This Week in Science

Science  06 Sep 2013:
Vol. 341, Issue 6150, pp. 1041
  1. Transforming Fat to Thin

    CREDIT: V. ALTOUNIAN/SCIENCE

    How much does the microbiota influence the host's phenotype? Ridaura et al. (1241214; see the Perspective by Walker and Parkhill) obtained uncultured fecal microbiota from twin pairs discordant for body mass and transplanted them into adult germ-free mice. It was discovered that adiposity is transmissible from human to mouse and that it was associated with changes in serum levels of branched-chain amino acids. Moreover, obese-phenotype mice were invaded by members of the Bacteroidales from the lean mice, but, happily, the lean animals resisted invasion by the obese microbiota.

  2. Pushy Black Hole

    The giant black holes that sit at the centers of most galaxies influence the way galaxies evolve in poorly understood ways. Morganti et al. (p. 1082; see the Perspective by McNamara) have acquired high-resolution radio images of a galaxy with an actively accreting black hole from which a jet of relativistic particles emanates. The observations show that a cloud of neutral hydrogen gas is being driven outward, possibly limiting star formation and galaxy growth.

  3. Downs and Ups

    Every spring, the concentration of CO2 in the atmosphere of the Northern Hemisphere decreases as terrestrial vegetation grows, and every fall, CO2 rises as vegetation dies and rots. Climate change has destabilized the seasonal cycle of atmospheric CO2 such that Graven et al. (p. 1085, published online 8 August; see the Perspective by Fung) have found that the amplitude of the seasonal cycle has exceeded 50% at some latitudes. The only way to explain this increase is if extratropical land ecosystems are growing and shrinking more than they did half a century ago, as a result of changes in the structure and composition of northern ecosystems.

  4. Lignin Biosynthesis Complications

    Lignin is a polymer that lends its sturdy properties to wood and makes plant cell walls tougher, which creates problems for chemists converting cellulosic plant biomass into biofuels. Vanholme et al. (p. 1103, published online 15 August; see the cover) have identified a new step in the biosynthetic pathway of lignin in Arabidopsis in which caffeoyl shikimate esterase catalyzes synthesis of caffeate. Cellulose from mutant plants, which had reduced amounts of lignin, was more efficiently processed into glucose.

  5. Fatal Chimeras

    Impaired DNA-methylation maintenance during early embryonic development may cause imprinting-related diseases. Lorthongpanich et al. (p. 1110) have devised a sensitive assay to probe multiple imprinted gene loci for their DNA-methylation state at the single-cell level. Blastomeres with defective imprinting showed complex, epigenetic chimeras developed with fatal defects. Pronuclear transfer restored normal mouse development, offering a therapeutic strategy to overcome epigenetic defects caused by maternal insufficiencies.

  6. Looking for the Dark

    Mature Drosophila larvae wander away from food and seek a dark site for pupation. While investigating this phenomenon Yamanaka et al. (p. 1113) found that four prothoracicotropic hormone (PTTH)–producing neurons mediate light preference in the central brain. PTTH circulates in the hemolymph and signals via its receptor, Torso, to two light sensors, sensitizing them for light detection. The larvae can then transform from wandering larvae into immobile pupae hidden from light and predatory eyes.

  7. Deafness and Misbehavior

    Behavioral problems accompanied by hyperactivity often occur in children with severe hearing loss and vestibular impairment. Explanations have focused on socioenvironmental factors, but Antoine et al. (p. 1120) found that inner ear defects can cause dysfunction in the striatum, which leads to abnormal behavior—especially hyperactivity—mediated by dopamine and glutamate signals, in an area of the striatum that is instrumental in controlling motor output. The abnormal behavior can be reversed by injection of an extracellular signal-regulated kinase inhibitor, which provides a novel target pathway for the treatment of behavioral disorders.

  8. Absolute Images

    CREDIT: PITZER ET AL.

