This Week in Science

Science  16 Jun 2017:
Vol. 356, Issue 6343, pp. 1134
  1. Plant Science

    Food for fungi

    1. Pamela J. Hines

    A cross section of a plant root showing arbuscular mycorrhizal fungus (purple) in the cortex

    PHOTO: MARC PERKINS/FLICKR

    A wide variety of plants form symbiotic relationships in their roots with arbuscular mycorrhizal fungi. The fungi channel inorganic and micronutrients from soil to the plant, and the plant supplies the fungi with organic nutrients. Jiang et al. and Luginbuehl et al. found that as part of this exchange, the plant supplies lipids to its symbiotic fungi, thus providing the fungi with a robust source of carbon for their metabolic needs.

    Science, this issue p. 1172; p. 1175

  2. Chemical Engineering

    Go with the flow in drug manufacturing

    1. Jake Yeston

    Although many commodity chemicals are manufactured using continuous flow techniques, pharmaceuticals are still mostly produced in large single batches. Cole et al. report a protocol for the small-volume continuous preparation of multi-kilogram quantities of a cancer drug candidate, prexasertib monolactate monohydrate, under current good manufacturing practices. Advantages of the approach include safer handling of hazardous reagents and intermediates, as well as yield and selectivity improvements in both the reaction and purification stages. Concurrent analytical monitoring also facilitated rapid trouble-shooting during the manufacturing process.

    Science, this issue p. 1144

  3. Evolution

    Bigger and badder

    1. Sacha Vignieri

    A Miocene bivalve (Astarte goldfussi) with a predatory gastropod drill hole

    PHOTO: ADIEL KLOMPMAKER

    The escalation hypothesis posits that predator size has increased over time, leading to increased motility and defense in prey organisms. Although influential, the hypothesis has been difficult to test. Klompmaker et al. looked at predator drill holes in bivalve shells across 500 million years. Drill-hole size did increase, whereas prey size remained relatively constant. This changing predator-prey size ratio suggests that the number of prey consumed likely increased, a factor facilitated by greater complexity of food webs and availability of nutrient-dense prey.

    Science, this issue p. 1178

  4. Geophysics

    Saving earthquakes for the wet season

    1. Brent Grocholski

    Earthquakes can be triggered by changes in crustal stress, such as variations in fluid pore pressure. As a result, the alternating wet and dry cycles in earthquake-prone California should affect the earthquake rate. Johnson et al. asked whether this is indeed the case by combining detailed earthquake records with high-resolution GPS data from the past 9 years. Slight changes in stress did indeed influence the timing of earthquakes, which confirms that the annual hydrological loading cycle modulates microseismicity in California.

    Science, this issue p. 1161

  5. Quantum Optics

    Space calling Earth, on the quantum line

    1. Ian S. Osborne

    A successful quantum communication network will rely on the ability to distribute entangled photons over large distances between receiver stations. So far, free-space demonstrations have been limited to line-of-sight links across cities or between mountaintops. Scattering and coherence decay have limited the link separations to around 100 km. Yin et al. used the Micius satellite, which was launched last year and is equipped with a specialized quantum optical payload. They successfully demonstrated the satellite-based entanglement distribution to receiver stations separated by more than 1200 km. The results illustrate the possibility of a future global quantum communication network.

    Science, this issue p. 1140

  6. Neurodevelopment

    Early life stress in depression susceptibility

    1. Pamela J. Hines

    The linkage between stress early in life and behavioral depression in adulthood is complex. Peña et al. were able to define a time period in early development when mice are especially susceptible to stress. Mice subjected to stress during this time period were less resilient to stress in adulthood. Genes regulated by the transcription factor orthodenticle homeobox 2 (OTX2) primed the response toward depression in adulthood. Although early stress could establish the groundwork for later depression, that priming could be undone by intervention at the right moment.

    Science, this issue p. 1185

  7. Nutrient Sensing

    Preparing for the feast during the fast

    1. Stella M. Hurtley

    A protein kinase complex known as mTORC1 plays a key role in cellular metabolism and nutrient sensing. Di Malta et al. elucidated a mechanism that regulates the metabolic changes that are necessary during the fast-to-feed transition. During starvation, a pair of transcription factors promotes the expression of a pair of guanosine triphosphatases that are required for mTORC1 activity and for its recruitment to the lysosome. However, mTORC1 activity also requires amino acids, which are lacking during starvation. Nevertheless, the cell becomes “primed” by this process so that on refeeding, it efficiently reactivates mTORC1, which is recruited to the lysosomal surface. This mechanism is particularly important in cancer cells.

