This Week in Science

Science  06 Jan 2012:
Vol. 335, Issue 6064, pp. 10
  1. Supersoldier Throwbacks


    Anomalous traits reflecting those of an ancestor sporadically appear in individuals that normally should not have them. Through their work with the hyperdiverse ant genus Pheidole, Rajakumar et al. (p. 79) suggest that these anomalies represent raw materials for selection to act upon. The ants possess an ancestral developmental potential, to produce “supersoldiers,” that has been retained for over 30 million years for which recurrent induction has facilitated the adaptive and parallel evolution of supersoldiers.

  2. Electrifying Prospects

    Greenhouse gas emissions need to be reduced in order to decrease the risk of dangerous climate change, and a commonly advocated intermediate step to decarbonizing our energy production is to cut emissions by 80% by the year 2050. Williams et al. (p. 53, published online 24 November) analyze the infrastructure and technology requirements required to meet this goal in California and conclude that simply using the most technologically advanced types of energy supply now available will not be enough. Instead, transportation and other sectors will need to be converted largely to electrical systems, which would make decarbonized electricity the dominant form of energy supply. Such a transformation will require technologies that are not yet commercialized and intensive public-private and interindustry coordination at every stage of the process.

  3. Wiring Up Silicon Surfaces


    One of the challenges in downsizing electronic circuits is maintaining low resistivity of wires, because shrinking their diameter to near atomic dimensions increases interface effects and can decrease the effectiveness of dopants. Weber et al. (p. 64; see the Perspective by Ferry) created nanowires on a silicon surface with the deposition of phosphorus atoms through decomposition of PH3 with a scanning tunneling microscope tip. A brief thermal annealing embedded these nanowires, which varied from 1.5 to 11 nanometers in width, into the silicon surface. Their resistivity was independent of width, and their current-carrying capability was comparable to that of thicker copper interconnects.

  4. In the Stick of It

    If a coating makes a surface nonstick, how do you stick the coating to the surface in the first place? For many nonstick coatings, this involves procedures to ensure good adhesion to the underlying surface though the use of surface roughening or intermediary layers. Deng et al. (p. 67, published online 1 December; see the cover) found a very simple route using little more than candle soot as a temporary sublayer that is coated with a silica shell and subsequently removed via calcination. Once top-coated with a semifluorinated silane, the resulting material possessed a low surface energy for water and also repelled oils, alchohols, and alkanes. While the coating could be damaged through mechanical wear, the remaining material continued to show superhydrophobic and superoleophobic behavior.

  5. Continental Thermocouple

    The patchy presence of billions-of-years-old continental crust indicates a complex coupling between the buoyant forces keeping the lithosphere floating on the mantle and the persistent erosional forces gradually wearing the crust away. Measuring long-term rates of exhumation—the creation of new rock surfaces due to erosion—can reveal how the crust is thermally coupled to the underlying mantle, but techniques to do so have often only been able to resolve a limited temperature range across narrow slices of geologic time. Blackburn et al. (p. 73) used uranium-lead thermochronology, which is sensitive to the much higher temperatures representative of lower crustal depths, to construct a long-term quantitative model of exhumation and erosion for North America.

  6. Plasmon Probe

    When light of certain wavelengths strikes a metal surface, it sets the metal's electrons in motion along trajectories termed “plasmon modes.” Yurtsever et al. (p. 59; see the Perspective by Batson) constructed a type of electron microscope that can probe the electric fields associated with this process by measuring the energy of a separate pulse of electrons that is bounced off the surface immediately (less than trillionths of a second) after the light strikes. The spatial resolution was sufficient to map intensities in distinct regions of a single silver nanoparticle.

  7. Stable Flow

    Whole-ocean deep circulation in the Atlantic, the Atlantic Meridional Overturning Circulation (AMOC), transports great quantities of heat from low latitudes to higher ones, which, for example, helps to warm Europe's climate. Matei et al. (p. 76) describe a modeling technique that allows AMOC strength to be predicted for up to 4 years in advance and suggests that AMOC should remain stable until at least 2014.

  8. Musical Chairs

    The plant hormone abscisic acid (ABA) helps plants to respond to changes in the environment, such as drought. Physiological responses are initiated when ABA binds to its receptor. In the absence of ABA, downstream kinases are held inactive by phosphatases. Soon et al. (p. 85, published online 24 November; see the Perspective by Leung) now show that both the hormone-receptor complex and the downstream kinase bind to the same site on the phosphatase. Thus, in the presence of hormone, the phosphatase is occupied and unable to interfere with downstream kinase activity.

  9. Going LARGE

    Dystroglycan (DG) is a highly glycosylated extracellular matrix (ECM) receptor involved in a variety of physiological processes, including maintenance of skeletal muscle membrane integrity and the structure and function of the central nervous system. The like-acetylglucosaminyltransferase (LARGE) is responsible for posttranslational modifications of alpha-dystroglycan (α-DG) required for its function. Now, Inamori et al. (p. 93) demonstrate that LARGE is a bifunctional glycosyltransferase able to transfer xylose and glucuronic acid. These modifications allow α-DG to bind the laminin-G domain–containing ECM ligands: laminin, agrin, and neurexin.

