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The Grapevine Root-Specific Aquaporin VvPIP2;4N Controls Root Hydraulic Conductance and Leaf Gas Exchange under Well-Watered Conditions But Not under Water Stress

Publication Type:Journal Article
Year of Publication:2012
Authors:Perrone, I, Gambino, G, Chitarra, W, Vitali, M, Pagliarani, C, Riccomagno, N, Balestrini, R, Kaldenhoff, R, UEHLEIN, NORBERT, Gribaudo, I, Schubert, A, LOVISOLO, CLAUDIO
Journal:Plant Physiology
Volume:160
Issue:2
Date Published:2012
ISBN Number:00320889
Keywords:Vitis, Vitis vinifera
Abstract:

We functionally characterized the grape (Vitis vinifera) VvPIP2; 4N (for Plasma membrane Intrinsic Protein) aquaporin gene. Expression of VvPIP2; 4N in Xenopus laevis oocytes increased their swelling rate 54-fold. Northern blot and quantitative reverse transcription-polymerase chain reaction analyses showed that VvPIP2; 4N is the most expressed PIP2 gene in root. In situ hybridization confirmed root localization in the cortical parenchyma and close to the endodermis. We then constitutively overexpressed VvPIP2; 4N in grape 'Brachetto', and in the resulting transgenic plants we analyzed (1) the expression of endogenous and transgenic VvPIP2; 4N and of four other aquaporins, (2) whole-plant, root, and leaf ecophysiological parameters, and (3) leaf abscisic acid content. Expression of transgenic VvPIP2; 4N inhibited neither the expression of the endogenous gene nor that of other PIP aquaporins in both root and leaf. Under well-watered conditions, transgenic plants showed higher stomatal conductance, gas exchange, and shoot growth. The expression level of VvPIP2; 4N (endogenous + transgene) was inversely correlated to root hydraulic resistance. The leaf component of total plant hydraulic resistance was low and unaffected by overexpression of VvPIP2; 4N. Upon water stress, the overexpression of VvPIP2; 4N induced a surge in leaf abscisic acid content and a decrease in stomatal conductance and leaf gas exchange. Our results show that aquaporin-mediated modifications of root hydraulics play a substantial role in the regulation of water flow in well-watered grapevine plants, while they have a minor role upon drought, probably because other signals, such as abscisic acid, take over the control of water flow.

URL:http://www.jstor.org/stable/41694814
Short Title:Plant Physiology
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