Editors' Choice

Science  18 May 2018:
Vol. 360, Issue 6390, pp. 749
  1. Plant Science

    Plants work out which way is up

    1. Pamela J. Hines

    Specialist plant cells contain gravity sensors to guide upright growth.

    PHOTO: MARTIN SHIELDS/SCIENCE SOURCE

    Gravity-sensing cells in plants contain tiny grains of starch called statoliths. The orientation of the statoliths changes with the plant's orientation. The gravity-sensing cells respond to even the slightest tilt off of the established plane. Plant statoliths seem to evade the rules of physics that govern other granular materials. In live-cell imaging of young wheat shoots, Bérut et al. observed that statolith piles behave more like slowly creeping liquids than like granular accumulations. The reason is that the individual statoliths are always jiggling around, perhaps because of interactions with the plant cytoskeleton.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1801895115 (2018).

  2. Circadian Regulation

    Timing metabolism in human muscle

    1. Beverly A. Purnell

    Circadian rhythms are driven by intrinsic biological clocks that regulate and coordinate activity and metabolism. Skeletal muscle is fueled by glucose, but if glucose sensing by the skeletal muscle clock is disrupted, metabolic disease can result. Perrin et al. used genome-wide transcription analysis to investigate clock-controlled circadian transcription in skeletal muscle and myotubes in vitro. Human biopsy samples exhibited rhythmic transcription, which occurred in two phases: Immune response genes were transcribed early in the day, whereas muscle contraction genes were expressed in the afternoon. In the absence of a fully functional clock, expression patterns of genes related to insulin response, myokine secretion, and lipid metabolism were strongly affected.

    eLife 10.7554/eLife.34114 (2018).

  3. Oceans

    Access to oxygen minimum zones

    1. Caroline Ash

    Remote-controlled submarines have supplied up-to-date oxygen data for the Gulf of Oman.

    PHOTO: LLOYD CLUFF/GETTY IMAGES

    Deoxygenation of the oceans is increasing alarmingly. In the absence of oxygen, the availability of dissolved nutrients for marine organisms is radically changed. Queste et al. recently succeeded in collecting data from one of the most intense marine oxygen minimum zones, located in the Arabian Sea. Research in this region has been limited by the risk from piracy and other geopolitical tensions. Hence, the authors deployed remote-controlled submarines called Seagliders in the Gulf of Oman to take oxygen measurements. The results show a startling decline in oxygen concentrations before the last direct measurements from about 20 years ago. These new data can be used to fill a key gap in Earth systems models.

    Geophys. Res. Lett. 10.1029/2017GL076666 (2018).

  4. Optical Devices

    Tunable on-chip optical beam splitter

    1. Ian S. Osborne

    Integrated optical approaches potentially offer a robust and compact platform to develop quantum-enhanced sensing and metrology technology. Bishop et al. describe an on-chip beam splitter in which the emission mode can be selected by electromechanically tuning the coupling of two suspended gallium arsenide waveguides. Using a quantum dot as a source of single photons pumped into the input arm of the waveguide, they show that the output port for the emitted photons can be selected by applying a small actuation voltage. Being compact, versatile, and scalable, the technique can be applied to tune other optical components, providing a powerful platform for the fabrication of on-chip quantum optical circuits.

    Opt. Lett. 43, 2142 (2018).

  5. Physics

    Watching magnetic atoms thermalize

    1. Jelena Stajic

    A multiparticle system displaced from its equilibrium state usually goes back to equilibrium in short order. Some systems, such as one-dimensional (1D) quantum gases, thermalize very slowly, first reaching an intermediate prethermalized state. To study how the prethermalized state evolves toward equilibrium, Tang et al. used ultracold dysprosium atoms arranged along hundreds of parallel 1D tubes. The atoms, which have high magnetic moments, interacted with other atoms in the same tube and with those in other tubes. The researchers found that both processes affected the dynamics of the system, which were nearly exponential after an initial prethermalization phase.

    Phys. Rev. X 8, 021030 (2018).

  6. Air Pollution

    A pause in progress on air pollution

    1. H. Jesse Smith

    Air pollution regulations in the United States have led to dramatic improvements in air quality over the past several decades. It therefore is discouraging to learn, as Jiang et al. report, that the reduction of nitrogen oxide and carbon monoxide emissions slowed sharply between 2011 and 2015. This is important because controlling these species is necessary for reducing tropospheric ozone pollution. A variety of factors likely caused this slowing of pollution reduction, including growing industrial contributions and a variety of vehicle-related trends. Improved satellite and model inversion technologies would help monitor changes in pollutant emissions and more precisely identify their sources.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1801191115 (2018).

  7. Appetite

    Heating up suppresses appetite

    1. Gemma Alderton

    Exercise can transiently suppress appetite, and it also makes you hot. Jeong et al. investigated whether loss of appetite is caused by increased body temperature. Hypothalamic neurons that express proopiomelanocortin control food intake. In mice, these neurons express a thermoreceptor called transient receptor potential vanilloid 1 (TRPV1). TRPV1s are activated when exercise increases physiological temperature, suppressing appetite. So, the heat of the moment directly mediates appetite, without invoking canonical nutrient-hormone pathways.

    PLOS Biol. 10.1371/journal.pbio.2004399 (2018).