Editors' Choice

Science  12 Dec 2014:
Vol. 346, Issue 6215, pp. 1339
  1. Aging in Yeast

    DNA circles involved in an aging SAGA

    1. Stella M. Hurtley

    Yeast cells help to reveal the secrets of aging

    CREDIT: BIOPHOTO ASSOCIATES/SCIENCE SOURCE

    Budding yeast cells provide a powerful model system to study the mechanisms of aging. As they grow older, yeast cells accumulate extra-chromosomal ribosomal DNA circles, a by-product of DNA repair processes. Somehow, during cell division, these circles are retained in the mother cell where they replicate and limit mother cell viability. Denoth-Lippuner et al. report that the yeast acetyl-transferase complex SAGA plays a role in this process. Cells lacking SAGA are long-lived. SAGA promotes the retention of DNA circles within the nucleus of yeast mother cells by anchoring them to nuclear pores. The nuclear pores and DNA circles accumulate in a sort of cap inside the nuclear envelope, which is preferentially retained in the mother cell.

    eLife 3, e03790 (2014).

  2. Sociology

    Networking doesn't always mean cooperating

    1. Barbara R. Jasny

    The relationship between network structure and cooperation has been hard to define. Rand et al. arranged sets of volunteers in fixed networks, where they could only interact with specific players, in a Prisoner's dilemma game. In this game, “defectors” earned points and “cooperators” paid a cost so that each of their neighbors benefited. After each round, players learned what their neighbors had done. Not all network conformations increased cooperation—the rewards relative to costs had to be greater than the number of linked players in order for cooperation to increase and clusters of cooperators to form.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1400406111 (2014).

  3. Plant Pathology

    Morning brew at risk

    1. Pamela J. Hines

    A coffee plant pathogen is leaving a trail through South America

    CREIDT: GERSON SOBREIRA/TERRASTOCK

    Coffee leaf scorch has affected yields of coffee in Brazil, the supplier of much of the world's coffee, since the 1990s. The disease is caused by Xylella fastidiosa, a bacterium that clogs xylem vessels and impedes transport of water and nutrients for the plant, resulting in a degradation of the quality and yield of the coffee beans and the eventual death of the plant. Nunney et al. genotyped bacterial samples from infected plants in Costa Rica to reconstruct the pathogen's progress as it slithers from Brazil and through the Americas. Citrus groves are also at risk because substrains of this pathogen hopscotch into new domains, perhaps using homologous recombination with strains already present.

    PLOS One 9, e112463 (2014).

  4. Water Structure

    Getting all wet 9 or 10 at a time

    1. Jake Yeston

    H2O seems like such a simple molecule. Why, then, haven't chemists definitively resolved the details of liquid water structure? The trouble is that hydrogen bonding—the attraction between an H on one molecule and an O on another—creates a cooperative net, where the orientation of each individual H2O depends sensitively on the orientations of all its neighbors. Pérez et al. take a close look at water clusters built up from 9 or 10 molecules, to help tease out the subtleties of hydrogen bonding behavior in a more manageable size regime. Using rotational spectroscopy in the microwave region, they observe several different arrangements at slightly varying energies, which accord with a straightforward cooperativity model.

    Angew. Chem. Int. Ed. 53, 10.1002/anie.201407447 (2014).

  5. Economics

    Working from home can work well

    1. Gilbert Chin

    In the U.S., telecommuting is most commonly observed for employees in the highest and lowest income deciles, yet there is little evidence about its benefits. Bloom et al. carried out the first randomized control trial of this management practice and report that performance of at-home workers increased by 13%. They found that Ctrip, a large, China-based travel agency, experienced lower turnover among its call-center workers, who also reported greater job satisfaction. When this program was rolled out to the entire company, some of the at-home employees elected to return to the office, whereas others switched to working from home; this reassortment improved the overall performance gain to 22%.

    Quart. J. Econ. 10.1093/qje/qju032 (2014)

  6. Ice Sheets

    Bottom-up effects on Northern glaciation

    1. H. Jesse Smith

    How much did the solid Earth contribute to the development of Northern Hemispheric glaciation around 3 million years ago? Much attention has been paid to the roles of solar insolation, distal orogeny, and the ocean, and now Steinberger et al. suggest that regional geodynamic processes also had a profound influence on the growth of major ice sheets. They argue that the mantle plume beneath Iceland thinned the lithosphere and caused regional uplift in Greenland, while Greenland was drifting northward due to plate tectonics and true polar wander. These factors could help explain the reappearance of major Northern Hemispheric ice sheets after an absence of more than 500 million years.

    Terra Nova 10.1111/ter.12133 (2014)

  7. Environmental Science

    A simple, efficient way to purify water

    1. Julia Fahrenkamp-Uppenbrink

    Unsafe drinking water is a serious public health issue that affects many millions of people worldwide. Improved methods for purifying water have the potential to save many lives in the developing world, but they have to be affordable. Ehdaie et al. have developed a prototype ceramic tablet that, when added to a container, can purify 10 liters of water each day for more than 154 days. The tablet works by releasing silver ions, which effectively destroy bacteria, viruses, and protozoa, but are safe for humans at the levels released. These devices are comparatively cheap and easy to produce from sawdust, clay, and silver nitrate. Differences in clay composition can affect the tablet properties, so the approach still must be tested under real-world conditions.

    Environ. Sci. Technol. 10.1021/es503534c (2014).

  8. Structural Biology

    HIV in 3D: Modeling the mesoscale

    1. Jon Cohen

    Structural biologists have one set of tools to visualize atomiclevel details of large structures and another that reveals the nuances of small ones. But detailed models of mediumsized viruses, synaptic vessels, plasma, and the like—objects at the so-called mesoscale, ranging from 10 to 100 nanometers—have largely remained in the dark. Now, Johnson et al. have developed cellPACK, freely available software that produces 3D images of biological systems at the mesoscale. As a demonstration of cellPACK's utility, the tool purports to resolve a longstanding debate about whether HIV surface proteins are randomly distributed on the virus's surface (spoiler alert: they are not).

    cellPACK's HIV model shows protein distribution on the virus's surface.

    CREIDT: GRAHAM JOHNSON AND LUDOVIC AUTIN/THE SCRIPPS RESEARCH INSTITUTE

    Nat. Methods, 10.1038/nmeth.3204 (2014)

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