This Week in Science

Science  14 Oct 2016:
Vol. 354, Issue 6309, pp. 192
  1. Forest Ecology

    Global biodiversity and productivity

    1. Andrew M. Sugden

    Loss of forest diversity leads to a loss of productivity. productivity.

    PHOTO: GREG ASNER, CARNEGIE AIRBORNE OBSERVATORY

    The relationship between biodiversity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from >770,000 sample plots in 44 countries. A positive and consistent relationship can be discerned between tree diversity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in biodiversity leads to a 3% loss in productivity. This means that the economic value of maintaining biodiversity for the sake of global forest productivity is more than fivefold greater than global conservation costs.

    Science, this issue p. 196

  2. Solar Cells

    Improving the stability of perovskite solar cells

    1. Phil Szuromi

    Inorganic-organic perovskite solar cells have poor long-term stability because ultraviolet light and humidity degrade these materials. Bella et al. show that coating the cells with a water-proof fluorinated polymer that contains pigments to absorb ultraviolet light and re-emit it in the visible range can boost cell efficiency and limit photodegradation. The performance and stability of inorganic-organic perovskite solar cells are also limited by the size of the cations required for forming a correct lattice. Saliba et al. show that the rubidium cation, which is too small to form a perovskite by itself, can form a lattice with cesium and organic cations. Solar cells based on these materials have efficiencies exceeding 20% for over 500 hours if given environmental protection by a polymer coating.

    Science, this issue pp. 203 and 206

  3. Vaccines

    A DNA vaccine candidate for Zika

    1. Kristen L. Mueller

    The ongoing Zika epidemic in the Americas and the Caribbean urgently needs a protective vaccine. Two DNA vaccines composed of the genes that encode the structural premembrane and envelope proteins of Zika virus have been tested in monkeys. Dowd et al. show that two doses of vaccine given intramuscularly completely protected 17 of 18 animals against Zika virus challenge. A single low dose of vaccine was not protective but did reduce viral loads. Protection correlated with serum antibody neutralizing activity. Phase I clinical trials testing these vaccines are already ongoing.

    Science, this issue p. 237

  4. Paleobiology

    The platypus's sixth sense cost it its teeth

    1. Shahid Naeem

    The platypus, Ornithorhyncus anatinus, has an electromechanical sensory apparatus in its bill. The sixth sense endowed by its remarkable bill allows the platypus to detect prey in murky waters with its eyes closed. Using comparative morphology and imaging techniques, Asahara et al. mapped the enlarged infraorbital canal that contains all the nerves and vessels that supply the bill. It seems that the evolution of this anatomical arrangement has limited space for the roots of teeth in modern platypuses. Platypuses can still “chew” their prey with horny pads.

    Platypuses use an electrical sixth sense to seek prey.

    PHOTO: JOHNCARNEMOLLA/ISTOCKPHOTO.COM

    Sci. Adv. 10.1126.sciadv.1601329 (2016).

  5. Signal Transduction

    A function for multisite phosphorylation

    1. L. Bryan Ray

    Many transcription factors are regulated by phosphorylation on multiple residues. Mylona et al. analyzed multisite phosphorylation in the transcription factor Elk-1 and showed that it may protect against excessive activation (see the Perspective by Whitmarsh and Davis). Phosphorylation by the kinase ERK2 occurred at eight sites, but the sites were phosphorylated at different rates. Those that were phosphorylated more quickly promoted transcriptional activation. Those that were phosphorylated more slowly dampened excessive activation by ERK2s without needing a phosphatase or any other negative regulatory component.

    Science, this issue p. 233; see also p. 179

  6. Protein Evolution

    Phosphorylation and fungal evolution

    1. Laura M. Zahn

    Phosphorylation after transcription modifies the activity of proteins. To understand how phosphorylation sites have evolved, Studer et al. studied a range of fungal species (see the Perspective by Matalon et al.). Only a few sites were apparently present in the common ancestor of all 18 species investigated. Evolutionary age appeared to predict the potential functional importance of specific conserved phosphosites.

    Science, this issue p. 229; see also p. 176

  7. HIV-1 Therapy

    Antibodies sustain viral control

    1. Kristen L. Mueller

    For many infected individuals, antiretroviral therapy (ART) means that an HIV-1 diagnosis is no longer a death sentence. But the virus persists in treated individuals, and complying with the intense drug regimen to keep virus loads down can be challenging for patients. Seeking an alternative, Byrareddy et al. treated ART-suppressed monkeys with antibodies targeting α4β7 integrin. When ART was halted in the antibody-treated animals, viral loads stayed undetectable, and normal CD4 T cell counts were maintained for over 9 months—and persisted—even after stopping the antibody therapy.

    Science, this issue p. 197

  8. Biophysics

    Two roads diverged in a yellow photolyase

    1. Jake Yeston

    Photolyase enzymes repair DNA that has been damaged by ultraviolet sunlight. The repair process begins when blue light absorption by a cofactor drives an electron transfer step. Zhang et al. applied ultrafast absorption spectroscopy to study the dynamics of this step. A bifurcation in the electron transfer pathway favors a direct tunneling mechanism in the prokaryotic enzymes and a two-step hopping mechanism in the eukaryotic variety. This difference explains the higher repair quantum yield seen in prokaryotes.

