Polypeptides Induced by Tobacco Rattle Virus during Multiplication in Tobacco Protoplasts

Tobacco protoplasts were irradiated with UV light, inoculated with tobacco rattle virus (TRV), and then cultured in media containing 35S-methionine. Polypeptides induced by TRV infection were detected by PAGE of protein extracts. Three 35S-labeled polypeptides (apparent molecular weights 187,000, 142,000, and 31,000) occurred in extracts of virus-infected protoplasts but not in extracts of buffer-inoculated protoplasts. The 31,000 mol. wt. polypeptides co-migrated with TRV coat protein in polyacrylamide gels and was not detected when inocula contained only the longer particle of TRV. The 187,000 and 142,000 mol. wt. polypeptides migrated in positions very close to products of in vitro translation of TRV RNA-1. Experiments in which 35S-methionine was supplied at different times during multiplication suggested that the bulk of translation of RNA-1 occurred sooner after inoculation than did that of RNA-2.