SEQUENCE AND STRUCTURE OF DEFECTIVE INTERFERING RNAS ASSOCIATED WITH CUCUMBER NECROSIS VIRUS-INFECTIONS

The presence of symptom-attenuating defective interfering (DI) RNAs in a laboratory culture of cucumber necrosis tombusvirus (CNV) was confi rmed. Sequencing of cDNA clones of these DI RNAs revealed that CNV DI RNAs retained sequences from the CNV 5'-untranslated and 3'-terminal r egions as well as a portion of the coding region for the 92K protein. Similar sequence arrangements were also observed in symptom-attenuatin g DI RNAs generated de novo from synthetic wild-type CNV transcripts. A comparison of the sequences and biological activities of these CNV D I RNAs is presented. In co-infections of synthetic wild-type CNV and C NV DI RNAs, prominent RNA species of a higher M(r) than the DI RNA use d in the co-infection were found. The possible nature of these RNA spe cies is discussed.