Geonomics & Science News

Geonomics & Science News

GENOMEWEB

Surprise Proposal - 27 May 2016


Sing It - 27 May 2016


This Week in Science - 27 May 2016


Regeneron Searches for Talent - 26 May 2016


Berg in at Science - 26 May 2016


Glossed Over It - 26 May 2016


This Week in Nature - 26 May 2016


Can It Be Done Again? - 25 May 2016


Just the One, Really - 25 May 2016


Prize for Directed Evolution Developer - 25 May 2016


SCIENCENOW

[Business Office Feature] Webinar | Key signaling pathways in cancer: Links to developmental biology - 27 May 2016

It is notable that the same pathways governing the cell growth, death, and differentiation decisions made during embryonic development are also common drivers of adult malignancy. In this webinar, we will explore the idea that a better understanding of developmental biology signaling pathways will advance our understanding of adult tumors and cancer stem cells as well as boost our ability to create effective therapeutics to fight a broad array of cancers.View the Webinar Authors: Elaine Fuchs, Benjamin L. Allen, Rik Derynck


[Research Article] Topoisomerase 1 inhibition suppresses inflammatory genes and protects from death by inflammation - 27 May 2016

The host innate immune response is the first line of defense against pathogens and is orchestrated by the concerted expression of genes induced by microbial stimuli. Deregulated expression of these genes is linked to the initiation and progression of diseases associated with exacerbated inflammation. We identified topoisomerase 1 (Top1) as a positive regulator of RNA polymerase II transcriptional activity at pathogen-induced genes. Depletion or chemical inhibition of Top1 suppresses the host response against influenza and Ebola viruses as well as bacterial products. Therapeutic pharmacological inhibition of Top1 protected mice from death in experimental models of lethal inflammation. Our results indicate that Top1 inhibition could be used as therapy against life-threatening infections characterized by an acutely exacerbated immune response. Authors: Alex Rialdi, Laura Campisi, Nan Zhao, Arvin Cesar Lagda, Colette Pietzsch, Jessica Sook Yuin Ho, Luis Martinez-Gil, Romain Fenouil, Xiaoting Chen, Megan Edwards, Giorgi Metreveli, Stefan Jordan, Zuleyma Peralta, Cesar Munoz-Fontela, Nicole Bouvier, Miriam Merad, Jian Jin, Matthew Weirauch, Sven Heinz, Chris Benner, Harm van Bakel, Christopher Basler, Adolfo García-Sastre, Alexander Bukreyev, Ivan Marazzi


[In Brief] News at a glance - 27 May 2016

In science news around the world, a new U.S. labor law would require more pay for postdocs—or that they receive overtime pay, the World Health Organization determines that yellow fever outbreaks in urban regions of Angola and the Democratic Republic of the Congo do not yet constitute an international health emergency, South Africa plans to launch a new trial of an HIV vaccine approach that showed modest efficacy 7 years ago in Thailand, the French government is tightening clinical trial rules in the aftermath of the final report about a study that killed one person and landed five others in the hospital earlier this year, U.S. President Barack Obama contends that funding proposals from the Senate and House of Representatives are both insufficient to effectively combat the Zika epidemic, and more. Also, just weeks after the announcement of the privately funded Breakthrough Starshot project to send tiny spacecraft to Alpha Centauri, a U.S. lawmaker urges NASA to develop its own interstellar probes bound for our nearest star neighbor. And dog lovers are flocking to a citizen science project that aims to study the genetic basis of canine behavior.


[This Week in Science] The promise of digital markets - 27 May 2016

Author: Julia Fahrenkamp-Uppenbrink


[In Depth] Near miss at Fukushima is a warning for U.S - 27 May 2016

Japan's chief cabinet secretary called it “the devil's scenario.” Two weeks after the 11 March 2011 earthquake and tsunami devastated the Fukushima Daiichi Nuclear Power Plant, causing three nuclear reactors to melt down and release radioactive plumes, officials were bracing for even worse. They feared that spent fuel stored in pools in the reactor halls would catch fire and might send radioactive smoke across a much wider swath of eastern Japan, including Tokyo. Thanks to a lucky break detailed in a report released last week by the U.S. National Academies of Science, Engineering, and Medicine, Japan dodged that bullet. But the report warns that spent fuel accumulating at U.S. nuclear plants is also vulnerable. Unpublished modeling presents chilling scenarios for a hypothetical spent fuel fire at the Peach Bottom nuclear power plant in southeastern Pennsylvania. Author: Richard Stone


