Editors' Choice

Science  24 Nov 2017:
Vol. 358, Issue 6366, pp. 1016
  1. Cactus Genomics

    Prickly problems of cacti phylogeny

    1. Laura M. Zahn

    The genomes and relationships of columnar cacti, such as the saguaro, have been resolved.

    PHOTO: JAYPIERSTORFF/SHUTTERSTOCK

    The evolutionary history of cacti has been difficult to resolve. Copetti et al. sequenced the genomes of four species of columnar cacti, including the icon of the American Southwest, the saguaro cactus. A single optimal phylogenetic tree was generated through analysis of these genomes. First, the connections between species confounded by parallel evolution had to be disentangled. Paradoxically, the relationships among most genes were discordant and did not fit the hypothesized species relationships. This was attributed to many factors, including divergent population dynamics and long life spans, as well as gene flow via hybridization (introgression) and incomplete lineage sorting of convergent evolutionary changes (hemiplasy).

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1706367114 (2017).

  2. Neuroscience

    Rescuing remyelination

    1. Lisa D. Chong

    Targeting the blood-clotting protein fibrinogen could help promote brain repair after injury. In many brain injuries and neurodegenerative diseases, such as multiple sclerosis, neurons lose their myelin coating, reducing their ability to transmit signals. Petersen et al. have discovered that when the blood-brain barrier is disrupted, fibrinogen from the blood leaks into the central nervous system and blocks myelination by activating the bone morphogenetic protein (BMP) signaling pathway in oligodendrocyte progenitor cells. These precursors then fail to differentiate into mature oligodendrocytes needed for myelin repair. Inhibiting a BMP receptor in cultured oligodendrocyte progenitor cells and depleting fibrinogen in an animal model of demyelination enhanced remyelination, raising the possibility of new therapies for brain damage.

    Neuron 96, 1 (2017).

  3. Optics

    Determining the twist of structured light

    1. Ian S. Osborne

    Light can encode information in several different ways, through parameters such as wavelength, polarization, pulse width, and amplitude. Light can also be prepared with optical angular momentum, whereby the propagating light is structured with a twist or spiral-like structure. However, a receiver typically finds it difficult to determine the twist of arbitrary or multimode structured light beams. D'Errico et al. introduce a simplified technique for disentangling complex twisted light beams. On the basis of inspection of an interference pattern created with a reference beam, they show that they can decompose complex structured light beams into the component optical angular momentum modes. The technique may present a practical route for incorporating twisted lights as an additional dimension for enhancing the capacity of communication channels.

    Optica 4, 1350 (2017).

  4. Transcription

    Coactivator starts and stalls

    1. Beverly A. Purnell

    In embryonic development and growth control, the histone acetyltransferase p300/CBP (CBP) serves as a transcriptional coactivator with hundreds of different partner transcription factors. By examining the role of CBP in fruitfly cells, Boija et al. have extended its functional repertoire in regulating gene expression. Promoters cobound with CBP and GAGA factor were among the most highly expressed and displayed the most highly paused polymerase (Pol) II. CBP kept Pol II in the stalled position but also aided subsequent transcription elongation through release at the first downstream nucleosome. In addition, CBP and the general transcription factor TFIIB recruited Pol II to the promoter. These CBP activities clarify the mechanism by which the ubiquitous CBP factor does its job as transcriptional coactivator for many cell processes.

    Mol. Cell 10.1016/j.molcel.2017.09.031 (2017).

  5. Climate Change

    Getting help from Mother Nature

    1. H. Jesse Smith

    Enlisting nature's help can go a long way toward keeping a future global temperature increase below 2°C.

    PHOTO: PETER ESSICK/AURORA PHOTOS

    The Paris Climate Agreement established the goal of holding climate warming below 2°C, an ambitious target that will require nations to take aggressive action to reduce carbon emissions. How much help can we expect to get from the environment? Griscom et al. outline the mitigation potential offered by available “natural climate solutions,” a set of 20 conservation, restoration, and land management actions that increase carbon storage or avoid greenhouse gas emissions. They find that these natural climate solutions can provide 37% of the carbon sink through 2030 needed to meet a target with which there is a >66% chance of holding warming below 2°C.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1710465114 (2017).

  6. Mosquito Biology

    Mosquito symbiont malaria defense

    1. Caroline Ash

    A bacterium in mosquitoes blocks malaria parasite transmission.

    PHOTO: JIM GATHANY/CDC

    The bacterium Wolbachia is found in many arthropods, in which it can manipulate host reproductive success. It has long been considered a candidate for controlling disease-carrying mosquitoes. Until recently, Wolbachia had not been found in anopheline malaria-transmitting mosquitoes. Gomes et al. add to recent discoveries by identifying a Wolbachia in Anopheles gambiae, called wAnga-Mali, in a large collection of >13,000 field-caught mosquitoes. Although the numbers of wAnga-Mali in the mosquitoes were very low, there was a strong negative correlation between the presence of Wolbachia and that of malaria parasites. Subsequent experimentation showed that coinfected mosquitoes tolerated early malaria parasite stages, but the plasmodium then failed to enter the insect's salivary glands and become infectious. Unfortunately, no evidence was found for mosquito reproductive manipulation by this strain of Wolbachia.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1716181114 (2017).

  7. Inorganic Chemistry

    High-symmetry silver

    1. Jake Yeston

    The high-symmetry “buckyball” structure of C60 captured the imagination as a reflection of nature's intrinsic elegance at the molecular scale. Wang et al. now report a similar icosahedral cage composed of 180 silver ions, capped and compensated by an array of organic thiolate and sulfonate ions. Fragile crystals emerged after heating simple precursors in methanol and were characterized by x-ray diffraction, mass spectrometry, and nuclear magnetic resonance spectroscopy. The ∼2.5-nanometer-diameter cage manifested weak luminescence in the near infrared.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1711972114 (2017).