Growth and immunity are opposing processes that compete for cellular resources,and proper resource allocation is crucial for plant survival.BSK1 plays a key role in the regulation of both growth and immunity by associating with BRI1 and FLS2,respectively.However,it remains unclear how two antagonistic signals co-opt BSK1 to induce signal-specific activation.Here we show that the dynamic spatial reorganization of BSK1 within the plasma membrane underlies the mechanism of signal-specific activation for growth or immunity.Resting BSK1 localizes to membrane rafts as complexes.Unlike BSK1-associated FLS2 and BRI1,fig22 or exogenous brassinosteroid (BR) treatment did not decrease BSK1 levels at the plasma membrane (PM) but rather induced BSK1 multimerization and dissociation from FLS2/BSK1 or BRI1/BSK1,respectively.Moreover,flg22-activated BSK1 translocated from membrane rafts to non-membrane-raft regions,whereas BR-activated BSK1 remained in membrane rafts.When applied together with flg22,BR suppressed various flg22-induced BSK1 activities such as BSK1 dissociation from FLS2/BSK1,BSK1 interaction with MAPKKK5,and BSK translocation together with MAPKKK5.Taken together,this study provides a unique insight into how the precise control of BSK1 spatiotemporal organization regulates the signaling specificity to balance plant growth and immunity.