Potato virus X-related single- and double-stranded RNAs: Characterization and identification of terminal structures

Six species of 3′-coterminal poly(A) -containing RNAs of subgenomic (sg) size have been found in plants infected with potato virus X (PVX): two major (0.9 kb — the coat protein mRNA, and 2.1 kb) and four minor (1.4, 1.8, 3.0 and 3.6 kb). The 5′-end of the shortest sgRNA is located 26 nucleotides upstream of the initiating codon of the coat protein gene (812 nucleotides from the 3′-terminal poly(A) tract of the PVX genomic RNA). Double-stranded analogues have been found for most sgRNAs. The genomic-size double-stranded RNA (the replicative form) is shown to carry a poly(A)-poly(U) hybrid of a predominant length of 150–250 bp on one end, and an unpaired G residue on the other (the 3′-end of the negative chain). In contrast to this(—) the chains of double-stranded 0.9 and 2.1 kbp sgRNAs lack the unpaired G and both end in C.