Potato virus X‐related single‐ and double‐stranded RNAs

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.