Expression of endogenous and transgenic VvPIP2;4N in cv Brachetto. A, Relative expression of VvPIP1;1, VvPIP2;1, VvPIP2;2, VvPIP2;3, and endogenous VvPIP2;4N was determined by qRT-PCR in roots (R) and leaves (L) of wild-type plants upon irrigated (IRR) and water stress (WS) conditions. For each gene, asterisks mark significant differences (P < 0.05) between stressed and irrigated conditions. B, Relative expression of transgenic VvPIP2;4N determined by qRT-PCR in roots and leaves belonging to six different transgenic lines (4, 16, 23, 24, 28, and 33) upon well-watered (IRR) and water stress (WS) conditions. For each line, asterisks mark significant (P < 0.05) differences between well-watered and water-stressed plants, while circles mark those between shoots and roots. The expression ratio of each target gene to the geometric mean of the housekeeping genes was further divided by the expression ratio of endogenous VvPIP2;4N in irrigated roots (IRR R). Significant differences were detected by means of Student’s t test. Data are means ± se (n = 3).