Solution structure of At3g04780.1-des15, an Arabidopsis thaliana ortholog of the C-terminal domain of human thioredoxin-like protein

The structure of At3g04780.1-des15, an Arabidopsis thaliana ortholog of the C-terminal domain of human thioredoxin-like protein, was determined by NMR spectroscopy. The structure is dominated by a beta-barrel sandwich. A two-stranded anti-parallel beta-sheet, which seals off one end of the beta-barrel, is flanked by two flexible loops rich in acidic amino acids. Although this fold often provides a ligand binding site, the structure did not reveal an appreciable cavity inside the beta-barrel. The three-dimensional structure of At3g04780.1-des15 provides an entry point for understanding its functional role and those of its mammalian homologs.     

Comparative analysis of population genetic structure in Athyrium distentifolium (Pteridophyta) using AFLPs and SSRs from anonymous and transcribed gene regions

To examine the performance and information content of different marker systems, comparative assessment of population genetic diversity was undertaken in nine populations of Athyrium distentifolium using nine genomic and 10 expressed sequence tag (EST) microsatellite (SSR) loci, and 265 amplified fragment length polymorphism (AFLP) loci from two primer combinations. In range-wide comparisons (European vs. North American populations), the EST-SSR loci showed more reliable amplification and produced more easily scorable bands than genomic simple sequence repeats (SSRs). Genomic SSRs showed significantly higher levels of allelic diversity than EST-SSRs, but there was a significant correlation in the rank order of population diversities revealed by both marker types. When AFLPs, genomic SSRs, and EST-SSRs are considered, comparisons of different population diversity metrics/markers revealed a mixture of significant and nonsignificant rank-order correlations. However, no hard incongruence was detected (in no pairwise comparison of populations did different marker systems or metrics detect opposingly significant different amounts of variation). Comparable population pairwise estimates of F(ST) were obtained for all marker types, but whilst absolute values for genomic and EST-SSRs were very similar (F(ST) = 0.355 and 0.342, respectively), differentiation was consistently higher for AFLPs in pairwise and global comparisons (global AFLP F(ST) = 0.496). The two AFLP primer combinations outperformed 18 SSR loci in assignment tests and discriminatory power in phenetic cluster analyses. The results from marker comparisons on A. distentifolium are discussed in the context of the few other studies on natural plant populations comparing microsatellite and AFLP variability.     

Diverse signaling pathways through the SDF-1/CXCR4 chemokine axis in prostate cancer cell lines leads to altered patterns of cytokine secretion and angiogenesis

The establishment of metastatic bone lesions in prostate cancer (CaP) is a process partially dependent on angiogenesis. Previously we demonstrated that the stromal-derived factor-1 (SDF-1 or CXCL12)/CXCR4 chemokine axis is critical for CaP cell metastasis. In this investigation, cell lines were established in which CXCR4 expression was knocked down using siRNA technology. When CaP cells were co-transplanted with human vascular endothelial cells into SCID mice, significantly fewer human blood vessels were observed paralleling the reductions in CXCR4 levels. Likewise, the invasive behaviors of the CaP cells were inhibited in vitro. From these functional observations we explored angiogenic and signaling mechanisms generated following SDF-1 binding to CXCR4. Differential activation of the MEK/ERK and PI3K/AKT pathways that result in differential secretion IL-6, IL-8, TIMP-2 and VEGF were seen contingent on the cell type examined; VEGF and TIMP-2 expression in PC3 cells are dependent on AKT activation and ERK activation in LNCaP and LNCaP C4-2B cells leads to IL-6 or IL-8 secretion. At the same time, expression of angiostatin levels were inversely related to CXCR4 levels, and inhibited by SDF-1 stimulation. These data link the SDF-1/CXCR4 pathway to changes in angiogenic cytokines by different signaling mechanisms and, suggest that the delicate equilibrium between proangiogenic and antiangiogenic factors may be achieved by different signal transduction pathways to regulate the angiogenic phenotype of prostate cancers. Taken together, our results provide new information regarding expression of functional CXCR4 receptor-an essential role and potential mechanism of angiogenesis upon SDF-1 stimulation.     

lin-17/Frizzled and lin-18 regulate POP-1/TCF-1 localization and cell type specification during C. elegans vulval development

