PEROXIDASE-MEDIATED FORMATION OF RESVERATROL OXIDATION-PRODUCTS DURING THE HYPERSENSITIVE-LIKE REACTION OF GRAPEVINE CELLS TO AN ELICITOR FROM TRICHODERMA-VIRIDE

Suspension cell cultures of grapevine (Vitis vinifera cv. Monastrell) treated with the elicitor Onozuka R-10 ccllulase, isolated from Trichoderma viride, showed a specific hypersensitive-like response characterized by the formation of resveratrol (3,5,4′-trihydroxystilbene) oxidation products (ROPs). Elicitor-induced formation of ROPs was partially stimulated by superoxide dismutase and only partially prevented by catalase. The inhibitor of polyphenol oxidase, L-mimosine, had no effect on the formation of ROPs, while tropolone and ascorbic acid inhibited their formation. The effect of tropolone may be due to its properties as a superoxide anion scavenger. Furthermore, tentoxin, a fungal toxin that inhibits the processing of nuclear-encoded chloroplast polyphenol oxidase also had no effect on the elicitor-mediated formation of ROPs. These results, and the previous observation that grapevine peroxidase is capable of oxidizing resveratrol-like stilbene model compounds, suggest an exclusive role for peroxidase in the elicitormediated formation of ROPs. In this context, elicitor treatment produced an increase in the level of extracellular peroxidases and the appearance of a new basic peroxidase isoenzyme, B3, which was correlated with the formation of ROPs. © 1994 Academic Press, Inc.