Function Of Wsv477 Gene And Identification Of IRES From White Spot Syndrome Virus (WSSV) And Function Analysis Of RanGTPase In Shrimp Antiviral Immunity

Diseases caused by white spot syndrome virus (WSSV) are the greatest challenge to the worldwide shrimp aquaculture. Thus the main problem for us is to prevent and inhibit the spread of the virus. It is well known that the development of diseases is caused by two aspects: virus and host. In this study, therefore, functional gene and gene regulation at translation level of WSSV, and antiviral immunity of shrimp were investigated, which would be helpful for shrimp disease control.In our study, a WSSV gene (wsv477) encoding 208 amino acids were characterized. The temporal analysis showed that the wsv477 was first transcribed at 4 h postinfection and expressed at 6 h postinfection detected by Western blot, suggesting that the wsv477 was an early gene of WSSV. As indicated by GTP-binding assay, the WSV477 protein had GTP-binding activity. During the analysis on vp28, an internal ribosome entry site (IRES) element was discovered in its leading sequence. Based on sequence orientation and deletion analyses, the IRES element was 180 nucleotides (nt) in length and orientation-dependent. Compared with that of cap-dependent initiation, the translation efficiency mediated by IRES was 98.77%.An important signal transduction factor (Ran) of shrimp was characterized in this investigation. The GTP-binding assay showed that the Ran had GTP-binding activity. It could be detected in six tissues of shrimp and located in nuclei of insect cells. As revealed by immuno-electron microscopy, Ran was only expressed in the dark bands of muscular tissues. It was revealed that Ran was up-regulated in WSSV-resistant shrimp. According to coimmunoprecipitation assays, it was found that the shrimp Ran protein was interacted with shrimp myosin and that the myosin was interacted with β-actin. These data indicated that the Ran might be involved in shrimp defense response through endocytosis. Therefore the putative passway for Ran protein in shrimp antiviral immunity might be Ran-myosin-actin-endocytosis. Compared with that in normal shrimp, dot mutations were found in Ran gene in WSSV-resistant shrimp.