(A, B) The serk2-1/bak1-5 and serk1-1/serk2-1/bak1-5 mutants show normal hypocotyl elongation in response to brassinolide (BL) treatment. The seedlings were grown under the light for 10 days on ½ MS plates with or without 100 nM BL (A), and hypocotyl lengths were quantified (B). Brackets indicate hypocotyl (A). The data are shown as mean + SD (n=15) (B). (C) BL treatment induces the dephosphorylation of BES1 in serk2-1/bak1-5 and serk1-1/serk2-1/bak1-5 mutants. Ten-day-old seedlings grown in liquid ½ MS medium were treated with 0 or 1 μM BL for 2 hr, and the total proteins were analyzed by immunoblotting with α-BES1 antibody (Top panel). The protein loading is shown by Coomassie Brilliant Blue (CBB) staining for RuBisCO (RBC) (bottom panel). (D, E) The serk1-8/bak1-4/serk4-1 mutant exhibits normal stomatal patterning and index. Confocal images were taken on the abaxial cotyledon epidermis of 10-day-old seedlings (D), and the stomatal indexes were quantified (E). The experiments were repeated twice with similar results.