    Science, this issue p. 1188

  8. Education

    Engaging local stakeholders

    1. Naomi Krogman

    Ecological knowledge in itself often fails to incite environmental behavior change. Thus, local stakeholders at the frontlines of ecological challenges are increasingly being involved in adaptive ecosystem management choices. Fujitani et al. performed a multiyear study on 181 members of a German angling club involved in adaptive management of fisheries. These members were more likely to retain knowledge of ecological topics and express pro-environmental behavior intentions compared with those receiving only a standard lecture. Engaging stakeholders with ecosystem management will be important for local decision-making related to sustainability.

    Sci. Adv. 10.1126/sciadv.1602516 (2017).

  9. Cancer

    A site-specific switch for cancer cells

    1. Leslie K. Ferrarelli

    To metastasize, cancer cells must switch from epithelial (polarized and fixed) into mesenchymal (motile and invasive) phenotypes to disseminate and colonize both primary and metastatic sites. Zhou et al. found that the long noncoding RNA H19 acted as a site-specific microRNA sponge to promote an epithelial or mesenchymal switch in tumor cells. In epithelial-like tumor cells in primary and metastatic sites, H19 sequestered miR-200b/c and ultimately inhibited migration. In mesenchymal-like disseminated cells in circulation, H19 sequestered a different micoRNA, Let-7b, and ultimately promoted migration.

    Sci. Signal. 10, eaak9557 (2017).

  10. Membranes

    Filtering through to what's important

    1. Marc S. Lavine

    Membranes are widely used for gas and liquid separations. Historical analysis of a range of gas pair separations indicated that there was an upper bound on the trade-off between membrane permeability, which limits flow rates, and the selectivity, which limits the quality of the separation process. Park et al. review the advances that have been made in attempts to break past this upper bound. Some inspiration has come from biological membranes. The authors also highlight cases where the challenges lie in areas other than improved separation performance.

    Science, this issue p. eaab0530

  11. Geophysics

    Silently taking up the slack

    1. Brent Grocholski

    Megathrust earthquakes occur when locked subduction zone faults suddenly slip, unleashing shaking and causing tsunamis. However, seismically silent slow earthquakes also relieve slip on these dangerous faults. Araki et al. present data from ocean boreholes with which they analyze eight slow-slip events near the Nankai trench off the coast of Japan. These events accommodated up to half of the plate convergence over 6 years. The events appear to occur regularly, which has a long-term impact on hazard assessment for the region.

    Science, this issue p. 1157

  12. Malarial Genomics

    Pathogens select for genomic variants

    1. Laura M. Zahn

    Large-scale deletions and duplications of genes, referred to as structural variants (SVs), are common within the human genome and have been linked to disease. Examining a genomic region that appears to confer a selective benefit, Leffler et al. used fine mapping to identify a specific SV that reduces the risk of severe malaria by an estimated 40% (see the Perspective by Winzeler). Data from African individuals revealed that populations harbor different SVs in this region. Furthermore, by dissecting a highly complex genomic region, the authors identified the likely causal element. This element encodes hybrid genes that affect glycophorin proteins, which are used by the malarial parasite in infection and are associated with resistance to severe disease.

    Science, this issue p. eaam6393; see also p. 1122

  13. Cell Adhesion

    Helping a cell to migrate in 3D space

    1. Stella M. Hurtley

    Clathrin-coated pits are well known to be involved in receptor-mediated endocytosis. Independent of their role in endocytosis, Elkhatib et al. observed that clathrin-coated structures strongly accumulated along collagen fibers in migrating cells. Clathrin-coated structures assembled on and then partially wrapped around and pinched the fibers. In a three-dimensional (3D) network, this mechanism provided multiple anchoring points along cellular protrusions. In the absence of clathrin-coated structures, protrusions were shorter and migration was impaired. This mode of adhesion may cooperate with classical focal adhesions to help cancer cells move in a 3D environment.

    Science, this issue p. eaal4713

  14. Laser Physics

    Two different combs from a single source

    1. Jake Yeston

    Combs of light divide the optical frequency spectrum into closely spaced tines that can measure molecular absorption spectra with exceptional precision. One appealing method to extend this precision down into the microwave regime is to simultaneously use two slightly distinct combs that differ in spacing by the magnitude of a microwave frequency. The challenge is ensuring that the combs remain synchronized. Link et al. solve this problem by generating both combs from the same semiconductor laser source. The resultant dual comb delivers highly accurate spectra of water vapor, and the approach could be generalized across the optical spectrum by tuning the semiconductor source.

