JASMONATE-INSENSITIVE1 Encodes a MYC Transcription Factor Essential to Discriminate between Different Jasmonate-Regulated Defense Responses in Arabidopsis[W]

In spite of the importance of jasmonates (JAs) as plant growth and stress regulators, the molecular components of their signaling pathway remain largely unknown. By means of a genetic screen that exploits the cross talk between ethylene (ET) and JAs, we describe the identification of several new loci involved in JA signaling and the characterization and positional cloning of one of them, JASMONATE-INSENSITIVE1 (JAI1/JIN1). JIN1 encodes AtMYC2, a nuclear-localized basic helix-loop-helix-leucine zipper transcription factor, whose expression is rapidly upregulated by JA, in a CORONATINE INSENSITIVE1-dependent manner. Gain-of-function experiments confirmed the relevance of AtMYC2 in the activation of JA signaling.…