Analysis of ESTs and expression of two peroxiredoxins in the thermally stressed Antarctic bivalve Laternula elliptica

A total of 2592 expressed sequenced tags (ESTs) were generated from a cDNA library of the Antarctic bivalve Laternula elliptica, which is an important species in Antarctic coastal ecosystems. A cluster of 1789 unique sequences was revealed, which consisted of 273 contigs and 1076 singletons. Based on BLAST searches, we identified 508 genes, 56 of which were functionally related to immunity and stress responses, including the peroxiredoxins (Prxs). Prxs comprise an antioxidant protein family with conserved catalytic redox-active cysteine residues. We characterised two full-length cDNAs of the genes that encode peroxiredoxin V (lePrxV) and peroxiredoxin VI (lePrxVI) in L. elliptica. The lePrxV cDNA contains a 480-bp open reading frame (ORF), which encodes 159 amino acids, including two conserved cysteine residues that are characteristic of the atypical 2-Cys subgroup of the Prx family. LePrxVI contains a 702-bp ORF, which encodes 233 amino acids, including one conserved cysteine residue that is characteristic of the 1-Cys subgroup of the Prx family. RT-PCR analysis revealed the presence of lePrxV and lePrxVI transcripts in all the examined tissues. In addition, real-time PCR analysis indicated significant increases in the levels of lePrxV and lePrxVI transcripts were induced by thermal stress. These results suggest that lePrxV and lePrxVI play protective roles against oxidative stress caused by thermal exposure.