Regulation of Secondary Metabolism by Jasmonate Hormones

The biosynthesis of many different types of secondary metabolites that serve defensive functions in different plant species is regulated by hormones belonging to the group of jasmonate compounds. Regulation acts at the level of transcription of structural genes encoding biosynthetic enzymes. Here we review recent insights into the mechanisms of signal transduction initiated by jasmonates leading to the activation of transcription factors. We present models for jasmonate signal transduction regulating tobacco alkaloid biosynthesis and terpenoid indole alkaloid biosynthesis in Catharanthus roseus. The models propose that perception of a bioactive jasmonate derivative by the receptor CORONATINE INSENSITIVE1 (COI1) results in the degradation of Jasmonate ZIM-domain (JAZ) proteins. Since these JAZ proteins repress the activity of the basic-Helix-Loop-Helix transcription factor MYC2, MYC2 then activates the expression of genes encoding certain members of the APETALA2/Ethylene Response Factor (AP2/ERF) family of transcription factors, which in turn activate the expression of alkaloid biosynthesis genes.