Infectious RNA transcripts from cloned cDNAs of cucumber mosaic viral satellites.

Complete cDNA copies of two variants of CARNA 5, the satellite of cucumber mosaic virus, have been cloned in the transcription vector pPM1. These two naturally-occurring CARNA 5s are capable and incapable, respectively, of inducing a lethal necrotic disease of tomato upon coinoculation with the genomic RNAs 1, 2, and 3 of cucumber mosaic virus. Uncapped transcripts synthesized in vitro from the two linearized, recombinant plasmids are infectious and each induces the appropriate symptomatology upon coinfection with cucumber mosaic viral RNAs on tomato plants. Progeny CARNA 5s isolated from such infected plants correspond to their natural CARNA 5 counterparts.