Editors' Choice

Science  26 Jan 2018:
Vol. 359, Issue 6374, pp. 408
  1. Tropical Deforestation

    Certification of oil palm production

    1. Andrew M. Sugden

    Certification reduces forest loss, but more needs to be done to make oil palm plantations truly sustainable.

    CREDIT: CALVIN CHAN/SHUTTERSTOCK.COM

    Sustainability certification, whereby commitments are made to produce only sustainable crops, is a tool that is increasingly used to limit the damage to tropical forests caused by large-scale agricultural production. Carlson et al. asked how effective this is by assessing the impact of certification schemes for oil palm in Indonesia. A comparison of the performance of certified versus noncertified oil palm plantations over a 15-year period showed that certification reduced the rate of deforestation by 33%—a significant reduction, yet most of the certified areas already retained little residual forest. Certification also failed to reduce fire or peatland clearance. The authors recommend wider adoption of certification schemes in more forested areas to improve the outlook for remaining forest.

    Proc. Natl. Acad. Sci. U.S.A. 115, 121 (2018).

  2. Physics

    Reviving a quantum spin chain

    1. Jelena Stajic

    Quantum systems evolve in time but are expected to experience periodic “revivals”—returns to near-initial state—whose period depends on the energy spectrum of the system. The more complex the spectrum, the longer the period, which makes revivals tricky to observe in systems with long-range interactions. Zeiher et al. used a long-range interacting spin chain of 10 ultracold atoms optically “dressed” to a Rydberg state to observe the revivals of magnetization up to very long times. The findings may form the foundation for the use of Rydberg atoms in quantum annealing and similar protocols.

    Phys. Rev. X 7, 041063 (2017).

  3. Chromosome Activation

    Reawakening your X

    1. Lisa D. Chong

    X chromosome inactivation (XCI) ensures that only one X chromosome in a pair is expressed in a female somatic cell. A heterozygous X-linked mutation therefore affects about half of the somatic cells. In Rett syndrome, such a mutation in methyl-CpG–binding protein 2 (MECP2) causes motor and cognitive abnormalities. Carrette et al. identify a combination treatment that “reawakens” the silenced X chromosome, allowing production of normal MECP2 in cultured cells. Treatment involves an antisense oligonucleotide that blocks Xist, a noncoding RNA that facilitates XCI. When combined with a chemical inhibitor of DNA methylation (a modification that represses genes), MECP2 expression rose to 5% of the normal level, pointing to the therapeutic potential of partial X chromosome reactivation in the brain.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1715124115 (2018).

  4. Gene Regulation

    Regulation through the core

    1. Beverly A. Purnell

    Enhancers play a pivotal role in gene regulation. These elements can be localized far from the promoter, with looped sequences bringing them together to effect regulated expression. Batut and Gingeras used high-throughput transcription start site mapping and expression patterns to examine promoter activity during early development in five different Drosophila species. During early, intermediate, and late embryogenesis, specific core promoters are active, with each core promoter class associated with specific sets of transcription factors. Coarse- and fine-grained developmental regulation are proposed relative to core promoter and enhancer activity, respectively. Genome-wide analysis of long noncoding RNAs (lncRNAs) reveals 3973 promoters, most of which are unannotated, driving expression during embryo development and showing deep conservation of lncRNA promoters. This work shows that enhancers are not the only sequence regulating transcription; core promoters are also key.

    eLife 10.7554/eLife.29005 (2017).

  5. Ultrafast Optics

    Clocking the dynamics of effective mass

    1. Ian S. Osborne

    Electrons propagating through a solid interact with the crystal lattice, modifying the electronic motion and giving rise to an effective electron mass. The idea of an effective electron mass is based on the assumption of an unbounded crystal lattice, so the question arises of whether this understanding applies at the scale of small electronic devices. Using ultrafast pump-probe spectroscopy, Kasmi et al. studied the temporal dynamics of photoemitted electrons from a copper target. They found that the electrons require up to 350 attoseconds to reach their effective mass, equating to a propagation distance of just two atomic layers. The results could have bearing on the performance of shrinking electronic circuits, as well as in correctly interpreting ultrafast photoemission process from solids.

    Optica 4, 1492 (2017).

  6. Animal Migration

    Guiding forces

    1. Sacha Vignieri

    Planetary cues, such as magnetic inclination and moon phase, guide northern elephant seals and other large vertebrates over long distances and across time.

    PHOTO: NNEHRING/ISTOCK.COM

    Although much research has focused on understanding how animals guide their migrations across large regions of the planet, we know very little about this phenomenon, particularly for large, difficult-to-track species. Horton et al. tackled this question for some of the largest and farthest-traveling animals on Earth, a set of marine species including humpback whales, white sharks, and northern elephant seals. Using satellite tracking technologies, they found that both individual paths and general routes of travel were often consistent across years, suggesting consistent cues or memories. Further, departure time and routes of travel were correlated with physical cues such as magnetic inclination, moon phase, and gravitational signals. Although purely correlational at this stage, these results suggest that these animals use a suite of planetary indicators to guide them over extremely long distances on consistent routes and with consistent timing.

    Front. Mar. Sci. 10.3389/fmars.2017.00422 (2017).

  7. Polymer Chemistry

    Boron sneaks polarity into polystyrene

    1. Jake Yeston

    The properties of plastics can often benefit from the use of a mix of polar and nonpolar building blocks in their preparation. However, these different building blocks may be chemically incompatible or vary substantially in their solubility and reactivity, complicating synthetic planning. Van de Wouw et al. used boron and nitrogen to endow a nonpolar monomer with latent prospects for polarization. The BN aromatic was easily copolymerized with styrene. Peroxide treatment then replaced the dangling boron-bearing ring with a hydroxyl group that would have been challenging to introduce evenly at the outset.

    Angew. Chem. Int. Ed. 10.1002/anie.201711650 (2018).