[Report] Nuclear-localized cyclic nucleotide–gated channels mediate symbiotic calcium oscillations - 27 May 2016

Nuclear-associated Ca2+ oscillations mediate plant responses to beneficial microbial partners—namely, nitrogen-fixing rhizobial bacteria that colonize roots of legumes and arbuscular mycorrhizal fungi that colonize roots of the majority of plant species. A potassium-permeable channel is known to be required for symbiotic Ca2+ oscillations, but the calcium channels themselves have been unknown until now. We show that three cyclic nucleotide–gated channels in Medicago truncatula are required for nuclear Ca2+ oscillations and subsequent symbiotic responses. These cyclic nucleotide–gated channels are located at the nuclear envelope and are permeable to Ca2+. We demonstrate that the cyclic nucleotide–gated channels form a complex with the postassium-permeable channel, which modulates nuclear Ca2+ release. These channels, like their counterparts in animal cells, might regulate multiple nuclear Ca2+ responses to developmental and environmental conditions. Authors: Myriam Charpentier, Jongho Sun, Teresa Vaz Martins, Guru V. Radhakrishnan, Kim Findlay, Eleni Soumpourou, Julien Thouin, Anne-Aliénor Véry, Dale Sanders, Richard J. Morris, Giles E. D. Oldroyd


[In Depth] Shooting for a star - 27 May 2016

Last month, Russian internet billionaire Yuri Milner announced plans to send thousands of tiny spacecraft to visit Alpha Centauri, the closest star system to Earth. In order to cover the vast distance—41 trillion kilometres—in a reasonable time, the proposed spacecraft will each weigh less than a gram and will unfurl lightweight sails to catch laser beams shot from Earth, accelerating them to one-fifth the speed of light. But the proposal has polarized opinion: Some are enthused by its ambition, whereas others say it is costly and unnecessary, isn't feasible, or is downright dangerous. Milner speaks with Science about the challenges facing the project and how he answers his critics. Author: Zeeya Merali


[This Week in Science] Cold atoms do geometry - 27 May 2016

Author: Jelena Stajic


[In Depth] Government ‘nudges’ prove their worth - 27 May 2016

Over the past 5 years, on behalf of state governments, nearly 100,000 Americans were gently manipulated by a team of social scientists. In 15 randomized, controlled trials, people in need of social services either encountered the standard application process or received a psychological nudge, in which the information was presented slightly differently—a postcard reminded them of deadlines, for example, or one choice was made easier than another. In 11 of the trials, the nudge modestly increased a person's response rate or influenced them to make financially smarter choices. The results, presented this week at a meeting in Chicago, add to the growing evidence that nudges developed by psychologists can make a real difference in the success of government programs. Author: John Bohannon


[Editors' Choice] Crowd-sourcing craters on the Moon - 27 May 2016

Author: H. Jesse Smith


[In Depth] India nears putting GM mustard on the table - 27 May 2016

Six years after it backed down from approving cultivation of a transgenic food crop, India's government is trying again. But it is encountering stiff headwinds as it mulls whether to approve what would be India's first such crop, a genetically modified (GM) mustard. Environmentalists argue that the mustard, grown for its edible leaves and for cooking oil, could harm local varieties and that the toxicity tests being carried out to evaluate GM mustard's safety as a food are inadequate. Heightening suspicion, regulators have repeatedly spurned calls to release biosafety data. But India's environment minister, Prakash Javadekar, is determined to open the door to GM food technologies, saying they can help ensure food security and that rejecting them is like "saying 'no' to science." Author: Priyanka Pulla


