A striking change in symptoms on cucumber mosaic virus-infected tobacco plants induced by a satellite RNA.

The small RNA from cucumber mosaic virus (CMV) we had formerly referred to as RNA 5 was shown to have a satellite nature similar to CARNA 5 (Kaper and Tousignant, 1977, Virology 80, 186-195) and Sat-RNA (Mossop and Francki, 1978, Virology 86, 562-566). Our satellite RNA has a great deal in common with CARNA 5 and Sat-RNA in many respects, except that its replication causes a striking change in symptoms on tobacco and on some species of Nicotiana infected with CMV. Large amounts of satellite RNA were found in RNAs of naturally occurring CMV isolates which induced a unique brilliant yellow symptom on tobacco. When purified satellite RNA was inoculated onto tobacco after being mixed with CMV isolates which contained no satellite RNA and which normally produced ordinary green mosaic symptoms, all of the infected tobacco developed the brilliant yellow symptom along with some symptom attenuation. Virions isolated from those plants contained much satellite RNA. CMV could be freed from satellite RNA by local lesion transfer and selection. Satellite RNA had substantial stability in vivo and in vitro. It caused the severe necrotic symptom or ultimate death of tomato like CARNA 5 but unlike Sat-RNA.