GLV signaling positively regulates root gravitropism in an RGI-dependent manner. A) and E) Representative images of 4 dag seedlings after 6 h of gravistimulation. Images at the right show a higher magnification of the bending root tip (framed in the left image); 100 nM GLV11p A) or 2 μM estradiol E) were used. Scale bars in the left images represent 1 cm and bars in the right images represent 1 mm. B) Root gravitropic bend in rgi mutants. Distribution of the root bending angle after gravistimulation for the indicated genotypes represented as nightingale plots (bin = 10°). Dunn test, preceded by Kruskal–Wallis test, was performed when comparing wild-type with rgi mutants and comparing rgi5-1 mutant with rgi1 rgi5, rgi2 rgi5, and rgi125. *P < 0.05; ****P < 0.0001; and ns indicates no significant difference (P < 0.05). Experiments were done in 3 replicates with similar results. C) Expression of RGI5-GFP/Venus driven by its native promoter in rgi5-1 complemented its gravitropism defect. Distribution of the root bending angle after gravistimulation for the indicated genotypes represented as nightingale plots (bin = 10°). Dunn test is preceded by Kruskal–Wallis test. *P < 0.05, and ns indicates no significant difference (P < 0.05). Experiments were done in 2 replicates with similar results. D) Root gravitropic bend in tpst-1 mutant. Distribution of the root bending angle after gravistimulation for the indicated genotypes represented as nightingale plots (bin = 10°). Significant differences were determined using Kolmogorov–Smirnov test, *P < 0.05. Experiments were done in 2 replicates with similar results. F) iGLV6/rgi1 rgi5 suppressed GLV6^OE-induced root agravitropic phenotype upon estradiol treatment. Distribution of the root bending angle after gravistimulation for the indicated genotypes/treatment represented as nightingale plots (bin = 10°); 2 μM estradiol was used. Significant differences were determined using 2-way ANOVA and followed by the Sidak test. **P < 0.01, and ns indicates no significant difference (P < 0.05). This experiment was done 2 times with similar results. G) rgi125 suppressed GLV11p-induced agravitropic phenotype upon GLV11p treatment. Distribution of the root bending angle after gravistimulation for the indicated genotypes represented as nightingale plots (bin = 10°); 100 nM GLV11p was used. Dunn test is preceded by Kruskal–Wallis test. ****P < 0.0001, and ns indicates no significant difference (P < 0.05). Experiments were done in 3 replicates with similar results. H) Time-course analysis of gravitropic curvature in wild-type and rgi5-1 mutant. Error bars represent the standard error of the mean. Significant differences between wild type and rgi5-1 in each time point were determined using Kolmogorov–Smirnov test, *P < 0.05 and **P < 0.01. Experiments were done in 2 replicates with similar results. WT, wild type.