Date of this Version
Gel-separated RNAs of the wild-type (WT), Lab 1 and Lab 2 isolates of soil-borne wheat mosaic virus (SBWMV) were transferred to nitrocellulose filters and hybridized with specific cDNA. RNA I, but not RNA II, from all three SBWMV isolates hybridized to cDNA copied from SBWMV WT RNA I. RNA II from all three SBWMV isolates hybridized to cDNA copied from SBWMV WT RNA II, confirming the hypothesis that the Lab 1 and Lab 2 isolates arose by deletion of part of RNA II of WT virions. RNA I1 from SBWMV WT (0∙5L RNA) or from SBWMV Lab 1 (0.35L RNA) did not bind to oligo(dT)-ceUulose in high-salt buffer, or stimulate cDNA synthesis when primed with oligo(dT), suggesting that it has no 3'-poly(A) or oligo(A) sequences. No genome-linked protein was detected at the 5' ends of either RNA II by iodination, nor did the cap analogue 7-methylguanosine phosphate have an effect on their translation in vitro, indicating no cap structure at their 5' ends. RNA II was 5' endlabelled with [3-'P]ATP and T4 polynucleotide kinase after dephosphorylation with bacterial alkaline phosphatase, but all four bases were labelled, indicating heterogeneity at the 5" end.