COAT PROTEIN OF CUCUMBER NECROSIS VIRUS IS NOT REQUIRED FOR EFFICIENTGENERATION OR ACCUMULATION OF DEFECTIVE INTERFERING RNAS

It is generally assumed that defective interfering (DI) forms of virus es are encapsidated in structural proteins encoded by the helper virus . Virion RNA extracts from cucumber necrosis virus (CNV) infections sh owing high levels of cellular DI RNAs contain barely detectable levels of DI RNAs, suggesting that DI RNAs are encapsidated very inefficient ly. In addition, accumulation of CNV DI RNAs occurs at equal efficienc y in coinoculated plants using either synthetic wild-type CNV genomic RNA as helper or a mutant of CNV which lacks the coat protein-coding s equence. Together this shows that the CNV coat protein is not required for efficient accumulation of CNV DI RNA in plants. Factors that coul d account for the high level of CNV DI RNAs in plants are discussed.