| The nucleotide sequences of RNAs 1 and 2 of the Fny strain (Subgroup 1) of cucumber mosaic virus (CMV) were determined and compared at both the nucleic acid and protein levels with the corresponding sequences of RNAs 1 and 2 of the Q strain (Subgroup II). Fny-CMV RNAs 1 and 2 consisted of 3357 nucleotides and 3050 nucleotides, respectively, and encode proteins containing 993 amino acids and 857 amino acids, respectively. There were 76% and 71% nucleotide sequence homologies, and 85% and 73% protein homologies between Fny-CMV and Q-CMV RNAs 1 and 2, respectively. RNAs 1 translation product homology was greater in both the N-terminal and the C-terminal thirds than in the central third while the converse was true for the RNAs 2 translation product homology. The tRNA-like secondary structures formed by the 3{dollar}spprime{dollar}-terminal non-coding regions of the RNAs were strikingly similar, even though the nucleotide sequence homologies between RNAs 1 and between RNAs 2 in this region were only 64% and 62% respectively. The evolutionary relationships and the divergence and retention of specific sequences among the two strains and other plant viruses are discussed.; Full-length cDNA copies of Fny-CMV RNAs 1 and 2 were cloned downstream of bacteriophage T7 promoters. In one pair of clones, transcription proceeded from an unaltered T7 promoter such that transcripts representing RNAs 1 and 2 contained an additional 17 nucleotides at their 5{dollar}spprime{dollar} termini. In a second pair of clones, the T7 promoter/cDNA junction was altered by oligonucleotide-directed mutagenesis such that resultant transcripts contained only an additional G residue at their 5{dollar}spprime{dollar} ends. In addition, a full-length cDNA copy of Fny-CMV RNA 3 was cloned downstream of an altered T7 promoter such that resultant transcripts also contained only an additional G residue at their 5{dollar}spprime{dollar} ends. Transcripts derived from all clones contained an additional C residue at their 3{dollar}spprime{dollar} ends. A modified T7 promoter that would have given transcripts having no additional 5{dollar}spprime{dollar}-terminal nucleotides was shown to be virtually inactive. In vitro translation of transcripts representing RNAs 1, 2 and 3 gave products having the same mobilities on SDS-polyacrylamide gels as translation products of the corresponding virion RNAs. Transcripts representing RNAs 1, 2 and 3 which contained an additional residue at each terminus were shown to be infectious together in Chenopodium quinoa. |
