Sequence features and expression profiles of a novel α-amylase gene from Chinese mitten crab Eriocheir sinensis

Amylase is the main digestive enzyme in crustaceans, and plays extremely important roles in metabolism, growth and development. Some studies have also shown that amylase may play a role in the immune defense system of aquatic organisms. In this study, a novel alpha-amylase gene (designated as EsAMY) was cloned and identified from Chinese mitten crab Eriocheir sinensis. The complete cDNA sequence of EsAMY contained a 5' untranslated region (UTR) of 39 bp, a 3' UTR of 70 bp with a polyA tail, and an open reading frame (ORF) of 1554 bp encoding a polypeptide of 517 amino acids with the predicted molecular weight of 56.9 kDa. The deduced amino acids sequence of EsAMY contained conserved cysteine site, active catalytic site, calcium binding site and chloride binding site, which was similar with previously identified alpha-amylase genes in other species. Quantitative real-time PCR (qPCR) analysis showed that EsAMY transcripts were detectable in all the tested tissues, with the highest mRNA expression levels in hemocytes. Both Aeromonas hydrophila and polybrominated diphenyl ether-47 (BDE-47) stimulation could significantly induce the mRNA expression of EsAMY gene in hemocytes, and its responses to A. hydrophila was more intense than those of BDE-47. These results indicate that EsAMY is a new member of the amylase family and may be involved in the immune response of Chinese mitten crab to both invasive microorganisms and external pollutant stimulation.