Editors' Choice

Science  29 Sep 2017:
Vol. 357, Issue 6358, pp. 1367
  1. Group Behavior

    Gesundheit!

    1. Sacha Vignieri

    African wild dogs vote with sneezes.

    PHOTO: WIM VAN DEN HEEVER/MINDEN PICTURES

    What drives group actions in social species has long been of interest. After all, even among humans, who can actively negotiate, group actions can be challenging. In some cases, such as fish schooling, the driver can be a majority of movement in a certain direction. Often, however, there is an initiator, or a quorum decision among participants is reached. African wild dogs are a highly social and cooperative species with a strong dominance hierarchy. Walker et al. characterized prehunting rallies in this species and found that individual dogs vote with sneezes. Specifically, when more dogs sneeze, the pack is more likely to head out on a hunting trip. Dominant individuals required fewer sneezes to initiate a trip, but even they needed sneeze support. Thus, each dog has a voice in the decision.

    Proc. R. Soc. B 10.1098/rspb.2017.0347 (2017).

  2. Neuroscience

    Intermittent brain stimulation

    1. Lisa D. Chong

    Electrical stimulation of the brain to improve its function has been much debated. In an experimental test of working memory, Liu et al. showed that intermittent stimulation of the nucleus basalis in the forebrain of young adult Rhesus macaques improved their memory by up to five times. In contrast, continuous stimulation of the same region impaired memory. Improved memory depended on the neurotransmitter acetylcholine, given that the effect was blocked by antagonists of cholinergic receptors. The drug donepezil, which blocks cholinesterase's ability to degrade acetylcholine, restored memory performance in animals that received continual stimulation. Intermittent deep brain stimulation could boost the effects of acetylcholine on neurons and/or increase blood flow to the brain to improve memory.

    Curr. Biol. 10.1016/j.cub.2017.07.021 (2017).

  3. Impact Events

    A shocking discovery

    1. H. Jesse Smith

    Lightning strikes can produce shocked quartz.

    PHOTO: MARTIN SHIELDS/SCIENCE SOURCE

    Shocked quartz—whose crystalline structure is deformed along planes inside the crystal, a result of sudden high pressure and heating—long has been considered to be an unequivocal signature of the impact of an extraterrestrial object such as a meteorite. This favorite tool of geologists searching for proof of an impact may not be so foolproof after all, though. Chen et al. simulated the pressure and temperature caused by an idealized lightning strike on rocks and found that lightning can produce the same conditions and effects caused by impact events. Therefore, the presence of shock features in quartz should not be taken as unequivocal evidence for an extraterrestrial impact.

    Geophys. Res. Lett. 10.1002/2017GL073843 (2017).

  4. Cell Ablation

    Lighting the way to cell death

    1. Valda Vinson

    Early insights into how the brain controls behavior came from surgical ablation of neural tissue. More recent optogenetic techniques allow higher precision but induce other cellular damage. Smart et al. used light to activate a natural cell death pathway. Based on an understanding that caspase-3, a key protein in apoptotic cell death, is activated by releasing tension in a linker sequence, they inserted a domain into the linker that expands when it is illuminated. With optimized placement of this LOV2 domain, they built a light-activated caspase-3, “Caspase-LOV.” Neural degeneration can be monitored in flies engineered to express Caspase-LOV in retinal, sensory, and motor neurons. The tool has potential in applications that require specific temporal and spatial ablation of cells.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1705064114 (2017).

  5. Plant Biology

    Apples surviving in a thirsty landscape

    1. Pamela J. Hines

    Apple production in the semiarid Loess Plateau in China is susceptible to water deficiencies. Sun et al. have engineered an avenue for drought resistance into apple trees. Overexpression of the apple (Malus domestica) gene MdATG18a (encoding autophagy-related protein 18a), which is normally up-regulated in response to drought, allowed transgenic plants to better survive a dry spell. The amount of cellular damage, as measured by, for example, membrane integrity and accumulation of reactive oxygen species, was reduced. MdATG18a overexpression also caused increased accumulation of autophagosomes. The authors suggest that the improved intracellular physiology left by hypervigilant autophagy systems allowed the cells to survive suboptimal conditions.

    Plant Biotechnol. J. 10.1111/pbi.12794 (2017).

  6. Glass Transition

    Getting to the source of the slowdown

    1. Brent Grocholski

    Measuring the response of a viscous liquid approaching the glass transition provides vital information about this important process, especially across a wide range of time scales. Hecksher et al. consider the mechanical response of silicone oil across an impressive 13 decades by combining seven experimental methods. This molecular glass former follows scaling laws derived in the 1980s called mode-coupling theory. The strategy is generally applicable to a variety of substrates and should provide deep insight into the enigmatic glass transition.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1707251114 (2017).

  7. Optical Imaging

    Taking tabletop tomography to extremes

    1. Ian S. Osborne

    The practice of slicing through a sample at various depths with extreme ultraviolet (XUV) light to build up a three-dimensional picture of it is usually confined to synchrotron facilities. Intense infrared laser pulses impinging onto a gas cell of noble atoms generates high harmonics and provides access to the short wavelengths of XUV light with a tabletop source. Fuchs et al. show that filtering and focusing the high harmonics can narrow the range of wavelengths to produce a coherent XUV source. They demonstrate extreme coherent tomography by building up a three-dimensional image of a structured semiconductor sample with a depth resolution of 24 nanometers, providing an example of a tabletop laser source for highly spatially and temporally resolved coherent imaging applications.

    Optica 4, 903 (2017).