X glucuronide

The histochemical GUS staining was performed as previously described (Ying et al., 2022 (link)). Briefly, seedlings were incubated in a GUS staining solution containing 100 mM sodium phosphate (pH 7.0), 1 mM EDTA, 0.05% (v/v) Triton X-100, 1 mM potassium ferricyanide/ferrocyanide, and 0.5 mg mL⁻¹ X-glucuronide (Goldbio) at 37°C for 1–3 h. Then samples were progressively cleared in gradient ethanol solution for 30 min. Images were acquired using a Nikon SMZ1500 stereomicroscope.

Histochemical GUS activity assays were performed as previously described (Jefferson et al., 1987 (link)). Briefly, seedlings were incubated in a GUS staining solution containing 100 mM sodium phosphate (pH 7.0), 1 mM ethylenediaminetetraacetic acid (EDTA), 0.05% (v/v) Triton X‐100, 1 mM potassium ferricyanide/ferrocyanide and 0.5 mg ml⁻¹ X‐glucuronide (Goldbio) at 37°C for 1–3 h. Then, samples were then cleared in a graded series of 30%, 50%, 70% and 100% (v/v) ethanol for 30 min. Images were acquired using a Nikon SMZ1500 stereomicroscope. GFP fluorescence of the proRXR3::RXR3‐GFP complementation plants was imaged with a Leica TCS SP8 confocal laser‐scanning microscope (Ex: 488 nm; Em 507 nm).

GUS activity was analyzed according to Jefferson et al. (1987 (link)). Briefly, tissues were incubated in a GUS staining solution containing 100 mM sodium phosphate (pH 7.0), 1 mM EDTA, 0.05% (v/v) Triton X‐100, 1 mM potassium ferricyanide/ferrocyanide, and 0.5 mg ml⁻¹ X‐glucuronide (Goldbio, Ann Arbor, MI, USA) at 37°C for 1 to 3 h. After removal of the staining solution, tissues were cleared in 70% (v/v) ethanol. Images were acquired using Nikon SMZ1500 stereomicroscope. Green fluorescent protein (GFP) fluorescence in pRXR1::RXR1‐GFP plants was detected and imaged with a Leica TCS SP8 confocal laser‐scanning microscope (excitation (Ex): 488 nm; emission (Em): 507 nm). Propidium iodide (PI, 1 µg ml⁻¹) was applied to visualize the cell shape.