Increasing sucrose concentrations promote phenylpropanoid biosynthesis in grapevine cell cultures.

Vitis vinifera cell suspensions are a suitable model system to study the metabolic regulation of a large range of high valuable polyphenols that are important in understanding the physiology of the plant and for nutraceutical, pharmaceutical and medical purposes. Increasing sucrose concentrations were found to promote cell growth and phenylpropanoid biosynthesis in grape cell cultures obtained from cv. Barbera immature berries. This led to an intracellular accumulation and/or release into the media of specific polyphenol families (in particular, anthocyanins, catechins and stilbenes). This effect was partially correlated with a sucrose modulation of the transcription of some key biosynthetic enzymes, such as phenylalanine ammonia lyase, chalcone synthase, chalcone-flavanone isomerase and stilbene synthase. Total catechin amounts, both endogenous and released in the media, were increased in proportion to the sugar concentration, as were anthocyanin and stilbene production. Sugar treatment notably improved the endogenous accumulation and release in the culture media of resveratroloside, a resveratrol mono-glycoside, which is the most abundant stilbene found in grape cultures, especially in cv. Barbera. We hypothesize that high sucrose concentrations (exceeding those naturally-occurring in ripe berries) could play a role in plant defense via the induction of secondary metabolites, such as stilbenes.

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