This Week in Science

Science  17 May 2013:
Vol. 340, Issue 6134, pp. 785
  1. Surprise Attack


    Humans conduct the largest ecological experiment ever by continually moving species between continents. For example, the harlequin ladybird beetle, native to Asia, has become highly invasive in many regions after being introduced for biological control, but we do not understand why this species should so readily outcompete native ladybirds. Vilcinskas et al. (p. 862; see the Perspective by Reynolds) show that harlequin beetles have parasitic microsporidia within their hemolymph, which are fatal to other ladybird beetles that prey on harlequin beetle eggs and larvae. Harlequin beetles thus have an innate advantage over species that are otherwise equivalent in their abilities, but this sort of competitive advantage can be hard to spot.

  2. Fracturing Hydrology?

    Hydraulic fracturing, widely known as "fracking," is a relatively inexpensive way to tap into what were previously inaccessible natural gas resources. Vidic et al. (p. 1235009) review the current status of shale gas development and discuss the possible threats to water resources. In one of the hotbeds of fracking activity, the Marcellus Shale in the eastern United States, there is little evidence that additives have directly entered groundwater supplies, but the risk remains. Ensuring access to monitoring data is an important first step toward addressing any public and environmental health concerns.

  3. Fabricating Quartz

    Quartz is used industrially as an abrasive, as an inert glassy material, or for high-quality crystals in microelectronics. It is also valued for its piezoelectronic properties. However, it is hard to grow quartz as a patterned material or to integrate it into nanostructured devices. Carretero-Genevrier et al. (p. 827; see the Perspective by Brinker and Clem) have developed a method for preparing oriented epitaxial thin films of polycrystalline α-quartz on single-crystal silicon substrates using ambient pressure and temperatures below 1000°C. Different processing conditions can be used to fabricate quartz films with a variety of pore sizes or as a dense nonporous α-quartz film.

  4. Falling Out

    During simple precipitation, molecules fall out of solution from locations of highest concentration and, consequently, the shape of the precipitate will be dictated by its crystallization thermodynamics. Noorduin et al. (p. 832; see the Perspective by Vlieg) designed micrometer-scale structures by varying the reaction conditions for silica and carbonate precipitation in which precipitation changes the local concentration and acidity to alter the next stage of precipitation, thus controlling whether the solid phase grows toward or away from the bulk solution. The result is the ability to design and generate a variety of complex structures by simple reaction-diffusion processes.

  5. Stress Inside Out

    In Gram-negative bacteria, the integrity of the outer membrane is crucial for survival and is an important aspect of resistance to antibiotics. The biogenesis of the major components lipopolysaccharide (LPS) and outer-membrane protein (OMP) of the outer membrane begins in the cytoplasmic compartment, involves export across the inner membrane and transport through the periplasm, and finally requires active insertion into the outer membrane by specialized assembly machines. Lima et al. (p. 837) supply results for a model in which serious defects in LPS biogenesis also create problems for OMP biogenesis, thereby producing the two signals needed to activate the σE stress response pathway.

  6. ATAXIN Clock

    Although core components of circadian clocks in flies and mammals are transcriptional circuits, recent evidence indicates posttranscriptional regulation of the clock occurs. Studies from Lim and Allada (p. 875) and Zhang et al. (p. 879) converge to show that the protein ATAXIN-2, associated with neurodegenerative diseases in humans, is a regulator of translation required for normal clock function in pacemaker neurons and for daily rhythms of behavior. ATAXIN is an RNA-binding protein and cooperates in the accumulation of the Per (Period) protein, a core transcriptional regulatory component of the clock.

  7. Melting Away


    We assume the Greenland and Antarctica ice sheets are the main drivers of global sea-level rise, but how large is the contribution from other sources of glacial ice? Gardner et al. (p. 852) synthesize data from glacialogical inventories to find that glaciers in the Arctic, Canada, Alaska, coastal Greenland, the southern Andes, and high-mountain Asia contribute approximately as much melt water as the ice sheets themselves: 260 billion tons per year between 2003 and 2009, accounting for about 30% of the observed sea-level rise during that period.

  8. Nuclear Actin in Action

    Actin polymerization is essential for structures in mammalian cells. Although actin filament network structures are observed in the cytoplasm and at the plasma membrane, monomeric actin is also seen in the nucleus. Baarlink et al. (p. 864, published online 4 April) directly visualized a distinct and dynamic actin network within the nucleus in living cells. The network spanned the entire nucleus and appeared to be enriched along the nuclear cortex. Transient formation of a nuclear actin network may be induced by the transcriptional serum response.

  9. Confined Helium

    Helium-3 (3He) has superfluid phases closely related to topological insulators and topological superconductors. In geometrical confinement, 3He is expected to support exotic excitations, but its phase diagram is largely unknown, as such measurements are experimentally challenging. Levitin et al. (p. 841) confine 3He in a slab geometry of defined height and use nuclear magnetic resonance as a probe. As predicted by theory, the authors find that the confinement stabilizes some of the superfluid phases across a larger portion of the phase diagram with respect to the bulk and potentially provides a testbed for topological superfluidity.

  10. Modules of Desire

    Using computational methods to design materials with specific properties has found some limited success. Dyer et al. (p. 847, published online 11 April) have devised a method, based on extended module materials assembly, that combines chemical intuition and ab initio calculations starting from fragments or modules of structure types that show the desired functionality. The method was tested by identifying materials suitable for a solid oxide fuel cell cathode.

  11. EZ Inhibition

    Missense mutations in the core constituents of the genome packaging material, chromatin, have been implicated in several of human cancers. Nucleosomes are made up of histones, and a mutation of lysine 27 (K27) to methionine in the N-terminal tail of histone variants H3.3 and H3.1 has been identified in various pediatric gliomas. Lewis et al. (p. 857, published online 28 March; see the Perspective by Morgan and Shilatifard) show that the polycomb enzyme complex, which can epigenetically modify K27 by addition of a methyl group—and which is often a silencing signal—is itself potently inhibited by replacement of the H3.3/3.1 K27 by methionine. The inhibition of the EZH2 subunit causes an overall reduction of K27 methylation. Methionine mutants of other methylated lysine residues in histone H3 cause similar reductions in methylation levels of the cognate lysine, altering the epigenetic profiles of such cancer cells.

  12. Signal Scaffolds

    Scaffolds in cellular signaling pathways are turning out to do way more than just hold proteins together in a complex. Kim et al. (p. 867, published online 11 April) showed the importance of the scaffold protein Axin as an active participant controlling the kinetics of activation of signaling through the pathways. Axin is part of two protein complexes that have opposing actions that may regulate the timing of signaling—either activating Wnt signaling, thus protecting β-catenin from destruction, or causing proteolytic destruction of β-catenin. Rock et al. (p. 871, published online 11 April) characterized the role of the scaffold protein Nud1 in the mitotic exit network and found that the kinase that produces the output from the signaling complex only interacts with a scaffold that is primed by its activator protein kinase, already bound to the scaffold and creating a docking site.

  13. Cheap Pix

    Three-dimensional (3D) images can be captured by, for example, holographic imaging or stereoimaging techniques. To avoid using expensive optical components that are limited to specialized bands of wavelengths, Sun et al. (p. 844; see the Perspective by Faccio and Leach) projected pulses of randomly textured light onto an object. They were able to reconstruct an image of the 3D object by detecting the reflected light with several photodetectors without any need for lenses. The patterned light beams can thus in principle be substituted for light sources of any wavelength.

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