[Report] A Schrödinger cat living in two boxes - 27 May 2016

Quantum superpositions of distinct coherent states in a single-mode harmonic oscillator, known as “cat states,” have been an elegant demonstration of Schrödinger’s famous cat paradox. Here, we realize a two-mode cat state of electromagnetic fields in two microwave cavities bridged by a superconducting artificial atom, which can also be viewed as an entangled pair of single-cavity cat states. We present full quantum state tomography of this complex cat state over a Hilbert space exceeding 100 dimensions via quantum nondemolition measurements of the joint photon number parity. The ability to manipulate such multicavity quantum states paves the way for logical operations between redundantly encoded qubits for fault-tolerant quantum computation and communication. Authors: Chen Wang, Yvonne Y. Gao, Philip Reinhold, R. W. Heeres, Nissim Ofek, Kevin Chou, Christopher Axline, Matthew Reagor, Jacob Blumoff, K. M. Sliwa, L. Frunzio, S. M. Girvin, Liang Jiang, M. Mirrahimi, M. H. Devoret, R. J. Schoelkopf


[In Depth] Brazilian crisis threatens science and environment - 27 May 2016

In the midst of Brazil's political turmoil, scientists and environmentalists are wondering whether they have an enemy in Interim President Michel Temer, who came to power after Dilma Rousseff was removed on 12 May. Days after Temer assumed office, the government merged the science ministry with the communications ministry, leaving researchers fearing for what's left of their already diminished budgets. Meanwhile, pro-development forces are moving ahead on a constitutional amendment that could speed approval for dams, highways, mines, and other megaprojects. The measure has alarmed scientists, environmentalists, and indigenous rights advocates, who fear it would gut the country's environmental licensing process. Author: Lizzie Wade


[Report] Gene-microbiota interactions contribute to the pathogenesis of inflammatory bowel disease - 27 May 2016

Inflammatory bowel disease (IBD) is associated with risk variants in the human genome and dysbiosis of the gut microbiome, though unifying principles for these findings remain largely undescribed. The human commensal Bacteroides fragilis delivers immunomodulatory molecules to immune cells via secretion of outer membrane vesicles (OMVs). We reveal that OMVs require IBD-associated genes, ATG16L1 and NOD2, to activate a noncanonical autophagy pathway during protection from colitis. ATG16L1-deficient dendritic cells do not induce regulatory T cells (Tregs) to suppress mucosal inflammation. Immune cells from human subjects with a major risk variant in ATG16L1 are defective in Treg responses to OMVs. We propose that polymorphisms in susceptibility genes promote disease through defects in “sensing” protective signals from the microbiome, defining a potentially critical gene-environment etiology for IBD. Authors: Hiutung Chu, Arya Khosravi, Indah P. Kusumawardhani, Alice H. K. Kwon, Anilton C. Vasconcelos, Larissa D. Cunha, Anne E. Mayer, Yue Shen, Wei-Li Wu, Amal Kambal, Stephan R. Targan, Ramnik J. Xavier, Peter B. Ernst, Douglas R. Green, Dermot P. B. McGovern, Herbert W. Virgin, Sarkis K. Mazmanian


[Feature] The battery builder - 27 May 2016

Yi Cui, a materials scientist at Stanford University in Palo Alto, California, is trying to take lithium-ion batteries to the next level. He's not alone: Massive corporations are also attempting to make batteries smaller, lighter, and more powerful. But unlike others who focus on tweaking the chemical composition of a battery's electrodes or its charge-conducting electrolyte, Cui—and his startup, Amprius—are marrying battery chemistry with nanotechnology. He is building intricately structured battery electrodes that can soak up and release charge-carrying ions in greater quantities, and faster, than standard electrodes can, without producing troublesome side reactions. The nanoscale architectures he is exploring have already led to phone batteries that store 10% more energy than the best conventional lithium-ion batteries on the market, and better ones are in the works. If the technologies live up to their promise, Amprius could one day supply car batteries able to store up to 10 times more energy than today's top performers. Author: Robert F. Service


