Increased Soil Frost Versus Summer Drought as Drivers of Plant Biomass Responses to Reduced Precipitation: Results from a Globally Coordinated Field Experiment

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze–thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level, and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity.     

Immunological and functional characterization of Mycobacterium leprae protein antigens: an overview

A major focus of leprosy research in the last 10 years has been the identification and characterization of antigens of Mycobacterium leprae that interact with antibodies and T cells of the host's immune response. Through the combined efforts of many different laboratories, a substantial number of protein antigens have been identified and characterized. In this MicroReview we present an updated list of M. leprae protein antigens, and, with emphasis on recent developments, summarize what is known regarding their functional and immunological features.     

Side-chain conformation and dynamics in a solid peptide: CP-MAS NMR study of valine rotamers and methyl-group relaxation in fully 13C-labelled antamanide

The effect of the crystal lattice on the side-chain conformation andside-chain dynamics in peptides is investigated by solid-state NMR, using thecyclic decapeptide antamanide as an example. The study takes advantage of the¹³C assignment of the backbone and side chains based on theresolution-enhanced 2D spin-diffusion spectra by heteronuclear and homonucleardecoupling. The spectra even allow for a stereospecific assignment of the-carbons of the valine residue. It is found that the valine side chaincoexists in two static rotamer conformations which have not been observed byX-ray crystallography. In addition, remarkable effects of the crystal packingon the methyl-group rotation frequency are found from ¹³Crelaxation measurements.     

Coos,booms, and hoots: The evolution of closed‐mouth vocal behavior in birds

Most birds vocalize with an open beak, but vocalization with a closed beak into an inflating cavity occurs in territorial or courtship displays in disparate species throughout birds. Closed‐mouth vocalizations generate resonance conditions that favor low‐frequency sounds. By contrast, open‐mouth vocalizations cover a wider frequency range. Here we describe closed‐mouth vocalizations of birds from functional and morphological perspectives and assess the distribution of closed‐mouth vocalizations in birds and related outgroups. Ancestral‐state optimizations of body size and vocal behavior indicate that closed‐mouth vocalizations are unlikely to be ancestral in birds and have evolved independently at least 16 times within Aves, predominantly in large‐bodied lineages. Closed‐mouth vocalizations are rare in the small‐bodied passerines. In light of these results and body size trends in nonavian dinosaurs, we suggest that the capacity for closed‐mouth vocalization was present in at least some extinct nonavian dinosaurs. As in birds, this behavior may have been limited to sexually selected vocal displays, and hence would have co‐occurred with open‐mouthed vocalizations.     

Growth discrepancy between filament and style facilitates self‐fertilization in Brandisia hancei (Paulowniaceae)

Self‐pollination has been hypothesized to be beneficial in environments where pollinators are rare as it can provide reproductive assurance. This study presents evidence for an autonomous self‐fertilization mechanism in the winter flowering plant, Brandisia hancei. To determine changes in the spatial separation of stigma and anthers, the length of style and stamens was recorded. Additionally, pollination treatments were carried out to test fruit‐set and seed production. Brandisia hancei is herkogamic in the early flowering stages. However, different growth rates of the filament and style lead to contact of stigma and anthers in the later stages, thereby facilitating self‐pollination. The highest seeds number is produced under an out‐crossing scenario but plants produce a considerable number of seeds even when purely selfed. Although pollinators are scarce, autonomous selfing alleviates the pollen limitation in B. hancei. Self‐fertilization in B. hancei seems to be an adaptive strategy to ensure reproduction when pollinators are scarce.     

AtRAD5A is a DNA translocase harboring a HIRAN domain which confers binding to branched DNA structures and is required for DNA repair in vivo

DNA lesions such as crosslinks represent obstacles for the replication machinery. Nonetheless, replication can proceed via the DNA damage tolerance pathway also known as postreplicative repair pathway. SNF2 ATPase Rad5 homologs, such as RAD5A of the model plant Arabidopsis thaliana, are important for the error‐free mode of this pathway. We able to demonstrate before, that RAD5A is a key factor in the repair of DNA crosslinks in Arabidopsis. Here, we show by in vitro analysis that AtRAD5A protein is a DNA translocase able to catalyse fork regression. Interestingly, replication forks with a gap in the leading strand are processed best, in line with its suggested function. Furthermore AtRAD5A catalyses branch migration of a Holliday junction and is furthermore not impaired by the DNA binding of a model protein, which is indicative of its ability to displace other proteins. Rad5 homologs possess HIRAN (Hip116, Rad5; N‐terminal) domains. By biochemical analysis we were able to demonstrate that the HIRAN domain variant from Arabidopsis RAD5A mediates structure selective DNA binding without the necessity for a free 3′OH group as has been shown to be required for binding of HIRAN domains in a mammalian RAD5 homolog. The biological importance of the HIRAN domain in AtRAD5A is demonstrated by our result that it is required for its function in DNA crosslink repair in vivo.