Fig. 3. Complementation of gpa1-3 mutant phenotypes by AtGPA1(S52C) and AtGPA1(Q222L).

(A) qRT-PCR analysis of the expression of AtGPA1 variants relative to SAND (AT2G28390) in 14-day-old Arabidopsis transgenic lines (Ln) in the gpa1-3 background. Data are means ± SEM from five experiments. (B) Western blotting analysis of AtGPA1 variants was performed on 6-day-old seedlings of Col-0, gpa1-3, and gpa1-3–expressing GPA1(WT), AtGPA1(S52C) Ln1, and AtGPA1(Q222L) Ln1. The bar graph represents the intensity of bands corresponding to the AtGPA1 variants relative to those representing α-tubulin. Data are means ± SEM from three experiments. **P < 0.01 by unpaired two-tailed Student’s t test in comparison with gpa1-3. Blots are representative of three experiments. (C) Representative rosette, flower, and silique morphologies in Col-0, gpa1-3, and gpa1-3–expressing AtGPA1(WT), AtGPA1(S52C) Ln1, and AtGPA1(Q222L) Ln1. Scale bars, 1 mm. (D) Ratios of rosette leaf length:width of 5-week-old plants. Data are means ± SEM of 14 to 18 plants per genotype. (E) Petiole lengths of 5-week-old plants. Data are means ± SEM of 12 to 15 plants per genotype. (F) Hypocotyl lengths of 2-day-old etiolated seedlings. Data are means ± SEM from three experiments with at least 10 to 24 seedlings per genotype per experiment. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 by one-way ANOVA with Tukey’s multiple comparisons test [for (A) and (D) to (F)]. (G) Stomatal opening index evaluated by the width:length ratio of stomatal apertures after exposure to 50 μM ABA for 3 hours in the presence of white light (120 μmol/m² s¹). Data are means ± SEM from three plants with 26 to 49 stomatal apertures measured per sample. ***P < 0.005 by unpaired two-tailed Student’s t test for comparison between ABA-treated and untreated plants per genotype. ns, not significant.