Molecular characterization and metal induced gene expression of the novel glutathione peroxidase 7 from the chordate invertebrate Ciona robusta

In the present study, we describe the identified and characterized the gene and the transcript of a novel glutathione peroxidase-7 (GPx7) from the solitary ascidian Ciona robusta, an invertebrate chordate widely distributed in temperate shallow seawater. The putative nucleotide and amino acid sequences were compared with those of GPx7 from other metazoans and phylogenetic analysis suggests the presence of a high evolutionary pressure in the contest of neutral evolution. The mRNA of CrGPx7 is located in hemocytes and ovarian follicular cells, as revealed by in situ hybridization. The time course of CrGPx7 mRNA levels in the presence of Cd, Cu and Zn, showed upregulation in the final stages of the experiments, suggesting a role of GPx7 in late protection from oxidative stress. Our in silico analyses of the crgpx7 promoter region revealed putative consensus sequences similar to mammalian metal-responsive elements (MRE) and xenobiotic-responsive elements (XRE), suggesting that the transcription of these genes directly depends on metals. Cell-free extract from C. robusta tissues show the presence of selenium-independent GPx activity that is inhibited by the presence of metals.