Changes in grapevine DNA methylation and polyphenols content induced by solar ultraviolet-B radiation, water deficit and abscisic acid spray treatments.

Environment and crop management shape plant's phenotype. Argentinean high-altitude vineyards are characterized by elevated solar ultraviolet-B radiation (UVB) and water deficit (D) that enhance enological quality for red winemaking. These signals promote phenolics accumulation in leaves and berries, being the responses mediated by abscisic acid (ABA). DNA methylation is an epigenetic mechanism that regulates gene expression and may affect grapevine growth, development and acclimation, since methylation patterns are mitotically heritable. Berry skins low molecular weight polyphenols (LMWP) were characterized in field grown Vitis vinifera L. cv. Malbec plants exposed to contrasting UV-B, D, and ABA treatments during one season. The next season early fruit shoots were epigenetically (methylation-sensitive amplification polymorphism; MSAP) and biochemically (LMWP) characterized. Unstable epigenetic patterns and/or stochastic stress-induced methylation changes were observed. UV-B and D were the treatments that induced greater number of DNA methylation changes respect to Control; and UV-B promoted global hypermethylation of MSAP epiloci. Sequenced MSAP fragments associated with UV-B and ABA showed similarities with transcriptional regulators and ubiquitin ligases proteins activated by light. UV-B was associated with flavonols accumulation in berries and with hydroxycinnamic acids in the next season fruit shoots, suggesting that DNA methylation could regulate the LMWP accumulation and participate in acclimation mechanisms.