Figure 6.

CPK33 overexpression resulted in ABA hyposensitivity of guard cell movement, slow anion channel regulation, and decreased drought tolerance. A, qPCR-based assessment of CPK33 expression in Col-0 and overexpression lines 1 and 2 (CPK33-OE-1 and CPK33-OE-2). ACTIN2 was used as an internal control. B and C, ABA-induced promotion of stomatal closure in Col-0 and CPK33 overexpression lines. Shown: Photos (B) and width/length ratio analysis of the stomatal aperture (C). Error bars represent the se (n = 3). At least 60 stomata were measured for each genotype per replication. Bar in B = 10 µm. D, Water loss rates from detached leaves of Col-0 and CPK33 overexpression lines. Error bars represent the se (n = 3). E, Decreased tolerance to drought in CPK33 overexpression lines. The experiments were repeated three times with similar results. F, Patch-clamp whole-cell recordings of the slow anion currents in guard cell protoplasts isolated from Col-0 and CPK33 overexpression lines with or without 50 μm ABA. Time and voltage scales are as shown. G, Current/voltage relationships of whole-cell slow anion currents as illustrated in F. The numbers of guard cells measured were: Col-0 (8), Col-0-ABA (8), CPK33-OE-1 (7), CPK33-OE-1-ABA (7), CPK33-OE-2 (9), and CPK33-OE-2-ABA (10). Data are shown in the form mean ± se. Asterisks in C, D, and G indicate significant differences between means (P < 0.05).