Differentiation of repetitive DNA sites and sex chromosome systems reveal closely related group in Parodontidae (Actinopterygii: Characiformes)

Parodon and Apareiodon lack sufficiently consistent morphological traits to be considered a monophyletic group in Parodontidae. Species within this family are either sex-homomorphic or sex-heteromorphic (i.e., lacking a differentiated sex chromosome system, ZZ/ZW or ZZ/ZW(1)W(2)). In this study, a DNA fragment from the heterochromatin segment of the W chromosome of Apareiodon ibitiensis (named WAp) was microdissected and used for in situ mapping of nine Parodontidae species. The species were also characterized using a satellite DNA probe (pPh2004). The species were phylogenetically clustered according to 17 characters, which were examined by both classical and molecular cytogenetic techniques. Given the present results, the single ZZ/ZW sex chromosome system seems to have been derived from a paracentric inversion of a terminal WAp site onto the proximal regions of the short arms of a metacentric chromosome pair, followed by WAp site amplification. We reason that these events restrained recombination and favored differentiation of the W chromosome in some species. Moreover, co-hybridization experiments targeting the WAp and pPh2004 repetitive DNA sites of A. affinis suggest that the ZZ/ZW(1)W(2) sex chromosomes of this species may have arisen from a translocation between the proto-sex chromosome and an autosome. Our phylogenetic analysis corroborates the hypothesis of sex chromosome differentiation and establishes groups of closely related species. The phylogenetic reorganization in response to these new data supports the presence of internal monophyletic groups within Parodontidae.     

P2RY1/ALK3-Expressing Cells within the Adult Human Exocrine Pancreas Are BMP-7 Expandable and Exhibit Progenitor-like Characteristics

1. Download high-res image (223KB)
2. Download full-size image

     

Regulation of RasGRP via a Phorbol Ester-Responsive C1 Domain

As part of a cDNA library screen for clones that induce transformation of NIH 3T3 fibroblasts, we have isolated a cDNA encoding the murine homolog of the guanine nucleotide exchange factor RasGRP. A point mutation predicted to prevent interaction with Ras abolished the ability of murine RasGRP (mRasGRP) to transform fibroblasts and to activate mitogen-activated protein kinases (MAP kinases). MAP kinase activation via mRasGRP was enhanced by coexpression of H-, K-, and N-Ras and was partially suppressed by coexpression of dominant negative forms of H- and K-Ras. The C terminus of mRasGRP contains a pair of EF hands and a C1 domain which is very similar to the phorbol ester- and diacylglycerol-binding C1 domains of protein kinase Cs. The EF hands could be deleted without affecting the ability of mRasGRP to transform NIH 3T3 cells. In contrast, deletion of the C1 domain or an adjacent cluster of basic amino acids eliminated the transforming activity of mRasGRP. Transformation and MAP kinase activation via mRasGRP were restored if the deleted C1 domain was replaced either by a membrane-localizing prenylation signal or by a diacylglycerol- and phorbol ester-binding C1 domain of protein kinase C. The transforming activity of mRasGRP could be regulated by phorbol ester when serum concentrations were low, and this effect of phorbol ester was dependent on the C1 domain of mRasGRP. The C1 domain could also confer phorbol myristate acetate-regulated transforming activity on a prenylation-defective mutant of K-Ras. The C1 domain mediated the translocation of mRasGRP to cell membranes in response to either phorbol ester or serum stimulation. These results suggest that the primary mechanism of activation of mRasGRP in fibroblasts is through its recruitment to diacylglycerol-enriched membranes. mRasGRP is expressed in lymphoid tissues and the brain, as well as in some lymphoid cell lines. In these cells, RasGRP has the potential to serve as a direct link between receptors which stimulate diacylglycerol-generating phospholipase Cs and the activation of Ras.     

Correlative immunocytochemical and electron microscopic studies: Identification of (Entero)glucagon-somatostatin- and pancreatic polypeptide-like-containing cells in the human colon

Summary Correlative immunocytochemical and electron microscopic studies, using the semi thin-thin technic, were performed to identify the (entero) glucagon, somatostatin and pancreatic polypeptide-like immunoreactive cells of the human colonic mucosa. Mean granule diameter for each cell type was estimated according to two methods and histograms showing the granule size distribution were constructed. A total of 139 immunostained cells identified at the ultrastructural level were analyzed. Mean granule diameter for (entero)glucagon-containing cells was 318±11 nm but a reduction of granule size with age was noteworthy: granules were larger in the fetus (mean diameter 350±15) than in adults (mean diameter 310±10 nm). Somatostatin-containing cells, very rare in adults, were present in the fetal distal colon. Their general mean granule diameter was 354±18 nm but many cells had a mean granule diameter of more than 400 nm. A pancreatic polypeptidelike immunoreactivity was found only in (entero)glucagon-containing cells, pointing out the possible occurrence of both peptides (or of similar sequences) in the same cells. Previous ultrastructural studies dealing with a tentative classification of the human colonic endocrine cells were compared with the present data.This work was supported by the Institut National de la Santé et de la Recherche Médicale (INSERM).     

Microbial interactions in alcoholic beverages

International Microbiology - This review examines the different types of interactions between the microorganisms involved in the fermentation processes of alcoholic beverages produced all over the...     

Changes in native and introduced host–parasite networks

Biological Invasions - Introduced species can alter the dynamics and structure of a native community. Network analysis provides a tool to study host–parasite interactions that can help to...     

Earthworm effects on plant growth do not necessarily decrease with soil fertility

Earthworms are known to generally increase plant growth. However, because plant-earthworm interactions are potentially mediated by soil characteristics the response of plants to earthworms should depend on the soil type. In a greenhouse microcosm experiment, the responsiveness of plants (Veronica persica, Trifolium dubium and Poa annua) to two earthworm species (in combination or not) belonging to different functional groups (Aporrectodea. caliginosa an endogeic species, Lumbricus terrestris an anecic species) was measured in term of biomass accumulation. This responsiveness was compared in two soils (nutrient rich and nutrient poor) and two mineral fertilization treatments (with and without). The main significant effects on plant growth were due to the anecic earthworm species. L. terrestris increased the shoot biomass and the total biomass of T. dubium only in the rich soil. It increased also the total biomass of P. annua without mineral fertilization but had the opposite effect with fertilization. Mineral fertilization, in the presence of L. terrestris, also reduced the total biomass of V. persica. L. terrestris did not only affect plant growth. In P. annua and V. persica A. caliginosa and L. terrestris also affected the shoot/root ratio and this effect depended on soil type. Finally, few significant interactions were found between the anecic and the endogeic earthworms and these interactions did not depend on the soil type. A general idea would be that earthworms mostly increase plant growth through the enhancement of mineralization and that earthworm effects should decrease in nutrient-rich soils or with mineral fertilization. However, our results show that this view does not hold and that other mechanisms are influential.