Intracellular location of double-stranded plant viral ribonucleic acid

Abstract

1. 1. Double-stranded viral RNA was detected in turnip yellow mosaic virusinoculated chinese cabbage leaves 3 days after inoculation, during the latent period preceding the appearance of virus. The appearance of double-stranded viral RNA before whole virus supports the view that the viral duplex RNA is the replicative form of turnip yellow mosaic virus RNA. 2. 2. Double-stranded viral RNA was not detected in the inner leaves of chinese cabbage 8 days after inoculation of the outer leaves with virus and just before systemic symptoms and virus appeared at 9–10 days. It would therefore appear that systemic infection is not preceded by a prolonged period during which turnip yellow mosaic virus duplex RNA replicates. 3. 3. In leaves systemically infected with turnip yellow mosaic virus, 32P-labelled, double-stranded viral RNA was associated with the chloroplast fraction and not with the nuclei or cell cytoplasm. 4. 4. Double-stranded tobacco mosaic virus RNA in tobacco mosaic virus inoculated tobacco leaves was present in the cytoplasmic fraction of leaf homogenates and was not found in association with chloroplasts or nuclei. Sedimentation studies suggested that the viral duplex RNA may be associated with mitochondria.