4.5 GUS staining
The promoter of bes1 was cloned into PBI121 vector and introduced into Col-0 by Agrobacterium tumefaciens-mediated floral transformation to generate proBES1::GUS transgenic plant. Five-day-oldproBES1::GUS was grown in long day growth chamber (16-h light and 8-h dark, 120 μmol.m–2·s–1, LED fluorescent tube) at 22℃, then seedlings were subjected to priming assays and sampled at different time points. Seedlings were stained at 37℃ in the dark for 2.5 h using GUS Staining Solution (Sangon Biotech, Cat no. A610085-0025, Shanghai). After staining, the seedlings were washed with 75% ethanol and the image was captured using a fluorescence microscope (Leica, Wetzlar, Germany).