Fine scale gene expression dynamics at the foliar level reveal grapevine strategies to cope with recurrent drought stress

Background: The frequency of consecutive and often leading to extreme drought events is increasing in the Mediterranean region, shaping the physiological strategies that grapevine plants employ to cope with recurring water stress. This study evaluates the effects of two recurrent drought cycles, each followed by rewatering, on potted plants of Vitis vinifera L. cv. Sauvignon blanc. Results: Physiological measurements were combined with transcriptomic analysis, performed on leaf samples collected every six hours during the last day of drought cycle and subsequent rewatering. RNA-Seq results showed temporal and cycle-dependent dynamics in genes associated with carbohydrate metabolism, abscisic acid, and photosynthesis. By analyzing gene expressions throughout the day in both drought cycles, we observed conserved and distinct transcriptional patterns, with different processes activated or repressed depending on the time of day and the cycle (drought or recovery). Conserved genes such as galactinol synthase and dehydrin were present in both cycles most of the time. On the other hand, it was observed that plants change from immediate defense and stress mitigation in the first drought cycle to more centered on metabolic changes and acclimative adjustments during the second drought and at the end of the day. Conclusions: These findings suggest that grapevines adjust their molecular responses after an initial drought episode, consistent with acclimation or possible stress-priming mechanisms, useful to better cope with subsequent water deficits. This fine-scale temporal perspective provides insight into the strategies that Vitis vinifera implement to survive recurring drought, with relevance for improving grapevine management under climate change.