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Intensifying postfire weather and biological invasion drive species loss in a Mediterranean-type biodiversity hotspot [Environmental Sciences]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Prolonged periods of extreme heat or drought in the first year after fire affect the resilience and diversity of fire-dependent ecosystems by inhibiting seed germination or increasing mortality of seedlings and resprouting individuals. This interaction between weather and fire is of growing concern as climate changes, particularly in systems subject...

Neurophysiological dynamics of phrase-structure building during sentence processing [Neuroscience]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Although sentences unfold sequentially, one word at a time, most linguistic theories propose that their underlying syntactic structure involves a tree of nested phrases rather than a linear sequence of words. Whether and how the brain builds such structures, however, remains largely unknown. Here, we used human intracranial recordings and...

Immunomodulation-accelerated neuronal regeneration following selective rod photoreceptor cell ablation in the zebrafish retina [Neuroscience]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Müller glia (MG) function as inducible retinal stem cells in zebrafish, completely repairing the eye after damage. The innate immune system has recently been shown to promote tissue regeneration in which classic wound-healing responses predominate. However, regulatory roles for leukocytes during cellular regeneration—i.e., selective cell-loss paradigms akin to degenerative disease—are...

Insect haptoelectrical stimulation of Venus flytrap triggers exocytosis in gland cells [Plant Biology]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
The Venus flytrap Dionaea muscipula captures insects and consumes their flesh. Prey contacting touch-sensitive hairs trigger traveling electrical waves. These action potentials (APs) cause rapid closure of the trap and activate secretory functions of glands, which cover its inner surface. Such prey-induced haptoelectric stimulation activates the touch hormone jasmonate (JA)...

Experimental dispersal reveals characteristic scales of biodiversity in a natural landscape [Ecology]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Ecological theory posits that dispersal among habitat patches links local communities and is a key “regional” process that maintains biological diversity. However, manipulations required to experimentally test regional processes are infeasible for most systems, and thus more work is needed to detect the scales at which regional processes manifest and...

Peter C. Nowell (1928-2016) [Retrospectives]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
The pioneering cancer cytogeneticist, Peter C. Nowell, died on December 26, 2016, from complications of Alzheimer’s disease at the age of 88. His work laid the foundation for the recognition of the genetic basis of cancer that paved the way for modern targeted cancer therapeutics. Nowell’s observations of changes in...

Correction for Padilla et al., AgRP to Kiss1 neuron signaling links nutritional state and fertility [Corrections]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
PHYSIOLOGY Correction for “AgRP to Kiss1 neuron signaling links nutritional state and fertility,” by Stephanie L. Padilla, Jian Qiu, Casey C Nestor, Chunguang Zhang, Arik W. Smith, Benjamin B. Whiddon, Oline K. Rønnekleiv, Martin J. Kelly, and Richard D. Palmiter, which appeared in issue 9, February 28, 2017, of Proc...

Structural and functional innovations in the real-time evolution of new ({beta}{alpha})8 barrel enzymes [Evolution]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
New genes can arise by duplication and divergence, but there is a fundamental gap in our understanding of the relationship between these genes, the evolving proteins they encode, and the fitness of the organism. Here we used crystallography, NMR dynamics, kinetics, and mass spectrometry to explain the molecular innovations that...

Knockout of the LRRC26 subunit reveals a primary role of LRRC26-containing BK channels in secretory epithelial cells [Physiology]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Leucine-rich-repeat-containing protein 26 (LRRC26) is the regulatory γ1 subunit of Ca2+- and voltage-dependent BK-type K+ channels. BK channels that contain LRRC26 subunits are active near normal resting potentials even without Ca2+, suggesting they play unique physiological roles, likely limited to very specific cell types and cellular functions. By using Lrrc26...

Contractile and chiral activities codetermine the helicity of swimming droplet trajectories [Physics]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Active fluids are a class of nonequilibrium systems where energy is injected into the system continuously by the constituent particles themselves. Many examples, such as bacterial suspensions and actomyosin networks, are intrinsically chiral at a local scale, so that their activity involves torque dipoles alongside the force dipoles usually considered....

