NUCLEOTIDE-SEQUENCE AND GENOME CHARACTERIZATION OF RICE YELLOW MOTTLEVIRUS-RNA

The genome of rice yellow mottle virus (RYMV) is a single-stranded pos itive-sense RNA that is not polyadenylated, and has an M(r) of 1.4 x 1 0(6). We present here the 4550 nucleotide (nt) sequence of RYMV RNA, a nd its predicted genomic organization. The RYMV genomic RNA contains f our open reading frames (ORFs). The first (nt 80 to 553) encodes a pro tein containing 157 amino acids with a predicted M(r) of 17.8K. No fun ction has yet been attributed to this product. ORF2 (nt 608 to 3607) e ncodes a polyprotein of 999 amino acids, with a predicted M, of 110.7K . The first 134 amino acids of ORF2 are predicted to be the genome-lin ked protein, VPg, followed by the viral protease, the helicase and the RNA-dependent RNA polymerase. ORF3 is within the boundaries of ORF2 a nd is predicted to encode a polypeptide with 126 amino acids and an M( r) of 13.7K. No function has yet been attributed to this protein. ORF4 (nt 3447 to 4166), which overlaps the 3' terminus of ORF2, encodes a 26K protein. This polypeptide has been identified as the RYMV coat pro tein. The data presented here confirm that RYMV belongs to the sobemov irus group and thus is a member of the picorna-like family of plant vi ruses.