First report of two thioredoxin homologues in crustaceans: Molecular characterization, genomic organization and expression pattern in swimming crab Portunus trituberculatus

Previously, we had reported two homologues of the thioredoxin (Trx) super-family (PtTrx1 and PtTrx2) identified from eyestalk and haemocytes cDNA library of swimming crab Portunus trituberculatus, respectively. It was the first report of two thioredoxin homologues from the same crustacean species. Here, we focused on the molecular characterization, genomic organization and expression pattern of PtTrx1 and PtTrx2. The full-length cDNA sequences of PtTrx1 and PtTrx2 were 739 and 1300 bp, encoding 105 and 133 amino acids, respectively. They both had a conserved CGPC active site and highly similar tertiary structures, which containing four β-sheets and four α-helixes. Specifically, PtTrx2 was encoded by a nuclear gene and its cellular localization was targeted to mitochondria by an N-terminal mitochondrial pre-sequence. Sequence analysis revealed PtTrx1 and PtTrx2 were encoded by different genomic locus. As the first analyzed genomic structure of PtTrxs in crustaceans, two introns with microsatellites were found in the open reading frame region of these genes. Quantitative real-time PCR analysis revealed the mRNA expression of PtTrx1 transcripts were mainly detected in gill, while, PtTrx2 in eyestalk and gill. The temporal expression levels of PtTrxs transcripts in haemocytes showed different expression patterns after challenge with Vibrio alginolyticus, Micrococcus luteus and Pichia pastoris. These results together indicate that PtTrxs should be involved in the responses to pathogen challenge of P. trituberculatus.

► Two thioredoxin homologues were characterized from swimming crab.
► Sequence analysis revealed PtTrx1 and PtTrx2 were encoded by different genomic locus.
► First PtTrxs genomic structure analysis in crustaceans was revealed.
► PtTrx1 mRNA was mainly detected in gill, while, PtTrx2 in eyestalk and gill.
► PtTrxs mRNA showed different expression profile after three microorganisms challenge.