Editors' Choice

Science  08 Sep 2017:
Vol. 357, Issue 6355, pp. 1012
  1. Microbiota

    Coral reefs, colored food, and huge bacteria

    1. Caroline Ash

    Surgeonfishes harbor huge bacteria that help digest seaweed.

    CREDIT: LUIS JAVIER SANDOVAL/GETTY IMAGES

    Healthy coral reefs depend on grazing fishes, such as surgeonfishes and tangs, to supress blanketing algal growth. These fishes host a diversity of enormous Epulopiscium bacteria, which are visible to the naked eye. Using single-cell genomics on these uncultured organisms, Ngugi et al. monitored the bacteria's metabolic contribution to their host fish. Surgeonfishes are specialist feeders—some enjoy brown algae, whereas others have a taste for reds and greens. The range of algal polysaccharides consumed by the surgeonfishes is reflected in the range of carbohydrate-active enzymes, agarases, and alginate lyases produced by their giant symbionts. Hence, dietary specialism among surgeonfishes appears to have coevolved with the digestive talents of the Epulopiscium spp. that they harbor and, in turn, is reflected in their feeding ecology.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1703070114 (2017).

  2. Corals

    A proto-particular path to corals

    1. H. Jesse Smith

    False color image of a Stylophora pistillata coral skeleton

    CREDIT: PUPA GILBERT, CHANG-YU SUN, CAYLA STIFLER, UNIVERSITY OF WISCONSIN–MADISON, AND MATTHEW MARCUS, ADVANCE LIGHT SOURCE, LAWRENCE BERKELEY NATIONAL LABORATORY

    Coral skeletons form less directly than has long been thought. The classical picture of skeleton formation, involving simple inorganic precipitation of aragonite (a form of calcium carbonate) from a calcifying fluid, is now being supplanted by a body of research that identifies biologically controlled processes occurring within cells as the ones responsible. Mass et al. present spectromicroscopic evidence from Stylophora pistillata coral showing that amorphous calcium carbonate particles first form within the coral's organic tissue and then attach to the surface of the coral skeleton, where they soon crystallize into aragonite. This allows corals to grow faster than through ion-by-ion growth from solution and may make them less vulnerable to the harmful consequences of ocean acidification than has been assumed.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1707890114 (2017).

  3. Cell Biology

    Memories of past morphologies

    1. Stella M. Hurtley

    When developing neurons round and divide during neuronal differentiation, daughter cells tend to take up the same morphology exhibited by their mother. Boubakar et al. set up a chick embryo slice model to image the polarization of dorsal root ganglion neurons. These neurons differentiate from neural crest cells (NCCs) generated by bipolar progenitors. The authors examined the young neurons directly after their migration or after additional division in situ. Bipolar NCCs lost their polarity and retracted their processes to round for division. The daughter neurons directly acquired bipolar morphology by emitting processes in the same location. The morphological polarity features appeared to be stored by a polarity-associated protein known as Septin-7. Septin-7 “tagged” the process sites during NCC remodeling, allowing the cells to recolonize the original footprints after division.

    Neuron 95, 834 (2017).

  4. Graphene

    Navigating through graphene

    1. Jelena Stajic

    In some materials, current flow resembles the flow of viscous fluids. To reach this so-called hydrodynamic regime, researchers have to tune temperature to the right range. Krishna Kumar et al. studied the hydrodynamic flow of the electron liquid in graphene as it passed through narrow passages called constrictions. They found that the electrons flowed through the constrictions with a higher conductance than one would expect from noninteracting electrons; the electron-electron interactions helped the electron liquid avoid momentum loss from bumping into sample boundaries.

    Nat. Phys. 10.1038/nphys4240 (2017).

  5. Heart Regeneration

    Cells that fix the heart

    1. Beverly A. Purnell

    The adult heart is thought to lack the capacity to self-repair. Any injury after, say, a heart attack causes scarring and may result in heart failure. In some animals, particularly when very young, heart muscle regeneration does occur. Even in adult mammals, new heart muscle cells (cardiomyocytes) can arise, but they are rare. Most maturing mammalian cardiomyocytes become binucleated and polyploid, and these seem to be incapable of regeneration. Patterson et al. found that a few “normal” mononucleated diploid cardiomyocytes (MNDCMs) occur in mice. Some individuals have more MNDCMs than others, and these individuals are better able to recover after heart injury. A gene called Tnni3k limits the number of MNDCMs, and it is this that appears to control the capacity for recovery after heart injury.

    Nat. Genet. 10.1038/ng.3929 (2017).

  6. Agricultural Science

    Crop yields expected to fall as temperatures rise

    1. Emily Morris

    Climate change may reduce the yields of many cereal crops, including rice.

    PHOTO: LUKCHAI CHAIMONGKON/SHUTTERSTOCK

    Climate change will affect agriculture, but unfortunately predicting how is not simple. Zhao et al. combined four analytical methods to predict the impact of global temperature increases on the yields of four crops. The results consistently indicate that rising temperatures will lead to reductions in crop yields. An increase of 1°C would be more severe for global maize yield (7.4% decrease) than for rice (3.2% decrease), and decreases in maize yield in the United States would be twice those seen in India (10.3 and 5.2%, respectively). Although this work points to worrying consequences of a warming world, it remains very difficult to predict the cumulative impact of multiple factors related to climate change, such as elevated atmospheric carbon dioxide concentrations and precipitation.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1701762114 (2017).

  7. Solar Cells

    Purple power leaves the window open

    1. Jake Yeston

    Certain tunable coatings can render windows “smart” by modulating the amount of heat and light passing through them, depending on the desired temperature indoors. Powering these windows with photovoltaics seems sensible, but it is inefficient for the power source to absorb the same light that the coating is meant to regulate. Davy et al. resolve this conundrum by preparing a class of solar cells that absorb at the boundary between violet and ultraviolet. Composed from hexabenzocoronene organic semiconductors, these cells interfaced effectively with electrochromic window coatings on square-centimeter scales, leaving the rest of the optical and near-infrared regime open for modulation.

    Nat. Energy 2, 17104 (2017).

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