabidopsis</I>, BUPS1 and BUPS2, and their peptide ligands, RALF4 and RALF19, are pollen tube&ndash;expressed and are required to maintain pollen tube integrity. BUPS1 and BUPS2 interact with receptors ANXUR1 and ANXUR2 via their ectodomains, and both sets of receptors bind RALF4 and RALF19. These receptor-ligand interactions are in competition with the female-derived ligand RALF34, which induces pollen tube bursting at nanomolar concentrations. We propose that RALF34 replaces RALF4 and RALF19 at the interface of pollen tube&ndash;female gametophyte contact, thereby deregulating BUPS-ANXUR signaling and in turn leading to pollen tube rupture and sperm release.</p>

RALF4/19 peptides interact with LRX proteins to control pollen tube growth in Arabidopsis

<p>The communication of changes in the extracellular matrix to the interior of the cell is crucial for a cell&rsquo;s function. The extracellular peptides of the RAPID ALKALINIZATION FACTOR (RALF) family have been identified as ligands of receptor-like kinases of the <I>Cr</I>RLK1L subclass, but the exact mechanism of their perception is unclear. We found that <I>Arabidopsis</I> RALF4 and RALF19 redundantly regulate pollen tube integrity and growth, and that their function depends on pollen-expressed proteins of the LEUCINE-RICH REPEAT EXTENSIN (LRX) family, which play a role in cell wall development but whose mode of action is not understood. The LRX proteins interact with RALFs, monitoring cell wall changes, which are communicated to the interior of the pollen tube via the <I>Cr</I>RLK1L pathway to sustain normal growth.</p>

Variation in the AvrSr35 gene determines Sr35 resistance against wheat stem rust race Ug99

<p><I>Puccinia graminis</I> f. sp. <I>tritici</I> (<I>Pgt</I>) causes wheat stem rust, a devastating fungal disease. The <I>Sr35</I> resistance gene confers immunity against this pathogen&rsquo;s most virulent races, including Ug99. We used comparative whole-genome sequencing of chemically mutagenized and natural <I>Pgt</I> isolates to identify a fungal gene named <I>AvrSr35</I> that is required for <I>Sr35</I> avirulence. The <I>AvrSr35</I> gene encodes a secreted protein capable of interacting with Sr35 and triggering the immune response. We show that the origin of <I>Pgt</I> isolates virulent on <I>Sr35</I> is associated with the nonfunctionalization of the <I>AvrSr35</I> gene by the insertion of a mobile element. The discovery of <I>AvrSr35</I> provides a new tool for <I>Pgt</I> surveillance, identification of host susceptibility targets, and characterization of the molecular determinants of immunity in wheat.</p>

Loss of AvrSr50 by somatic exchange in stem rust leads to virulence for Sr50 resistance in wheat

<p>Race-specific resistance genes protect the global wheat crop from stem rust disease caused by <I>Puccinia graminis</I> f. sp. <I>tritici</I> (<I>Pgt</I>) but are often overcome owing to evolution of new virulent races of the pathogen. To understand virulence evolution in <I>Pgt</I>, we identified the protein ligand (AvrSr50) recognized by the Sr50 resistance protein. A spontaneous mutant of <I>Pgt</I> virulent to <I>Sr50</I> contained a 2.5 mega&ndash;base pair loss-of-heterozygosity event. A haustorial secreted protein from this region triggers <I>Sr50</I>-dependent defense responses in planta and interacts directly with the Sr50 protein. Virulence alleles of <I>AvrSr50</I> have arisen through DNA insertion and sequence divergence, and our data provide molecular evidence that in addition to sexual recombination, somatic exchange can play a role in the emergence of new virulence traits in <I>Pgt</I>.</p>

Asylum applications respond to temperature fluctuations

<p>International negotiations on climate change, along with recent upsurges in migration across the Mediterranean Sea, have highlighted the need to better understand the possible effects of climate change on human migration&mdash;in particular, across national borders. Here we examine how, in the recent past (2000&ndash;2014), weather variations in 103 source countries translated into asylum applications to the European Union, which averaged 351,000 per year in our sample. We find that temperatures that deviated from the moderate optimum (~20&deg;C) increased asylum applications in a nonlinear fashion, which implies an accelerated increase under continued future warming. Holding everything else constant, asylum applications by the end of the century are predicted to increase, on average, by 28% (98,000 additional asylum applications per year) under representative concentration pathway (RCP) scenario 4.5 and by 188% (660,000 additional applications per year) under RCP 8.5 for the 21 climate models in the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP).</p>