Second thioredoxin from the mud crab Scylla paramamosain: cDNA cloning and mRNA expression analysis

Abstract

Thioredoxin, is a kind of ubiquitous small proteins with a redox active disulfide bridge, and has been found to play important regulatory roles in some vital biochemical reactions of metabolism. In the present study, a hepatopancreas cDNA library from the mud crab Scylla paramamosain Estampador, 1949 was constructed using the SMART technique. A complete cDNA sequence that showing high identity with the conserved sequence of the second thioredoxin gene (Trx2) was isolated from the cDNA library and subjected to further investigation. The full-length Trx2 of Scylla paramamosain consisted of 1336 bp and contained a complete open reading frame of 396 bp. The gene encoded a polypeptide of 131 amino acids and constituted a predicted molecular mass of 14.45 kDa and a theoretical isoelectric point of 8.08. Quantitative real-time PCR (qRT-PCR) analyses revealed that Trx2 expression was ubiquitous in various organs of Scylla paramamosain, including the gill, muscle, heart, haemocyte, testis, and hepatopancreas. The Trx2 expression level was the highest in the hepatopancreas and gill, and the lowest in the haemocyte. The result of the challenge experiment showed that Trx2 expression was up-regulated significantly after Vibrio parahaemolyticus challenge and reached the highest level at 6 h. This study provides useful information regarding the structure and functions of Trx2, suggesting that it may be a potential biomarker gene for evaluation of environmental stress in marine species.