Expression and trans-specific polymorphism of self-incompatibility RNases in Coffea (Rubiaceae)

Self-incompatibility (SI) is widespread in the angiosperms, but identifying the biochemical components of SI mechanisms has proven to be difficult in most lineages. Coffea (coffee; Rubiaceae) is a genus of old-world tropical understory trees in which the vast majority of diploid species utilize a mechanism of gametophytic self-incompatibility (GSI). The S-RNase GSI system was one of the first SI mechanisms to be biochemically characterized, and likely represents the ancestral Eudicot condition as evidenced by its functional characterization in both asterid (Solanaceae, Plantaginaceae) and rosid (Rosaceae) lineages. The S-RNase GSI mechanism employs the activity of class III RNase T2 proteins to terminate the growth of "self" pollen tubes. Here, we investigate the mechanism of Coffea GSI and specifically examine the potential for homology to S-RNase GSI by sequencing class III RNase T2 genes in populations of 14 African and Madagascan Coffea species and the closely related self-compatible species Psilanthus ebracteolatus. Phylogenetic analyses of these sequences aligned to a diverse sample of plant RNase T2 genes show that the Coffea genome contains at least three class III RNase T2 genes. Patterns of tissue-specific gene expression identify one of these RNase T2 genes as the putative Coffea S-RNase gene. We show that populations of SI Coffea are remarkably polymorphic for putative S-RNase alleles, and exhibit a persistent pattern of trans-specific polymorphism characteristic of all S-RNase genes previously isolated from GSI Eudicot lineages. We thus conclude that Coffea GSI is most likely homologous to the classic Eudicot S-RNase system, which was retained since the divergence of the Rubiaceae lineage from an ancient SI Eudicot ancestor, nearly 90 million years ago.United States National Science Foundation [0849186]; Society of Systematic Biologists; American Society of Plant Taxonomists; Duke University Graduate Schoolinfo:eu-repo/semantics/publishedVersio

Quantification des voies métaboliques de l'éthanol par le cytochrome P450 2E1 (rôles respectifs de l'acétaldéhyde et des radicaux libres hydroxyéthyles dans l'hépatotoxicité de l'éthanol)

L'hépatotoxicité alcoolique met en jeu les produits du métabolisme de l'éthanol par le cytochrome P450 2E1 (CYP2E1) tels que l'acétaldéhyde (oxydation bi-électronique) et les radicaux hydroxyéthyles (HER) (oxydation mono-électronique). Le CYP2E1 est le principal site d'oxydation micromal de l'éthanol (84% chez le rat, 30% chez l'Homme). L'oxydation produit de l'acétaldéhyde et des HER dans le rapport 9/1. La voie mono-électronique représente 5 à 7 %. L'incubation de guanine avec des HER produits in situ entraîne la formation d'adduits HER-guanine (HEG) (12% de la guanine). Les adduits HEG n'ont pas pu être détectés au niveau de l'Adn de patients alcooliques, d'hépatocytes en culture traotés à l'alcool, ni d'ADN incubé avec des microsomes et de l'alcool. L'étude de l'alkylation des protéines microsomales montre que les adduits HER se forment principalement avec le CYP2E1. Néanmoins, la formation d'HER-CYP2E1 n'affecte pas son activité catalytique sous des conditions normales.Hepatotoxicity of alcoholic intoxication brings into play the products resulting from the metabolism of ethanol by the cytochrome P4502E1 (CYP2E1): acetaldehyde (two-electron oxidation), and hydroxyethyl radicals (HER) (one electron-oxidation). This products can form adducts with surrounding molecules. CYP2E1 is the principal site of oxidation microsomal of ethanol (84% in the rat, only 30% in the Man ). Ethanol oxidation leads to the formation of acetaldehyde and HER in the 9/1 ratio. The contribution of the mono-electronics pathway, revealed by spin-trapping method of HER, accounts for 5 to 7 %. Incubation of guanine with HER formed in situ results in HER-guanine adducts (HEG) (12% of incubated guanine). However, HEG adducts could not be detected either in DNA from several biological materiels. Alkylation of the microsomals proteins shows that adduits HER are formed mainly with the CYP2E1. The formation of HER-CYP2E1 does not affect the catalytic activity under normal conditions.BREST-BU Médecine-Odontologie (290192102) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF