Editors' Choice

Science  31 Jul 2020:
Vol. 369, Issue 6503, pp. 520
  1. Biogeography

    Shrubification of peatlands

    1. Andrew M. Sugden

    Sphagnum moss, which forms peat and is a major carbon store, is at risk of drying out under climate change.

    CREDIT: BLICKWINKEL/ALAMY STOCK PHOTO

    Soil is a key player in the global carbon cycle. Peatlands are important because they contain more than half of global soil carbon, much of which is sequestered in slow-decaying Sphagnum moss. Hence, there is a need to understand how peatlands will respond to the rapidly changing climate. Malhotra et al. assessed the response of plant roots to experimental warming in a peatbog ecosystem in the state of Minnesota, United States. The growth of fine roots of shrubs and trees over two growing seasons rapidly increased by 130% for each 1°C temperature increase, mainly because of the drying of the soil and the increase in the duration of the growing season. The authors suggest that over the longer term, drying will allow replacement of Sphagnum moss by other plants and hasten the loss of soil carbon.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.2003361117 (2020).

  2. Organic Chemistry

    A switch in time saves ligand

    1. Jake Yeston

    Isolating just one of two mirror-image products, or enantiomers, is essential in pharmaceutical synthesis. Often distinct enantiomeric ligands must be appended to a catalyst to steer the reaction one way or the other. Tu et al. report an intriguing case in which a single catalyst produces either product enantiomer, depending on reaction time. An iridium-catalyzed allylation of hydroxyisoquinolines yields one product within 10 minutes via kinetic resolution of the allyl precursors. Over 10 more hours, this initial product comes apart via a catalyzed reaction with the solvent, whereas its enantiomer steadily builds up and stays intact.

    Nat. Chem. 10.1038/s41557-020-0489-1 (2020).

  3. Cell Biology

    Too much of a good thing

    1. Stella M. Hurtley

    The membrane remodeling machinery known as ESCRT-III plays a role in maintaining nuclear integrity. Chromosomal disruption and the formation of micronuclei in a process known as chromothripsis can lead to pathologies, including cancer. Using a combination of live-cell imaging and electron tomography in tissue culture cells, Vietri et al. found that the nuclear integrity surveillance system paradoxically drives micronuclear catastrophe. The authors characterized the role of the cytosolic ESCRT-III binding protein CHMP7 and its intranuclear partner LEMD2, which together detect ruptures in the nuclear envelope and then trigger envelope repair. Ruptured micronuclei, however, were unable to control this system, which led to the accumulation of ESCRT-III subunits. This accumulation drove membrane aberrations and thereby torsional stress–induced DNA damage. These findings elucidate the chromosome-shattering process associated with chromothripsis that potentially drives cancer development.

    Nat. Cell Biol. 22, 856 (2020).

  4. Anthropology

    Inside the Paleolithic mind

    1. Caroline Ash

    A rare handaxe tool made from hippopotamus bone indicates highly skilled workmanship by Homo erectus 1.75 million years ago.

    PHOTO: SANO ET AL., PROC. NATL. ACAD. SCI. U.S.A. 10.1073/PNAS.2006370117 (2020)

    It is not often that we gain insight into the cognitive functions of our forebears. A very rare type of tool made from a hippopotamus bone has been discovered at the Konso Formation in southern Ethiopia. This artifact represents a technological breakthrough achieved 1.75 million years ago. Bone is tricky to shape and requires considerable judgment and skill to form successfully. Sano et al. show how this large (>10 centimeter) fragment was intentionally shaped by a controlled knapping technique and turned into a handaxe. This breakthrough represents a step-change from the conservative thinking of previous tool makers. By analyzing the scarring around the edges of the superbly preserved tool, the authors inferred that the maker, probably Homo erectus, was able to adjust the thickness on both sides of the material by a distinctive flaking technique. This allowed it to be used for precise purposes, such as butchering animal carcasses.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.2006370117 (2020).

  5. Neuroscience

    Autobiographical subnetworks

    1. Peter Stern

    The brain is organized into large networks that can be identified during brain scanning. Not every region of the human brain is functionally connected with all the other regions. One of the best-studied networks is the so-called default-mode network, which is commonly associated with autobiographical memory and other types of internally oriented cognition. Gordon et al. identified nine subnetworks within the default-mode network that were found consistently in human participants. These results create an organizational framework for the investigation of the default-mode network in individual subjects. The authors hypothesize that such a subnetwork structure is likely a general feature of all human brain networks.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.2005238117 (2020).

  6. Electronics

    From my hand to your ears

    1. Marc S. Lavine

    Sign language—in the form of hand, face, and body gestures—is a broadly used technique for communicating with people who are partially or fully deaf. However, most nondeaf people do not know sign language, making communication between the two groups challenging. Zhou et al. developed a wearable device that can convert hand motions or facial expressions into sound. At its core are two dissimilar soft materials with opposite triboelectric polarizations woven into a yarn that can effectively convert a small tensile force or pressure into electricity. Thus, finger or facial movements generate specific voltage pulses that can be recognized as individual letters or words or phrases.

    Nat. Electron. 10.1038/s41928-020-0428-6 (2020).

  7. Light Pollution

    Dimming Tucson's street lighting

    1. Keith T. Smith

    Poorly designed artificial lighting wastes energy and produces light pollution, with damaging effects on the natural environment, human health, and astronomy. Dimming or extinguishing street lights can reduce light pollution, but its efficacy has been difficult to measure. Barentine et al. monitored the sky brightness over the city of Tucson, United States, during a test of a new municipal street lighting system. The city authorities dimmed their streetlights at midnight, allowing the authors to determine that street lighting now contributes only 14% of Tucson's total light pollution. Further reductions must focus on other sources, such as private businesses and illuminated advertising.

    J. Quant. Spectrosc. Radiat. Transf. 253, 107120 (2020).

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