Estimates of Molecular Weights of Nepovirus RNA Species by Polyacrylamide Gel Electrophoresis under Denaturing Conditions

The mol. wt. of the RNA components of twelve nepoviruses were estimated by electrophoresis at 60 °C in 2.0% polyacrylamide gels containing 8 m-urea. This method gave estimates of RNA mol. wt. that were very reproducible and those for RNA-2 are considered more accurate than values published hitherto. Most of the viruses fell into one of three clusters with RNA-2 mol. wt. of about 1.45 × 106, 1.65 × 106 and 2.0 × 106. For all the viruses, the estimates for RNA-1 (2.08 to 2.19 × 106) were considerably lower than previously published values but may not be more accurate. Three viruses had additional RNA components (RNA-3) with mol. wt. 0.4 to 0.5 × 106. The implications of these findings for the packaging of the RNA molecules and for classification of the viruses is discussed.