Figure 5.

A simplified model of JA-Ile perception and signaling via the SCF^COI1-JAZ co-receptor complex. At low level of JA-Ile, the JAZ repressors recruit the co-repressor complex consisting of NINJA, TOPLESS (TPL) and the histone deacetylase (HDA), interact with and repress positive regulators of JA signaling such as the transcription activator MYC2, and also inhibits negative regulators of JA signaling such as the transcriptional repressors IIId bHLH factors. Upon external stimuli or developmental changes levels of JA-Ile are elevated leading to perception of JA-Ile by the COI1-JAZ co-receptor and degradation of JAZs via the 26S proteasome. The downstream transcription factors are activated to regulate synergistically or antagonistically expression of JA-responsive genes and JA responses. MYC2 associates with the MED25 subunit of the mediator complex, binds to the G-box motif of the target promoters and activates JA-responsive genes. The IIId bHLH factors antagonize MYC2 via competitive binding to the G-box motif and inhibiting JA-responsive genes. COI1, ASK2, CULLIN1, Rbx and E2 are components of the SCF^COI1 complex. Ub, ubiquitin. Modified with permission from Reference [3] (color in print).