NUCLEOTIDE-SEQUENCE OF BOTH GENOMIC RNAS OF A NORTH-AMERICAN TOBACCO RATTLE VIRUS ISOLATE

The complete sequence of a North American tobacco rattle virus (TRV) i solate, 'Oregon yellow' (ORY), was determined from cDNA and RT-PCR clo nes derived from the two genomic RNAs of this isolate. The RNA-1 is 67 90 bases and RNA-2 is 3261 bases. The sequence of TRV-ORY RNA-1 was si milar to RNA-1 of TRV isolate SYM, and differs in 48 nucleotides. TRV- ORY RNA-1 was one base shorter than -SYM, and had 47 base substitution s resulting in 12 amino acid substitutions of which 4 were conservativ e. The RNA-2 of TRV-ORY was distinct from RNA-2 of other characterized TRV isolates and contained three open reading frames (ORFs) that coul d potentially code for proteins of MW 22.4 kDa, 37.6 kDa and 17.9 kDa. Based on the homology of the predicted amino acid sequence with those of other tobraviruses, ORF1 of RNA-2 encodes the coat protein (CP). T he protein sequence of ORF2 had regions of limited similarity with tho se of ORF2 of two other TRV isolates and pea early browning tobravirus . The ORF3 was unique to TRV-ORY. Phylogenetic analysis of tubravirus CPs indicated that TRV-ORY was most closely related to pepper ringspot tobravirus and TRV-TCM. The relationship of tobravirus CPs to other r od-shaped tubular plant viruses is also discussed.