Climate change decreases the cooling effect from postfire albedo in boreal North America

Fire is a primary disturbance in boreal forests and generates both positive and negative climate forcings. The influence of fire on surface albedo is a predominantly negative forcing in boreal forests, and one of the strongest overall, due to increased snow exposure in the winter and spring months. Albedo forcings are spatially and temporally heterogeneous and depend on a variety of factors related to soils, topography, climate, land cover/vegetation type, successional dynamics, time since fire, season, and fire severity. However, how these variables interact to influence albedo is not well understood, and quantifying these relationships and predicting postfire albedo becomes increasingly important as the climate changes and management frameworks evolve to consider climate impacts. Here we developed a MODIS‐derived ‘blue sky’ albedo product and a novel machine learning modeling framework to predict fire‐driven changes in albedo under historical and future climate scenarios across boreal North America. Converted to radiative forcing (RF), we estimated that fires generate an annual mean cooling of ?1.77 ± 1.35 W/m² from albedo under historical climate conditions (1971–2000) integrated over 70 years postfire. Increasing postfire albedo along a south–north climatic gradient was offset by a nearly opposite gradient in solar insolation, such that large‐scale spatial patterns in RF were minimal. Our models suggest that climate change will lead to decreases in mean annual postfire albedo, and hence a decreasing strength of the negative RF, a trend dominated by decreased snow cover in spring months. Considering the range of future climate scenarios and model uncertainties, we estimate that for fires burning in the current era (2016) the cooling effect from long‐term postfire albedo will be reduced by 15%–28% due to climate change.     

Towards the integration of animal‐borne instruments into global ocean observing systems

Marine animals are increasingly instrumented with environmental sensors that provide large volumes of oceanographic data. Here, we conduct an innovative and comprehensive global analysis to determine the potential contribution of animal‐borne instruments (ABI) into ocean observing systems (OOSs) and provide a foundation to establish future integrated ocean monitoring programmes. We analyse the current gaps of the long‐term Argo observing system (>1.5 million profiles) and assess its spatial overlap with the distribution of marine animals across eight major species groups (tuna and billfishes, sharks and rays, marine turtles, pinnipeds, cetaceans, sirenians, flying seabirds and penguins). We combine distribution ranges of 183 species and satellite tracking observations from >3,000 animals. Our analyses identify potential areas where ABI could complement OOS. Specifically, ABI have the potential to fill gaps in marginal seas, upwelling areas, the upper 10 m of the water column, shelf regions and polewards of 60° latitude. Our approach provides the global baseline required to plan the integration of ABI into global and regional OOS while integrating conservation and ocean monitoring priorities.     

Slr4, a newly identified S-layer protein from marine Gammaproteobacteria,is a major biofilm matrix component

S-layers are paracrystalline proteinaceous lattices that surround prokaryotic cells, forming a critical interface between the cells and their extracellular environment. Here, we report the discovery of a novel S-layer protein present in the Gram-negative marine organism, Pseudoalteromonas tunicata D2. An uncharacterized protein (EAR28894) was identified as the most abundant protein in planktonic cultures and biofilms. Bioinformatic methods predicted a beta-helical structure for EAR28894 similar to the Caulobacter S-layer protein, RsaA, despite sharing less than 20% sequence identity. Transmission electron microscopy revealed that purified EAR28894 protein assembled into paracrystalline sheets with a unique square lattice symmetry and a unit cell spacing of ~9.1 nm. An S-layer was found surrounding the outer membrane in wild-type cells and completely removed from cells in an EAR28894 deletion mutant. S-layer material also appeared to be “shed” from wild-type cells and was highly abundant in the extracellular matrix where it is associated with outer membrane vesicles and other matrix components. EAR28894 and its homologs form a new family of S-layer proteins that are widely distributed in Gammaproteobacteria including species of Pseudoalteromonas and Vibrio, and found exclusively in marine metagenomes. We propose the name Slr4 for this novel protein family.     

Simple inheritance,complex regulation: Supergene‐mediated fire ant queen polymorphism

The fire ant Solenopsis invicta exists in two alternate social forms: monogyne nests contain a single reproductive queen and polygyne nests contain multiple reproductive queens. This colony‐level social polymorphism corresponds with individual differences in queen physiology, queen dispersal patterns and worker discrimination behaviours, all evidently regulated by an inversion‐based supergene that spans more than 13 Mb of a “social chromosome,” contains over 400 protein‐coding genes and rarely undergoes recombination. The specific mechanisms by which this supergene influences expression of the many distinctive features that characterize the alternate forms remain almost wholly unknown. To advance our understanding of these mechanisms, we explore the effects of social chromosome genotype and natal colony social form on gene expression in queens sampled as they embarked on nuptial flights, using RNA‐sequencing of brains and ovaries. We observe a large effect of natal social form, that is, of the social/developmental environment, on gene expression profiles, with similarly substantial effects of genotype, including: (a) supergene‐associated gene upregulation, (b) allele‐specific expression and (c) pronounced extra‐supergene trans‐regulatory effects. These findings, along with observed spatial variation in differential and allele‐specific expression within the supergene region, highlight the complex gene regulatory landscape that emerged following divergence of the inversion‐mediated Sb haplotype from its homologue, which presumably largely retained the ancestral gene order. The distinctive supergene‐associated gene expression trajectories we document at the onset of a queen’s reproductive life expand the known record of relevant molecular correlates of a complex social polymorphism and point to putative genetic factors underpinning the alternate social syndromes.     

Water structure around a left-handed Z-DNA fragment analyzed by cryo neutron crystallography

Even in high-quality X-ray crystal structures of oligonucleotides determined at a resolution of 1 Å or higher, the orientations of first-shell water molecules remain unclear. We used cryo neutron crystallography to gain insight into the H-bonding patterns of water molecules around the left-handed Z-DNA duplex [d(CGCGCG)]₂. The neutron density visualized at 1.5 Å resolution for the first time allows us to pinpoint the orientations of most of the water molecules directly contacting the DNA and of many second-shell waters. In particular, H-bond acceptor and donor patterns for water participating in prominent hydration motifs inside the minor groove, on the convex surface or bridging nucleobase and phosphate oxygen atoms are finally revealed. Several water molecules display entirely unexpected orientations. For example, a water molecule located at H-bonding distance from O6 keto oxygen atoms of two adjacent guanines directs both its deuterium atoms away from the keto groups. Exocyclic amino groups of guanine (N2) and cytosine (N4) unexpectedly stabilize waters H-bonded to O2 keto oxygens from adjacent cytosines and O6 keto oxygens from adjacent guanines, respectively. Our structure offers the most detailed view to date of DNA solvation in the solid-state undistorted by metal ions or polyamines.     

The multifaceted role of mTORC1 in the control of lipid metabolism

The mechanistic target of rapamycin is a protein kinase that, as part of the mechanistic target of rapamycin complex 1 (mTORC1), senses both local nutrients and, through insulin signalling, systemic nutrients to control a myriad of cellular processes. Although roles for mTORC1 in promoting protein synthesis and inhibiting autophagy in response to nutrients have been well established, it is emerging as a central regulator of lipid homeostasis. Here, we discuss the growing genetic and pharmacological evidence demonstrating the functional importance of its signalling in controlling mammalian lipid metabolism, including lipid synthesis, oxidation, transport, storage and lipolysis, as well as adipocyte differentiation and function. Defining the role of mTORC1 signalling in these metabolic processes is crucial to understanding the pathophysiology of obesity and its relationship to complex diseases, including diabetes and cancer.