This Week in Science

Science  03 Aug 2018:
Vol. 361, Issue 6401, pp. 463
  1. Optical Seismology

    Submarine fiber optic earthquake detection

    1. Brent Grocholski

    A subsea cable coiled on board a ship, ready for deployment

    CREDIT: RUN STUDIOS

    Seismic networks detect earthquakes and are common on continents, where they are easy to install. However, most of Earth's surface is under the oceans, where placing seismometers is difficult. Marra et al. now find that ordinary submarine telecommunication cables can be used to detect earthquakes. Small strain changes associated with the passage of seismic waves were detected with laser light sent through in-use fiber optic cables by ultrastable lasers. This strategy could turn intercontinental fiber optic cables into ocean-bottom strain sensors, dramatically improving our ability to record earthquakes.

    Science, this issue p. 486

  2. Paleoclimatology

    Falling from a fall in rainfall

    1. H. Jesse Smith

    How much did rainfall have to decrease to trigger the collapse of Lowland Classic Maya civilization during the Terminal Classic Period? This collapse is a well-cited example of how past climate change—in this case, drought—can disrupt a population. Evans et al. measured the isotopic composition of water in Lake Chichancanab, Mexico, to quantify how much precipitation decreased during that period. Annual rainfall must have fallen by around 50% on average and by up to 70% during peak drought conditions.

    Science, this issue p. 498

  3. Superconductivity

    Cranking up the field

    1. Jelena Stajic

    Cuprate superconductors have many unusual properties even in the “normal” (nonsuperconducting) regions of their phase diagram. In the so-called “strange metal” phase, these materials have resistivity that scales linearly with temperature, in contrast to the usual quadratic dependence of ordinary metals. Giraldo-Gallo et al. now find that at very high magnetic fields—up to 80 tesla—the resistivity of the thin films of a lanthanum-based cuprate scales linearly with magnetic field as well, again in contrast to the expected quadratic law. This dual linear dependence presents a challenge for theories of the normal state of the cuprates.

    Science, this issue p. 479

  4. Human Genomics

    The genetics of human short stature

    1. Laura M. Zahn

    Flores Island in Indonesia has a long history of hominin occupation, including by the extinct Homo floresiensis and a more recent settlement by modern humans. Furthermore, Flores has an extant population of pygmy humans, and H. floresiensis exhibited a diminutive adult size relative to other hominins. Tucci et al. examined genetic variation among 32 individuals, including 10 sequenced genomes, from a population of pygmies living close to the cave where H. floresiensis remains were discovered. These individuals exhibit signatures of polygenic selection explaining the short stature and have genomic content from both Neanderthals and Denisovans, but no additional archaic lineages. Thus, restricted height is under selection at this location and has evolved independently at least twice in hominins.

    Science, this issue p. 511

  5. Synthetic Biology

    Hands-on biology education kits

    1. Nicholas A. Peppas

    Synthetic biology is a defining technology of the 21st century. Implementing hands-on synthetic biology in teaching environments is challenging because specialized equipment and expertise are needed to grow living cells. Huang et al. developed two shelf-stable “just add water” synthetic biology education kits using freeze-dried cell-free (FD-CF) reactions. The inexpensive kits are designed to engage the sense of sight, smell, and touch. The kits establish an educational platform for implementing FD-CF reactions in classrooms and other low-resource environments.

    Sci. Adv. 10.1126/sciadv.aat5105 (2018).

  6. Plant Evolution

    Fluctuating selection in nature

    1. Laura M. Zahn

    Monkeyflower, Mimulus guttatus

    PHOTO: JOSEPHINE MARSDEN/ALAMY STOCK PHOTO

    Natural environmental variation can lead to individuals within a species experiencing different selective parameters. Seep monkeyflower (Mimulus guttatus) populations are constrained by local moisture availability and the onset of summer drought. This results in a selective tradeoff between the amount of seed set, which is determined by plant size, and the timing of reproduction. Troth et al. sequenced and phenotyped 187 M. guttatus plants and identified genetic variants associated with plant and flower size and rapid flowering. In wild populations surveyed over 3 years, the magnitude of selection changed depending on the rainfall patterns. Thus, fluctuating selection may maintain genetic variation in this species.

