The Mode of Inhibition of TMV‐ and PVX‐Induced RNA‐Dependent RNA Polymerases by some Antiphytoviral Drugs

Six nucleobase and nucleoside analogues (6‐aminouracil [6‐AU], 6‐aminothymin [6‐AT], 6‐fluorothymin [6‐FT], 2,4‐dioxohexahydro‐1,3,5‐triazine [DHT], 9‐(2,3‐dihydroxypropyl) adenine [DHPA] and 1‐β‐D‐ribofuranosyl‐1,2,4‐triazol‐3‐carboxamid [ribavirin]) with potential antiphytoviral activity were tested in an in vitro replication system for their effect on tobacco mosaic virus (TMV)‐and potato virus X(PVX)‐induced RNA dependent RNA polymerase. 6‐AU, 6‐AT, 6‐FT, and DHPA inhibited both polymerases which may be a target of these compounds. A Putative noncompetitive mode of inhibition is discussed. Whereas ribavirin did not affect the in vitr RNA synthesis in the established systems, the uracil‐derivative DHT inhibited only the PVX‐specific enzyme.