    Science, this issue p. 209

  9. Sickle Cell Disease

    Hammering out the sickle cell mutation

    1. Yevgeniya Nusinovich

    Sickle cell disease is a genetic disorder caused by a mutation in one of the hemoglobin genes. This causes deformation of red blood cells and results in occlusion of blood vessels, severe pain, and progressive organ injury. To correct the mutation that causes this disease, De Witt et al. modified hematopoietic stem cells from sickle cell disease patients by using a CRISPR-Cas9 gene editing approach. The corrected cells successfully engrafted in a mouse and produced enough normal hemoglobin to indicate a potential clinical benefit in ameliorating sickle cell disease.

    Sci. Transl. Med. 8, 360ra134 (2016).

  10. Quantum Materials

    A layered approach for nanophotonics

    1. Ian S. Osborne

    Nanophotonics aims to combine the speed of optics with the small size scale of electronics for ultrahigh-speed technology. However, several order differences in length scale have to be bridged. Basov et al. review how van der Waal materials, which are two-dimensional layered structures, can span such length-scale differences. The wide range of materials available, as well as their broad range of optical and electronic properties, offer opportunities to make devices with desirable optoelectronic functionality.

    Science, this issue p. 195

  11. Political Science

    A consensus in Europe about asylum seekers

    1. Gilbert Chin

    Violent conflicts between groups often generate large numbers of noncombatant refugees. Bansak et al. surveyed western European attitudes toward such asylum seekers. They found that voters favor applicants who will contribute to the recipient country's economy, who have suffered severe physical or mental distress rather than economic hardship, and who are Christian rather than Muslim. These preferences are similar across countries and independent of the voters' personal characteristics.

    Science, this issue p. 217

  12. Global Climate Change

    An impactful event

    1. H. Jesse Smith

    Glassy silica spherules have been found in marine sediments from three sites across a wide area off the Atlantic coast of the United States, near the stratigraphic level of the Paleocene-Eocene boundary. The characteristics of these specimens are consistent with those of microtektites associated with extraterrestrial impact events. This discovery by Schaller et al. is evidence of an impact event at the time of the Paleocene-Eocene Thermal Maximum, a period during which global temperatures increased rapidly and the carbon cycle was substantially perturbed.

    Science, this issue p. 225

  13. Microbial Physiology

    Microbes make methane from coal

    1. Nicholas S. Wigginton

    Methane associated with coal beds is an important global resource of natural gas. Much of the methane in coal comes from microbial methanogenesis. Mayumi et al. characterized a strain of Methermicoccus shengliensis that, unexpectedly, is capable of making methane from the dozens of methoxylated aromatic compounds found in a variety of coal types (see the Perspective by Welte). Isotope tracer experiments showed that this organism could also incorporate carbon dioxide into methane.

    Science, this issue p. 222; see also p. 184

  14. Influenza

    Migration of influenza in wild birds

    1. Caroline Ash

    Virus surveillance in wild birds could offer an early warning system that, combined with adequate farm hygiene, would lead to effective influenza control in poultry units. The Global Consortium for H5N8 and Related Influenza Viruses found that the H5 segment common to the highly pathogenic avian influenza viruses readily reassorts with other influenza viruses (see the Perspective by Russell). H5 is thus a continual source of new pathogenic variants. These data also show that the H5N8 virus that recently caused serious outbreaks in European and North American poultry farms came from migrant ducks, swans, and geese that meet at their Arctic breeding grounds. Because the virus is so infectious, culling wild birds is not an effective control measure.

    Science, this issue p. 213; see also p. 174

  15. Climate Change

    The negative emissions gamble

    1. Julia Fahrenkamp-Uppenbrink

    Scenarios for how global warming can be kept below 2°C rely heavily on the large-scale use of technologies that remove carbon from the atmosphere. They are attractive to policy-makers because they reduce the perceived need for reductions in carbon emissions in the short term. In a Perspective, Anderson and Peters argue that it may not be possible or advisable to deploy these technologies at the scale required. For example, bioenergy with carbon capture and storage is seen as particularly promising, yet it would require vast areas of land that would then no longer be available for food production or for wildlife. By relying on these speculative technologies, humanity could miss a crucial window of opportunity for directly mitigating climate change.

    Science, this issue p. 182

  16. Vascular Biology

    Relaxing in response to pressure

    1. Wei Wong

    Small-diameter arteries link main arteries to capillary beds that feed tissues and organs. Persistent constriction of these arteries may generate high blood pressure (hypertension). Khavandi et al. (see also Hill and Braun) found that arterial constriction initiated the production of reactive oxygen species that oxidized and activated the kinase PKG, which opens a potassium channel that induces blood vessel relaxation. These results may explain why some drugs that generate reactive oxygen species are effective in treating hypertension.

    Sci. Signal. 9, ra100 and fs15 (2016).