This Week in Science

Science  01 Jun 2018:
Vol. 360, Issue 6392, pp. 976
  1. Plant Science

    Controls on seed dormancy

    1. Pamela J. Hines

    Seeds of the small mustard plant Arabidopsis thaliana in their pod

    CREDIT: DENNIS KUNKEL MICROSCOPY/SCIENCE SOURCE

    Herbivores and an inopportune cold snap can destroy fragile plant seedlings. Plants control the dormancy of their seeds in anticipation of more favorable growth conditions. Chen and Penfield analyzed the molecular controls on seed dormancy in the model plant Arabidopsis thaliana. Two genes and an antisense RNA, known from the process of vernalization, integrate ambient temperature to control seed dormancy via their opposing configurations.

    Science, this issue p. 1014

  2. Sustainability

    The global impacts of food production

    1. Andrew M. Sugden

    Food is produced and processed by millions of farmers and intermediaries globally, with substantial associated environmental costs. Given the heterogeneity of producers, what is the best way to reduce food's environmental impacts? Poore and Nemecek consolidated data on the multiple environmental impacts of ∼38,000 farms producing 40 different agricultural goods around the world in a meta-analysis comparing various types of food production systems. The environmental cost of producing the same goods can be highly variable. However, this heterogeneity creates opportunities to target the small numbers of producers that have the most impact.

    Science, this issue p. 987

  3. Evolution

    Predation favors the unadventurous

    1. Sacha Vignieri

    The Caribbean brown anole lizard, Anolis sagrei

    CREDIT: REPTILES4ALL/SHUTTERSTOCK.COM

    Selection is likely to shape behavior by acting on behavioral differences between individuals. Testing this idea has been challenging. Lapiedra et al. took advantage of a chain of small islands in the Caribbean colonized by anole lizards. A series of repeated behavioral selection experiments were set up in which brown anole populations were established with and without predators. On predator-free islands, animals that were more exploratory were favored, whereas when predators were present, less adventurous animals survived better. Selection for behavior occurred simultaneously with morphological selection but was predominant when predators were present.

    Science, this issue p. 1017

  4. Induced Seismicity

    Triggering quakes in a geothermal space

    1. Brent Grocholski

    Enhanced geothermal systems (EGSs) provide a potentially clean and abundant energy source. However, two magnitude-5 earthquakes recently occurred in South Korea during EGS site development. Grigoli et al. and Kim et al. present seismic and geophysical evidence that may implicate the second of these earthquakes, which occurred in Pohang, as an induced event. The combination of data from a local seismometer network, well logs, satellite observations, teleseismic waveform analysis, and stress modeling leads to the assessment that the earthquake was probably or almost certainly anthropogenically induced. The possibility remains that the earthquake occurred coincidentally at the EGS site location, but the aftershock distribution and other lines of evidence are concerning for future development of this geothermal resource.

    Science, this issue p. 1003, p. 1007

  5. Political Science

    Curtailed conversations

    1. Andrew M. Sugden,
    2. Gilbert Chin

    Most articles written about U.S. politics in the past few years have mentioned the increasing polarization of the electorate. But is this real, or does it merely reflect the increasing polarization of the media? Chen and Rohla estimate that in 2016, Thanksgiving dinners in which the hosts and guests lived in oppositely voting precincts were up to 50 minutes shorter than same-party-precinct dinners. That is, family members, adjured to avoid talking about contentious subjects, may have simply talked less.

    Science, this issue p. 1020

  6. Organic Chemistry

    Arenes get a light boost onto copper

    1. Jake Yeston

    Insertion of palladium into an aryl halide bond is the first step in numerous variants of cross-coupling chemistry used to make carbon-carbon bonds. Copper is an appealing alternative catalyst for such reactions because of its abundance and downstream reactivity profile. However, this preliminary step, termed oxidative addition, is often prohibitively slow for the cheaper metal. Le et al. report a photocatalytic way around this problem. A photoredox catalyst paired with a silane can activate aryl bromides to react with copper, likely via aryl radicals. The copper in this case then catalyzes trifluoromethylation of the arenes.