Structure and mechanics of aegagropilae fiber network [Applied Physical Sciences]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Fiber networks encompass a wide range of natural and manmade materials. The threads or filaments from which they are formed span a wide range of length scales: from nanometers, as in biological tissues and bundles of carbon nanotubes, to millimeters, as in paper and insulation materials. The mechanical and thermal...

Discovery of chemoautotrophic symbiosis in the giant shipworm Kuphus polythalamia (Bivalvia: Teredinidae) extends wooden-steps theory [Microbiology]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
The “wooden-steps” hypothesis [Distel DL, et al. (2000) Nature 403:725–726] proposed that large chemosynthetic mussels found at deep-sea hydrothermal vents descend from much smaller species associated with sunken wood and other organic deposits, and that the endosymbionts of these progenitors made use of hydrogen sulfide from biogenic sources (e.g., decaying...

SNAT7 is the primary lysosomal glutamine exporter required for extracellular protein-dependent growth of cancer cells [Biochemistry]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Lysosomes degrade cellular components sequestered by autophagy or extracellular material internalized by endocytosis and phagocytosis. The macromolecule building blocks released by lysosomal hydrolysis are then exported to the cytosol by lysosomal transporters, which remain undercharacterized. In this study, we designed an in situ assay of lysosomal amino acid export based...

NGF-TrkA signaling in sensory nerves is required for skeletal adaptation to mechanical loads in mice [Medical Sciences]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Sensory nerves emanating from the dorsal root extensively innervate the surfaces of mammalian bone, a privileged location for the regulation of biomechanical signaling. Here, we show that NGF-TrkA signaling in skeletal sensory nerves is an early response to mechanical loading of bone and is required to achieve maximal load-induced bone...

Correction for Mann, Core Concept: Unraveling the enigma of fast radio bursts [Corrections]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
CORE CONCEPTS Correction for “Core Concept: Unraveling the enigma of fast radio bursts,” by Adam Mann, which appeared in issue 13, March 28, 2017, of Proc Natl Acad Sci USA (114:3269–3271; 10.1073/pnas.1703512114). Victoria Kaspi was incorrectly identified as the principal investigator of the Canadian Hydrogen Intensity Mapping Experiment. Kaspi should...

Sensorimotor-independent development of hands and tools selectivity in the visual cortex [Psychological and Cognitive Sciences]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
The visual occipito-temporal cortex is composed of several distinct regions specialized in the identification of different object kinds such as tools and bodies. Its organization appears to reflect not only the visual characteristics of the inputs but also the behavior that can be achieved with them. For example, there are...

Using microsecond single-molecule FRET to determine the assembly pathways of T4 ssDNA binding protein onto model DNA replication forks [Biophysics and Computational Biology]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
DNA replication is a core biological process that occurs in prokaryotic cells at high speeds (∼1 nucleotide residue added per millisecond) and with high fidelity (fewer than one misincorporation event per 107 nucleotide additions). The ssDNA binding protein [gene product 32 (gp32)] of the T4 bacteriophage is a central integrating...

Computational modeling of epiphany learning [Psychological and Cognitive Sciences]

PNAS Early Edition Articles - Mon, 04/17/2017 - 12:49
Models of reinforcement learning (RL) are prevalent in the decision-making literature, but not all behavior seems to conform to the gradual convergence that is a central feature of RL. In some cases learning seems to happen all at once. Limited prior research on these “epiphanies” has shown evidence of sudden...

Climate change: River redirected

Nature Geoscience Advanced Online - Sun, 04/16/2017 - 23:00

Nature Geoscience. doi:10.1038/ngeo2946

Author: Rachel M. Headley

Glaciers and ice sheets are retreating in response to climate warming. An analysis of drainage patterns of a huge glacier in Yukon, Canada shows that glacier retreat has led to a drastic change in the destination of its meltwater in spring 2016.

Inland thinning on the Greenland ice sheet controlled by outlet glacier geometry

Nature Geoscience Advanced Online - Sun, 04/16/2017 - 23:00

Nature Geoscience. doi:10.1038/ngeo2934

Authors: Denis Felikson, Timothy C. Bartholomaus, Ginny A. Catania, Niels J. Korsgaard, Kurt H. Kjær, Mathieu Morlighem, Brice Noël, Michiel van den Broeke, Leigh A. Stearns, Emily L. Shroyer, David A Sutherland & Jonathan D. Nash

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