    Science, this issue p. 475

  7. Martian Geology

    Liquid water under Mars' southern ice cap

    1. Keith T. Smith

    Mars is known to host large quantities of water in solid or gaseous form, and surface rocks show clear evidence that there was liquid water on the planet in the distant past. Whether any liquid water remains on Mars today has long been debated. Orosei et al. used radar measurements from the Mars Express spacecraft to search for liquid water in Mars' southern ice cap (see the Perspective by Diez). They detected a 20-km-wide lake of liquid water underneath solid ice in the Planum Australe region. The water is probably kept from freezing by dissolved salts and the pressure of the ice above. The presence of liquid water on Mars has implications for astrobiology and future human exploration.

    Science, this issue p. 490; see also p. 448

  8. Tissue Engineering

    New life for lungs

    1. Caitlin Czajka

    Lungs are complex organs to engineer: They contain multiple specialized cell types in an extracellular matrix with a distinctive architecture that must maintain integrity during respiration. Nichols et al. tackled the challenges of vascular perfusion, recellularization, and engraftment of tissue-engineered lungs in a clinically relevant pig model. Nanoparticle and hydrogel delivery of growth factors promoted cell adhesion to whole decellularized pig lung scaffolds. Autologous cell–seeded bioengineered lungs showed vascular perfusion via collateral circulation within 2 weeks after transplantation. The transplanted bioengineered lungs became aerated and developed native lung–like microbiomes. One pig survived for 2 months after transplant. This work brings tissue-engineered lungs closer to the realm of clinical possibility.

    Sci. Transl. Med. 10, eaao3926 (2018).

  9. Cell Biology

    It's all about your contacts

    1. Stella M. Hurtley

    Membrane contact sites have recently come to the fore of our understanding of interorganelle communication. Wu et al. review how these important structures help to promote a variety of key functions, including organelle division and lipid transfer. Focusing on contacts between the endoplasmic reticulum and a variety of organelles or the plasma membrane reveals the generality and importance of these contacts in cellular homeostasis and organismal health.

    Science, this issue p. eaan5835

  10. Neuroscience

    Leadership and responsibility

    1. Peter Stern

    Leadership of groups is of paramount importance and pervades almost every aspect of society. Leadership research has rarely used computational modeling or neuroimaging techniques to examine mechanistic or neurobiological underpinnings of leadership choices. Edelson et al. found empirically and theoretically that the choice to lead rests on a metacognitive process (see the Perspective by Fleming and Bang). Individuals who showed less “responsibility aversion” had higher leadership scores. A computational model combining signal detection theory with prospect theory provided a mechanistic understanding of this preference. Neuroimaging experiments showed how the key theoretical concepts are encoded in the activity and connectivity of a brain network that comprises the medial prefrontal cortex, the superior temporal gyrus, the temporal parietal junction, and the anterior insula.

    Science, this issue p. eaat0036; see also p. 449

  11. Cell Biology

    Making multiplexed subcellular protein maps

    1. Stella M. Hurtley

    Being able to visualize protein localizations within cells and tissues by means of immuno-fluorescence microscopy has been key to developments in cell biology and beyond. Gut et al. present a high-throughput method that achieves the detection of more than 40 different proteins in biological samples across multiple spatial scales. This allows the simultaneous quantification of their expression levels in thousands of single cells; captures their detailed subcellular distribution to various compartments, organelles, and cellular structures within each of these single cells; and places all this information within a multicellular context. Such a scale-crossing dataset empowers artificial intelligence–based computer vision algorithms to achieve a comprehensive profiling of intracellular protein maps to measure their responses to different multicellular, cellular, and pharmacological contexts, and to reveal new cellular states.

    Science, this issue p. eaar7042

  12. Microbiology

    Interchanging species of similar function

    1. Caroline Ash

    Under natural conditions, bacteria form mixed, interacting communities. Understanding how such communities assemble and stabilize is important in a range of contexts, from biotechnological applications to what happens in our guts. Goldford et al. sampled the microbial communities from soil and plants containing hundreds to thousands of sequence variants. The organisms were passaged after culture in low concentrations of single carbon sources and were cross-fed with each other's metabolites; then, the resulting communities were sequenced using 16S ribosomal RNA, and the outcomes were modeled mathematically. The mix of species that survived under steady conditions converged reproducibly to reflect the experimentally imposed conditions rather than the mix of species initially inoculated—although at coarse phylogenetic levels, taxonomic patterns persisted.

