The cDNA of cucumber mosaic virus-associated satellite RNA has in vivo biological properties.

Two isolates of cucumber mosaic virus (CMV)-associated satellite RNA, differing in their biological properties, have been reverse transcribed. One was able to induce the tomato necrotic syndrome whereas the other one attenuated fernleaf symptoms on tomato plants after co-inoculation with the helper virus. cDNAs representing partial or full-length copies have been cloned in the plasmid pAT 153 and sequenced. The two RNAs showed a very limited number of variations (2 to 5 substitutions depending on the clones and a one base deletion). Full-length cDNA copies possessed the same biological properties that characterized the parent satellite RNA. Efficiency of the cDNA depended upon its form in the inoculum (circular or linear plasmid or excised cDNA) and upon the form of the helper virus (viral RNAs or virions) with which it seemed to compete for installation and/or expression.