Great Genetic Differentiation among Populations of Meconopsis integrifolia and Its Implication for Plant Speciation in the Qinghai-Tibetan Plateau

The complex tectonic events and climatic oscillations in the Qinghai-Tibetan Plateau (QTP), the largest and highest plateau in the world, are thought to have had great effects on the evolutionary history of the native plants. Of great interest is to investigate plant population genetic divergence in the QTP and its correlation with the geologic and climatic changes. We conducted a range-wide phylogeographical analysis of M. integrifolia based on the chloroplast DNA (cpDNA) trnL-trnF and trnfM-trnS regions, and defined 26 haplotypes that were phylogenetically divided into six clades dated to the late Tertiary. The six clades correspond, respectively, to highly differentiated population groups that do not overlap in geographic distribution, implying that the mountain ranges acting as corridors or barriers greatly affected the evolutionary history of the QTP plants. The older clade of M. integrifolia only occurs in the southwest of the species' range, whereas the distributions of younger clades extend northeastward in the eastern QTP, suggesting that climatic divergence resulting from the uplift of the QTP triggered the initial divergence of M. integrifolia native to the plateau. Also, the nrDNA ITS region was used to clarify the unexpected phylogenetic relationships of cpDNA haplotypes between M. integrifolia and M. betonicifolia. The topological incongruence between the two phylogenies suggests an ancestral hybridization between the two species. Our study indicates that geographic isolation and hybridization are two important mechanisms responsible for the population differentiation and speciation of Meconopsis, a species-rich genus with complex polyploids

Multiplying Diversity: Family Unification and the Regional Origins of Late-Age US Immigrants

Building on claims that the family unification provisions of 1965 Amendments drive changes in both the age composition and the regional origins of US legal permanent residents, we use administrative data to examine empirically whether and how chain migration links these two trends. Specifically, we ask: (1) How does the prevalence of family chain migration differ among major sending regions, and (2) how does the surge in late-age immigration since 1980 vary by source regions and major sending countries? Specifically, we derive age-specific migration multipliers for the major sending regions and the four top source countries. These nations also feature the largest backlogs for numerically capped family visas (Wasem 2012), which has implications for the age composition of sponsored relatives who age as they wait for visas in multi-year queues. In addition to improving on prior estimates of chain migration, our analyses clarify why the age composition of the foreign stock population from Asia and Latin America diverged (He 2002; Grieco et al. 2012). Before describing the data and estimation methods we provide a brief overview of the logic that led to Congress’s gross miscalculation of the impact of the 1965 Amendments on the regional origins of US immigrants. The concluding section discusses the implications of family chain migration in the context of an aging society and contemplated comprehensive reform

Molecular Control of Innate Immune Response to Pseudomonas aeruginosa Infection by Intestinal let-7 in Caenorhabditis elegans

The microRNA (miRNA) let-7 is an important miRNA identified in Caenorhabditis elegans and has been shown to be involved in the control of innate immunity. The underlying molecular mechanisms for let-7 regulation of innate immunity remain largely unclear. In this study, we investigated the molecular basis for intestinal let-7 in the regulation of innate immunity. Infection with Pseudomonas aeruginosa PA14 decreased let-7::GFP expression. Intestine- or neuron-specific activity of let-7 was required for its function in the regulation of innate immunity. During the control of innate immune response to P. aeruginosa PA14 infection, SDZ-24 was identified as a direct target for intestinal let-7. SDZ-24 was found to be predominantly expressed in the intestine, and P. aeruginosa PA14 infection increased SDZ-24::GFP expression. Intestinal let-7 regulated innate immune response to P. aeruginosa PA14 infection by suppressing both the expression and the function of SDZ-24. Knockout or RNA interference knockdown of sdz-24 dampened the resistance of let-7 mutant to P. aeruginosa PA14 infection. Intestinal overexpression of sdz-24 lacking 3'-UTR inhibited the susceptibility of nematodes overexpressing intestinal let-7 to P. aeruginosa PA14 infection. In contrast, we could observed the effects of intestinal let-7 on innate immunity in P. aeruginosa PA14 infected transgenic strain overexpressing sdz-24 containing 3'-UTR. In the intestine, certain SDZ-24-mediated signaling cascades were formed for nematodes against the P. aeruginosa PA14 infection. Our results highlight the crucial role of intestinal miRNAs in the regulation of the innate immune response to pathogenic infection