Four Crustins Are Involved In Antibacterial Response In Marsupenaeus Japonicus

Crustins are a family of cationic, cysteine-rich antimicrobial peptides with a whey acidic protein (WAP) domain in the C-terminal. There are three groups of crustins (Cru Ⅰ, Ⅱ and Ⅲ) identified in crustaceans. They have diverse functions in antimicrobial immune responses. In this study, we identified four crustins in kuruma shrimp Marsupenaeus japonicus, and named them MjCrusl,2,3and4. The open reading frames of four crustins are294bp,375bp,333bp and342bp, encoding four proteins contain97,124,110and113residues respectively. All the four crustins belong to the crustin I. Tissue distribution displays that MjCrusl,2,3have higher expression in hemocytes and gill, while MjCrus4is distributes all tissues detected. The MjCrus1to4show different expression patterns after Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Vibrio anguillarum) and white spot syndrome virus (WSSV) challenge. MjCrusl,3,4were all up-regulated significantly after bacterial chanllenge, while MjCrus2is induced by virus challenge. The four crustins were all recombinant expressed in Escherichia coli, and the purified proteins show little antimicrobial activities. The inhibition activity against bacteria secreted proteases was analyzed. MjCnxs1,2and3show different inhibiting ability to bacteria secreted proteases. RNA interference is performed for function analysis. After knockdown of MjCrus1, the bacterial scavenging ability to V. anguillarumwas impaired. These results suggested that the crustins play an important role in shrimp innate immunity, against different pathogens invasion.