[This Week in Science] A radical route to ophiobolin rings - 27 May 2016

Author: Jake Yeston


[Perspective] How to break down crystalline cellulose - 27 May 2016

Biomass-degrading microorganisms use lytic polysaccharide monooxygenase (LPMO) enzymes to help digest cellulose, chitin, and starch. By cleaving otherwise inaccessible crystalline cellulose chains, these enzymes provide access to hydrolytic enzymes. LPMOs are of interest to biotechnology because efficient depolymerization of cellulose is a major bottleneck for the production of biologically based chemicals and fuels. On page 1098 of this issue, Kracher et al. (1) compare LPMO-reducing substrates in fungi from different taxonomic groups and lifestyles, based on both biochemical and genomic evidence. The results provide insights into reductive activation of LPMO that are important for developing more efficient industrial enzymes for lignocellulose biorefineries. Author: Angel T. Martínez


[This Week in Science] A new metal scavenger for bacteria - 27 May 2016

Author: Nicolas S. Wigginton


[Perspective] The cancer predisposition revolution - 27 May 2016

Studies of rare cancer predisposition syndromes often lead to the identification of genes critical to carcinogenesis. In 1969, Li and Fraumeni described a constellation of various cancers in the family members of four unrelated children who were diagnosed with soft tissue sarcomas (1). They posited that the cancers best fit an autosomal dominant pattern of inheritance, attributable to a genetic defect. At that time, cancer was not generally thought of as a genetic disease. Their hypothesis set the stage for establishing germline mutations in the tumor suppressor gene TP53 as the underlying genetic event in Li-Fraumeni syndrome (LFS) families (2) (see the figure). It also foreshadowed dozens of discoveries, still ongoing, that associate mutations in tumor suppressor genes, activated oncogenes, mitochondrial genes, and DNA repair genes with cancer predisposition phenotypes in which multiple different neoplasms occur across generations. Authors: David Malkin, Judy E. Garber, Louise C. Strong, Stephen H. Friend


[Editors' Choice] Pluripotency factor opens chromatin - 27 May 2016

Author: Beverly A. Purnell


[Perspective] Organic photocatalysts for cleaner polymer synthesis - 27 May 2016

The material properties of synthetic polymers can be tuned by changing their chain length and branching and the way in which monomer units repeat. For example, high-density polyethylene, which has little chain branching, is a stiff polymer used for food containers and drain pipes, whereas low-density polyethylene, which has more chain branching, is flexible and used to make grocery bags and bottles for chemicals. Polymers are usually made through thermal polymerization, but recent efforts focusing on green chemistry have led to a push toward using solar energy to drive chemical reactions. On page 1082 of this issue, Theriot et al. (1) report on metal-free visible-light photocatalysts that produce well-defined polymers free of metal contamination through radical polymerization. Authors: Sivaprakash Shanmugam, Cyrille Boyer


[Editors' Choice] The wet and the dry - 27 May 2016

Author: H. Jesse Smith


[Perspective] A metal shuttle keeps pathogens well fed - 27 May 2016

Staphylococcus aureus is a Gram-positive bacterium that is a leading cause of life-threatening infections in humans. Knowledge of how this pathogen colonizes the human host and causes disease is crucial for the development of strategies to prevent and treat S. aureus infections (see the image, next page). On page 1105 of this issue, Ghssein et al. report the discovery, isolation, and functional evaluation of staphylopine (see the figure), a compound biosynthesized by S. aureus that captures metal ions from the pathogen's surroundings and thereby enables it to grow (1). Author: Elizabeth M. Nolan


[Report] Enantioselective synthesis of an ophiobolin sesterterpene via a programmed radical cascade - 27 May 2016

Cyclase enzymes weave simple polyprenyl chains into the elaborate polycyclic ring systems of terpenes, a sequence that is often difficult to emulate under abiotic conditions. Here we report a disparate synthetic approach to complex terpenes whereby simple prenyl-derived chains are cyclized using radical, rather than cationic, reaction pathways. This strategy allowed us to efficiently forge the intricate 5-8-5 fused ring systems found in numerous complex natural product classes and also enabled a nine-step total synthesis of (–)-6-epi-ophiobolin N, a member of the large family of cytotoxic ophiobolin sesterterpenes. A small-molecule thiol catalyst was found to override the inherent diastereoselectivity observed during a reductive radical cascade cyclization process. This work lays the foundation for efficient synthesis of terpenoid ring systems of interest in medicinal research, particularly those that have been historically challenging to access. Authors: Zachary G. Brill, Huck K. Grover, Thomas J. Maimone


