Editors' Choice

Science  27 Jan 2017:
Vol. 355, Issue 6323, pp. 364
  1. Cytokinesis

    Lord of the incomplete rings

    1. Stella M. Hurtley

    Final stages of cell division in the worm rely on actomyosin contractile rings.

    PHOTO: STEVE GSCHMEISSNER/SCIENCE SOURCE

    Cytokinesis, the final stage of cell division, requires the assembly and constriction of an actomyosin contractile ring. Silva et al. combined laser microsurgery with live imaging in the Caenorhabditis elegans early embryo. They used the laser to introduce gaps into the constricting contractile ring of the worm's cells very precisely. The contractile rings were able to repair gaps in their structure so that cytokinesis always completed successfully. Once gaps were repaired, the rings transiently constricted more rapidly, allowing the cell to complete cytokinesis within the normal schedule. Unexpectedly, a continuous actomyosin ring structure was not required for constriction; an open ring was able to constrict and could recover from successive cuts. —

    J. Cell Biol. 215, 789 (2016).

  2. Neuroscience

    Claustro-cortical connectivity

    1. Peter Stern

    The claustrum is a brain structure that receives inputs from nearly all of the neocortex and, in return, coordinates the activity of many brain regions. How the information that is collected in the claustrum is transmitted back to individual cortical areas is still unclear. Kitanishi and Matsuo studied the function of selected claustro-cortical projections in mice. A group of neurons in the anterior claustrum projects extensively into the medial entorhinal cortex, a brain region that plays a key role in spatial and contextual information processing. This circuit was activated by novel context exposure, and silencing it selectively during fear conditioning suppressed memory retrieval later. This pathway thus influences medial entorhinal cortex function precisely without affecting broad cortical activity.

    J. Neurosci. 10.1523/jneurosci.1360-16.2017 (2017).

  3. Optoelectronics

    Inducing activity in flat optics

    1. Ian S. Osborne

    It is now possible to manipulate the phase and amplitude of propagating light with carefully designed subwavelength features patterned into thin layers of metal and dielectric films. These metasurfaces offer the possibility to control light with optical devices that are orders of magnitude smaller than the familiar bulk optical components of lenses and mirrors. Using a specially prepared silicon-based grating structure covered with indium tin oxide (a commonly used transparent conducting oxide), Kim and Brongersma showed that gating the structure with applied voltage can reversibly change the surface from nearly transparent to reflective. Being able to electrically switch the properties of the metasurface provides additional functionality for developing active nanophotonic devices based on a flat optics platform.

    Opt. Lett. 42, 5 (2017).

  4. Nanomaterials

    Repacking rhodium

    1. Phil Szuromi

    Rhodium packs as a face-centered cubic (fcc) crystal, but Huang et al. now report two routes for creating hexagonally close-packed (hcp) Rh as nanoparticles. In transmission electron microscopy studies of free-standing Rh monolayers, they observed irradiation-induced formation of hcp nanoparticles. A solvothermal synthesis route also produced hcp nanoparticles that in some cases had surface regions with fcc structure. First-principles calculations indicate that the hcp nanoparticles are stabilized relative to fcc crystals by having a lower surface energy. The hcp nanoparticle lattice is also expanded by 6%, versus a 0.4% expansion for a bulk crystal, and this expansion affects electronic properties and likely increases surface reactivity.

    J. Am. Chem. Soc. 10.1021/jacs.6b09730 (2017).

  5. Plant Science

    Biosynthesis of lipids for flavor

    1. Pamela J. Hines

    Coffee aroma is a complex mix of metabolites and lipids.

    PHOTO: FLORIANA

    Coffee is so much more than caffeine. Its aroma and flavor come from a complex mix of secondary metabolites characteristic of each coffee strain. Lipids such as cafestol and kahweol in the coffee bean endosperm add to flavor. In the context of human health, these lipids are linked to increased cholesterol levels, but also to anti-inflammatory and antioxidant properties. Ivamoto et al. surveyed both the production of these diterpenes and the transcriptional activity of cytochrome P450s during development of the coffee bean. The results highlight likely components of the final stages in the flavor biosynthetic pathways.

    Plant Physiol. Biochem. 10.1016/j.plaphy.2016.12.004 (2017).

  6. Functional Genomics

    Pushing the limits of functional genomics

    1. L. Bryan Ray

    CRISPR-based technology is making the analysis of complex phenotypes possible on a large scale. Adamson et al. and Dixit et al. present methods to analyze the effects of multiple perturbations on gene expression. They combined CRISPR-mediated partial or complete deletion of multiple gene products with single-cell RNA sequencing, with the latter identifying each particular cell by a “barcode” delivered with the CRISPR vector. Computational analyses allowed clustering of genes and characterization of processes and state s in individual cells. The responses of mouse immune cells to manipulation of 24 transcription factors alone and in combination, as well as that of human cells to perturbation of the 100 genes implicated in the unfolded protein response, show that the methods can help clarify complex regulatory programs in cells.

    Cell 10.1016/j.cell.2016.11.048, 10.1016/j.cell.2016.11.038 (2016).

  7. Geophysics

    Mega-earthquake supercycle

    1. Brent Grocholski

    Aftermath of the 2016 magnitude 7.8 Pedernales earthquake in Ecuador

    PHOTO: ASSOCIATED PRESS

    The recent magnitude 7.8 Pedernales earthquake in Ecuador killed nearly 700 people and caused widespread destruction. Nocquet et al. also thought it looked rather familiar. The earthquake may have ruptured at least part of the same fault as a magnitude 7.8 earthquake that occurred in 1942. The repeat points to an earthquake supercycle and the potential for much larger earthquakes than expected from the long-term accumulation of energy along megathrust faults.

    Nat. Geosci. 10.1038/ngeo2864 (2017).

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