Abstract

The mud crabs, Scylla spp., are economically valuable marine species, which are distributed in many coastal countries. Here, an anionic trypsin (EC 3.4.21.4) gene was isolated from Scylla paramamosain, the most common mud crab in southeast China. The full-length cDNA (GenBank No. FJ917598, denoted as SpTryp) was 881 bp, with a 780-bp open reading frame encoding a polypeptide of 259 amino acid residues. Comparison with genomic DNA revealed that it contained two introns. The deduced monomer of trypsin had a molecular weight of 28.15 kD and the isoelectric point was 4.49. Alignment analysis and structure prediction showed that SpTryp shared high homologies with other trypsin genes. The phylogenetic tree of trypsins indicated that S. paramamosain clustered with crustacean group. Real-time quantitative PCR analysis demonstrated that trypsin mRNA accumulated most abundantly in zoeal I stage, the expression level declined with little fluctuation in the latter stages of larval ontogeny, and abruptly increased again in crab I stage. The transcript of trypsin gene was proposed to correlate with the dietary condition. The characterization of trypsin gene in S. paramamosain would contribute to the understanding of trypsin gene in crustacean.

Key words: Larval development, mud crab, real-time quantitative PCR, Scylla paramamosain, trypsin.