Ecological factors influencing tetraploid speciation in snow buttercups (Ranunculus Adoneus): niche differentiation and tetraploid establishment

Chromosome doubling plays an important role in generating new species of flowering plants. However, reproductive incompatibilities between newly formed tetraploid plants and their diploid progenitors are expected to create a significant barrier to the persistence and establishment of neopolyploid populations. Ecological differentiation can reduce this barrier via prezygotic isolation arising from spatial separation. Alternatively, superior viability or fecundity of neotetraploid plants might compensate for the reproductive cost of incompatible pollen from diploid neighbors. The performance of plants of both cytotypes can be assessed in their respective habitats through reciprocal transplants, although such experiments have not been used previously in the study of tetraploid speciation. We used a series of seed and seedling transplant experiments to assess ecological differentiation and competitive ability during early establishment phases for tetraploid and diploid forms of the snow buttercup (Ranunculus adoneus). At two sites, seeds from diploids and tetraploids had similar germination probabilities. Tetraploid snow buttercup seedlings had a significant growth advantage in a controlled environment chamber experiment. However, in the field diploid and tetraploid buttercup seedlings did not differ consistently in survival or growth, nor did the two cytotypes show reciprocal advantages in performance, as expected if ecological differentiation has occurred. At the seed and seedling stages, neither niche differentiation nor tetraploid competitive superiority appears sufficient to explain neotetraploid success in the presence of their diploid progenitors.     

Selection of control genes for quantitative RT-PCR based on microarray data

Use of internal reference gene(s) is necessary for adequate quantification of target gene expression by RT-PCR. Herein, we elaborated a strategy of control gene selection based on microarray data and illustrated it by analyzing endomyocardial biopsies with acute cardiac rejection and infection. Using order statistics and binomial distribution we evaluated the probability of finding low-varying genes by chance. For analysis, the microarray data were divided into two sample subsets. Among the first 10% of genes with the lowest standard deviations, we found 14 genes common to both subsets. After normalization using two selected genes, high correlation was observed between expression of target genes evaluated by microarray and RT-PCR, and in independent dataset by RT-PCR (r = 0.9, p < 0.001). In conclusion, we showed a simple and reliable strategy of selection and validation of control genes for RT-PCR from microarray data that can be easily applied for different experimental designs and tissues.     

Reproductive division of labor, dominance, and ecdysteroid levels in hemolymph and ovary of the bumble bee Bombus terrestris

To determine whether ecdysteroids are associated with reproductive division of labor in Bombus terrestris, we measured their levels in hemolymph and ovaries of queens and workers. Queens heading colonies had large active ovaries with high ecdysteroid content, whereas virgin gynes and mated queens before and after diapause had undeveloped ovaries with low ecdysteroid content. The hemolymph ecdysteroid titer was rather variable, but in a pooled analysis of mated queens before and after diapause versus colony-heading queens, ecdysteroid titers were higher in the latter group. In workers, agonistic behavior, ovarian activity, ovarian ecdysteroid content, and hemolymph ecdysteroid titers were positively correlated, and were lowest when a queen was present. In queenless workers, ecdysteroid levels were elevated in dominant workers, and were also influenced by the presence of brood and by group demography; hormone levels were higher in bees kept in larger groups. These findings are consistent with the premise that in B. terrestris the ovary is the primary site of ecdysteroid synthesis, and they show that ecdysteroids levels vary with the social environment.     

Chronic somatostatin treatment affects pituitary gonadotrophs, ovaries and onset of puberty in rats

The effects of chronic somatostatin (SRIH-14) treatment on the pituitary gonadotrophs (FSH and LH cells) and ovaries of female Wistar rats were examined. Females were given 20 microg/100 g b.w. twice per day from the immature (23rd day) till the adult period of life (71st day). The onset of puberty was determined by daily examination for vaginal opening. The peroxidase-antiperoxidase immunocytochemical procedure was used to study the gonadotrophs. Changes in the number per unit area (mm2), cell volume and volume densities of LH- and FSH-immunoreactive cells were evaluated by morphometry and stereology. Ovaries were analysed by simple point counting of follicles and corpora lutea (CL). Follicles were divided by size according to the classification of Gaytán and Osman. The mitotic indexes of granulosa and theca cells in the follicles were estimated at all stages of folliculogenesis. The number, volume and the volume density of FSH- and LH-immunoreactive cells decreased after chronic SRIH-14 treatment, particularly the latter. In the ovary, SRIH-14 treatment decreased the number of healthy follicles at all phases of folliculogenesis, lowered the mitotic indexes of granulosa and theca cells but increased the number of atretic follicles. Healthy CL were fewer in number, while regressive CL were increased. Vaginal opening occurred at a later age in treated females. It can be concluded that chronic SRIH-14 treatment markedly inhibited LH cells and to a lesser extent FSH cells. In the ovary SRIH-14 inhibited folliculogenesis, enhanced atretic processes and lowered proliferative activity of granulosa and theca cells. It also delayed puberty onset.     