    Science, this issue p. 1010

  7. Neuroprosthetics

    A leg up for neuroprosthetics

    1. Caitlin Czajka

    Amputation severs bone, nerves, and muscles needed for limb movement, limiting an amputee's ability to sense and control a prosthesis. Clites et al. tested autologous muscle-nerve interfaces made at the time of below-knee amputation in a human subject. In comparison with traditional amputations, the subject who received myoneural interfaces in his residuum (which were connected via synthetic electrodes to his powered prosthesis) had better control during stair walking. This person noted little delay between intention and movement of his prosthesis and expressed a strong sense that the prosthesis was part of him.

    Sci. Transl. Med. 10, eaap8373 (2018).

  8. Immune Regulation

    Unexpected basophil activation

    1. Christiana N. Fogg

    Basophils are granulocytes that exist at a relatively rare frequency in the blood but are critical mediators of allergic and inflammatory responses. Regulatory T cells (Tregs) suppress the functions of different immune cells. Sharma et al. examined how Tregs regulate basophil functions. Unexpectedly, resting human basophils were activated and not suppressed in the presence of Tregs. The activated basophils expressed activation markers—CD69, CD203c, and CD13—and released interleukin-4 (IL-4), IL-8, and IL-13. Treg-induced activation of basophils involved IL-3 and STAT5 but was not contact-dependent. These counterintuitive results showing activation mediated by Tregs provide insight into how basophils are regulated.

    Sci. Immunol. 3, eaan0829 (2018).

  9. Single-Cell Analysis

    Mapping the vertebrate developmental landscape

    1. Beverly A. Purnell

    As embryos develop, numerous cell types with distinct functions and morphologies arise from pluripotent cells. Three research groups have used single-cell RNA sequencing to analyze the transcriptional changes accompanying development of vertebrate embryos (see the Perspective by Harland). Wagner et al. sequenced the transcriptomes of more than 90,000 cells throughout zebrafish development to reveal how cells differentiate during axis patterning, germ layer formation, and early organogenesis. Farrell et al. profiled the transcriptomes of tens of thousands of embryonic cells and applied a computational approach to construct a branching tree describing the transcriptional trajectories that lead to 25 distinct zebrafish cell types. The branching tree revealed how cells change their gene expression as they become more and more specialized. Briggs et al. examined whole frog embryos, spanning zygotic genome activation through early organogenesis, to map cell states and differentiation across all cell lineages over time. These data and approaches pave the way for the comprehensive reconstruction of transcriptional trajectories during development.

    Science, this issue p. 981, p. eaar3131, p. eaar5780; see also p. 967

  10. Planetary Science

    Methane ice dunes on Pluto

    1. Keith T. Smith

    Wind-blown sand or ice dunes are known on Earth, Mars, Venus, Titan, and comet 67P/Churyumov-Gerasimenko. Telfer et al. used images taken by the New Horizons spacecraft to identify dunes in the Sputnik Planitia region on Pluto (see the Perspective by Hayes). Modeling shows that these dunes could be formed by sand-sized grains of solid methane ice transported in typical Pluto winds. The methane grains could have been lofted into the atmosphere by the melting of surrounding nitrogen ice or blown down from nearby mountains. Understanding how dunes form under Pluto conditions will help with interpreting similar features found elsewhere in the solar system.

    Science, this issue p. 992; see also p. 960

  11. Biomaterials

    I've got a feeling

    1. Marc S. Lavine

    Sensory (or afferent) nerves bring sensations of touch, pain, or temperature variation to the central nervous system and brain. Using the tools and materials of organic electronics, Kim et al. combined a pressure sensor, a ring oscillator, and an ion gel–gated transistor to form an artificial mechanoreceptor (see the Perspective by Bartolozzi). The combination allows for the sensing of multiple pressure inputs, which can be converted into a sensor signal and used to drive the motion of a cockroach leg in an oscillatory pattern.

