This Week in Science

Science  06 Jun 2014:
Vol. 344, Issue 6188, pp. 1128
  1. Sheep Genome

    A genome for ewe and ewe

    1. Laura M. Zahn
    PHOTOS: (TOP TO BOTTOM) ROB_LAN/ISTOCK PHOTO; © JUNIORS BILDARCHIV GMBH/ALAMY

    Sheep-specific genetic changes underlie differences in lipid metabolism between sheep and other mammals, and may have contributed to the production of wool. Jiang et al. sequenced the genome of two Texel sheep, a breed that produces high-value meat, milk, and wool. The genome information will provide an important resource for livestock production and aid in the understanding of mammalian evolution.

    Science, this issue p. 1168

  2. Sleep and Learning

    To sleep, perchance to remember

    1. Peter Stern

    Many researchers believe sleep helps us consolidate our memories, but no one knows quite how. Yang et al. investigated the precise role of sleep in changing mouse brain structures (see the Perspective by Euston and Steenland). When mice learned motor tasks, small protuberances—or “spines”—formed on some of the dendritic branches of specific brain neurons. These spines represent the physical correlate of a memory. But the neurons grew and retained these spines better when the mice slept after learning the task. Neurons that fired during learning fired again during subsequent slow-wave sleep, allowing the mice to conserve the newly formed spines—and memories.

    Science, this issue p. 1173; see also p. 1087

  3. Cloud Physics

    Invigorating convection in warm clouds

    1. H. Jesse Smith

    Atmospheric aerosols—tiny airborne particles—affect the way clouds form and how they affect climate. Koren et al. investigated how the formation of warm clouds, such as those that form over the oceans, depends on pollution levels (see the Perspective by Remer). Aerosols affect cloud formation in cleaner air disproportionately more than in more polluted air. Before the widespread air pollution of the industrial era, it seems, warm convective clouds may have covered much less of the oceans than they do today.

    Science, this issue p. 1143; see also p. 1089

  4. Sensory Biology

    Hold your breath or the catfish will find you

    1. Sacha Vignieri

    Finding prey is hard enough in the light of day, but animals that are nocturnal or live in murky conditions face even greater challenges. Caprio et al. describe a sense that allows a marine catfish to detect the mere “breathing” of their prey target. External sensors on the catfish's whiskers detect pH changes generated by hidden, respiring polychaete worms.

    Science, this issue p. 1154

  5. Interfacial Chemistry

    Monitoring water interfaces in motion

    1. Jake Yeston

    Water behaves differently at interfaces—where it meets the air, or a solid surface—than it does in the middle of the liquid. Past laboratory studies of this phenomenon have mainly focused on still samples, despite the fact that in natural settings such as rivers and rain, the water moves along the surfaces. Lis et al. used a microfluidics apparatus and a spectroscopy technique called sum frequency generation to study the effects of flow on aqueous chemistry at silica and fluorite surfaces (see the Perspective by Waychunas). The flow of fresh water along the surfaces disrupts the equilibrium of dissolved ions, substantially changing the surface charge and the molecular orientation of the water at the interface.

    Science, this issue p. 1138; see also p. 1094

  6. Membrane Biology

    How cells haul down their “eat me” flags

    1. Stella M. Hurtley

    Dead and dying cells expose a membrane lipid called phosphatidylserine (PS) on their cell surface as a sort of “eat me” signal. Segawa et al. identified the membrane enzyme responsible for flipping any PS that inadvertently makes it way from the inner to the outer leaflet of the plasma membrane lipid bilayer. Without the enzyme, macrophages gobbled up healthy cells.

    Science, this issue p. 1164

  7. Lunar Formation

    An analysis of motes of the Moon maker

    1. Margaret M. Moerchen

    The Moon shows evidence of past collisions.

    PHOTO: NASA

    How did the Moon form? According to the prevailing hypothesis, a Mars-sized body known as Theia smashed into Earth. Herwartz et al. analyzed fresh basalt samples from three Apollo landing sites and compared them with several samples of Earth's mantle. The oxygen isotope values measured in these lunar rocks differ significantly from the terrestrial material, supporting the giant-impact hypothesis.

