Characterization of double-stranded ribonucleic acid in tobacco leaves.

Double-stranded RNA was isolated from tobacco leaves and characterized in terms of base composition, density, and nuclease resistance. Although its role in the plant's physiology is not clear, evidence was adduced that it is the product of the RNA-dependent RNA polymerase previously shown to occur in this and other plants. The fact that twice as much fully than partially double-stranded RNA appears to be made favors a regulatory role for the double-stranded RNA rather than a transcriptional intermediate role.