Changes of Profiles of Genes Involved in the Synthesis of Phenolic Compounds during Grapevine Fruit Ripening: the Role of Light

Flavonoids and stilbenes are the most important classes of polyphenolics found in grapes and wine. They play crucial roles in both plant metabolism, acting as defence compounds against biotic and abiotic stresses and, indirectly, in the wine sensorial and nutraceutical quality. Their production is controlled by internal (physiological and developmental) stimuli as well as by environmental stimuli. Therefore, factors affecting qualitative and quantitative changes in the berry interact in a complex way. This work is part of a larger project aimed at considering the effects of the environment on plant metabolism and its consequences on product quality. Gene expression changes were investigated in two red-skinned grapevine cultivars ('Carmenere' and 'Cannonau') subjected to a modification of the radiative microclimate of the grapes during berry development. Light shielding was achieved by means of Tetra Pak (TM) boxes designed following the agrometeorological specifications in order not to alter the other physical parameters (temperature and gas exchanges). Gene expression profiles for the two cultivars were compared to those of the controls grown under natural-light conditions. A preliminary analysis was performed on some of the key structural and regulatory genes of the phenylpropanoid pathway using real-time PCR. Differences in gene expression within and between cultivars are also discussed.