Glycolate oxidase persulfidation mediates the salicylic acid-modulated GC switch to regulate photorespiratory H2O2 levels.

Glycolate oxidase (GLO)-derived hydrogen peroxide (H2O2) is a main H2O2 source in plants and plays crucial roles in various biological functions. However, the mechanisms regulating H2O2 homeostasis are still not fully understood. We previously proposed a distinct mechanism, in which salicylic acid (SA) physically modulates photorespiratory H2O2 levels by impacting the interaction between GLO and catalase (CAT) (GC switch) in plants. Here, we demonstrate that SA induces GLO and CAT persulfidation in rice (Oryza sativa), where H2S serves as a direct regulator. Persulfidation of GLO at Cys344, rather than CAT, reduces the GLO-CAT interaction. Moreover, persulfidation of CAT, not GLO, marginally inhibits its enzymatic activity. GLO persulfidation and the associated diminished GLO-CAT interaction trigger photorespiratory H2O2 production. In turn, the elevated H2O2 levels reverse GLO and CAT persulfidation, forming a negative feedback mechanism to balance H2O2 levels. Collectively, our results suggest that GLO persulfidation mediates the SA-modulated GC switch to regulate photorespiratory H2O2 production, and the redox-mediated persulfidation of the GC switch plays important roles in maintaining H2O2 homeostasis in plants.