    Science, this issue p. 1164

  15. Volcanology

    Quick eruption after a long bake

    1. Brent Grocholski

    Minerals such as zircon can record the storage conditions of magma before volcanic eruption. Rubin et al. combined traditional 238U-230Th dating with lithium concentration profiles in seven zircons from the Taupo supervolcanic complex in New Zealand to determine magma storage conditions. The zircons spent more than 90% of their lifetime in an uneruptible, mostly crystalline, and deep magmatic reservoir. The zircons were eventually transported to hotter, shallower, and eruptible magma bodies, where they spent only decades to hundreds of years before eruption. The result suggests a two-stage model for magmatic systems with large thermal variations.

    Science, this issue p. 1154

  16. Chemical Physics

    A detailed look at an electron's exit

    1. Jake Yeston

    When a burst of light ejects an electron from an atom, the later detection of two charged particles masks a great deal of intermittent quantum mechanical complexity. Villeneuve et al. provide a striking look at the wavelike properties of the electron just as it emerges from neon, expelled by two photons from an attosecond pulse train in a strong infrared field. The phase distribution displays the characteristic three-node structure of an f-wave, which the Stark shift from the strong field appears to select with a single magnetic quantum number of 0.

    Science, this issue p. 1150

  17. Climate Change

    The vegetation-climate loop

    1. H. Jesse Smith

    Just as terrestrial plant biomass is growing in response to increasing atmospheric CO2, climate change, and other anthropogenic influences, so is climate affected by those variations in vegetation. Forzieri et al. used satellite observations to analyze how changes in leaf area index (LAI), a measure of vegetation density, have influenced the terrestrial energy balance and local climates over the past several decades. An increase in LAI has helped to warm boreal zones through a reduction of surface albedo and to cool arid regions of the southern hemisphere by increasing surface evaporation. Furthermore, more densely vegetated areas displayed a greater capacity to mitigate the impact of rapid climate fluctuations on the surface energy budget.

    Science, this issue p. 1180

  18. Pain Regulation

    MicroRNAs in functional and dysfunctional pain

    1. Pamela J. Hines

    Pain serves the useful purpose of alerting us to danger. Chronic pain, however, can arise from dysfunctional responses. Peng et al. found that a cluster of microRNAs regulates the gene networks behind both physiological and dysfunctional pain (see the Perspective by Cassels and Barde). The recruitment of genes that regulate a subset of the light-touch mechanoreceptors found in hairy skin was critical to the generation of dysfunctional pain.

    Science, this issue p. 1168; see also p. 1134

  19. Anthropology

    Joined-up research brings rewards

    1. Julia Fahrenkamp-Uppenbrink

    Studies of ancient DNA have proliferated over the past decade, providing insight into human movements and the biological relationships between populations. In a Perspective, Johannsen et al. argue that effective collaboration between geneticists and archaeologists is needed to understand the cultural causes and consequences of these movements. For example, populations moving into Europe in the sixth and third millennium BCE encountered very different cultural contexts that influenced how they interacted with local populations. Studies that combine genetics with archaeology have the potential to yield fundamental insights into human history.

    Science, this issue p. 1118

  20. Cancer

    An antisensible approach to target KRAS

    1. Yevgeniya Nusinovich

    Mutations that cause activation of the KRAS oncogene are common in human cancer, including treatment-resistant tumor types such as lung and pancreatic cancer. KRAS is notoriously difficult to target with small molecules. To overcome this issue, Ross et al. turned to genetic technology to develop an antisense oligonucleotide–based therapy for inhibiting KRAS. The antisense oligonucleotide was chemically modified to allow systemic delivery through subcutaneous injection, avoiding the need for a specialized delivery vehicle. The authors tested the efficacy of this therapy in multiple mouse models of non–small cell lung cancer and evaluated its safety in primates, demonstrating its potential suitability for translation to humans.

    Sci. Transl. Med. 9, eaal5253 (2017).

  21. Molecular Separation

    Selecting against cis conformers

    1. Phil Szuromi

    Before 1,3-butadiene can be used to make polymers, it must be separated from similar hydrocarbons in an energy-intensive distillation process. Liao et al. show that a zinc metal–organic framework can accommodate the cis isomer of 1,3-butadiene. It binds less tightly than butane and butene because its π-bond conjugation is broken. They used this preferential desorption to separate 1,3-butadiene with ≥99.5% purity under ambient conditions.

    Science, this issue p. 1193

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