[Perspective] Matching markets in the digital age - 27 May 2016

Recent advances in information technology are enabling new markets and revolutionizing many existing markets. For example, taxicabs used to find passengers through chance drive-bys or slow central dispatching (see the photo). Location tracking, computer navigation, and dynamic pricing now enable ride-sharing services such as Uber to offer low and consistent delay times of only a few minutes. In a recent study, Cramer and Krueger (1) show that ride-sharing has dramatically increased the usage of drivers and their cars, cutting costs for riders. The results highlight the opportunities provided by digital markets. Further efficiency gains may come from academia-industry collaborations, which could also help to ensure that the markets develop in ways that further the public interest. Authors: Eduardo M. Azevedo, E. Glen Weyl


[Report] Bloch state tomography using Wilson lines - 27 May 2016

Topology and geometry are essential to our understanding of modern physics, underlying many foundational concepts from high-energy theories, quantum information, and condensed-matter physics. In condensed-matter systems, a wide range of phenomena stem from the geometry of the band eigenstates, which is encoded in the matrix-valued Wilson line for general multiband systems. Using an ultracold gas of rubidium atoms loaded in a honeycomb optical lattice, we realize strong-force dynamics in Bloch bands that are described by Wilson lines and observe an evolution in the band populations that directly reveals the band geometry. Our technique enables a full determination of band eigenstates, Berry curvature, and topological invariants, including single- and multiband Chern and Z2 numbers. Authors: Tracy Li, Lucia Duca, Martin Reitter, Fabian Grusdt, Eugene Demler, Manuel Endres, Monika Schleier-Smith, Immanuel Bloch, Ulrich Schneider


[Perspective] Unwinding inducible gene expression - 27 May 2016

The inflammatory response is coordinated by hundreds of genes that promote host defense against infection and injury. Inducible expression of these genes is mediated by distinct mechanisms, including transcriptional elongation, histone modifications, and nucleosome remodeling. On page 1074 of this issue, Rialdi et al. (1) report that a subset of the genes activated by viral infections depends on topoisomerase 1 (Top1) for induced expression. Pharmacological targeting of specific gene subsets has many clinical applications in inflammatory diseases. Because Top1 inhibition primarily affects genes dependent on nucleosome remodeling, many of which are key drivers of inflammation, it holds promise for gene-specific manipulation of the inflammatory response. Authors: Scott D. Pope, Ruslan Medzhitov


[Report] New particle formation in the free troposphere: A question of chemistry and timing - 27 May 2016

New particle formation (NPF) is the source of over half of the atmosphere’s cloud condensation nuclei, thus influencing cloud properties and Earth’s energy balance. Unlike in the planetary boundary layer, few observations of NPF in the free troposphere exist. We provide observational evidence that at high altitudes, NPF occurs mainly through condensation of highly oxygenated molecules (HOMs), in addition to taking place through sulfuric acid–ammonia nucleation. Neutral nucleation is more than 10 times faster than ion-induced nucleation, and growth rates are size-dependent. NPF is restricted to a time window of 1 to 2 days after contact of the air masses with the planetary boundary layer; this is related to the time needed for oxidation of organic compounds to form HOMs. These findings require improved NPF parameterization in atmospheric models. Authors: F. Bianchi, J. Tröstl, H. Junninen, C. Frege, S. Henne, C. R. Hoyle, U. Molteni, E. Herrmann, A. Adamov, N. Bukowiecki, X. Chen, J. Duplissy, M. Gysel, M. Hutterli, J. Kangasluoma, J. Kontkanen, A. Kürten, H. E. Manninen, S. Münch, O. Peräkylä, T. Petäjä, L. Rondo, C. Williamson, E. Weingartner, J. Curtius, D. R. Worsnop, M. Kulmala, J. Dommen, U. Baltensperger


[Policy Forum] Paying for future success in gene therapy - 27 May 2016

Imagine a young man with hemophilia A who no longer has to self-administer factor VIII replacement; an individual with sickle cell disease who is free of chronic pain and intermittent crises; a girl functionally blind since the age of 5 who can now see; or a baby rescued from a fatal, inherited neurodegenerative disease. For decades, gene therapy has tantalized us with such futuristic scenarios. However, these goals are now coming into focus, and it is the time to consider some of the consequences of success. Authors: Stuart H. Orkin, Philip Reilly


