Editors' Choice

Science  27 Sep 2013:
Vol. 341, Issue 6153, pp. 1431
  1. Cell Signaling

    Fueling Reproduction

    1. L. Bryan Ray

    New studies in yeast may improve our understanding of human metabolic disorders. Clement et al. characterized regulation of the heterotrimeric guanine nucleotide–binding protein (G protein) alpha subunit Gpa1 in yeast. Gpa1 is part of the G protein that facilitates signaling by the receptor for mating pheromone. Clement et al. report that Gpa1 provides a molecular link to signaling pathways that monitor nutrient availability. The same enzymes that regulated phosphorylation of the yeast homolog of AMPK (adenosine monophosphate–activated protein kinase, an enzyme critical to energy sensing in mammals) also regulated phosphorylation of Gpa1 when cells were deprived of glucose. Such phosphorylation-modulated activity of Gpa1 thus couples mating efficiency to nutrient availability. These signaling pathways are highly conserved, and thus these results suggest possible crosstalk between nutrient and energy-sensing pathways and G protein–coupled receptor–regulated processes in higher organisms as well. Schmidt provides context in a Perspective.

    Sci. Signal. 6, 10.1126/scisignal.2004143; 10.1126/scisignal.2004589 (2013).

  2. Geochemistry

    Banding Together

    1. H. Jesse Smith

    Speleothems (stalagmites, stalagtites, and related secondary mineral deposits formed in caves) are commonly dated by counting the growth bands they contain and assuming that those bands are annual markers. How good is this assumption? Shen et al. present results of a study of a 300-year-old laminated stalagmite from Xianren Cave, China, using high-precision radiometric 230Th dating with a 2σ precision of half a year. They find that the layers of the speleothem do not always deposit annually, as is commonly assumed, and that band counting can under- or overcount elapsed time by several years or more per decade in some cases. Thus, caution needs to be applied when using band counting as a dating tool for speleothems, particularly because even small errors in dating can affect the interpretation of some rapid climate change events; high-precision absolute-dated radiometric chronologies should be used when possible.

    Sci. Rep. 3, 2633 (2013).

  3. Physics

    Tricky Anomaly

    1. Jelena Stajic

    A quantum point contact is a narrow conducting channel that can be shaped by applying variable voltage to electrodes placed above a two-dimensional electron gas in semiconductor nanostructures. As a function of the voltage, the conductance of the contact exhibits equally spaced plateaus corresponding to sequential openings of transport channels; however, an additional feature that appears at the conductance value of roughly 0.7 of the step still lacks a detailed theoretical explanation. Bauer et al. argue that it is a consequence of the structure of the local density of states. They developed a one-dimensional tight-binding model—in which a singularity in the density of states resulted in enhanced electronic interactions—that was able to account for data taken in varying experimental conditions. Iqbal et al. ascribe the feature to localized spins and the Kondo effect. They performed their experiments on quantum point contacts of varying length and found that the conductance of the anomaly varied periodically with the length; in their model, the number of localized states increased with the length, explaining the periodicity. Both models offer considerable and complementary insights into the problem.

    Nature 501, 73; 79 (2013).

  4. Animal Behavior

    Queenless Altruism

    1. Beverly A. Purnell

    The activity of honey bee (Apis mellifera) colonies is centered around a single reproductive female, the queen. Sterile worker females populate the majority of the hive, with the remainder composed of a small number of males. Worker tasks vary and include foraging, care for the queen and young, and hive construction and defense, with tasks largely corresponding to age (younger bees care for young, whereas older ones forage and defend the hive). In a hive that has lost its queen, some workers start to lay eggs, but their offspring will all be male. Kin selection theory suggests that worker altruism in queenless colonies will be reduced because the workers are less related to the sibling's progeny than that of the queen. Naeger et al. examine altruism and social organization in a queenless hive. They find that egg-laying workers were as likely to forage or participate in hive defense as non–egg layers, who have less developed ovaries. Further, reproductive workers were metabolically invested in brood food and wax production. This results in a hive with decreased task specialization, so that bees that forage also care for the brood and maintain the structure of the hive; a case more similar to what is seen in solitary social bees. This work supports kin selection models in that reproductive conflict is increased in queenless colonies but altruism is still present. Queenless workers participate in their own reproduction but also display altruistic behaviors that benefit the colony.

    Curr. Biol. 23, 1574 (2013).