A Reactive Antagonist Strategy: Cysteine‐Directed Covalent Molecular Glue in Plant Hormone Receptor Regulation

Controlling protein-protein interactions (PPIs) remains a challenge in modern chemistry. In plants, jasmonoyl-L-isoleucine (JA-Ile) acts as a molecular glue that facilitates PPIs between the F-box protein COI1 and JAZ repressors, leading to transcriptional reprogramming. However, the functional redundancy of JAZ proteins complicates biological studies. To overcome this, we introduce a reactive antagonist (RA) strategy that selectively induces COI1-JAZ interactions for a Cys-mutated JAZ mutant while inhibiting interactions with wild-type JAZs. We designed and synthesized COR-oxime derivatives, identifying O-bromo-ethyl COR-oxime as an optimal RA, functioning as a Cys-directed covalent molecular glue. Mass spectrometry and fluorescence anisotropy assays confirmed its selective covalent binding to Cys-mutated JAZ1, leading to targeted degradation in Arabidopsis. This strategy enables precise functional dissection of JAZ subtypes without affecting endogenous pathways. Given the genetic redundancy in many biological systems, the RA strategy provides a powerful chemical biology tool for dissecting complex signaling networks beyond plant hormone research.