[Report] A force-generating machinery maintains the spindle at the cell center during mitosis - 27 May 2016

The position and orientation of the mitotic spindle is precisely regulated to ensure the accurate partition of the cytoplasm between daughter cells and the correct localization of the daughters within growing tissue. Using magnetic tweezers to perturb the position of the spindle in intact cells, we discovered a force-generating machinery that maintains the spindle at the cell center during metaphase and anaphase in one- and two-cell Caenorhabditis elegans embryos. The forces increase with the number of microtubules and are larger in smaller cells. The machinery is rigid enough to suppress thermal fluctuations to ensure precise localization of the mitotic spindle, yet compliant enough to allow molecular force generators to fine-tune the position of the mitotic spindle to facilitate asymmetric division. Authors: Carlos Garzon-Coral, Horatiu A. Fantana, Jonathon Howard


[Book Review] Navigating the cascades of circumstance - 27 May 2016

In his new book, Serendipity, eminent ecologist James A. Estes deftly weaves rigorous science with personal reflection to create an absorbing and introspective read that is equal parts memoir, ecological textbook, and motivational guidebook for young ecologists. Emphasizing the role of chance encounters in creating career opportunities, the book serves as a revitalizing reminder of the self-doubt and exhilaration that go hand-in-hand with scientific discovery. Authors: Elizabeth Forbes, Ana Miller ter Kuile, Devyn Orr, Georgia Titcomb


[Editorial] Implicit bias - 27 May 2016

We all have it. Implicit bias was the shorthand that allowed our distant ancestors to make split-second decisions (friend or foe?) based on incomplete information. It provided a razor-thin reaction-time advantage that could mean life or death. But today, we no longer need to assume that people who do not look or sound like us pose an immediate threat. Instead, successful organizations and people welcome those who do not necessarily look, think, and act like they do. They must overcome that implicit bias wired into the human DNA if they are to reap the benefits of diversity. To explore the extent of implicit bias in peer review, and what can be done to counter it, the American Association for the Advancement of Science (AAAS, the publisher of Science) recently convened a day-long forum of editors, publishers, funders, and experts on implicit bias in Washington, DC (see p. 1067). Author: Marcia McNutt


[Book Review] Like. Share. Retweet - 27 May 2016

Tom Vanderbilt's You May Also Like: Taste in an Age of Endless Choice sets out to understand this mysterious phenomenon of how our preferences change and come to be. Jockeying between the various definitions of taste (what one likes; what our society sanctions as good or bad standards of judgment; the sensory experience itself), the book moves on a whirlwind tour of taste across its many domains, from food and music to color and even cats. Author: Sheena Iyengar


[This Week in Science] Precise control from a metal-free catalyst - 27 May 2016

Author: Jake Yeston


[Letter] Public participation in China's project plans - 27 May 2016

Authors: Guoyou Qi, Yanhong Jia, Saixing Zeng, Jonathan J. Shi


[This Week in Science] The fuel for fungal enzymes - 27 May 2016

Author: Nicolas S. Wigginton


[Letter] Infection and the first eukaryotes - 27 May 2016

Author: Sven B. Gould


[This Week in Science] Phosphorylation cues exit from mitosis - 27 May 2016

Author: L. Bryan Ray


[Letter] Infection and the first eukaryotes—Response - 27 May 2016

Authors: Steven G. Ball, Debashish Bhattacharya, Andreas P. M. Weber


[Editors' Choice] Killing promotes killing - 27 May 2016

Author: Sacha Vignieri


[Association Affairs] Journals and funders confront implicit bias in peer review - 27 May 2016

Experts brainstorm ways to allow a more diverse community of science and technology innovators Author: Ginger Pinholster


[Editors' Choice] Lupus: subdivide in order to conquer? - 27 May 2016

Author: Paula A. Kiberstis


[Association Affairs] Research shows gun owners support gun-violence prevention - 27 May 2016

