Chemoproteomic Profiling Reveals Chlorogenic Acid as a Covalent Inhibitor of <i>Arabidopsis</i> Dehydroascorbate Reductase 1

Chlorogenic acid (CA) is an abundant plant secondary metabolite with promising allelopathic effects on weed growth. However, the molecular targets and mechanism of action of CA in plants remain elusive. Here, we report the employment of a clickable photoaffinity probe in identifying the protein targets of CA in <i>Arabidopsis</i> seedling proteomes. CA specifically binds <i>Arabidopsis</i> dehydroascorbate reductase 1 (<i>At</i>DHAR1), an enzyme responsible for ascorbate regeneration in plants, by covalent alkylating Cys20 within the catalytic center, thereby inhibiting its activity. In vivo application of CA reduced the pool size and redox state of ascorbate, leading to H₂O₂ accumulation in <i>Arabidopsis</i> seedlings. In agreement with these results, CA significantly induced the upregulation of antioxidant enzymes and downregulation of proteins involved in water transport and photosynthesis, as evidenced by quantitative proteomics. Taken together, this study revealed DHAR1 as a functional target underlying CA's allelopathic activity in plants, which opens new opportunities for the development of novel herbicides from naturally existing resources.