Abstract
BackgroundGrape leaves provide the biochemical substrates for berry development. Thus, understanding the regulation of grapevine leaf metabolism can aid in discerning processes fundamental to fruit development and berry quality. Here, the temporal alterations in leaf metabolism in Merlot grapevine grown under sufficient irrigation and water deficit were monitored from veraison until harvest.ResultsThe vines mediated water stress gradually and involving multiple strategies: osmotic adjustment, transcript-metabolite alteration and leaf shedding. Initially stomatal conductance and leaf water potential showed a steep decrease together with the induction of stress related metabolism, e.g. up-regulation of proline and GABA metabolism and stress related sugars, and the down-regulation of developmental processes. Later, progressive soil drying was associated with an incremental contribution of Ca2+ and sucrose to the osmotic adjustment concomitant with the initiation of leaf shedding. Last, towards harvest under progressive stress conditions following leaf shedding, incremental changes in leaf water potential were measured, while the magnitude of perturbation in leaf metabolism lessened.ConclusionsThe data present evidence that over time grapevine acclimation to water stress diversifies in temporal responses encompassing the alteration of central metabolism and gene expression, osmotic adjustments and reduction in leaf area. Together these processes mitigate leaf water stress and aid in maintaining the berry-ripening program.
Highlights
Grape leaves provide the biochemical substrates for berry development
Leaf metabolic and physiological responses of Merlot grapevine showed different temporal pattern of changes during the long-term deficit irrigation: (1) In the very first days (i.e. 0 to 5 DAT) a swift alteration in the leaf metabolism and transcriptional program occurred in parallel to a steep decline in stomatal conductance and leaf water potential (Fig. 1a), (2) a transient settling of the leaf physiology was recorded, i.e. leaf water potential reached a low steady-state level (i.e. 5–20 DAT); (3) a gradual reduction in total leaf area (Fig. 1b) and increased accumulation of osmolites leading to a leaf osmotic adjustment were accompanied by the reverse pattern of change in leaf water potential and the lessening of metabolic perturbation
In association with the decrease in soil water content [23], stomatal conductance of water stressed vines eventually reached the lowest point at day 8 and remained at that level thereafter (15–20 mmol H2O m− 2 s− 1) (Additional file 1: Table S1A)
Summary
Grape leaves provide the biochemical substrates for berry development. understanding the regulation of grapevine leaf metabolism can aid in discerning processes fundamental to fruit development and berry quality. Seasonal drought and high summer temperatures have been increasingly affecting the viticulture industry worldwide, given the negative association between water scarcity and grapevine growth, productivity and quality [5,6,7,8,9,10]. Such trend implies severe consequences when considering that two-thirds of world’s viticulture regions have annual rainfall of less. Combining plant physiology with metabolomics and RNAseq analysis we characterized the response of leaves to a seasonal-long drought in Merlot vines
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