Early and Late Responses of Grapevine (Vitis vinifera L.) to Water Deficit: A Proteomics Perspective

Water deficit progressively reduced growth of Cabernet Sauvignon shoots with time over a 16-day period. Water deficit decreased shoot elongation, stomatal conductance and photosynthesis after day 4; 2277 proteins in shoot tips were identified by shotgun proteomics with an average CV of 9% for the protein abundance of all proteins. There were 472 out of 942 (50%) proteins found in all samples that were significantly affected by water deficit. The 472 proteins clustered into four groups: increased and decreased abundance of early- and late-responding protein profiles. Vines sensed the water deficit early, prior to any physiological responses, because the abundance of some proteins changed before decreases in shoot elongation, stomatal conductance and photosynthesis. Predominant functional categories of the early-responding proteins included photosynthesis, glycolysis, translation, and growth-related categories (steroid metabolism and water transport), whereas those for late-responding proteins were involved with transport, antioxidants, amino acid and carbohydrate metabolism. Many of these early-responding proteins are likely to be regulated by post-transcriptional modifications.