Molecular characterization and expression analysis of a novel dual-CRD C-type lectin in kuruma shrimp(Marsupenaeus japonicus)
C-type lectins are among the most significant pattern recognition receptors(PRRs) found in invertebrate. They are a class of carbohydrate-binding proteins that can recognize specific sugar moieties on the surface of pathogens. In the present study, a novel C-type lecitn(termed Mj Lectin) from kuruma shrimp Marsupenaeus japonicus was identified. The full-length c DNA of Mj Lectin was 1 245 bp with a 1 011 bp open reading frame(ORF) that encoded a polypeptide of 336 amino acid residues. Mj Lectin consisted of two tandemly arrayed carbohydrate-recognition domains(CRDs), unlike other reported M. japonicus C-type lectins with only one CRD. It showed a high similarity to other shrimp dual-CRD lectins. Among the Ca2+-binding Site 2, the tripeptide motif dictating the carbohydrate binding specificity was exhibited as a rare mutant LPN(Leu134-Pro135-Asn136) in CRD1 and a traditional EPN(Glu299-Pro300-Asn301) in CRD2, respectively. Mj Lectin showed a specific expression pattern in both tissue and cellular levels, for its m RNA transcript was mainly expressed in the F-cells of the hepatopancreas. After white spot syndrome virus(WSSV) challenge(3.6×108 virions/μL), the expression of Mj Lectin in the hepatopancreas was up-regulated significantly at 48 h(P<0.01) compared with the control group. These results suggested that Mj Lectin might be involved in the innate immune defense against WSSV infection.