    Molecules are held together by a balance of charge between negative electrons and positive nuclei. When multiple electrons are expelled by laser irradiation, the remaining, mutually repulsive nuclei fly apart in a Coulomb explosion. Instead of traditional x-ray diffraction methods that require crystalline samples, Pitzer et al. (p. 1096) show that by tracking the fragment trajectories from laser-induced Coulomb explosions of relatively simple gas phase molecules, they can determine the absolute stereochemical configuration of enantiomers (mirror-image isomers).

  9. Wind of Change

    The flow of interstellar gas and dust through the solar system was thought to be unvarying, but Frisch et al. (p. 1080) show that there has been a significant variation of the direction of the flow of interstellar helium through the solar system over the past 40 years. The data, collected by 10 different spacecraft over much of the space age, hint of changes rather than constancy in the solar system's galactic environment.

  10. Quantum Collision Course

    Our experience of a world apparently governed by classical physics is a consequence of the fact that quantum mechanical effects average out in size regimes much larger than nanometers. Even at the molecular level, the quantized nature of rotational energy distributions is often obscured by averaging effects. Chefdeville et al. (p. 1094; see the Perspective by Casavecchia and Alexander) have observed a striking manifestation of quantized rotation in the scattering trajectories of colliding H2 and O2 molecular beams. The experimentally resolved partial wave resonances show essentially complete agreement with theoretical calculations and deviate starkly from classical collision paradigms.

  11. Stitching in Fluoroacetate

    Polyketide synthase enzymes stitch together an impressively diverse series of organic compounds from simple acetate and propionate building blocks. Walker et al. (p. 1089) now show that these biochemical pathways can be engineered to incorporate fluoroacetate—a primary product of the only known native enzymatic fluorination route—into tri- and tetraketides. In Escherichia coli cells, this process shows potential as a versatile means of inserting fluorine substituents into a range of complex molecules for use in pharmaceutical and agrochemical research.

  12. Number Sense

    CREDIT: HARVEY ET AL.

    Numerosity perception resembles primary sensory perception and, indeed, it has been called the number sense. As all primary senses are organized topographically in the cortex, Harvey et al. (p. 1123) tested the hypothesis that numerosity is also organized topographically. Applying ultrahigh-field functional brain scanning and using custom-designed analysis, they confirmed that a topographical numerosity map occurs in the human parietal cortex, which displays conventional characteristics, such as a systematic relationship between the cortical location's preferred numerosity and cortical magnification and tuning width.

  13. Plant Protection

    The Convention on Biological Diversity's 20 Aichi Targets, agreed in October 2010, extend to 2020 an international commitment to halt the loss of biodiversity. Using data from “The Plant List” (www.theplantlist.org), Joppa et al. (p. 1100), show that ∼65% of plant species are endemic to 17% of the terrestrial land surface and include many islands, with mainland contributions concentrated heavily in central and southern America and Asia. These regions include 75% of all plant species. These regions are also important for terrestrial vertebrates—containing most of all—bird, mammal, and amphibian species, but less than one-sixth of this land surface is under protection.

  14. More Determined Sex

    Although several transcription factors participate in mammalian sex determination, the contribution from specific epigenetic regulation is just being revealed. Kuroki et al. (p. 1106) show that a JmjC domain–containing protein, Jmjd1a, catalyzes H3K9 demethylation of the Y-linked sex-determining gene Sry in mice to enable its expression above the required threshold level. Ablation of Jmjd1a function results in mouse male-to-female sex reversal, hence not only revealing a mechanism of Sry regulation but also the pivotal role of epigenetic regulation in mammalian sex determination.

  15. smORFing for Calcium

    Genomes contain thousands of small open reading frames (smORFs), short DNA sequences coding for peptides of less than 100 amino acids. Magny et al. (p. 1116, published on 22 August) describe two smORF-encoded peptides of less than 30 amino acids regulating calcium transport and, hence, regular heart contraction, in the fruit fly Drosophila. These peptides seem to have been conserved for more than 550 million years in a range of species from flies to humans, where they have been implicated in severe heart diseases. Such conservation suggests that smORFs might be an ancient part of our functional genome.

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