Is local adaptation in Mimulus guttatus caused by trade‐offs at individual loci?

Local adaptation is considered to be the result of fitness trade‐offs for particular phenotypes across different habitats. However, it is unclear whether such phenotypic trade‐offs exist at the level of individual genetic loci. Local adaptation could arise from trade‐offs of alternative alleles at individual loci or by complementary sets of loci with different fitness effects of alleles in one habitat but selective neutrality in the alternative habitat. To evaluate the genome‐wide basis of local adaptation, we performed a field‐based quantitative trait locus (QTL) mapping experiment on recombinant inbred lines (RILs) created from coastal perennial and inland annual races of the yellow monkeyflower (Mimulus guttatus) grown reciprocally in native parental habitats. Overall, we detected 19 QTLs affecting one or more of 16 traits measured in two environments, most of small effect. We identified 15 additional QTL effects at two previously identified candidate QTLs [DIV ERGENCE (DIV)]. Significant QTL by environment interactions were detected at the DIV loci, which was largely attributable to genotypic differences at a single field site. We found no detectable evidence for trade‐offs for any one component of fitness, although DIV2 showed a trade‐off involving different fitness traits between sites, suggesting that local adaptation is largely controlled by non‐overlapping loci. This is surprising for an outcrosser, implying that reduced gene flow prevents the evolution of individuals adapted to multiple environments. We also determined that native genotypes were not uniformly adaptive, possibly reflecting fixed mutational load in one of the populations.     

Hypoglycosylated E-cadherin promotes the assembly of tight junctions through the recruitment of PP2A to adherens junctions

Epithelial cell-cell adhesion is controlled by multiprotein complexes that include E-cadherin-mediated adherens junctions (AJs) and ZO-1-containing tight junctions (TJs). Previously, we reported that reduction of E-cadherin N-glycosylation in normal and cancer cells promoted stabilization of AJs through changes in the composition and cytoskeletal association of E-cadherin scaffolds. Here, we show that enhanced interaction of hypoglycosylated E-cadherin-containing AJs with protein phosphatase 2A (PP2A) represents a mechanism for promoting TJ assembly. In MDCK cells, attenuation of cellular N-glycosylation with siRNA to DPAGT1, the first gene in the N-glycosylation pathway, reduced N-glycosylation of surface E-cadherin and resulted in increased recruitment of stabilizing proteins γ-catenin, α-catenin, vinculin and PP2A to AJs. Greater association of PP2A with AJs correlated with diminished binding of PP2A to ZO-1 and claudin-1 and with increased pools of serine-phosphorylated ZO-1 and claudin-1. More ZO-1 was found in complexes with occludin and claudin-1, and this corresponded to enhanced transepithelial resistance (TER), indicating physiological assembly of TJs. Similar maturation of AJs and TJs was detected after transfection of MDCK cells with the hypoglycosylated E-cadherin variant, V13. Our data indicate that E-cadherin N-glycans coordinate the maturity of AJs with the assembly of TJs by affecting the association of PP2A with these junctional complexes.     

The small RNA expression profile of the developing murine urinary and reproductive systems

microRNAs (miRNAs) are small non-coding RNAs with fundamental roles in the regulation of gene expression. miRNAs assemble with Argonaute (Ago) proteins to miRNA-protein complexes (miRNPs), which interact with distinct binding sites on mRNAs and regulate gene expression. Specific miRNAs are key regulators of tissue and organ development and it has been shown in mammals that miRNAs are also involved in the pathogenesis of many diseases including cancer. Here, we have characterized the miRNA expression profile of the developing murine genitourinary system. Using a computational approach, we have identified several miRNAs that are specific for the analyzed tissues or the developmental stage. Our comprehensive miRNA expression atlas of the developing genitourinary system forms an invaluable basis for further functional in vivo studies.     

Controlling death--compromising life: chronic disease, prognostication, and the new biotechnologies

Within the modern culture of control, patients and physicians seek to actively shape the uncertainty of prognostications concerning the course of disease and the anticipated effects of therapeutic and surgical interventions. This article discusses the results of a three-year ethnographic study of persons with cystic fibrosis (CF) who undergo double-lung transplant. It draws on interviews with a difficult-to-access patient group, adult CF sufferers, and investigates their dilemmas with regard to having or not having a double-lung transplant. It situates their decisions within a complex framework: the denial of death and disability in technological modernity, the consequent emphasis on cure and saving life at any cost, rather than the management of chronic illness, the extent to which health and illness constitute identity, and the problems of CF patients conceiving their life narrative when life will be short. This framework produces two key questions: Do patient beliefs in the progress narratives of medicine overshadow other considerations, and are biotechnologies such as organ transplant a calculated gamble on a better life or an uncertain reliance on biomedical expertise? I argue that risk interpretation is heavily influenced by the constant introduction of new therapeutics that intersect with social technologies of normalization to strongly influence patient decisions concerning the pursuit of high-risk surgeries such as organ transplant, surgeries that sometimes hasten a patient's decline and death.