Abstract
Cucumber mosaic virus (CMV) strain Y from Japan was propagated in Xanthi tobacco. Virus isolated from four successive passages was analysed for its constituent RNAs by polyacrylamide gel electrophoresis (PAGE) under semi-denaturing and fully denaturing conditions. This revealed the initial presence of the 368-nucleotide satellite RNA Y-CARNA 5 (for Y-CMV-associated RNA 5) and the subsequent emergence of a small RNA in the 335-nucleotide size range, which we termed Yn-CARNA 5. The appearance of the smaller Yn-CARNA 5 correlated positively with the increasing tomato necrosis-inducing properties of tissue extracts from the later tobacco passages. After sucrose gradient ultracentrifugation of total CMV-Y RNA, the fraction containing Y-CARNA 5 and Yn-CARNA 5 was subjected to PAGE under semi-denaturing conditions, which provided highly purified gel-eluted preparations of the two CARNA 5 species. When tested for their tomato necrosis-inducing capability in the presence of helper virus genomic RNAs, Y-CARNA 5 was shown to be incapable of eliciting lethal necrosis in Rutgers tomato whereas Yn-CARNA 5 was highly necrogenic.