The effect of defective interfering RNAs on the accumulation of tomato bushy stunt virus proteins and implications for disease attenuation.

Tombusviruses, of which tomato bushy stunt virus (TBSV) is the type member, spontaneously generate defective interfering RNAs (DIs) that are known to interfere with viral accumulation and symptom development. We show that co-infection with TBSV and DIs causes a dramatic reduction in accumulation of TBSV subgenomic RNAs and corresponding TBSV proteins with a less dramatic reduced accumulation of the genomic RNA and the replicase proteins. Associated with this differentially regulated suppression was a greatly reduced expression of both the p19 protein, which is responsible for severe symptoms, and the p22 protein, which is associated with cell-to-cell movement of the virus. Therefore, the results suggest that the protective effect of DIs may be due to selective inhibition of p19 and p22 expression in addition to reduced replication of genomic RNA.