Analysis of phenolic biosynthesis in Vitis vinifera L. cell suspension cultures to visible light, UV light, and methyl jasmonate treatments

Cell cultures of grape (cv. Gamay Freaux) produce both anthocyanin pigments as well as the stilbenoids resveratrol and piceid. These cells can be induced to alter their production of phenolics by light, both visible and UVC, and by treatments with the stress hormone methyl jasmonate. Visible light and methyl jasmonate treatments induced the accumulation of anthocyanins. Neither the activity of phenylalanine-ammonia lyase (PAL) nor that of dihydroflavonol reductaes (DFR) changed under the treatments in a way that explained the difference in formation of products. Methyl jasmonate treatments also induced the accumulation of piceid and resveratrol. The activity of the enzyme that glucosylates resveratrol was increased by methyl jasmonate treatments. This enzyme had maximal activity at pH 8.5--9, its Km for UDP-glucose was 1.2 mM, and its Km for resveratrol was 0.06 mM. This enzyme's activity was not significantly affected by any of the light treatments. Based on the responses to light, I hypothesize that there are at least three distinct phenolic glucosyltransferases present in the cell cultures: one that utilizes anthocyanidins as the phenolic substrate and was induced by growth of the cells in light compared to dark grown cells, one that utilized quercetin and was induced only by UVC irradiation, and the enzyme capable of glucosylating resveratrol, the activity of which was not greatly affected by light treatments.