MYC5 is Involved in Jasmonate-Regulated Plant Growth, Leaf Senescence and Defense Responses

: Jasmonates (JAs), lipid-derived phytohormones, regulate plant growth, development and defenses against biotic stresses. CORONATINE INSENSITIVE1 perceives bioactive JA and recruits JASMONATE ZIM-DOMAIN (JAZ) proteins for ubiquitination and subsequent degradation via the 26S proteasome, which de-represses JAZ-targeted transcription factors that regulate diverse JA responses. Recent studies showed that the Arabidopsis basic helix-loop-helix transcription factor MYC5 interacts with JAZs and regulates stamen development. However, whether MYC5 mediates other JA responses is unclear. Here, we show that MYC5 functions redundantly with MYC2, MYC3 and MYC4 to modulate JA-regulated root growth inhibition and plant defenses against insect attack and pathogen infection, and that it positively regulates JA-induced leaf senescence. Our findings define MYC5 as an important regulator that is essential for diverse JA responses.