Abstract

H 2 O 2 functions as a signaling molecule regulating plant growth, development, and stress responses; however, its role in jasmonic acid (JA) signaling transduction and JA-regulated biological processes remains elusive. Here, we report that General regulatory factor 8 (GRF8) is a critical factor inhibiting JA signaling, while H 2 O 2 removes this inhibition to facilitate the JA response during root growth and leaf senescence in Arabidopsis . GRF8 interacts with and inhibits MYC2, the key transcription factor in JA signaling. It recruits Jasmonate-ZIM domain (JAZ) repressors to enhance their interaction with and inhibition of MYC2. Additionally, GRF8 competes with Mediator 25 (MED25), a subunit of the Mediator coactivator complex, to interact with MYC2. Upon increased JA levels, H 2 O 2 sulfenylates GRF8 at cysteine-103, reducing its interaction with MYC2 and thereby releasing MYC2 activity to stimulate the JA response. Together, our findings suggest that H 2 O 2 -mediated sulfenylation of GRF8 provides a redox-based mechanism to modulate JA signaling in Arabidopsis .