Studies On Rice Stripe Virus Zhejiang Isolate

Recent years, rice stripe disease has been broadly prevalent and caused great loss of rice yield in the Jiangsu and Zhejiang province, eastern China. The pathogens of rice stripe diseases from seven counties or cities in Zhejiang province were characterized by enzyme linked immunosorbent assay (ELISA), SDS-PAGE, electronic microscope, and RT-PCR techniques. The results indicated all these viral pathogens shared closely serological relationship with rice stripe virus Jiangsu isolate (RSV-Js). The viral particles displayed 3-10nm wide and 500-2000nm long filamentous morphology, which is extremely flexual and readily unfolded under the condition of low concentration. The SDS-PAGE revealed the viral particles contained one kind of nucleocapsid protein (N protein or coat protein) with estimated molecular weight of 35.5±0.5 kDa. In the meantime, RSV-specific antiserums were prepared by immunizing mouse and rabbit with purified virus particles and were used to develop a double antibodies sandwich ELISA (DAS-ELISA) method for rapid and sensitive detection of the virus. Based on the known sequence information, the nucleocapsid protein was successfully expressed in E. coli and the complete sequences of genome segment RNA1 of RSV Zhejiang isolate (RSV-Zj) were determined by RT-PCR technique. The total genome seg(?)ent RNA1 of RSV-Zj comprised 8968 nucleotides (nt) and its organization was similar to those of other RSV isolates. The RSV-Zj RNA1 also contained only one large open reading frame (ORF), which can encoded a protein, designed pc1, of 2919 amino acids (aa) with a predicted molecular mass of nearly 337 kDa. Sequence analysis showed that the genome segment of RSV-Zj shared 92-97% and 97-99% homologies with other RSV isolates at levels of nucleotide and amino acid, respectively. Multiple alignments showed the proteins encoded on RNA1 of RSV-Zj shared 30-46% homologies with their counterparts of other tenuivirus. Domain analysis Tevealed that, in addition to the bunyaviral RNA dependent RNA polymerase (RdRp) domain, the proteins encoded on RNA1 harboured an ovarian tumour (OTU) -like cysteine protease signature at its N-terminal part, suggesting that the protein should be a polyprotein of OTU-like protease family and yield viral polymerase and one or more additional proteins by autoproteolytic cleavage.