Molecular characterization of the nitric oxide synthase gene and its immunomodulation of nitric oxide production in the triangle shell mussel (Hyriopsis cumingii)

Nitric oxide synthase (NOS) is a critical enzyme that catalyzes nitric oxide biosynthesis and orchestrates various immunological responses mediated by nitric oxide (NO) in host animals. In this study, the NOS gene was identified in the triangle shell mussel (Hyriopsis cumingii) (HcNOS). HcNOS was highly conserved in the characteristic gene structures of NOS. Phylogenetic analysis suggested that HcNOS was a typical invertebrate NOS. Further gene expression analysis, NOS activity assays and nitric oxide content measurements demonstrated the inducibility of HcNOS in responses to lipopolysaccharide (LPS) challenge and during tissue transplantation. Of note, mantle grafting induced a prolonged HcNOS/NO response, suggesting that through the HcNOS/NO system, multiple immunomodulators may play decisive roles in tissue grafting in triangle shell mussels. Thus, HcNOS appears to be a crucial player in responding to both bacterial infection and tissue transplantation.