Transcriptional regulation of plant inducible defenses against herbivores: a mini-review

Inducible plant defenses against herbivores are controlled by a transient burst of jasmonic acid (JA) and its conversion to the active hormone (3R,7S)-jasmonoyl-L-isoleucine (JA-Ile). JA-Ile shows high affinity for binding to the COI1 protein complex with JAZ repressor protein(s), a multi component JA-Ile receptor, promoting hormone-dependent ubiquitination and degradation of JAZ transcriptional repressors. Degradation of JAZ proteins in Arabidopsis leads to the release of a bHLH transcription factor, MYC2, which functions as a master regulator of JA-dependent defense responses. Because the activity of the MYC2 coincides with the presence of active jasmonate in cells, it is unlikely that MYC2, alone, regulates prolonged transcriptional responses of genes encoding enzymes required for the accumulation of defense metabolites. In this review, we focus on MYC2 and a specific group of MYC2-regulated 'secondary' transcription factors as critical components of the JA signal transduction pathway that controls inducible chemical defense responses in plants.