With federal funding of firearm injury prevention stalled, a top scientist says policies to reduce gun violence not as polarizing as politicians may think Author: Kathleen O'Neil


[Editors' Choice] Watching phonons propagate - 27 May 2016

Author: Jelena Stajic


[This Week in Science] Evidence for ice ages on Mars - 27 May 2016

Author: Keith T. Smith


[Editors' Choice] A secret(e) weapon for food poisoning - 27 May 2016

Author: Caroline Ash


[This Week in Science] Quantum cats here and there - 27 May 2016

Author: Ian S. Osborne


[Report] An ice age recorded in the polar deposits of Mars - 27 May 2016

Layered ice deposits at the poles of Mars record a detailed history of accumulation and erosion related to climate processes. Radar investigations measure these layers and provide evidence for climate changes such as ice advance and retreat. We present a detailed analysis of observational data showing that ~87,000 cubic kilometers of ice have accumulated at the poles since the end of the last ice age ~370,000 years ago; this volume is equivalent to a global layer of ~60 centimeters. The majority of the material accumulated at the north pole. These results provide both a means to understand the accumulation history of the polar deposits as related to orbital Milankovitch cycles and constraints for better determination of Mars’ past and future climates. Authors: Isaac B. Smith, Nathaniel E. Putzig, John W. Holt, Roger J. Phillips


[This Week in Science] Rhythm remodeling traced to tiny RNA - 27 May 2016

Author: Megan Frisk


[Report] Organocatalyzed atom transfer radical polymerization driven by visible light - 27 May 2016

Atom transfer radical polymerization (ATRP) has become one of the most implemented methods for polymer synthesis, owing to impressive control over polymer composition and associated properties. However, contamination of the polymer by the metal catalyst remains a major limitation. Organic ATRP photoredox catalysts have been sought to address this difficult challenge but have not achieved the precision performance of metal catalysts. Here, we introduce diaryl dihydrophenazines, identified through computationally directed discovery, as a class of strongly reducing photoredox catalysts. These catalysts achieve high initiator efficiencies through activation by visible light to synthesize polymers with tunable molecular weights and low dispersities. Authors: Jordan C. Theriot, Chern-Hooi Lim, Haishen Yang, Matthew D. Ryan, Charles B. Musgrave, Garret M. Miyake


[This Week in Science] Designing better estrogens - 27 May 2016

Author: Wei Wong


[Report] Experimental reconstruction of the Berry curvature in a Floquet Bloch band - 27 May 2016

Topological properties lie at the heart of many fascinating phenomena in solid-state systems such as quantum Hall systems or Chern insulators. The topology of the bands can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Using fermionic ultracold atoms in a hexagonal optical lattice, we engineered the Berry curvature of the Bloch bands using resonant driving and show a full momentum-resolved measurement of the ensuing Berry curvature. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures. Authors: N. Fläschner, B. S. Rem, M. Tarnowski, D. Vogel, D.-S. Lühmann, K. Sengstock, C. Weitenberg


[This Week in Science] Calcium signals the making of symbiosis - 27 May 2016

Author: Pamela J. Hines


[Report] Extracellular electron transfer systems fuel cellulose oxidative degradation - 27 May 2016

Ninety percent of lignocellulose-degrading fungi contain genes encoding lytic polysaccharide monooxygenases (LPMOs). These enzymes catalyze the initial oxidative cleavage of recalcitrant polysaccharides after activation by an electron donor. Understanding the source of electrons is fundamental to fungal physiology and will also help with the exploitation of LPMOs for biomass processing. Using genome data and biochemical methods, we characterized and compared different extracellular electron sources for LPMOs: cellobiose dehydrogenase, phenols procured from plant biomass or produced by fungi, and glucose-methanol-choline oxidoreductases that regenerate LPMO-reducing diphenols. Our data demonstrate that all three of these electron transfer systems are functional and that their relative importance during cellulose degradation depends on fungal lifestyle. The availability of extracellular electron donors is required to activate fungal oxidative attack on polysaccharides. Authors: Daniel Kracher, Stefan Scheiblbrandner, Alfons K. G. Felice, Erik Breslmayr, Marita Preims, Karolina Ludwicka, Dietmar Haltrich, Vincent G. H. Eijsink, Roland Ludwig


