The functional significance of ribosomal (r)DNA variation: Impacts on the evolutionary ecology of organisms.

■ Abstract The multigene family that encodes ribosomal RNA (the rDNA) has been the subject of numerous review articles examining its structure and function, as well as its use as a molecular systematic marker. The purpose of this review is to integrate information about structural and functional aspects of rDNA that impact the ecology and evolution of organisms. We examine current understanding of the impact of length heterogeneity and copy number in the rDNA on fitness and the evolutionary ecology of organisms. We also examine the role that elemental ratios (biological stoichiometry) play in mediating the impact of rDNA variation in natural populations and ecosystems. The body of work examined suggests that there are strong reciprocal feedbacks between rDNA and the ecology of all organisms, from microbes to metazoans, mediated through increased phosphorus demand in organisms with high rRNA content

The functional significance of ribosomal (r)DNA variation: Impacts on the evolutionary ecology of organisms.

■ Abstract The multi-gene family that encodes ribosomal RNA (the rDNA) has been the subject of numerous review articles examining its structure and function, as well as its use as a molecular systematic marker. The purpose of this review is to integrate information about structural and functional aspects of rDNA that impact the ecology and evolution of organisms. We examine current understanding of the impact of length heterogeneity and copy number in the rDNA on fitness and the evolutionary ecology of organisms. We also examine the role that elemental ratios (biological stoichiometry) play in mediating the impact of rDNA variation in natural populations and ecosystems. The body of work examined suggests that there are strong reciprocal feedbacks between rDNA and the ecology of all organisms, from microbes to metazoans, mediated through increased phosphorus demand in organisms with high rRNA content

Variations in the Abundances of Potassium and Thorium on the Surface of Mercury: Results from the MESSENGER Gamma-Ray Spectrometer

A technique for converting gamma-ray count rates measured by the Gamma-Ray Spectrometer on the MESSENGER spacecraft to spatially resolved maps of the gamma-ray emission from the surface of Mercury is utilized to map the surface distributions of the elements Si, O, and K over the planet's northern hemisphere. Conversion of the K gamma-ray count rates to elemental abundances on the surface reveals variations from 300 to 2400 ppm. A comparison of these abundances with models for the maximum surface temperature suggests the possibility that a temperature-related process is controlling the K abundances on the surface as well as providing K to the exosphere. The abundances of K and Th have been determined for several geologically distinct regions, including Mercury's northern smooth plains and the plains interior to the Caloris basin. The lack of a significant variation in the measured Th abundances suggests that there may be considerable variability in the K/Th abundance ratio over the mapped regions

Major-Element Abundances on the Surface of Mercury: Results from the MESSENGER Gamma-Ray Spectrometer

Orbital gamma-ray measurements obtained by the MESSENGER spacecraft have been analyzed to determine the abundances of the major elements Al, Ca, S, Fe, and Na on the surface of Mercury. The Si abundance was determined and used to normalize those of the other reported elements. The Na analysis provides the first abundance estimate of 2.9 plus or minus 0.1 wt% for this element on Mercury's surface. The other elemental results (S/Si = 0.092 plus or minus 0.015, Ca/Si = 0.24 plus or minus 0.05, and Fe/Si = 0.077 plus or minus 0.013) are consistent with those previously obtained by the MESSENGER X-Ray Spectrometer, including the high sulfur and low iron abundances. Because of different sampling depths for the two techniques, this agreement indicates that Mercury's regolith is, on average, homogenous to a depth of tens of centimeters. The elemental results from gamma-ray and X-ray spectrometry are most consistent with petrologic models suggesting that Mercury's surface is dominated by Mg-rich silicates. We also compare the results with those obtained during the MESSENGER flybys and with ground-based observations of Mercury's surface and exosphere

A Yeast Model of FUS/TLS-Dependent Cytotoxicity

FUS/TLS is a nucleic acid binding protein that, when mutated, can cause a subset of familial amyotrophic lateral sclerosis (fALS). Although FUS/TLS is normally located predominantly in the nucleus, the pathogenic mutant forms of FUS/TLS traffic to, and form inclusions in, the cytoplasm of affected spinal motor neurons or glia. Here we report a yeast model of human FUS/TLS expression that recapitulates multiple salient features of the pathology of the disease-causing mutant proteins, including nuclear to cytoplasmic translocation, inclusion formation, and cytotoxicity. Protein domain analysis indicates that the carboxyl-terminus of FUS/TLS, where most of the ALS-associated mutations are clustered, is required but not sufficient for the toxicity of the protein. A genome-wide genetic screen using a yeast over-expression library identified five yeast DNA/RNA binding proteins, encoded by the yeast genes ECM32, NAM8, SBP1, SKO1, and VHR1, that rescue the toxicity of human FUS/TLS without changing its expression level, cytoplasmic translocation, or inclusion formation. Furthermore, hUPF1, a human homologue of ECM32, also rescues the toxicity of FUS/TLS in this model, validating the yeast model and implicating a possible insufficiency in RNA processing or the RNA quality control machinery in the mechanism of FUS/TLS mediated toxicity. Examination of the effect of FUS/TLS expression on the decay of selected mRNAs in yeast indicates that the nonsense-mediated decay pathway is probably not the major determinant of either toxicity or suppression.Fidelity Biosciences (Firm)Fidelity Biosciences (Firm) (Research Inititative)ALS Therapy AllianceNational Institutes of Health (U.S.) (NIH 1RC1NS06839)National Institutes of Health (U.S.) (NIH U01NS05225-03)National Institutes of Health (U.S.) (NIH R01NS050557-05)National Institutes of Health (U.S.) (NIH 1RC2NS070342-01)Pierre L. de Bourgknecht ALS Research FoundationNational Science Foundation (U.S.) (NS614192

