Refugial isolation and divergence in the Narrowheaded Gartersnake species complex (Thamnophis rufipunctatus) as revealed by multilocus DNA sequence data

Glacial–interglacial cycles of the Pleistocene are hypothesized as one of the foremost contributors to biological diversification. This is especially true for cold‐adapted montane species, where range shifts have had a pronounced effect on population‐level divergence. Gartersnakes of the Thamnophis rufipunctatus species complex are restricted to cold headwater streams in the highlands of the Sierra Madre Occidental and southwestern USA. We used coalescent and multilocus phylogenetic approaches to test whether genetic diversification of this montane‐restricted species complex is consistent with two prevailing models of range fluctuation for species affected by Pleistocene climate changes. Our concatenated nuDNA and multilocus species analyses recovered evidence for the persistence of multiple lineages that are restricted geographically, despite a mtDNA signature consistent with either more recent connectivity (and introgression) or recent expansion (and incomplete lineage sorting). Divergence times estimated using a relaxed molecular clock and fossil calibrations fall within the Late Pleistocene, and zero gene flow scenarios among current geographically isolated lineages could not be rejected. These results suggest that increased climate shifts in the Late Pleistocene have driven diversification and current range retraction patterns and that the differences between markers reflect the stochasticity of gene lineages (i.e. ancestral polymorphism) rather than gene flow and introgression. These results have important implications for the conservation of T. rufipunctatus (sensu novo), which is restricted to two drainage systems in the southwestern US and has undergone a recent and dramatic decline.     

Heme requirement and intracellular trafficking in Trypanosoma cruzi epimastigotes

Epimastigotes multiplies in the insect midgut by taking up nutrients present in the blood meal including heme bound to hemoglobin of red blood cell. During blood meal digestion by vector proteases in the posterior midgut, hemoglobin is clipped off into amino acids, peptides, and free heme. In this paper, we compared the heme and hemoglobin uptake kinetics and followed their intracellular trafficking. Addition of heme to culture medium increased epimastigote proliferation in a dose-dependent manner, while medium supplemented with hemoglobin enhanced growth after 3-day lag phase. Medium supplemented with globin-derived peptides stimulated cell proliferation in a dose-independent way. Using Palladium mesoporphyrin IX (Pd-mP) as a fluorescent heme-analog, we observed that heme internalization proceeded much faster than that observed by hemoglobin-rhodamine. Binding experiments showed that parasites accumulated the Pd-mP into the posterior region of the cell whereas hemoglobin-rhodamine stained the anterior region. Finally, using different specific inhibitors of ABC transporters we conclude that a P-glycoprotein homologue transporter is probably involved in heme transport through the plasma membrane.     

Endothelium-dependent vasodilation induced by Hancornia speciosa in rat superior mesenteric artery

The vasodilator effect of the ethanolic extract of leaves from Hancornia speciosa Gomes (HSE) was evaluated in superior mesenteric artery rings. HSE produced a concentration-dependent vasodilation (IC50 = 10.8 +/- 4.0 microg/mL) in arterial rings pre-contracted with phenylephrine, which was completely abolished in endothelium-denuded vessels. Endothelium-dependent vasodilation induced by HSE was strongly reduced by L-NAME (100 microM), a nitric oxide (NO) synthase inhibitor, but neither by atropine, a muscarinic receptor antagonist (1 microM), nor by indomethacin (10 microM), a cyclooxygenase inhibitor. In rings pre-contracted with 80 mM KCl, the vasodilator effect of HSE was shifted to the right and was completely abolished in the presence of L-NAME (100 microM). Similar effects were obtained in mesenteric rings pre-contracted with phenylephrine in the presence of KCl 25 mM alone or in addition to 100 microM L-NAME. In addition, BaCl2 (1 mM) dramatically reduced the vasodilation induced by HSE. Together, these findings led us to conclude that HSE induces an endothelium-dependent vasodilation in rat mesenteric artery, by a mechanism dependent on NO, on the activation of potassium channels and endothelium-derived hyperpolarizing factor release. Rutin, identified as a major peak in the HPLC fingerprint obtained for HSE, might contribute for the observed vasodilator effect, since it was able to induce an endothelium-dependent vasodilation in rat superior mesenteric arteries.     

