Editors' Choice

Science  22 Jan 2016:
Vol. 351, Issue 6271, pp. 351
  1. Genomics

    Humans and mites: A love story

    1. Caroline Ash

    Mites and humans have a long evolutionary history

    PHOTO: ANDREW SYRED/SCIENCE SOURCE

    Like it or not, skin mites can inhabit our skin. They live—mostly harmlessly—deep in our pores and sebaceous glands. To better understand their genetic diversity, Palopoli et al. took skin samples from 70 people living in the United States with a variety of ancestries. Genetic sequencing of their mitochondria allowed the scientists to calculate the rate of the mites' evolution. This revealed an evolutionary timeline for the mite variants and, therefore, of their human hosts. The results show that mites have been associates of humans since we evolved. Specifically, people of African descent have the greatest mite strain variance and those of European descent, the least, with a range of distinct geographically distributed variants in between.

    Proc. Natl. Acad. Sci. U.S.A. 112, 15958 (2015).

  2. Climate Change

    Variations in lake temperature trends

    1. H. Jesse Smith

    A section of Lake Como, Italy

    PHOTO: © DANIEL SCHOENEN/DANIEL SCHÖNEN/LOOK-FOTO/CORBIS

    Lake ecosystems are very sensitive to even small changes in water temperature, so knowing how their temperatures are changing in response to global warming is important for understanding nutrient cycling, ecosystem productivity, and food web interactions within them. O'Reilly et al. combined satellite and in situ surface summertime water temperature data for nearly 250 lakes worldwide, in order to determine broad trends as well as variability across a range of lake sizes and geomorphologies. They show that surface-water warming rates depend both on climate and local factors, and they find that there is less regional consistency in lake warming than has been supposed. This implies that predicting how lake ecosystems will respond to climate change depends on much more than simply where the lake is located.

    Geophys. Res. Lett. 10.1002/2015GL066235 (2015).

  3. Graphene

    Stretching a graphene nanoribbon

    1. Jelena Stajic

    External magnetic fields can have a profound effect on the behavior of electrons in a material, but creating sufficiently large fields is tricky. In graphene, however, researchers have shown that straining the material leads to large “pseudomagnetic” fields that affect the electrons in a similar way. These fields tend to be non-uniform and concentrated in small areas. Using the theory of elasticity and computer simulations, Zhu et al. now show that it is possible to create the desirable uniform fields of tailored strengths by pulling on the ends of a graphene nanoribbon. The trick is in the tapered shape of the nanoribbon; varying the shape and the length of the ribbon produces fields of different strengths.

    Phys. Rev. Lett. 115, 245501 (2015).

  4. Photocatalysis

    Titanium and oxygen pulled apart by light

    1. Jake Yeston

    Light absorption often prompts extremely rapid chemical changes in the absorbing medium that in turn can stimulate chemical reactivity. Yoo et al. applied ultrafast electron microscopy to elucidate these changes in a class of titanium silicate catalysts that harness light to transform nitric oxide, CO2, and various other small molecules. The titanium centers start out in a square pyramid geometry with a double-bonded oxygen at the apex. Less than trillionths of a second after the light absorption, the microscopy data captured a lengthening of this bond that was consistent with reduction of the titanium to a Ti3+-O1− motif primed for ensuing reactivity.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1522869113 (2016).

  5. Psychology

    Studying improves learning, too

    1. Gilbert Chin

    Fifteen years ago, the passage of the No Child Left Behind Act in the United States ushered in an era of increased testing, for the purpose of measuring achievement, in primary and secondary schools. Eight years ago, a seminal study demonstrated that repeatedly testing already-learned information in one group of students enhanced their retention of those items, whereas repeated studying in another group seemed to have little effect. Soderstrom et al. use both modes of repetition in individual students and replicate the earlier results, but also find that spaced restudy of those items further increases learning beyond the effect of repeated testing.

    Psychol. Sci. 10.1177/0956797615617778 (2015).

  6. Plant Science

    For rRNAs, it's location, location, location

    1. Pamela J. Hines

    Genes that encode ribosomal RNAs (rRNAs), key components of the protein synthesis machinery, are found in many copies in tandem. Epigenetic chromatin modifications silence excess rRNAs, but scientists do not fully understand what regulates such silencing. Studying the plant Arabidopsis, Chandrasekhara et al. mapped individual rRNA genes to their specific chromosomes and found that location matters: Arabidopsis leaves expressed rRNAs located on chromosome 4 but not those on chromosome 2. Relocating rRNA genes on chromosome 2 to chromosome 4 led to their expression. Thus, transcription of rRNA genes may be regulated in one fell swoop by a chromosomal regulatory control center.

    Genes Dev. 30, 10.1101/gad.273755.115 (2016).

  7. Cancer Metastasis

    Suppressing cancer spread

    1. Lisa D. Chong

    Preventing cancer metastasis is a major challenge, but the discovery of potential new metastasis suppressor genes may help guide new therapies. Ozturk et al. now show that relative to nonmetastatic cells, metastatic breast cancer cell lines express lower amounts of the protein serum deprivation response (SDPR). When the authors overexpressed SDPR in metastatic breast cancer cells, the cells migrated poorly in culture, and when injected into mice, they showed a reduced ability to disseminate to the lung. Analysis of gene expression data sets indicated a loss of SDPR in multiple tumor types. The gene encoding SDPR appears to be silenced by an epigenetic mechanism: DNA methylation of its promoter.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1514663113 (2016).

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