Phytohormones jasmonic acid, salicylic acid, gibberellins, and abscisic acid are key mediators of plant secondary metabolites

Until recently, many studies on the role of phytohormones in plant secondary metabolism focused on jasmonic acid (JA), salicylic acid (SA), gibberellins (GA), and abscisic acid (ABA). It is now clear that phytohormone-induced regulation of signaling occurs via regulation of the biosynthetic pathway genes at the transcriptional level or through posttranslational regulation, or an increase in secondary metabolite deposition (e.g., trichomes). Here, we summarize recent advances, updating the current reports on the molecular machinery of phytohormones JA, SA, GA, and ABA involved in plant secondary metabolites. This review emphasizes the differences and similarities among the four phytohormones in regulating various secondary metabolic biosynthetic pathways and also provides suggestions for further research.