CHARACTERIZATION OF DEFECTIVE RNAS DERIVED FROM RNA-3 OF THE FNY STRAIN OF CUCUMBER MOSAIC CUCUMOVIRUS

Two defective RNAs (designated D RNA 3 alpha and D RNA 3 beta) were found to be associated with the Fny strain of cucumber mosaic cucumovirus but not with the Sny strain after serial passages in a tobacco host, The D RNAs were derived from RNA 3 by single, in-frame deletions within the 3a open reading frame. A full-length cDNA clone from which biologically active transcripts can be produced in vitro has been constructed for D RNA 3 beta. This transcript can be replicated in tobacco plants infected with subgroup I acid II: cucumber mosaic cucmnovirus strains and with peanut stunt cucumovirus. Translation of D RNA 3 beta in vitro produced a 20-kDa peptide, which was consistent with the predicted coding capacity of the deleted 3a open reading frame. D RNA 3 beta was also associated with polyribosomes isolated from infected tobacco plants, The presence of the D RNAs had no apparent effect upon helper virus yield or symptom production.