[This Week in Science] Narrowing down genetic loci of interest - 27 May 2016

Author: Laura M. Zahn


[Report] Biosynthesis of a broad-spectrum nicotianamine-like metallophore in Staphylococcus aureus - 27 May 2016

Metal acquisition is a vital microbial process in metal-scarce environments, such as inside a host. Using metabolomic exploration, targeted mutagenesis, and biochemical analysis, we discovered an operon in Staphylococcus aureus that encodes the different functions required for the biosynthesis and trafficking of a broad-spectrum metallophore related to plant nicotianamine (here called staphylopine). The biosynthesis of staphylopine reveals the association of three enzyme activities: a histidine racemase, an enzyme distantly related to nicotianamine synthase, and a staphylopine dehydrogenase belonging to the DUF2338 family. Staphylopine is involved in nickel, cobalt, zinc, copper, and iron acquisition, depending on the growth conditions. This biosynthetic pathway is conserved across other pathogens, thus underscoring the importance of this metal acquisition strategy in infection. Authors: Ghassan Ghssein, Catherine Brutesco, Laurent Ouerdane, Clémentine Fojcik, Amélie Izaute, Shuanglong Wang, Christine Hajjar, Ryszard Lobinski, David Lemaire, Pierre Richaud, Romé Voulhoux, Akbar Espaillat, Felipe Cava, David Pignol, Elise Borezée-Durant, Pascal Arnoux


[This Week in Science] Genes and microbes converge in colitis - 27 May 2016

Author: Kristen L. Mueller


[Report] CRISPR-directed mitotic recombination enables genetic mapping without crosses - 27 May 2016

Linkage and association studies have mapped thousands of genomic regions that contribute to phenotypic variation, but narrowing these regions to the underlying causal genes and variants has proven much more challenging. Resolution of genetic mapping is limited by the recombination rate. We developed a method that uses CRISPR (clustered, regularly interspaced, short palindromic repeats) to build mapping panels with targeted recombination events. We tested the method by generating a panel with recombination events spaced along a yeast chromosome arm, mapping trait variation, and then targeting a high density of recombination events to the region of interest. Using this approach, we fine-mapped manganese sensitivity to a single polymorphism in the transporter Pmr1. Targeting recombination events to regions of interest allows us to rapidly and systematically identify causal variants underlying trait differences. Authors: Meru J. Sadhu, Joshua S. Bloom, Laura Day, Leonid Kruglyak


[This Week in Science] Forcing the spindle to the cell center - 27 May 2016

Author: Beverly A. Purnell


[Report] Cyclin-dependent kinase 1–dependent activation of APC/C ubiquitin ligase - 27 May 2016

Error-free genome duplication and segregation are ensured through the timely activation of ubiquitylation enzymes. The anaphase-promoting complex or cyclosome (APC/C), a multisubunit E3 ubiquitin ligase, is regulated by phosphorylation. However, the mechanism remains elusive. Using systematic reconstitution and analysis of vertebrate APC/Cs under physiological conditions, we show how cyclin-dependent kinase 1 (CDK1) activates the APC/C through coordinated phosphorylation between Apc3 and Apc1. Phosphorylation of the loop domains by CDK1 in complex with p9/Cks2 (a CDK regulatory subunit) controlled loading of coactivator Cdc20 onto APC/C. A phosphomimetic mutation introduced into Apc1 allowed Cdc20 to increase APC/C activity in interphase. These results define a previously unrecognized subunit-subunit communication over a distance and the functional consequences of CDK phosphorylation. Cdc20 is a potential therapeutic target, and our findings may facilitate the development of specific inhibitors. Authors: Kazuyuki Fujimitsu, Margaret Grimaldi, Hiroyuki Yamano


[This Week in Science] From neutral to new - 27 May 2016

Author: H. Jesse Smith


[New Products] New Products - 27 May 2016

A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.


[This Week in Science] Unwinding DNA and unleasing inflammation - 27 May 2016

Author: Kristen L. Mueller


[Working Life] Three strikes and research is out - 27 May 2016

Author: Michael J. Orsini


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