- Volume 73, Issue 9, 1992

RNA-2 of carnation ringspot virus (CRSV), the type member of the dianthovirus group, has been cDNA cloned and sequenced. CRSV RNA-2 is 1394 nucleotides in length and contains a single open reading frame encoding a 304 amino acid polypeptide of 33.8K. Amino acid sequence alignment of this polypeptide with the cell-to-cell movement proteins encoded by RNA-2 of red clover necrotic mosaic virus (RCNMV) Australian (Aus) and Czechoslovakian (TpM-34) isolates indicates 59.6% and 55.7% sequence identity, respectively. The N-terminal 230 amino acids are more highly conserved, with 64.3% and 62.6% sequence identity, respectively. The cell-to-cell movement proteins of the two RCNMV isolates are themselves 82.5% and 91.7% identical when the amino-terminal 230 amino acids are compared. Structural prediction comparison of the RCNMV-Aus, RCNMV-TpM-34 and tobacco mosaic virus cell-to-cell movement proteins to the putative CRSV RNA-2-encoded movement protein suggests that even though no primary amino acid sequence similarity exists, the movement protein polypeptides are possibly similar in structure and function.

The nucleotide sequences of the RNA-2s of two strains of sweet clover necrotic mosaic virus (SCNMV-38 and -59) have been determined. The RNA-2s of SCNMV-38 and -59 consist of 1446 and 1449 nucleotides, respectively, and both contain one major open reading frame (ORF) which potentially can encode polypeptides of 326 amino acid residues (about 36.5K), designated SC38P2 and SC59P2, respectively. The nucleotide sequences of SCNMV-38 and -59 RNA-2s show 93.2% similarity, and the amino acid sequences of SC38P2 and SC59P2 are 91.7% identical, although the identical nucleotides and amino acids are not distributed uniformly in RNA-2 and the encoded proteins. Two highly conserved regions (from positions 23 to 221 and 297 to 326) and a relatively divergent region (from positions 222 to 296) are found in the P2 proteins of these strains. A similar pattern is apparent on comparison of the nucleotide and deduced amino acid sequences of RNA-2 of these SCNMV strains with those of the Australian and Czechoslovakian isolates of red clover necrotic mosaic virus.