Electron microscopy of double-stranded RNA induced by turnip yellow mosaic virus and tobacco mosaic virus

Summary

Double-stranded RNA isolated by phenol extraction from turnip yellow mosaic virus-infected chinese cabbage leaves and from tobacco mosaic virus-9nfected tobacco leaves was rotary shadowed and examined in the electron microscope. The TYMV and TMV molecules are similar in appearance, having uniform width and a linear configuration similar to that previously described for double-stranded RNA and double-stranded DNA molecules. More than 99.5% of the molecules of each virus fall within the range 0.1 μ to 2.2 μ, there being a predominance of smaller molecules in both cases (TYMV mean=0.24 μ, TMV mean 0.42 μ). The mode of the larger molecules of TYMV ≃ 1.92 μ and of TMV ≃ 1.8 μ. These values are close to the expected lengths of whole molecules, calculated from biophysical data. Apparently branched molecules were observed in preparations of both TYMV and TMV double-stranded RNA. It was found, however, that the number of such branches per unit length of RNA decreases with a decrease in density of the RNA in the fields examined.