Effect of 2-Thiouracil on RNA and Protein Synthesis in Synchronous and Asynchronous Infections of Tobacco Mosaic Virus

Examination of the effect of 2-thiouracil on tobacco mosaic virus (TMV) RNA and protein synthesis in synchronous and asynchronous systems of replication in tobacco leaves demonstrated that 2-thiouracil does not prevent synthesis of TMV RNA, as suggested by previous studies, but inhibits some earlier function. When added at different times after mechanical inoculation, 1 mM 2-thiouracil partially inhibited both viral RNA and protein synthesis, with greater inhibition when treatment began nearer the time of inoculation. In leaves systemically inoculated with TMV using a differential temperature inoculation procedure to synchronize the infection, 1 mM 2-thiouracil inhibited viral protein and RNA synthesis totally when treatment began within the first 4 h after initiation of replication, but not at all when treatment began at 12 h or later, even though earlier reports had shown that most RNA and protein synthesis occurred after 12 h.