    Science, this issue p. 998; see also p. 966

  12. Human Evolution

    Founder effects in modern populations

    1. Laura M. Zahn

    The genomes of ancient humans can reveal patterns of early human migration (see the Perspective by Achilli et al.). Iceland has a genetically distinct population, despite relatively recent settlement (∼1100 years ago). Ebenesersdóttir et al. examined the genomes of ancient Icelandic people, dating to near the colonization of Iceland, and compared them with modern-day Icelandic populations. The ancient DNA revealed that the founders had Gaelic and Norse origins. Genetic drift since the initial settlement has left modern Icelanders with allele frequencies that are distinctive, although still skewed toward those of their Norse founders. Scheib et al. sequenced ancient genomes from the Channel Islands of California, USA, and Ontario, Canada. The ancient Ontario population was similar to other ancient North Americans, as well as to modern Algonquian-speaking Native Americans. In contrast, the California individuals were more like groups that now live in Mexico and South America. It appears that a genetic split and population isolation likely occurred during the Ice Age, but the peoples remixed at a later date.

    Science, this issue p. 1028, p. 1024; see also p. 964

  13. Pesticides and Society

    Glyphosate: Menace or savior?

    1. Julia Fahrenkamp-Uppenbrink

    The herbicide glyphosate is used in numerous products, including Roundup, to kill weeds that compete with crops and to dry out crops, making them easier to harvest. In a Perspective, van Straalen and Legler highlight the recent decision by the European Union to reapprove glyphosate for another 5 years. Although several assessments have concluded that glyphosate does not pose a danger to humans at the concentrations typically encountered, these assessments do not account for the combinatorial effects of other chemicals in the herbicide products. Because little is known about how glyphosate affects ecosystems, increasing its use is worrisome. Societal concerns about reliance on pesticides need to be considered through socioeconomic impact analysis as part of the decision-making process.

    Science, this issue p. 958

  14. Cancer Metabolism

    Metabolic plasticity foils drug development

    1. Gemma Alderton

    The metabolism of cancer cells is increasingly being targeted in drug development, but the results in patients are not always consistent with preclinical models. In a Perspective, Muir and Vander Heiden discuss the importance of nutrient availability in the microenvironment as a determinant of responses to drugs that target metabolism and how metabolic targets in cancer cells might be identified more effectively.

    Science, this issue p. 962

  15. Ecology

    Reducing bycatch while sustaining harvests

    1. Philippa J. Benson

    Reducing bycatch—the capture of nontarget marine species—remains challenging for global fisheries, which provide essential sources of protein for billions of people. Even in well-managed fisheries, the ensnaring of species such as turtles, seabirds, and sharks is a problem. For many species, the solutions used to mitigate bycatch have not been successful. Focusing on the California drift gillnet fishery, Hazen et al. developed a multispecies ocean management approach that combines several types of historical data on multiple species' movement to predict daily catch. With this tool, they discovered that operating the California drift gillnet fishery on the basis of daily oceanographic conditions, instead of more static approaches based on rigid boundaries, could greatly reduce bycatch while maintaining fish harvests.

    Sci. Adv. 10.1126/sciadv.aar3001 (2018).

  16. Actuators

    Strength and stability through opposition

    1. Rachel Kline

    Biohybrid robots that combine living muscles with synthetic skeletons can be limited in their utility by the muscles spontaneously shrinking over time. Morimoto et al. used antagonistic pairs of skeletal muscle tissues to prevent this shrinkage and extend the robot's life span. They attached myoblast-laden hydrogel sheets to both sides of a jointed resin skeleton; the sheets formed into antagonistic muscles after 10 days of culture. The resulting robot achieved large actuation over a long lifetime and used finger-like movements to pick and place a ring onto a pillar.

    Sci. Robot. 3, eaat4440 (2018).