Fig. 4: Regulation of auxin-mediated inhibition on endocytosis by SLs in Arabidopsis.

a, c, e Effect of GR24 on NAA-inhibited FM4-64 uptake. GR24 (1 μM), which alone had no detectable effect on FM4-64 uptake, largely diminished the NAA (10 μM) action of inhibiting FM4-64 uptake (a, c). Quantitative evaluation of FM4-64 uptake: the quotient between mean fluorescence intensity of the intracellular and PM in the roots was scored (c n ≥ 150 cells). GR24 treatment also effectively attenuated NAA-mediated inhibition of FM4-64 uptake, when protein synthesis was inhibited by 50 μM cycloheximide (CHX; e n ≥ 91 cells). Arrowheads indicate endosomal compartments of FM4-64. Scale bars: 5 µm. Data are expressed as mean ± s.e.m. Means with different letters are significantly different at P < 0.05 (one-way ANOVA with Fisher LSD test). b, d Effect of GR24 on NAA-regulated clathrin localization. CLC-GFP distributed at the trans-Golgi network and the PM. NAA (30 μM) treatment induced a transient decrease of the CLC-GFP signal at the PM. GR24 (10 μM), which alone had no detectable effect on CLC-GFP signal, largely prevented NAA action on depletion of CLC-GFP signal from the PM. The percentage of root cells showing CLC-GFP labeling at the PM was scored (d n ≥ 7 roots). Arrows indicate CLC-GFP distribution at the PM. Scale bars: 5 µm. Data are expressed as mean ± s.e.m. Means with different letters are significantly different at P < 0.05 (one-way ANOVA with Fisher LSD test). The above experiments were repeated three times with similar results. Images shown are representative of each treatment. Source data of c–e are provided in the Source data file.