    Science, this issue p. 1146

  8. Quantum Information

    Electrical control of nuclear spin qubits

    1. Jelena Stajic

    Quantum bits of information (qubits) that are based on spins of atomic nuclei are an attractive option for quantum information processing. It can sometimes be tricky to manipulate these qubits using magnetic fields directly. Thiele et al. developed a technique for electrically controlling a nuclear spin qubit in the single-molecule magnet TbPc2. When they hit the qubit with a microwave pulse, the microwave's electric field generated effective magnetic fields much larger than those available previously.

    Science, this issue p. 1135

  9. Plant Biology

    ABA tells roots to stop and then grow

    1. Jason D. Berndt

    Plants initially grow a primary vertical root. The primary root then puts out horizontal lateral roots, which help to anchor the plant and take up water and nutrients from the soil. But to make the most of precious resources, plants use the hormone abscisic acid to stop lateral roots from growing in times of drought. Zhao et al. found that after a time, plants resume lateral root growth. This process paradoxically also uses abscisic acid, which binds to a different receptor and triggers changes in the expression of genes involved in resuming lateral root growth.

    Sci. Signal. 7, ra53 (2014).

  10. Calcium Channels

    Allowing calcium to leak across a membrane

    1. Valda Vinson

    Cells maintain a balance between calcium in the cytosol and calcium stored in organelles—too much stored calcium kills cells. Transmembrane Bax inhibitor motif (TMBIM) proteins form channels in organelle membranes that allow calcium to leak out. Chang et al. show that this calcium leak is pH-dependent. A bacterial homolog of TMBIM proteins converts between an open channel at low pH and a closed channel at high pH. Although the channel is open at low pH, calcium leakage is low because the inside of the channel remains at a neutral pH. Thus, at physiological pH, these channels will be in equilibrium between the open and closed states, so that excess calcium can leak through.

    Science, this issue p. 1131

  11. Planetary Formation

    The chronology of planetary embryos

    1. Nicholas S. Wigginton

    Protoplanets, or early planetary embryos such as iron meteorite parent bodies, formed in the early protoplanetary disk from dust, debris, and planetesimals. Defining the precise chronology of accretion and differentiation—including core formation—of these planetary embryos will aid in a richer understanding of the chemical evolution of the solar system. Through high-precision tungsten isotope measurements, Kruijer et al. show that the timing of accretion and core formation for iron meteorite groups falls within 0.6 to 2 million years of the age of the solar system (see the Perspective by Elliott). Differences of timing within this group are probably a function of volatile contents of the parent bodies or spatial and chemical heterogeneity within the protoplanetary disk.

    Science, this issue p. 1150; see also p. 1086

  12. Pluripotency Program

    Predicting stem cell renewal or differentiation

    1. Beverly A. Purnell

    Predicting complex mammalian cell behavior is extremely challenging. Dunn et al. developed a computational model that predicts when embryonic stem cells will self-renew or differentiate. The model revealed an essential program governing pluripotency and identifies a minimal set of components and interactions that accurately predict responses to genetic perturbation.

    Science, this issue p. 1156

  13. Schizophrenia

    Genes, synapses, and hallucinations

    1. Peter Stern

    In a schizophrenia mouse model, Chun et al. found that an abnormal increase of dopamine D2 receptors in the brain's thalamic nuclei caused thalamocortical synapse deficits owing to reduced glutamate release. Antipsychotic agents or a dopamine receptor antagonist reversed this down-regulation. The defect was associated with the loss of a component of the microRNA processing machinery encoded by the dgcr8 gene.

    Science, this issue p. 1178

  14. Plant Growth

    Emerging from the shade into the light

    1. Pamela J. Hines

    As a growing seedling emerges into the light, it needs to shift its developmental program to grow toward the light. Signaling components that flip the switch from growth in the shade to growth in the light include phytochromes, which are sensitive to red light, and transcription factors that drive the shade-adapted pattern of development. Ni et al. now show how phosphorylation sets these signaling partners up for destruction. The signaling established by red light invokes photomorphogenesis by promoting the destruction of the photoreceptor and its signaling partner.

    Science, this issue p. 1160

  15. Neurodevelopment

    Wiring the developing insect brain

    1. Beverly A. Purnell

    Developmental brain wiring requires a complex set of cellular interactions often orchestrated by a large number of surface receptors. Thousands of Dscam1 receptor isoforms function as “surface tags” endowing neurons with unique molecular identities. These isoforms are important for neuronal self-recognition and dendrite self-avoidance. He et al. report that the diversity of Dscam1 isoforms is also essential for complex axonal branching of sensory neurons in developing fruit flies.

    Science, this issue p. 1182