Transcriptional regulation of selenium-dependent glutathione peroxidase from Venerupis philippinarum in response to pathogen and contaminants challenge

Glutathione peroxidases (GPx) are key enzymes in the antioxidant systems of living organisms by catalyzing the reduction of peroxides to non-reactive products. In the present study, the full-length cDNA encoding a selenium-dependent GPx was identified from Venerupis philippinarum (designated as VpSe-GPx), and the spatial and temporal expression patterns post-Vibrio anguillarum, heavy metals and benzo[a]pyrene (B[a]P) challenge were also investigated. VpSe-GPx possessed all the conserved features critical for the fundamental structure and function of glutathione peroxidase. The VpSe-GPx mRNA was found to be most abundantly expressed in hepatopancreas. Vibrio challenge could significantly up-regulate the mRNA expression of VpSe-GPx, and the highest expression level was detected at 24 h post-infection with 6.5-fold increase compared with that in the control group. For heavy metals exposure, the expression of VpSe-GPx was significantly induced by 20, 40 μg L^-1 Cd and 10, 20 μg L^-1 Cu but depressed by 10 μg L^-1 Cd and 40 μg L^-1 Cu. With regards to B[a]P exposure, the expression of VpSe-GPx mRNA was significantly induced at 48 and 96 h post challenge. All these results suggested that VpSe-GPx was potentially involved in mediating the immune response and antioxidant defense in V. Philippinarum.