RESVERATROL OXIDATION IN BOTRYTIS-CINEREA CONIDIA

Observations using light microscopy showed that approximately 30% of B otrytis cinerea conidia treated with semi-lethal concentrations (i.e., 60 mu g/ml) of the grapevine phytoalexin resveratrol possessed intrac ellular brown coloration. This coloration was never observed in the ab sence of resveratrol or in conidia treated with resveratrol together w ith sulfur dioxide (antioxidant compound) or sodium diethyldithiocarba mate (inhibitor of laccase action), suggesting that discoloration resu lted from the laccase-mediated oxidation of resveratrol. Further studi es using transmission electron microscopy enabled the observation of p articular intravacuolar spherical vesicles and of granular material de posits along the tonoplast. These observations are likely to be relate d to the oxidation of resveratrol by an intracellular laccase-like sti lbene oxidase of B. cinerea.