A multidisciplinary approach to understand the control of flavonol synthesis in grape berry

Flavonols are flavonoids found in most higher plants, usually in glycosidic forms. They are products of the flavonoid biosynthetic pathway, which also give rise to anthocyanins and to condensed tannins in grapes. In grapevine, they are predominantly synthesized in inflorescence and berry skin, while no detectable levels are found in pulp or seeds (Downey et al., 2003). They act as UV-protectants and as anthocyanin co-pigments in flowers and fruits. For this reason they play a role in defence and pollinators attraction and in conferring stability to the colour of red wines. Although the general flavonol pathway has been genetically and biochemically elucidated in many plant species and most recently also in grapevine (Matus et al., 2009), (Czemmel et al., 2009), its regulation still remains not completely characterized. A population from the cross Syrah x Pinot Noir, segregating for the flavonol content, is being studied to identify the genetic determinants of flavonol accumulation in the berry cells by a biochemical and transcriptional characterization. Individuals of the progeny showing high- and low- flavonol content were selected and characterized at different stages of berry development by a microarray approach. Among the differentially expressed identified genes, we focused our attention on a transcription factor not yet characterized in grapevine. To prove its involvement in the control of flavonoid pathway we identified its targets by a promoter assay approach and we analyzed the phenotype of transgenic tobacco lines overexpressing this gene. Preliminary results will be presented. References Downey et al. .2003. Synthesis of flavonols and expression of flavonol synthase genes in the developing grape berries of Shiraz and Chardonnay (Vitis vinifera L.). Aust J Grape and Wine Res, 9: 110-121 Matus et al. (2009). Post-veraison sunlight exposure induces MYB-mediated transcriptional regulation of anthocyanin and flavonol synthesis in berry skins of Vitis vinifera. J Exp Bot;60(3):853-67 Czemmel et al. (2009). The grapevine R2R3-MYB transcription factor VvMYBF1 regulates flavonol synthesis in developing grape berries. Plant Physiol, 151:1513-30.