Heat shock proteins (HSPs) are proteins that are expressed more strongly when the cells are exposed to physiological and stressful conditions. In this study, the full-length cDNAs of heat shock proteins 40 (MjHSP40), 70 (MjHSP70) and 90 (MjHSP90) were cloned from kuruma shrimp Marsupenaeus japonicus. The open reading frames (ORFs) of the cDNA clones have lengths of 1,191, 1,959 and 2,172 bp and encode 396, 652 and 723 amino acid residues, respectively. The predicted MjHSP40 amino acid sequence contains a J domain, a glycine/phenylalanine-rich region, and a central domain containing four repeats of a CxxCxGxG motif, indicating that it is a type I HSP40 homolog. The signature sequences of the HSP70 and HSP90 gene families are conserved in the MjHSP70 and MjHSP90 amino acid sequences. The deduced amino acid sequences of MjHSP70 and MjHSP90 share high identity with previously reported shrimp HSP70s and HSP90s, respectively. The expression of MjHSP90 mRNA increased at 32°C. Additionally, the expressions of MjHSP40, MjHSP70 and MjHSP90 mRNAs increased in defense-related tissues (i.e., hemocytes and lymphoid organ) when the shrimp were challenged with white spot syndrome virus.

The mRNA encoding chymotrypsin-like serine protease (Mj-chy) from a kuruma shrimp Marsupenaeus japonicus hepatopancreas was identified as a peptidoglycan-inducible gene by 5 0 -end serial analysis of gene expression. The transcript of Mj-chy consists of a 816-nucleotide open reading frame encoding 271 amino acids, including a signal peptide of 17 amino acids and a trypsinlike serine protease domain of 219 amino acids. Like most serine proteases, Mj-chy has a catalytic triad consisting of histidine, aspartic acid and serine, and six cysteine residues forming three disulfide bridges. In a phylogenetic analysis, the trypsin-like serine protease domain clustered with invertebrate chymotrypsins and was closely related to chymotrypsin-like serine protease from Chinese shrimp Fenneropenaeus chinensis and chymotrypsin BI from Pacific white shrimp Litopenaeus vannamei. Mj-chy was detected in the hepatopancreas, stomach and intestine, and exhibited increased expression in defense-related tissues (i.e., hemocytes, lymphoid organ and hepatopancreas) after peptidoglycan stimulation.