Transgenic tobacco plants over-expressing a salicylate- and pathogen-inducible glucosyltransferase (TOGT) acting on various phenylpropanoids show enhanced resistance against infection with potato virus Y (PVY). The transgenic plants are characterized by a several-fold increased glucosyltransferase activity in leaves as well as in roots. Under non-infectious conditions profiles of phenylpropanoids in leaves of transgenic lines were similar to that of controls. Feeding experiments with leaf-discs demonstrated a higher capacity for glucosylation of the coumarin scopoletin. After inoculation with PVY the transgenic lines showed similar formation of necrotic leaf lesions but significantly decreased levels of virus coat-protein when compared with control plants. Thus, our results imply that the activity of TOGT and the subsequent accumulation of glucosylated coumarins represent an important step in the cascade of events resulting in confinement of viral pathogens.