(A) Autophosphorylation of phototropins (phot1 and phot2). Guard cell protoplasts were illuminated with RL (300 μmol m⁻² s⁻¹) for 30 min in the presence of acrolein, and then a pulse of BL (100 μmol m⁻² s⁻¹, 30 s) was applied. The autophosphorylation was determined by the electrophoretic shift using anti-phot1 and anti-phot2 antibodies. (B) Phosphorylation of the BLUS1. Immunoblot was performed using anti-pSer348 BLUS1 and anti-BLUS1 antibodies. (C) Quantification of the phosphorylation level of BLUS1 using ImageJ software. Phosphorylation level is expressed as a percentage relative to that of control irradiated with BL. Data are represented as mean ± SD (n = 3). ns indicates no significant difference (P < 0.01; Student’s t-test).