Two FK506-binding proteins, OsFKBP57 and OsFKBP73, confer salt tolerance by enhancing the SOS pathway but decrease grain protein accumulation by inhibiting BCAT activity in rice

accumulation in rice and enhances salt tolerance. Concurrently, OsFKBP57 and OsFKBP73 interact with the branched-chain amino acid transaminase OsBCAT1, inhibiting its enzymatic activity and regulating the amino acid levels in grains under salt stress. Knockout of OsFKBP57 and OsFKBP73 increases glutelin accumulation in grains and degrades rice quality under saline conditions. Together, these actions directly mediate total grain protein content in rice under salt stress. Our study identifies these genes as central regulators that coordinate salt tolerance and grain quality in rice.