Biogeographic significance of low-elevation records for Neotoma cinerea from the northern Bonneville Basin, Utah

The existence of low-elevation populations of Neotoma cinera in the northern Bonneville Basin shows either that these mammals can survive thousands of years in xeric habitats or that they can move across xeric lowlands far more readily than has been appreciated, or both. Current models of Great Basin small mammal biogeography are far too static to encompass properly the interaction of the wide range of geographical and biological variability that has produced the modern distribution of those mammals that have, for several decades, been treated as ""montane"" within the Great Basin.     

Long-term fire history in Great Basin sagebrush reconstructed from macroscopic charcoal in spring sediments, Newark Valley, Nevada

We use macroscopic charcoal analysis to reconstruct fire history in sagebrush ( Artemisia tridentata var. wyomingensis and A. tridentata var. tridentate ), in Newark Valley, Nevada. We analyzed charcoal at continuous 1-cm intervals (～7-127 years), and pollen at 2- to 10-cm intervals (～70-263 years) in a core spanning the last 5500 cal yr BP (calendar years before present). A charcoal peak in the historic period was associated with a >1400-ha fire dated to 1986 that burned in the watershed. We reconstructed the prehistoric fire history by inferring fires from similar charcoal peaks that were significantly greater than the background charcoal accumulation. Our results suggest the fire regime is climate and fuel driven. During periods of wetter climate, sagebrush increased and fires were more abundant, and during extended dry periods when sagebrush decreased, fires were less frequent. Our method does not allow calculation of a fire-return interval; however, our results support models that estimate a mean fire-return interval of up to a century in Artemisia tridentata var. wyomingensis . The charcoal record indicates that fires have increased within the historic period. This contrasts with pinyon/juniper studies that indicate an expansion of woodland associated with fewer fires in the historic period. We suggest that in the central Great Basin, a regime of frequent fires in sagebrush that limits woodland expansion is true for the sagebrush-woodland ecotone, but in sagebrush-dominated valleys with lower fuel loads, fires have always been less frequent. Protecting sagebrush-dominated valleys from frequent fire would appear to be consistent with the prehistoric fire regime.     

<Emphasis Type="Italic">O</Emphasis>-Mannosylation and human disease

Glycosylation of proteins is arguably the most prevalent co- and post-translational modification. It is responsible for increased heterogeneity and functional diversity of proteins. Here we discuss the importance of one type of glycosylation, specifically O-mannosylation and its relationship to a number of human diseases. The most widely studied O-mannose modified protein is alpha-dystroglycan (α-DG). Recent studies have focused intensely on α-DG due to the severity of diseases associated with its improper glycosylation. O-mannosylation of α-DG is involved in cancer metastasis, arenavirus entry, and multiple forms of congenital muscular dystrophy [1, 2]. In this review, we discuss the structural and functional characteristics of O-mannose-initiated glycan structures on α-DG, enzymes involved in the O-mannosylation pathway, and the diseases that are a direct result of disruptions within this pathway.     

Defining the core Arabidopsis thaliana root microbiome

Land plants associate with a root microbiota distinct from the complex microbial community present in surrounding soil. The microbiota colonizing the rhizosphere (immediately surrounding the root) and the endophytic compartment (within the root) contribute to plant growth, productivity, carbon sequestration and phytoremediation. Colonization of the root occurs despite a sophisticated plant immune system, suggesting finely tuned discrimination of mutualists and commensals from pathogens. Genetic principles governing the derivation of host-specific endophyte communities from soil communities are poorly understood. Here we report the pyrosequencing of the bacterial 16S ribosomal RNA gene of more than 600 Arabidopsis thaliana plants to test the hypotheses that the root rhizosphere and endophytic compartment microbiota of plants grown under controlled conditions in natural soils are sufficiently dependent on the host to remain consistent across different soil types and developmental stages, and sufficiently dependent on host genotype to vary between inbred Arabidopsis accessions. We describe different bacterial communities in two geochemically distinct bulk soils and in rhizosphere and endophytic compartments prepared from roots grown in these soils. The communities in each compartment are strongly influenced by soil type. Endophytic compartments from both soils feature overlapping, low-complexity communities that are markedly enriched in Actinobacteria and specific families from other phyla, notably Proteobacteria. Some bacteria vary quantitatively between plants of different developmental stage and genotype. Our rigorous definition of an endophytic compartment microbiome should facilitate controlled dissection of plant-microbe interactions derived from complex soil communities.     

SAR11 clade dominates ocean surface bacterioplankton communities

The most abundant class of bacterial ribosomal RNA genes detected in seawater DNA by gene cloning belongs to SAR11-an alpha-proteobacterial clade. Other than indications of their prevalence in seawater, little is known about these organisms. Here we report quantitative measurements of the cellular abundance of the SAR11 clade in northwestern Sargasso Sea waters to 3,000 m and in Oregon coastal surface waters. On average, the SAR11 clade accounts for a third of the cells present in surface waters and nearly a fifth of the cells present in the mesopelagic zone. In some regions, members of the SAR11 clade represent as much as 50% of the total surface microbial community and 25% of the subeuphotic microbial community. By extrapolation, we estimate that globally there are 2.4 x 10(28) SAR11 cells in the oceans, half of which are located in the euphotic zone. Although the biogeochemical role of the SAR11 clade remains uncertain, these data support the conclusion that this microbial group is among the most successful organisms on Earth.     

Defects in RGS9 or its anchor protein R9AP in patients with slow photoreceptor deactivation

The RGS proteins are GTPase activating proteins that accelerate the deactivation of G proteins in a variety of signalling pathways in eukaryotes. RGS9 deactivates the G proteins (transducins) in the rod and cone phototransduction cascades. It is anchored to photoreceptor membranes by the transmembrane protein R9AP (RGS9 anchor protein), which enhances RGS9 activity up to 70-fold. If RGS9 is absent or unable to interact with R9AP, there is a substantial delay in the recovery from light responses in mice. We identified five unrelated patients with recessive mutations in the genes encoding either RGS9 or R9AP who reported difficulty adapting to sudden changes in luminance levels mediated by cones. Standard visual acuity was normal to moderately subnormal, but the ability to see moving objects, especially with low-contrast, was severely reduced despite full visual fields; we have termed this condition bradyopsia. To our knowledge, these patients represent the first identified humans with a phenotype associated with reduced RGS activity in any organ.     

Two mitotic kinesins cooperate to drive sister chromatid separation during anaphase

During anaphase identical sister chromatids separate and move towards opposite poles of the mitotic spindle. In the spindle, kinetochore microtubules have their plus ends embedded in the kinetochore and their minus ends at the spindle pole. Two models have been proposed to account for the movement of chromatids during anaphase. In the 'Pac-Man' model, kinetochores induce the depolymerization of kinetochore microtubules at their plus ends, which allows chromatids to move towards the pole by 'chewing up' microtubule tracks. In the 'poleward flux' model, kinetochores anchor kinetochore microtubules and chromatids are pulled towards the poles through the depolymerization of kinetochore microtubules at the minus ends. Here, we show that two functionally distinct microtubule-destabilizing KinI kinesin enzymes (so named because they possess a kinesin-like ATPase domain positioned internally within the polypeptide) are responsible for normal chromatid-to-pole motion in Drosophila. One of them, KLP59C, is required to depolymerize kinetochore microtubules at their kinetochore-associated plus ends, thereby contributing to chromatid motility through a Pac-Man-based mechanism. The other, KLP10A, is required to depolymerize microtubules at their pole-associated minus ends, thereby moving chromatids by means of poleward flux.