OsMYC2 mediates numerous defence-related transcriptional changes via jasmonic acid signalling in rice

Jasmonic acid (JA) plays central roles in various events in plants, especially defence against pathogens and insects. The basic helix-loop-helix (bHLH) transcription factor MYC2 has attracted attention as a master regulator of JA signalling in dicotyledonous plants. However, how MYC2 functions in monocotyledonous plants, including agriculturally important crops such as cultivated rice, has been poorly understood. To elucidate the comprehensive effects of rice MYC2 (OsMYC2) on the JA-inducible transcriptional modifications, we performed RNA-sequencing by using OsMYC2-knockdown plants (osmyc2RNAi). In osmyc2RNAi, JA-inducible expression of many defence-related genes, for example chitinases and proteinase inhibitors, was compromised. Decrease in JA-dependent activation of the biosynthetic pathways of specialised metabolites, especially defence compounds, was also evident in the osmyc2RNAi line. Furthermore, a substantial change was noted in the expression of distinct types of transcription factors, such as MYB-type factors, likely depicting the importance of OsMYC2 in not only defence responses but also other morphogenetic events. Our findings provide fundamental information to understand the overall functions of MYC2 in JA signalling in monocotyledonous plants, which might yield agricultural benefits.