Identification of genes involved in the response of haemocytes of Penaeus japonicus by suppression subtractive hybridization (SSH) following microbial challenge.

Penaeus japonicus were injected with a heat-killed microorganism suspension and 291 randomly selected cDNA fragments generated by suppression subtractive hybridization (SSH) were sequenced. A total of 71 cDNA clones corresponding to 25 genes were found to have enhanced expression, of which eight are found for the first time in shrimp. The most abundant gene in the subtractive library was Kunitz-type protease inhibitor, clearly indicating this protease inhibitor in the response. A number of genes encoding signaling molecules, such as Ras-related nuclear protein (Ran), growth factor receptor bound protein (Grb), TGF-beta receptor interacting protein, integrin binding protein and interferon receptor bound protein were found for the first time in the shrimp, and they may be involved in the regulation of the host defense against the injected microbes. Furthermore, cDNAs of chaperonin, proteasome, antioxidant as well as genes associated with actin reorganization, which may be necessary for phagocytosis and encapsulation, were also expressed at a higher level after the challenge. These results may facilitate the understanding of shrimp immune responses.