    Science, this issue p. 469

  13. Black Hole Physics

    An expanding radio jet from a destroyed star

    1. Keith T. Smith

    If a star gets too close to a supermassive black hole, it gets ripped apart in a tidal disruption event (TDE). Mattila et al. discovered a transient source in the merging galaxy pair Arp 299, which they interpret as a TDE. The optical light is hidden by dust, but the TDE generated copious infrared emission. Radio observations reveal that a relativistic jet was produced as material fell onto the black hole, with the jet expanding over several years. The results elucidate how jets form around supermassive black holes and suggest that many TDEs may be missed by optical surveys.

    Science, this issue p. 482

  14. Thin Films

    An epitaxial route to strain

    1. Jelena Stajic

    Strain can have a dramatic effect on the properties of materials. Zhang et al. introduced a large strain in the material PbTiO3 by growing it epitaxially in a composite with PbO. On the boundaries between the two materials, their normally different lattice constants were matched, giving rise to the strain. As a consequence, the films exhibited a very large electric polarization even in the absence of an electric field. The method may be applicable to generating other functional materials.

    Science, this issue p. 494

  15. Plant Science

    Enough but not too many stem cells

    1. Pamela J. Hines

    In the shoot apical meristem of plants, just the right number of stem cells generates a steady supply of cells with which to build differentiated tissues. Too few stem cells, and the plant cannot grow. Too many, and growth runs amok. Zhou et al. analyzed the controls on stem cell proliferation. They found that the HAIRY MERISTEM proteins define a domain within which WUSCHEL (WUS) cannot work, but beyond which WUS is left free to promote stem cell proliferation.

    Science, this issue p. 502

  16. Structural Biology

    A channel for calcium

    1. Valda Vinson

    Maintaining the correct balance of calcium concentrations between the cytosol and the mitochondria is essential for cellular physiology. A calcium-selective channel called the mitochondrial calcium uniporter (MCU) mediates calcium entry into mitochondria. Yoo et al. report the high-resolution structure of MCU from Neurospora crassa. The channel is formed by four MCU protomers with differing symmetry between the soluble and membrane domains. The structure, together with mutagenesis, suggests that two acidic rings inside the channel provide the selectivity for calcium.

    Science, this issue p. 506

  17. Genetics

    Altering wheat for pathogen resistance

    1. Gemma Alderton

    Wheat provides ∼20% of calories and protein per person globally, yet the elite crop cultivars that we grow today are beset by poor pathogen resistance. This has led to concerns about food security as emerging pests decimate wheat crops. In a Perspective, Wulff and Dhugga discuss the challenge and potential of introducing pathogen-resistance genes from wild wheats into elite cultivars through cross-breeding or genetic modification. This approach should allow us to improve and maintain the yield of this important food source.

    Science, this issue p. 451

  18. Marine Ecology

    Why seagrass meadows should be protected

    1. Julia Fahrenkamp-Uppenbrink

    Seagrasses are found along coastlines around the world but are under threat from human activities. In a Perspective, Cullen-Unsworth and Unsworth explain that seagrasses perform many important functions. For example, seagrasses provide a habitat for diverse marine species, including numerous commercial fish species, and store large amounts of carbon. Loss of seagrass meadows may thus contribute to rising carbon emissions and may threaten biodiversity and food security. Research into the extent and properties of seagrass meadows is helping to inform conservation efforts, but time is of the essence to avoid further losses of these important ecosystems.

    Science, this issue p. 446

  19. Inflammation

    An eye to evading the immune system

    1. Annalisa M. VanHook

    Some tissues, such as the eye, limit immune cell infiltration. Sakurai et al. found that a modified form of cholesterol inhibited the guanine nucleotide exchange factor DOCK2 and thus suppressed neutrophil and T cell migration. In mice, cholesterol sulfate was produced by the gland that secretes the lipids that form the outer layer of the tear film covering the eye. Mice lacking the major sulfotransferase that produces cholesterol sulfate had increased infiltration of immune cells into the conjunctiva and cornea, which was reversed by topical application of cholesterol sulfate.

    Sci. Signal. 11, eaao4874 (2018).