Brassinosteroid (BR) regulates a wide range of gene expression through its signal transduction pathway,results in diverse physiological responses in plants.BR signaling involves a number of molecules that relay signal from cell surface receptor kinase (BRI1) to nuclear transcription factors (BZR1/BES1).Of BR signaling components,BSU1 (bri1 Suppressor 1) and its homologs (BSL1,BSL2,and BSL3) comprise a small family that are classified into the PPKL (Protein Phosphatases with Kelch-Like repeat domains) family.