CHARACTERIZATION AND EXPRESSION OF CAFFEOYL-COENZYME-A 3-O-METHYLTRANSFERASE PROPOSED FOR THE INDUCED RESISTANCE RESPONSE OF VITIS-VINIFERAL

Cell-suspension cultures of Vitis vinifera L. cv Pinot Noir accumulate d resveratrol upon fungal elicitation, and the activity of S-adenosyl- L-methionine:trans-caffeoyl-coenzyme A 3-O-methyltransferase (CCoAOMT) , yielding feruloyl-CoA, increased to a transient maximum at 12 to 15 h. CCoAOMT cDNA was cloned from the elicited cells and was shown to en code a polypeptide highly homologous to CCoAOMTs from cells of Petrose linum species or Zinnia species. The expression of the cDNA in Escheri chia coli revealed that grapevine CCoAOMT methylates both caffeoyl- an d 5-hydroxyferuloyl-coenzyme A and is probably involved in phenolic es terification and lignification. Commercial plant activators induce the disease-resistance response of test plants and are considered to mimi c the action of salicylic acid. Among these chemicals, 2,6-dichloroiso nicotinic acid and benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methy l ester provoke systemic acquired resistance (SAR) and were also shown to induce the expression of class III chitinase in grapevine. The SAR response is classified by an unchanged phenotype of tissues, but the mechanistic basis is unknown. Treatment of the cultured V. vinifera ce lls with either fungal elicitor or low concentrations of salicylic aci d and 2,6-dichloroisonicotinic acid, respectively, raised the CCoAOMT or stilbene synthase transcript abundance, suggesting that grapevine i s capable of the SAR response, whereas benzo(1,2,3)-thiadiazole-7-carb othioic acid S-methyl ester was ineffective. The data imply for the fi rst time (to our knowledge) that the expression of phenylpropanoid gen es in grapevine is induced by SAR activators without phenotypic conseq uences and suggest a role for CCoAOMT and stilbene synthase in the dis ease-resistance response leading beyond the level of pathogenesis-rela ted proteins as markers of the SAR.