Figure 11.

A model of JA-dependent and JA-independent signaling pathways in regulating the enzyme activity of myrosinase. When plants are attacked by diseases and insect pests, stressed plants could induce the expression of myrosinase genes to resist the stresses. There are two signaling pathways to mediate the expression of myrosinase genes: One is the JA-independent signaling pathway which regulates the expression of BGLU19, BGLU20, TGG4, and so on; the other one is the JA-dependent signaling pathway. For the JA-dependent signaling pathway in regulating the expression of myrosinase genes, when plants are attacked by diseases and insect pests, endogenous JA will be produced through inducing AOS expression. JA-Ile can be recognized by the receptor COI1 (SCF^COI1) and activate COI1. The activated COI1 can degrade the JAZ proteins, release the transcriptional activity of FAMA, and activate the downstream TGG1 gene expression to promote the synthesis of myrosinase, to promote the hydrolysis of glucosinolate. JA also mediates myrosinase activity by inducing or inhibiting the expression of other myrosinase genes. The final outcome of jasmonate regulation is the enhancement of myrosinase activity. Purple boxes represent the two types of myrosinases; the solid lines represent the pathways that have been clarified in this study; dashed lines represent the pathways that need further study; the question mark bubble represents the important unknown element in the regulation of TGG2 expression by JA, which needs further exploration.