Filarial Parasites Develop Faster and Reproduce Earlier in Response to Host Immune Effectors That Determine Filarial Life Expectancy

During larval development, filarial nematodes adjust their lifelong reproductive strategy to the presence of anti-parasitic immune cells that determine host resistance and experimental vaccine efficacy

Niche breadth and life history variation in a hybrid Daphnia complex

Laboratory life table experiments using multiple clones of Daphnia galeata, D. hyalina, and D. galeata x hyalina hybrids quantified differences in niche breadth among these taxa along a gradient of food carbon levels (0.2-2.0 mg/L). Two-way analysis of variance revealed significant main effects (i.e., species, food level) for all life history features examined, as well as significant species x food level interactions for several life history characters (e.g., age at first reproduction and intrinsic rate of increase, r). Nested analysis of variance revealed significant species level effects for all life history characters examined, as well as significant clone level effects for all characters except r. Overall, species level effects explained approximately twice the proportion of the total variance for individual traits when compared with clone level effects (means of 32.8 and 15.8%, respectively). Significant interspecific differences in breadth of response (i.e., niche breadth) were observed for estimates of r. D. galeata exhibited a significantly greater niche breadth across food treatments than D. hyalina; D. galeata x hyalina showed an intermediate response breadth, which was not significantly different from either parental species. The existence of considerable intraspecific (i.e., clonal) variation in several life history traits, implies that any interpretation of life history variation among members of hybrid species complexes may depend critically on the genetic (clonal) make-up of the populations examined. These results are discussed in reference to the coexistence of these taxa in nature

Spatial and Temporal Genetic Heterogeneity in a Natural Daphnia Population: Ecological and Physiological Differences Between Genotypes (Cladocera, Freshwater, Parthenogenesis)

167 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.A three and one-half year study of spatial and temporal genetic heterogeneity in a population of the cyclically, parthenogenetic cladoceran, Daphnia pulex, inhabiting a permanent farm pond in east-central Illinois, indicated that electrophoretically distinct genotypes (clones) are frequently distributed non-randomly in the pond, both vertically and horizontally. Spatial autocorrelation analysis indicated that the genotypic distributions exhibited significant horizontal spatial pattern on occasion. The horizontal pattern may be influenced greatly by the vertical component (depth factors at a given station) as demonstrated by a series of vertical-horizontal transect surveys.Diel vertical migration surveys demonstrated significant differences in vertical distribution and vertical migration activity among genotypes, strongly suggesting a genetic component to vertical migration, and implying that genetically determined habitat selection exists in this population.The effects of food concentration, temperature, and pond water quality on life histories of genotypes were examined in the laboratory. Results indicated significant genotype x environment interactions under certain treatments; no single genotype was most fit when raised under all experimental conditions, indicating that selection may be operating to favor genotypes in different spatial and/or temporal microhabitats.Dissolved oxygen experiments in the laboratory showed significant clonal differences in low oxygen tolerance and hemoglobin synthesis implying that low dissolved oxygen concentrations in nature may be an important selective pressure affecting the spatial and temporal genetic heterogeneity in planktonic cladoceran populations. The evolutionary and ecological implications of these data are discussed in reference to the maintenance of genetic variation in heterogeneous environments.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Postglacial dispersal, glacial refugia, and clonal structure in Russian/Siberian populations of the arctic Daphnia pulex complex

Results from an extensive allozymic survey of the genetic (clonal) structure of Russian/Siberian populations in the arctic Daphnia pulex complex yielded high clonal diversity/richness estimates, at both the intrapopulational and intraregional levels. Highest levels of clonal diversity were detected in the heart of the Beringian glacial refuge, with lower levels detected in glaciated regions (western Russia). mtDNA haplotype diversity (based on RFLPs) showed similar spatial trends, with the highest levels of haplotype diversity again being found in Beringia. Several haplotypes were extremely widespread (in the order of thousands of kilometres across the breadth of Eurasia), and evidence for presumed mutationally derived haplotypes was plentiful. Spatial autocorrelation analysis revealed a significant clinal pattern in the degree of genetic similarity among mtDNA haplotypes. In addition, similarity of clonal arrays (based on allozymes) showed a significant inverse association with geographical distance; i.e. similarity of clonal arrays between populations increased with decreasing geographical distance between populations. Sporadic sexual reproduction (based on Hardy-Weinberg expectations) was detected in Beringia, and has undoubtedly played a role in fuelling the production of novel genotypes. Our results suggest that vast expanses of northern Eurasia have been colonized by a small number of geographically widespread haplotypes, with more regionally restricted haplotypes constituting the remaining lineages. We discuss our results within the general framework of biogeographical colonization events of the Arctic by members of the D. pulex complex, and place these data into the broader picture of the importance of Beringia as a glacial refuge for many taxa during the Pleistocen