GLV-RGI signaling in the LRC is required for root gravitropism but not for RAM maintenance. A) Confocal images of SMBpro:RGI1-Venus/iGLV6/rgi1 rgi5 and RPS5Apro:RGI1-Venus/iGLV6/rgi1 rgi5 root tips. Images at the right show higher magnification of the framed area (LRC cells) in the left images. Cells were counter-stained with propidium iodide (PI). Arrowheads in RPS5Apro:RGI1-Venus/iGLV6/rgi1 rgi5 root tip indicate the LRC cells where Venus was not detected. Scale bars represent 50 μm. B) Representative images of 4 d after germination (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). Scale bars in the left images represent 1 cm and bars in right images represent 1 mm. C) Quantification of gravitropic bending angle in the iGLV6/rgi1 rgi5 mutant transformed with RGI1-Venus expressed in the LRC (SMBpro:RGI1-Venus/iGLV6/rgi1 rgi5) or other meristematic cells (RPS5Apro:RGI1-Venus/iGLV6/rgi1 rgi5). In the boxplot, boxes indicate ranges from the first to third quartiles, and the central lines display the median. Upper and lower whiskers extend to maximum or minimum values no further than 1.5 times IQR (interquartile range, the distance between the first and third quartiles). Dunn test is preceded by Kruskal–Wallis test. Lowercase letters indicate statistical differences between genotypes (P < 0.05). Experiments were done in 2 replicates with similar results. D) Complementation of the RAM size defect in the iGLV6/rgi1 rgi5 mutant by RGI1-Venus expression in the LRC (SMB promoter) or other meristematic cells (RPS5A promoter). Confocal images show cells stained with PI in 5 dag seedlings. Arrowheads indicate the end of RAM. Scale bars represent 50 μm. E) RAM size quantification in the iGLV6/rgi1 rgi5 mutant transformed with RGI1-Venus expressed in the LRC (SMBpro:RGI1-Venus/iGLV6/rgi1 rgi5, abbreviated as SMBpro) or other meristematic cells (RPS5Apro:RGI1-Venus/iGLV6/rgi1 rgi5, abbreviated as RPS5Apro). In the boxplot, boxes indicate ranges from the first to third quartiles, and the central lines display the median. Upper and lower whiskers extend to maximum or minimum values no further than 1.5 times IQR (interquartile range, the distance between the first and third quartiles). Significant differences were determined using 1-way ANOVA and followed by a Tukey’s test. Lowercase letters indicate statistical differences between genotypes (P < 0.05). Experiments were done in 2 replicates with similar results. F) Time-course analysis of gravitropic curvature in rgi125 and SMBpro:RGI1-Venus/rgi125 mutant. Error bars represent the standard error of the mean. Significant differences between rgi125 and SMBpro:RGI1-Venus/rgi125 mutant 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; Pro, promoter.