Ethanol triggers grape gene expression leading to anthocyanin accumulation during berry ripening

Abstract

Recent studies have shown that low doses of ethanol stimulate the maturation of some fruits. The present work showed that spraying Cabernet Sauvignon grapes, with 5% ethanol at veraison enhances the anthocyanin accumulation. Veraison is the time when the berries turn from green to purple. HPLC analysis showed a marked increase in the total concentrations of the derivatives of delphinidin, cyanidin, petunidin, peonidin and malvidin from the fourth day after the ethanol treatment until harvest. This was not linked to a difference in berry weight in comparison to controls. Two distinct expression patterns were found for anthocyanin biosynthesis genes in the treated and untreated berries. For one group, consisting of chalcone synthase, flavanone-3-hydroxylase, dihydroxyflavonol-4-reductase and leucoanthocyanidin dioxygenase, the expression was inhibited or unchanged by the ethanol treatment, whereas for UDP glucose-flavonoid 3-O-glucosyltransferase (UFGT) there was a marked increase in expression from 1 to 20 days after ethanol treatment. These results suggest that the UFGT gene is a key factor in the observed anthocyanin accumulation following ethanol treatment.