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 me mber, spontaneously generate defective interfering RNAs (Dls) that are known to interfere with viral accumulation and symptom development. W e show that co-infection with TBSV and Dls causes a dramatic reduction in accumulation of TBSV subgenomic RNAs and corresponding TBSV protei ns with a less dramatic reduced accumulation of the genomic RNA and th e replicase proteins. Associated with this differentially regulated su ppression was a greatly reduced expression of both the p19 protein, wh ich is responsible for severe symptoms, and the p22 protein, which is associated with cell-to-cell movement of the virus. Therefore, the res ults suggest that the protective effect of Dls may be due to selective inhibition of p19 and p22 expression in addition to reduced replicati on of genomic RNA. (C) 1995 Academic Press, Inc.