Figure 10.

Schematic Model of Regulation of JA-Mediated Defenses by Light Quality, through the Modulation of MYC and JAZ Stability.

R/FR ratios determine the balance of activation/deactivation (Pfr/Pr) of phytochromes, which differentially regulate the stability of MYC TFs and their JAZ repressors and, therefore, the defense output of the plant. Ambient light (high R/FR ratios; represented in yellow/light gray) shifts the Pr/Pfr equilibrium to the active Pfr form, which enhance JA-dependent defenses by mediating MYCs stabilization and allowing JA-mediated degradation of their JAZ repressors. Conversely, in shade conditions (low R/FR ratios; represented in brown/dark gray), the phytochrome equilibrium is shifted toward the inactive Pr form, thus reducing JA-dependent defenses by destabilizing MYCs and stabilizing JAZs. Thus, the balance of active phytochromes, which depends on the R/FR ratio, regulates the relative amount of MYCs and JAZ proteins and therefore defines the JA-dependent defense output of the plant. Brown (dark) and yellow (light) triangles represent the relative amount of the corresponding proteins (Pr and Pfr forms of phytochromes, as well as JAZ and MYC proteins) in each condition (shade, brown or dark gray; light, yellow or light gray)

[See online article for color version of this figure.]