BR directly binds to the extracellular domain of BRI1 creating a surface for dimerization with the co-receptor kinase BRI1-ASSOCIATED RECEPTOR KINASE1 (BAK1). BR is reported as the ?molecular glue? that bring together BRI1 and BAK1. These kinases are activated by squential transphosphorylation between the kinase domains of BRI1 and BAK1, and BRI1 in turn phosphorylates plasma membrane-anchored cytoplasmic kinase, BRASSINOSTEROID-SIGNALING KINASE1 (BSK1) (OsBSK1 is identified on the At gene orthology).
