Observations Préliminaires Sur Les Pali#x000E9;oenvironnements De L'ilerdien De Coustouge (Corbières,France)

The classic section of Ilerdian at Coustouge (Corbières, France) is analysed at an sedimentological and paleoecological angle. This study shows the deltaic character of sedimentation. The authors describe the distribution of faunas in prodelta, deltafront, beach ridges, tidal flats, bays, distributary channels and brackish marshes environments.     

Nuclear import defect of human immunodeficiency virus type 1 DNA flap mutants is not dependent on the viral strain or target cell type

We have previously established, using human immunodeficiency virus type 1 (HIV-1) strain LAI, that the HIV-1 central DNA Flap acts as a cis determinant of viral genome nuclear import. Although the impact of the DNA Flap on nuclear import has already found numerous independent confirmations in the context of lentivirus vectors, it has been claimed that it may be nonessential for infectious virus strains LAI, YU-2 (J. D. Dvorin et al., J. Virol. 76:12087-12096, 2002), HXB2, and NL4-3 (A. Limon et al., J. Virol. 76:12078-12086, 2002). We conducted a detailed analysis of virus infectivity using the provirus clones provided by the authors and analogous target cells. In contrast to published data, our results show that all cPPT mutant viruses exhibit reduced infectivity corresponding to a nuclear import defect irrespective of the viral genetic background or target cell.     

Evolution of substrate recognition across a multigene family of glycosyltransferases in Arabidopsis

The complete sequence of the Arabidopsis genome enables definitive characterization of multigene families and analysis of their phylogenetic relationships. Using a consensus sequence previously defined for glycosyltransferases that use small-molecular-weight acceptors, 107 gene sequences were identified in the Arabidopsis genome and used to construct a phylogenetic tree. Screening recombinant proteins for their catalytic activities in vitro has revealed enzymes active toward physiologically important substrates, including hormones and secondary metabolites. The aim of this study has been to use the phylogenetic relationships across the entire family to explore the evolution of substrate recognition and regioselectivity of glucosylation. Hydroxycoumarins have been used as the model substrates for the analysis in which 90 sequences have been assayed and 48 sequences shown to recognize these compounds. The study has revealed activity in 6 of the 14 phylogenetic groups of the multigene family, suggesting that basic features of substrate recognition are retained across substantial evolutionary periods.     

Replication-competent influenza A virus that encodes a split-green fluorescent protein-tagged PB2 polymerase subunit allows live-cell imaging of the virus life cycle

Studies on the intracellular trafficking of influenza virus ribonucleoproteins are currently limited by the lack of a method enabling their visualization during infection in single cells. This is largely due to the difficulty of encoding fluorescent fusion proteins within the viral genome. To circumvent this limitation, we used the split-green fluorescent protein (split-GFP) system (S. Cabantous, T. C. Terwilliger, and G. S. Waldo, Nat. Biotechnol. 23:102-107, 2005) to produce a quasi-wild-type recombinant A/WSN/33/influenza virus which allows expression of individually fluorescent PB2 polymerase subunits in infected cells. The viral PB2 proteins were fused to the 16 C-terminal amino acids of the GFP, whereas the large transcomplementing GFP fragment was supplied by transient or stable expression in cultured cells that were permissive to infection. This system was used to characterize the intranuclear dynamics of PB2 by fluorescence correlation spectroscopy and to visualize the trafficking of viral ribonucleoproteins (vRNPs) by dynamic light microscopy in live infected cells. Following nuclear export, vRNPs showed a transient pericentriolar accumulation and intermittent rapid (～1 μm/s), directional movements in the cytoplasm, dependent on both microtubules and actin filaments. Our data establish the potential of split-GFP-based recombinant viruses for the tracking of viral proteins during a quasi-wild-type infection. This new virus, or adaptations of it, will be of use in elucidating many aspects of influenza virus host cell interactions as well as in screening for new antiviral compounds. Furthermore, the existence of cell lines stably expressing the complementing GFP fragment will facilitate applications to many other viral and nonviral systems.     

Segregating random amplified polymorphic DNAs (RAPDs) in Betula alleghaniensis

Summary Molecular markers are currently being developed for Betula alleghaniensis Britton using random amplified polymorphic DNA (RAPD). Arbitrarily designed 11-mer primers were tested on three intraspecific controlled crosses for which more than 15 full-sibs were available. Using two of these primers, we were able to genetically characterize a total of nine polymorphic RAPD markers. Segregation of these markers was consistent with a biparental diploid mode of inheritance, and all appeared dominant. RAPDs were valuable in detecting contaminants and, therefore, in assessing the validity of controlled crosses. Limitations of the technique are discussed in relation to the determination of parental genotypes and construction of linkage maps for hardwood species.     

Microevolution in island forms: the roles of drift and directional selection in morphological divergence of a passerine bird

Abstract.— Theory predicts that in small isolated populations random genetic drift can lead to phenotypic divergence; however this prediction has rarely been tested quantitatively in natural populations. Here we utilize natural repeated island colonization events by members of the avian species complex, Zosterops lateralis , to assess whether or not genetic drift alone is an adequate explanation for the observed patterns of microevolutionary divergence in morphology. Morphological and molecular genetic characteristics of island and mainland populations are compared to test three predictions of drift theory: (1) that the pattern of morphological change is idiosyncratic to each island; (2) that there is concordance between morphological and neutral genetic shifts across island populations; and (3) for populations whose time of colonization is known, that the rate of morphological change is sufficiently slow to be accounted for solely by genetic drift. Our results are not consistent with these predictions. First, the direction of size shifts was consistently towards larger size, suggesting the action of a nonrandom process. Second, patterns of morphological divergence among recently colonized populations showed little concordance with divergence in neutral genetic characters. Third, rate tests of morphological change showed that effective population sizes were not small enough for random processes alone to account for the magnitude of microevolutionary change. Altogether, these three lines of evidence suggest that drift alone is not an adequate explanation of morphological differentiation in recently colonized island Zosterops and therefore we suggest that the observed microevolutionary changes are largely a result of directional natural selection.     

In vitro fertilization and cleavage of in vivo matured bovine oocytes

The effect of the interval between onset of estrus and oocyte collection on in vitro fertilization (IVF) rates has been investigated. The oocytes were surgically collected 6-18 h (Group I), 19-24 h (Group II), 25-29 h (Group III) and 30-36 h (Group IV) after the beginning of estrus. Recognizable stages of nuclear maturation were identified in 54.9% of the oocytes used for IVF (5.9% at germinal vesicle, 31.4% at metaphase I, 17.6% at metaphase II); the other 45.1% were degenerate. Considerable between- and within-cow variation in oocyte morphology, oocyte maturation and IVF results was observed. The cverall fertilization and cleavage rates (to four-cell stages) were 26.5 and 6.0%, respectively. The fertilization rate increased as the interval between onset of estrus and collection increased and was optimal 30-36 h after onset. Thus, onset of estrus proved an effective means of timing oocyte collection for IVF.     

Non-nucleoside inhibitors of the hepatitis C virus NS5B polymerase: discovery and preliminary SAR of benzimidazole derivatives

Benzimidazole 5-carboxamide derivatives from a combinatorial screening library were discovered as specific inhibitors of the NS5B polymerase of the hepatitis C virus (HCV). Initial hit-to-lead activities taking advantage of high-throughput parallel synthetic techniques, identified a 1,2-disubstituted benzimidazole 5-carboxylic acid scaffold as the minimum core for biological activity. Potent analogues in this series inhibit the polymerase at low micromolar concentrations and provide an attractive "drug-like" lead structure for further optimization and the development of potential HCV therapeutics.