RESUMEN
Highly abundant proteins tend to evolve slowly (a trend called E-R anticorrelation), and a number of hypotheses have been proposed to explain this phenomenon. The misfolding avoidance hypothesis attributes the E-R anticorrelation to the abundance-dependent toxic effects of protein misfolding. To avoid these toxic effects, protein sequences (particularly those of highly expressed proteins) would be under selection to fold properly. One prediction of the misfolding avoidance hypothesis is that highly abundant proteins should exhibit high thermostability (i.e., a highly negative free energy of folding, ΔG). Thus far, only a handful of analyses have tested for a relationship between protein abundance and thermostability, producing contradictory results. These analyses have been limited by 1) the scarcity of ΔG data, 2) the fact that these data have been obtained by different laboratories and under different experimental conditions, 3) the problems associated with using proteins' melting energy (Tm) as a proxy for ΔG, and 4) the difficulty of controlling for potentially confounding variables. Here, we use computational methods to compare the free energy of folding of pairs of human-mouse orthologous proteins with different expression levels. Even though the effect size is limited, the most highly expressed ortholog is often the one with a more negative ΔG of folding, indicating that highly expressed proteins are often more thermostable.
Asunto(s)
Pliegue de Proteína , Proteínas , Animales , Humanos , Ratones , Proteínas/genética , Proteínas/metabolismoRESUMEN
Despite the importance of effective population size (Ne) in evolutionary and conservation biology, it remains unclear what factors have an impact on this quantity. The Nearly Neutral Theory of Molecular Evolution predicts a faster accumulation of deleterious mutations (and thus a higher dN/dS ratio) in populations with small Ne; thus, measuring dN/dS ratios in different groups/species can provide insight into their Ne. Here, we used an exome data set of 1,550 loci from 45 species of marsupials representing 18 of the 22 extant families, to estimate dN/dS ratios across the different branches and families of the marsupial phylogeny. We found a considerable heterogeneity in dN/dS ratios among families and species, which suggests significant differences in their Ne. Furthermore, our multivariate analyses of several life-history traits showed that dN/dS ratios (and thus Ne) are affected by body weight, body length, and weaning age.
Asunto(s)
Rasgos de la Historia de Vida , Marsupiales , Animales , Evolución Molecular , Marsupiales/genética , Filogenia , Selección GenéticaRESUMEN
Population genetic analyses can evaluate how evolutionary processes shape diversity and inform conservation and management of imperiled species. Taimen (Hucho taimen), the world's largest freshwater salmonid, is threatened, endangered, or extirpated across much of its range due to anthropogenic activity including overfishing and habitat degradation. We generated genetic data using high throughput sequencing of reduced representation libraries for taimen from multiple drainages in Mongolia and Russia. Nucleotide diversity estimates were within the range documented in other salmonids, suggesting moderate diversity despite widespread population declines. Similar to other recent studies, our analyses revealed pronounced differentiation among the Arctic (Selenge) and Pacific (Amur and Tugur) drainages, suggesting historical isolation among these systems. However, we found evidence for finer-scale structure within the Pacific drainages, including unexpected differentiation between tributaries and the mainstem of the Tugur River. Differentiation across the Amur and Tugur basins together with coalescent-based demographic modeling suggests the ancestors of Tugur tributary taimen likely diverged in the eastern Amur basin, prior to eventual colonization of the Tugur basin. Our results suggest the potential for differentiation of taimen at different geographic scales, and suggest more thorough geographic and genomic sampling may be needed to inform conservation and management of this iconic salmonid.