How the whole plant acclimatizes to water scarcity and how short- and long-distance chemical and hydraulic signals intervene are reviewed. Chemical compounds synthesized in drying roots are shown to act as long-distance signals inducing leaf stomatal closure and/or restricting leaf growth. This explains why some plants endure soil drying without significant changes in shoot water status. The control of plant water potential by stomatal aperture via feed-forward mechanisms is associated with 'isohydric' behaviour in contrast to 'anysohydric' behaviour in which lower plant water potentials are attained. This review discusses differences in this respect between grapevines varieties and experimental conditions. Mild water deficits also exert direct and/or indirect (via the light environment around grape clusters) effects on berry development and composition; a higher content of skin-based constituents (e.g. tannins and anthocyanins) has generally being reported. Regulation under water deficit of genes and proteins of the various metabolic pathways responsible for berry composition and therefore wine quality are reviewed.

ORCID ID: 0000-0002-9663-5371 (RN).Accumulation of anthocyanins in the exocarp of red grapevine (Vitis vinifera) cultivars is one of several events that characterize the onset of grape berry ripening (véraison). Despite our thorough understanding of anthocyanin biosynthesis and regulation, little is known about the molecular aspects of their transport. The participation of ATP binding cassette (ABC) proteins in vacuolar anthocyanin transport has long been a matter of debate. Here, we present biochemical evidence that an ABC protein, ABCC1, localizes to the tonoplast and is involved in the transport of glucosylated anthocyanidins. ABCC1 is expressed in the exocarp throughout berry development and ripening, with a significant increase at véraison (i.e., the onset of ripening). Transport experiments using microsomes isolated from ABCC1-expressing yeast cells showed that ABCC1 transports malvidin 3-Oglucoside. The transport strictly depends on the presence of GSH, which is cotransported with the anthocyanins and is sensitive to inhibitors of ABC proteins. By exposing anthocyanin-producing grapevine root cultures to buthionine sulphoximine, which reduced GSH levels, a decrease in anthocyanin concentration is observed. In conclusion, we provide evidence that ABCC1 acts as an anthocyanin transporter that depends on GSH without the formation of an anthocyanin-GSH conjugate.

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In the present study, field grown Aragonez (Syn. Tempranillo) grapevines (Vitis vinifera L.) were subjected to three irrigation regimes (conventional sustained deficit irrigation (DI), regulated deficit irrigation (RDI) and non-irrigated (NI)) during two successive seasons (2007-2008). An integrative study was performed in grape berry skin tissues at four phenological stages of grape berry (pea size, véraison, mid-ripening and full maturation). The accumulation of flavonoid compounds, the profile of accumulation of abscisic acid (ABA) and jasmonic acid (JA) hormones were analysed during grape ripening. The non-enzymatic antioxidant capacity was also characterised. Principal component analysis followed by a between group analysis (PCA-BGA) showed a clear separation already at early stages of grape berry development between the three treatments in both years. The main compounds affected by water availability were proanthocyanidins and flavonols, which increased with irrigation at all phenological stages. In both years, concentrations of anthocyanin at full maturation were observed to be higher in the skin of berries belonging to DI and RDI vines than in NI ones. ABA accumulation was also regulated by the intensity of water stress since early stages of berry development. However, no differences in sugar accumulation were observed between treatments. The present study also shows that climatic conditions, namely temperature, play an important role in the ripening process of grape berries. This was clearly observed in NI vines during both years, in which a decrease in the quality parameters in grape skins is presumably related to high temperature and excessive cluster sunlight exposition more marked in 2007, the hotter year. This supports the crucial role of irrigation in maintaining the cluster microclimate in an optimum range, thus enabling a balanced synthesis of the compounds relevant to wine quality.