[Nucleotide and protein sequence analysis of rice dwarf virus replicase(segment S1)]

The full length cDNA of Rice Dwarf Virus (RDV) Fujian isolate genome segment S1 was cloned and full length sequence was determined. The results showed that S1 is 4422 bp in length and contains a major open reading frame which encodes a polypeptide with 1444 amino acids. The major ORF contains the RNA-dependent RNA polymerase (RDRP) consensus sequences, such as motif I (DXXXXD) motif II (SGXXXTXXXN) and motif III(GDD). In addition to the three motifs, a well-conserved region (EXXKXY) is found following motif III. Therefore, we suggest that the protein encoded by S1 encodes the virus RDRP. Homology comparison of the nucleotide and amino acid sequences of the RDV Fujian isolate with the known sequences of the Japanese isolate showed that the both isolate have 95% and 97% on nucleotide and amino acid sequences, respectively.