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Resveratrol Oxidation in Botrytis cinerea Conidia

First, fourth, and fifth authors: Laboratoire des Sciences de la Vigne, Institut Jules Guyot, Université de Bourgogne, BP 138, 21004 Dijon Cedex, France; second author: Biology Department, College of Sciences, Shiraz University, Shiraz, Iran; and third author: Laboratoire d'oenologie, UFR Sciences Exactes et Naturelles, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2, France

Observations using light microscopy showed that approximately 30% of Botrytis cinerea conidia treated with semi-lethal concentrations (i.e., 60 μg/ml) of the grapevine phytoalexin resveratrol possessed intracellular brown coloration. This coloration was never observed in the absence of resveratrol or in conidia treated with resveratrol together with sulfur dioxide (antioxidant compound) or sodium diethyldithiocarbamate (inhibitor of laccase action), suggesting that discoloration resulted from the laccase-mediated oxidation of resveratrol. Further studies using transmission electron microscopy enabled the observation of particular intravacuolar spherical vesicles and of granular material deposits along the tonoplast. These observations are likely to be related to the oxidation of resveratrol by an intracellular laccase-like stilbene oxidase of B. cinerea.