Editors' Choice

Science  06 Feb 2015:
Vol. 347, Issue 6222, pp. 624
  1. Climate Change

    California drought worst in the past millennium

    1. Julia Fahrenkamp-Uppenbrink

    The impact of drought on Lake Mead—pointer to California's future?

    PHOTOS: © JOHN LOCHER/AP/CORBIS; © THOMAS MARENT/VISUALS UNLIMITED/CORBIS

    Since 2012, California has been suffering a severe drought. Griffin and Anchukaitis use tree-ring records of past climate conditions to determine how the current drought compares to other droughts since 800 CE. Based on metrics for soil moisture and for precipitation, they conclude that 2014 was the worst single drought year in at least the past 1200 years, caused by very low (but not unprecedented) precipitation and record high temperatures. The 3-year period from 2012 to 2014 was the worst unbroken drought interval in the past millennium. Although the effects of climate change on rainfall patterns in California remain uncertain, higher temperatures may contribute to future droughts in the region.

    Geophys. Res. Lett. 10.1002/2014GL062433 (2014).

  2. Organic Chemistry

    How to bring two chlorines face to face

    1. Jake Yeston

    Organic chemists have known for well over a century how to chlorinate the carbons at both ends of a double bond. A vast array of different methods now exists to replace the chlorines with other molecular fragments. One persistent limitation, however, has been the tendency of the two chlorines to bond to opposite faces of the starting compound. Cresswell et al. now present a versatile method that adds both chlorines to the same face. The key is a selenium catalyst that probably binds to the face opposite the first chlorine, before being displaced from behind by the second.

    Nat. Chem. 10.1038/nchem.2141 (2015).

  3. Biotechnology

    Outsourcing production on a small scale

    1. Gilbert Chin

    Microbes are wizards at making structurally intricate and bioactive molecules, but their products are usually only made in small quantities for local consumption. Zhou et al. demonstrate how thoughtful design and a bit of tinkering can lead to much greater yields of oxygenated taxanes, a precursor of the antitumor drug paclitaxel. First they split the job between a bacterium and a yeast. Second, they switched the fuel for these microbial factories from glucose (which the yeast turned into ethanol, which sedated the bacteria) to xylose (which the bacteria consumed and turned into acetate, which fed the yeast).

    Nat. Biotechnol. 33, 10.1038/nbt.3095 (2015).

  4. Wound Healing

    Wound healing requires senescence

    1. Beverly A. Purnell

    Cells divide as tissues develop and regenerate, but they can only do so a limited number of times. Eventually they stop dividing and enter a state called cellular senescence. Senescent cells secrete a variety of factors, but scientists still do not fully understand the role senescent cells play in many physiological processes, such as wound healing. Demaria et al. now show that wounds close more slowly in mice genetically engineered to lack senescent cells. After wounding, endothelial and mesenchymal cells undergo senescence and secrete the protein PDGF-AA. PDGF-AA helps wounds to heal more quickly by causing myofibroblast cells to differentiate.

    Dev. Cell 31, 722 (2014).

  5. Inorganic Chemistry

    Taking another look at a BB triple bond

    1. Jake Yeston

    Carbon and boron are neighbors in the periodic table, and that proximity entices chemists to make them emulate one another, akin to dressing siblings in matching outfits. An exciting achievement in this area was the preparation of a compound with a BB triple bond, analogous to the CC bond in an alkyne. Köppe and Schnöckel now have analyzed this compound in a thermodynamic context that highlights the substantial stabilizing influence of the capping groups (N-heterocyclic carbenes) on each B atom. They further considered the stiffness of the BB bond reflected in vibrational analyses. On this basis, they suggest that the compound might be better considered to have a lower-order BB bond, with higher-order bonds to the capping groups.

    Chem. Sci. 10.1039/c4sc02997f (2014).

  6. Paleontology

    African origin for New World monkeys

    1. Carolyn Gramling

    South American silvery marmosets (Mico argentatus) had an African ancestor.

    PHOTO: © THOMAS MARENT/VISUALS UNLIMITED/CORBIS

    New World monkeys—smallish, flat-nosed primates with prehensile tails such as silvery marmosets, golden lion tamarins, and squirrel monkeys—have inhabited South America for at least 26 million years, but it is unclear when they arrived and where they originated. Many paleontologists suspect an African origin, based on skeletal resemblances to ancient African monkeys. Now, Bond et al. describe three 36 million-year-old fossil teeth found in the Peruvian Amazon that support this idea: The shape of the teeth and phylogenetic analyses link the fossils to monkeys that inhabited Africa during the late Eocene, about 38 million years ago. The discovery also pushes back the monkeys' arrival date—perhaps by vegetation raft across the Atlantic Ocean—by 10 million years.

    Nature, 10.1038/nature14120 (2014).

  7. Peer Review

    Gauging gatekeeper performance

    1. Barbara R. Jasny

    Researchers curse the peer review system after a rejection letter and praise it when their papers sail into publication. But do research journals make the right decisions? To find out, Siler et al. tracked the fates of over 1000 accepted and rejected manuscripts submitted to three leading medical journals. The authors found that overall the journals made good decisions: Manuscripts rejected without peer review received fewer citations than manuscripts rejected after peer review. However, the journals rejected the 14 most highly cited articles (12 without peer review), which may reveal issues in recognizing unconventional leaps.

    Proc. Natl. Aacd. Sci. U.S.A. 112, 360 (2015).

  8. Forest Ecology

    Pathogens promote forest diversity

    1. Andrew M. Sugden

    Environmental conditions affect the diversity of species, whether flora or fauna, in a particular habitat. But what keeps a tree that normally grows in a low-rainfall area from growing in a tropical forest? Spear et al. investigated this question by transplanting drought-resistant tree seedlings into wet forests. Although both wet-forest and drier-forest species suffered pathogen attacks, the damage and mortality associated with these attacks were worse in seedlings transplanted from drier forests. Together with the exclusion of wet-forest species from dry forests by drought, this result indicates that pathogens also promote and maintain the diversity of tree species in tropical forests.

    J. Ecol. 103, 165 (2015).