Editors' Choice

Science  18 Sep 2015:
Vol. 349, Issue 6254, pp. 1297
  1. Development

    The path to metamorphosis

    1. L. Bryan Ray

    Larval silkworms need an extra boost on their way to metamorphosing into adult moths

    PHOTO: DAVID M. PHILLIPS/SCIENCE SOURCE

    The metamorphosis of a caterpillar into a moth was classically thought to be controlled largely by two hormones: one that promotes metamorphosis and one that maintains juvenile characteristics. Daimon et al. definitively tested the role of the latter, juvenile hormone, in larval silk moths. They made knockout mutants that lacked an enzyme that catalyzes juvenile hormone synthesis or lacked the two juvenile hormone receptors. Analysis of these animals showed that juvenile hormone functioned only in the late larval stages, when it restrained metamorphosis until larvae reached a sufficient size. Competence to metamorphose depended not on release from juvenile hormone inhibition but rather on the accumulation of a yet-to-be-identified signal that controlled gene expression.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1506645112 (2015).

  2. Neuroscience

    Cost and outcome shape habit

    1. LNS

    When rodents or monkeys perform a learned task, neurons in the striatum are active right before and after the performance. Their activity is thought to encode expected and experienced cost and outcome. These signals may be disrupted in Parkinson's disease, manifesting as problems with the initiation of movements. Desrochers et al. asked whether these neurons participate in the formation of habits in naïve monkeys. They therefore measured activity in the striatum while monkeys learned to solve a visual task without instructions (“self-learning”). They found that before-and-after signals existed from the start and that a combination of cost and outcome signals afterward increased when monkeys got into the habit, and their performance improved.

    Neuron 87, 853, 10.1016/j. neuron.2015.07.019 (2015).

  3. Ecology

    A jellyfish smörgåsbord

    1. Guy Riddihough

    Thick-billed murres modify their hunting strategies when diving for fish among jellyfish blooms

    CREDIT: MILO BURCHAM /DESIGN PICS/GETTY IMAGES

    Jellyfish blooms are a common feature in oceans around the world. Because jellyfish hunt for zooplankton, crustaceans, and other lower-trophic-level prey, such blooms might disrupt food chains and have a negative impact on other marine predators. Sato et al. attached video and data loggers to thick-billed murres (Uria lomvia), diving seabirds that hunt in the Bering Sea. The seabirds successfully adapted their diving and hunting to feed on fish shoaling among the tentacles of large jellyfish, which suggests that blooms could have a beneficial impact on some seabirds.

    Biol. Lett. 10.1098/rsbl.2015.0358 (2015).

  4. Human Evolution

    Old and new immune genetic variation

    1. Laura M. Zahn

    The Khloe-San peoples of Africa are one of the most ancient lineages of humans and thus can be examined to identify both ancient and recent human-specific genetic variation. Investigating the alleles of the killer cell immunoglobulin-like receptors and their human leukocyte antigen class I ligands, which are involved in the immune response, Hilton et al. found evidence of both old and new genetic variants. Because these genes can affect pregnancy, the identification of one recently evolved variant at relatively high frequencies suggests that it may have conferred a selective advantage.

    PLOS Genet. 10.1371/journal.pgen.1005439 (2015).

  5. Molecular Physics

    Molecular simulation

    1. Ian S. Osborne

    Determining the electronic structure and dynamics of molecular systems presents an intractable computational challenge for all but the simplest of molecules. However, the ability to tune the interactions between atoms trapped in an optical lattice provides a versatile quantum system with which to simulate complex condensed-matter systems. Luhmann et al. show that such a cold-atom system can be used to simulate the electronic dynamics of complex molecules and to generate three-dimensional high-resolution images of their molecular orbitals, using benzene as an example.

    Phys. Rev. X 5, 31016 (2015).

    Calculated molecular single-particle orbitals of an artificial benzene molecule

    CREDIT: D. LÜHMANN ET AL., PHYSICAL REVIEW 5 (17 AUGUST 2015) © AMERICAN PHYSICAL SOCIETY
  6. Mechanochemistry

    Pulling for ketenes and imines

    1. Phil Szuromi

    Expanding the range of reactive functional groups that can be generated by polymer mechanochemistry—literally pulling the chains apart by applying force—is important for creating new self-healing materials. Robb and Moore show that the Staudinger cycloaddition [the formation of a four-membered β-lactam ring from an imine (=N–R, where R is an alkyl or aryl group) and a ketene (=C=O)] could be reversed mechanically. Poly(methyl acrylate) polymers with an internal β-lactam ring were cleaved by ultrasonication in organic solvent. The highly reactive ketene was scavenged with isobutanol.

    J. Am. Chem. Soc. 10.1021/jacs.5b07345 (2015).

  7. Enviromental Science

    Fertilizing water contamination

    1. Nicholas S. Wigginton

    Excess nutrients such as nitrogen and phosphorus can negatively affect aquatic ecosystems. Nutrient-rich fertilizer runoff stimulates productivity, which can lead to harmful algal blooms or fish kills. Nolan and Weber show that such pollution has another wide-ranging consequence: increasing the mobility of uranium in groundwater. Geochemical data for two major aquifers in the United States, which in combination provide drinking water to millions and irrigation for one-sixth of U.S. agriculture, show that increased nitrate levels correlate strongly with the presence of uranium. Nitrate can oxidatively dissolve naturally occurring uranium minerals, which in turn can lead to potentially harmful levels of soluble uranium in groundwater, especially in shallow aquifers.

    Environ. Sci. Technol. Lett. 10.1021/acs.estlett.5b00174(2015).

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