Jasmonic acid promotes leaf senescence through MYC2-mediated repression of CATALASE2 expression in Arabidopsis

Plants relocate nutrients and energy from aging leaves to developing tissues during leaf senescence, which is important for plant growth, development, and responses to various environmental stimuli. Both jasmonic acid (JA) and H₂O₂ are two crucial signalling molecules positively regulating leaf senescence, whereas whether and how they are coordinated in leaf senescence remains elusive. Here, we report that H₂O₂ accumulates in JA-treated leaves, while scavenging the increased H₂O₂ can significantly suppresses JA-induced leaf senescence and the expression of senescence-associated genes (SAGs). The mutant myc2 with a mutation of MYC2, a master transcription factor in JA signalling pathway, exhibits delayed leaf senescence with increased catalase activity and decreased H₂O₂ accumulation compared with the wild type upon JA treatment. Further study showed that MYC2 downregulates CATALASE 2 (CAT2) expression by binding to its promoter, thus promoting JA-induced H₂O₂ accumulation and leaf senescence. Moreover, the delayed leaf senescence with reduced H₂O₂ accumulation and SAGs expression of the myc2 mutant is significantly reverted by the cat2-1 mutation in myc2 cat2-1 double mutant. Thus, our study reveals that JA represses CAT2 expression to increase H₂O₂ accumulation, thus promoting leaf senescence in a MYC2 dependent manner in Arabidopsis.