Identification et étude de l'expression de gènes de détoxication chez les bivalves d'eau douce Unio tumidus et Corbicula fluminea : approches en laboratoire et en milieu naturel

Abstract : Environmental perturbations can induce genetic, biochemical and physiological changes in exposed organisms. To protect from oxidative stress, bivalves possess defences such as metallothionein (MT), superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathione peroxidase (Se-GPx) and pi class glutathione S-transferase (pi-GST). The aim of this study is to contribute to the understanding of the detoxification mechanisms in the freshwater bivalves Unio tumidus and Corbicula fluminea. Bivalve molluscs are appropriate sentinel species to study the quality of the aquatic environment. They are sedentary, filter-feeding species, bioaccumulating high amounts of environmental micropollutants and can easily be transferred to contaminated areas. The MT coding sequence of Corbicula fluminea and the MT, SOD and CAT coding sequences of Unio tumidus were identified by RT-PCR using degenerated primers. Then, the mRNA expression level of MT, SOD, CAT, Se-GPx and pi-GST was measured in different studies: (i) in bivalves sampled during a 1-year period in order to identify possible seasonal variations of the expression pattern, (ii) in Corbicula fluminea exposed to copper and cadmium, (iii) and in Unio tumidus transplanted in stations located along the Moselle River. Fluctuations of the mRNA level, supposed to correspond to seasonal parameter such as water temperature and reproductive statute, were noted, principally in Unio tumidus. Our results pointed out that MT, SOD, CAT, Se-GPx and GST-pi mRNA expression level could be used as early exposure biomarkers of copper and cadmium exposure in Corbicula fluminea. Variations of gene expression were observed in Unio tumidus, highlighting anthropic impacts on aquatic ecosystem no detected by chemical analysis. Biological approaches appear as essential tools to detect environmental degradations
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Aurélie Bigot. Identification et étude de l'expression de gènes de détoxication chez les bivalves d'eau douce Unio tumidus et Corbicula fluminea : approches en laboratoire et en milieu naturel. Sciences agricoles. Université Paul Verlaine - Metz, 2009. Français. ⟨NNT : 2009METZ025S⟩. ⟨tel-01752649⟩

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