Editors' Choice

Science  04 Oct 2019:
Vol. 366, Issue 6461, pp. 69
  1. Plant Science

    Light tuning of leaf size

    1. Pamela J. Hines

    Leaves developing in sunlight or shade differ in size because of differences in cell elongation.

    PHOTO: DULYANUT SWDP/GETTY IMAGES

    The Arabidopsis plant, when grown under intense light, develops thicker leaves than when grown under dim light. Hoshino et al. parse the various processes involved. Cell elongation and organized divisions underpin the thickness of leaves growing in intense light. Later in development, cell expansion and increases in intercellular spaces finalize the respective dimensions of leaves growing in sunlight or in shade. Blue-light signaling drives initial unequal cell elongation in sun-exposed leaves, whereas sucrose, a photosynthetic product, promotes the late phase of leaf thickening for both sun-exposed and shaded leaves. With leaf development linked to environmental signals, the plant's leaf structure can be fine-tuned to best suit its microenvironment.

    Plant J. 10.1111/tpj.14467 (2019).

  2. Stellar Astrophysics

    An ancient star missing its iron

    1. Keith T. Smith

    The Big Bang produced only hydrogen, helium, and traces of lithium. Heavier elements were forged within the first generation of stars, which then exploded as supernovae. A second stellar generation formed from gas polluted by those supernovae, and some of those stars are still around today. Nordlander et al. discovered a star with an extremely small amount of iron, much more carbon, and low abundances of several other elements. Comparison to supernova models indicates this is an old second-generation star enriched by a single supernova. The supernova ejected its outer carbon-rich layers, but the inner core of iron mostly fell back into the black hole formed during the explosion.

    Mon. Not. R. Astron. Soc. 488, L109 (2019).

  3. Neuroscience

    Merging motor and sensory

    1. Peter Stern

    Touch and corresponding whisker motion are represented in different layers of the brain.

    PHOTO: LIFE ON WHITE/GETTY IMAGES

    The posterior parietal cortex of the rat's brain is involved in a broad repertoire of behaviors. These range from integration of multiple sensory inputs to organizing the corresponding muscular responses. The function of the various microcircuit components is incompletely understood. Mohan et al. used several techniques to record from neurons in the different layers of the posterior parietal cortex in anesthetized and awake animals. The authors found that different parts of the processing circuits occurred in the different layers. Touch was encoded in layers 2 to 4, whereas exploratory whisker motion was represented in layers 2 to 4 and layer 6, but not in layer 5. These results may help the development of brain-machine interfaces needed to alleviate the effects of spinal cord injury.

    J. Neurosci. 39, 7332 (2019).

  4. Cancer

    T cells at work

    1. Paula A. Kiberstis

    Combining the three pillars of cancer treatment—surgery, radiotherapy, and chemotherapy—has greatly improved patient survival. With the recent development of effective cancer immunotherapies, oncologists now have a fourth pillar to consider in designing combination treatments. Previous work had suggested that radiotherapy damages T cells, leading to the perception that combining radiotherapy and immunotherapy would be ineffective. Studying mouse models of tumors that are already infiltrated with T cells, Arina et al. find that these T cells not only survive localized radiotherapy but also maintain excellent antitumor activity. This is because T cell reprogramming is facilitated by the tumor microenvironment. If human tumors behave in the same way, then we can expect more effective combinations of cancer treatments to be developed.

    Nat. Commun. 10, 3959 (2019).

  5. Animal Behavior

    Warty pig sticking

    1. Sacha Vignieri

    Not too long ago, it was argued that using tools was a hallmark of being human. However, this argument has been dispelled by more recent behavioral studies on other species—first by observations in great apes, then in species more distantly related to humans, such as crows and dolphins. Root-Bernstein et al. have discovered that the Visayan warty pig can use tools too. Female pigs of this critically endangered species from the Philippines use sticks and bark as digging tools during nest construction. The first observations were made opportunistically and then additional occurrences of the behavior were noticed after the motivation for digging was realized. Although these few observations were made on captive animals, they emphasize that we still have much to learn about the other animals that inhabit this planet even as they approach extinction.

    Mamm. Biol. 98, 102 (2019).

  6. Metabolic Origins

    Dawn of methylotrophy

    1. Michael A. Funk

    Methyl groups, including those derived from or ending up in methane, are managed through a dizzying array of metabolic pathways. Some of these originated early in life's history, and their evolution paralleled and contributed to Earth's chemistry. Adam et al. analyzed a set of bacterial and archaeal genomes, looking for patterns in the presence and divergence of enzymes in the tetrahydromethanopterin methyl branch of the Wood–Ljungdahl pathway, which is involved in carbon redox reactions. Expanding previous analyses narrowed the distance between bacterial and archaeal sequences, making horizontal transfer more plausible relative to an origin in the last universal common ancestor. An origin of this branch in Archaea is likely given wide distribution therein and enzyme phylogenies consistent with those of the organisms.

    Nat. Microbiol. 10.1038/s41564-019-0534-2 (2019).

  7. Actinide Chemistry

    Americium in a MOF

    1. Jake Yeston

    Americium is a by-product in nuclear reactors that continues to emit radiation for thousands of years. Its separation from spent nuclear fuels has therefore motivated copious study of its fundamental coordination chemistry. To this end, Cahill et al. have now incorporated trivalent 243Am ions into a metal-organic framework (MOF). The framework architecture was chosen on the basis of known analogs prepared from chemically similar but more stable lanthanide ions. Although radioactive decay progressively damaged the crystals, the authors were still able to refine structural data over the course of 3 months.

    Angew. Chem. Int. Ed. 10.1002/anie.201909988 (2019).