  10. From Nucleoside Recycling to Histiocytosis


    Macrophages remove billions of apoptotic cells daily, releasing their nucleic acid material through lysosomal degradation, which allows the resulting nucleosides to be recycled. Hsu et al. (p. 89, published online 15 December) found that the nucleoside transporter, equilibrative nucleoside transporter 3 (ENT3), was highly expressed in macrophages and showed that mice deficient in this transporter develop histiocytosis and features of lysosomal storage disease. When exposed to apoptotic cells, macrophages carrying human ENT3 mutations accumulated adenosine and increased their lysosomal pH. These changes contributed to an enhanced signaling through macrophage colony-stimulating factor (M-CSF) receptor and, ultimately, to M-CSF–driven myeloproliferative disease.

  11. Live Fast, Die Faster

    Treatment of Mycobacterium tuberculosis infections is complicated by the need for a prolonged course of antibiotics to fully eliminate all the bacteria present in an infected individual. Most antibiotics target growth and division machinery; thus, Aldridge et al. (p. 100, published online 15 November) postulated that heterogeneity in the growth properties of mycobacterial cells underlies variable antibiotic susceptibility. Cell division in mycobacteria was found to be asymmetrical, with one cell inheriting the growing pole and elongating rapidly, while the other cell elongated more slowly. Over multiple cell divisions, the rapidly growing cells became more susceptible to antibiotic treatment, helping to explain the observed heterogeneity in response to antibiotic therapy.

  12. The Dark Side of Langerhans Cells

    Several immune cell populations reside in the skin and are thought to provide a protective barrier against infections and to act as sentinels against malignant transformation. However, studies in mice that lack Langerhans cells, a subset of dendritic cells, have suggested that these cells may actually promote tumorigenesis. Using a mouse model of squamous cell carcinoma, Modi et al. (p. 104) now reveal how Langerhans cells may promote the transformation of skin epithelial cells. In response to the carcinogen 7,12-dimethylbenz[α]anthracene (DMBA), Langerhans cells increased their expression of the cytochrome P-450 enzyme CYP1B1, which can metabolize DMBA to the mutagenic DMBA-trans-3,4-diol. Thus, besides their functions in regulating the adaptive immune response, Langerhans cells may participate in the metabolism of environmental carcinogens.

  13. Stop, Don't Go There

    Decision-making in complex brains requires the reaching of a consensus based on information relayed by multiple neurons. A similar situation occurs in the decision-making process of swarming bees, where multiple individuals relay information about suitable hive sites, but a single site is chosen by the swarm. Seeley et al. (p. 108, published online 8 December; see the Perspective by Niven ) show that consensus in this system is reached as information from scouting bees accumulates within the hive. Stop signals were given by scout bees from a particular site to those scout bees signaling from other sites. As the signals accumulate, scouting ceases and the bees prepare to swarm to the site that was best represented among the scouts. When this process was simulated, the results indicated that cross-inhibition among the bees functions similarly to that which occurs among neurons within complex brains. In both cases, such cross-inhibition prevents the overall system from coming to an impasse.

  14. Controlling Zeolite Nucleation

    Small zeolite crystals are of increasing interest as catalysts and for membrane separations because they allow the high selectivity of their cages to be exploited while minimizing the kinetic limitations caused by diffusion. Ng et al. (p. 70, published online 8 December) synthesized ultrasmall crystals (6 to 15 nanometers) of the EMT zeolite, which has a low framework density and good catalytic properties for hydrocarbon “cracking” (conversion of a large hydrocarbon to smaller ones). The synthesis of EMT has normally required expensive organic templates that limit its industrial use. Careful control of the synthesis conditions, such as ratios of reactants and short bursts of microwave heating, allowed small EMT crystals to nucleate and avoid formation of zeolites with closely related structures.

  15. All Worms Are Not Equal

    Why do specific mutations not affect all individuals who inherit them? Casanueva et al. (p. 82, published online 15 December; see the Perspective by Deplancke and Verstrepen) found that prior exposure to mild environmental stimuli and the stimulation of a stress response in the nematode Caenorhabditis elegans reduced the detrimental effects of diverse mutations. Moreover, because of interindividual variation in stress signaling, this protective effect was not the same in all individuals. In the absence of mutations, a stronger response increased stress resistance but also delayed reproduction. Such variability among individuals may be beneficial in an unpredictable environment, acting as a “bet-hedging” strategy to diversify risk.

  16. Making Heterochromatin

    Heterochromatin is a particularly compact DNA-protein assembly that can repress gene expression. Constitutive heterochromatin is found, for example, at centromeres and the subtelomeric regions. Working with Schizosaccharomyces pombe, Zofall et al. (p. 96, published online 1 December) examined the heterochromatin islands often found near meiotic genes, which are maintained in a silenced state during vegetative growth. Heterochromatin formation at these loci did not generally involve the RNA interference machinery, as is observed at centromeres, but did require transcription. The exosome, an RNA-degrading machine, was involved in the formation of the heterochromatin islands, which could be remodeled in response to sexual differentiation.

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