Complete nucleotide sequence of RNA 3 from cucumber mosaic virus (CMV) strain O: comparative study of nucleotide sequences and amino acid sequences among CMV strains O, Q, D and Y

The complete nucleotide sequence (2217 residues) of RNA 3 of cucumber mosaic virus strain O (CMV-O) was determined. Two open reading frames were identified, encoding a 3A protein (279 amino acid residues) in the Y-proximal region and a coat protein (218 amino acid residues). The amino acid sequence of the coat protein C terminus was determined directly from purified protein, and confirmed the presence of the coat protein open reading frame in CMV-O RNA 3. Comparison of nucleotide sequences and amino acid sequences ofCMV strains O, Q, D and Y indicated the close relationship between these strains. A tRNA-like structure could be adopted by the 3' non-coding region, and this resembled a similar structure in CMV-Q in spite of nucleotide substitutions or deletions. Cucumber mosaic virus (CMV), a multicomponent virus of the cucumovirus group (Kaper & Waterworth, 1981), has a single-stranded plus-sense RNA genome consisting of three RNA species which are designated RNA 1, 2 and 3 in order of decreasing Mr. In addition, there is a fourth RNA, RNA 4, which is subgenomic toRNA 3 and is reported to serve as a monocistronic messenger for in vitro synthesis of the coat protein (Schwinghamer & Symons, 1977). RNA