The Caenorhabditis elegans vulva is comprised of highly similar anterior and posterior halves that are arranged in a mirror symmetric pattern. The cell lineages that form each half of the vulva are identical, except that they occur in opposite orientations with respect to the anterior/posterior axis. We show that most vulval cell divisions produce sister cells that have asymmetric levels of POP-1 and that the asymmetry has opposite orientations in the two halves of the vulva. We demonstrate that lin-17 (Frizzled type Wnt receptor) and lin-18 (Ryk) regulate the pattern of POP-1 localization and cell type specification in the posterior half of the vulva. In the absence of lin-17 and lin-18, posterior lineages are reversed and resemble anterior lineages. These experiments suggest that Wnt signaling pathways reorient cell lineages in the posterior half of the vulva from a default orientation displayed in the anterior half of the vulva.     

A biogeographic pattern in sparrow bill morphology: parallel adaptation to tidal marshes

The study of ecological convergence, the evolution of similar traits on multiple occasions in response to similar conditions, is a powerful method for developing and testing adaptive hypotheses. However, despite the great attention paid to geographic variation and the foraging ecology of birds, surprisingly few cases of convergent or parallel feeding adaptations have been adequately documented. In this study, we document a biogeographic pattern of parallel bill morphology across 10 sparrow taxa endemic to tidal marshes. All North American tidal marsh sparrows display parallel differentiation from close relatives in other habitats, suggesting that selection on bill morphology is strong. Relative to their body mass, tidal marsh sparrows have longer, thinner bills than their non-tidal marsh counterparts, which is likely an adaptation for consuming more invertebrates and fewer seeds, as well as for probing in sediment crevices to capture prey. Published data on tidal marsh food resources and diet of the relevant taxa support this hypothesis. This morphological differentiation is most pronounced between sister taxa with the greatest estimated divergence times, but is found even in taxa that show little or no structure in molecular genetic markers. We, therefore, speculate that tidal marsh ecosystems are likely settings for ecological speciation.     

Behavioral coping strategies in a cichlid fish: the role of social status and acute stress response in direct and displaced aggression

The African cichlid fish, Astatotilapia burtoni, has a complex social system with a sophisticated social hierarchy that offers unique opportunities to understand how social rank and its physiological substrates relate to behavioral strategies. In A. burtoni, a small fraction of the males are dominant (T, territorial), as distinguished by being large, brightly colored, reproductively active, and aggressively defending territories. In contrast, the majority of males are non-dominant (NT, non-territorial), being smaller, drably colored, sexually immature, and typically schooling with females. The social system is regulated by aggressive interactions between males and behavioral responses to aggression can be direct or displaced with respect to the animal that acts. To determine whether direct and displaced behaviors are differentially exhibited by T and NT males, individuals were shown a video presentation of a dominant male displaying aggressively. Analysis of aggressive acts toward the video display and displaced activity toward a tank mate revealed that T males exhibited more direct behavior (toward the video display), while NT males engaged in more displaced behavior (toward tank mates). Because similar experiments with primates suggest that shifts in behavioral strategies are linked to changes in the stress response (as measured by circulating cortisol levels), we measured cortisol levels of T and NT males following exposure to the aggressive stimulus. Although in some animals subordinate males are reported to have higher cortisol levels, here we show that in A. burtoni the endocrine response to specific situations can vary considerably even among animals of the same status. Interestingly, NT males with intermediate cortisol levels showed more directed behavior while NT males with both high and low cortisol levels showed more displaced. This suggests an optimal physiological stress response in NT males that predisposes them to challenge aggressors perhaps making it more likely for them to ascend in status.     

The nodPQ genes in Azospirillum brasilense Sp7 are involved in sulfation of lipopolysaccharides

Here we report on the presence of sulfated lipopolysaccharide molecules in Azospirillum brasilense, a plant growth-promoting rhizosphere bacterium. Chemical analysis provided structural data on the O-antigen composition and demonstrated the possible involvement of the nodPQ genes in O-antigen sulfation.     

Pscroph,a parasitic plant EST database enriched for parasite associated transcripts

Background  

Parasitic plants in the Orobanchaceae develop invasive root haustoria upon contact with host roots or root factors. The development of haustoria can be visually monitored and is rapid, highly synchronous, and strongly dependent on host factor exposure; therefore it provides a tractable system for studying chemical communications between roots of different plants.