Three gene products govern (p)ppGpp production by Streptococcus mutans

The current dogma implicating RelA as the sole enzyme controlling (p)ppGpp production and degradation in Gram-positive bacteria does not apply to Streptococcus mutans. We have now identified and characterized two genes, designated as relP and relQ, encoding novel enzymes that are directly involved in (p)ppGpp synthesis. Additionally, relP is co-transcribed with a two-component signal transduction system (TCS). Analysis of the (p)ppGpp synthetic capacity of various mutants and the behaviour of strains lacking combinations of the synthetase enzymes have revealed a complex regulon and fundamental differences in the way S. mutans manages alarmone production compared with bacterial paradigms. The functionality of the RelP and RelQ enzymes was further confirmed by demonstrating that expression of relP and relQ restored growth of a (p)ppGpp(0) Escherichia coli strain in minimal medium, SMG and on medium containing 3-amino-1,2,4-triazole, and by demonstrating (p)ppGpp production in various complemented mutant strains of E. coli and S. mutans. Notably, RelQ, and RelP and the associated TCS, are harboured in some, but not all, pathogenic streptococci and related Gram-positive organisms, opening a new avenue to explore the variety of strategies employed by human and animal pathogens to survive in adverse conditions that are peculiar to environments in their hosts.     

The Saccharomyces cerevisiae YFR041C/ERJ5 gene encoding a type I membrane protein with a J domain is required to preserve the folding capacity of the endoplasmic reticulum

YFR041C/ERJ5 was identified in Saccharomyces cerevisiae as a gene regulated by the unfolded protein response pathway (UPR). The open reading frame of the gene has a J domain characteristic of the DnaJ chaperone family of proteins that regulate the activity of Hsp70 chaperones. We determined the expression and topology of Erj5p, a type I membrane protein with a J domain in the lumen of the endoplasmic reticulum (ER) that colocalizes with Kar2p, the major Hsp70 in the yeast ER. We identified synthetic interactions of Deltaerj5 with mutations in genes involved in protein folding in the ER (kar2-159, Deltascj1Deltajem1) and in the induction of the unfolded protein response (Deltaire1). Loss of Erj5p in yeast cells with impaired ER protein folding capacity increased sensitivity to agents that cause ER stress. We identified the ERJ5 mRNA and confirmed that agents that promote accumulation of misfolded proteins in the ER regulate its abundance. We found that loss of the non-essential ERJ5 gene leads to a constitutively induced UPR, indicating that ERJ5 is required for maintenance of an optimal folding environment in the yeast ER.     

High Intake of Dietary Sugar Enhances Bisphenol A (BPA) Disruption and Reveals Ribosome-Mediated Pathways of Toxicity

Bisphenol A (BPA) is an organic compound to which human populations are ubiquitously exposed. Epidemiological data suggest BPA exposure might be associated with higher rates of diabetes and reproductive anomalies. Health concerns also include transgenerational consequences, but these mechanisms are crudely defined. Similarly, little is known about synergistic interactions between BPA and other substances. Here we show that acute and chronic exposure to BPA causes genome-wide modulation of several functionally coherent genetic pathways in the fruit fly Drosophila melanogaster. In particular, BPA exposure causes massive downregulation of testis-specific genes and upregulation of ribosome-associated genes widely expressed across tissues. In addition, it causes the modulation of transposable elements that are specific to the ribosomal DNA loci, suggesting that nucleolar stress might contribute to BPA toxicity. The upregulation of ribosome-associated genes and the impairment of testis-specific gene expression are significantly enhanced upon BPA exposure with a high-sugar diet. Our results suggest that BPA and dietary sugar might functionally interact, with consequences to regulatory programs in both reproductive and somatic tissues.