FIGURE 6.

Schematic model illustrating the conclusions. The role of CIII peroxidase-generated ROS in cuticle formation. (A) The constitutively enhanced accumulation of peroxidase-generated ROS was positively correlated with the increased permeability of the cuticle and negatively correlated with ABA-mediated signaling. Cuticular integrity was influenced by the repression of genes involved in cutin biosynthesis. Under conditions involving a perturbed cuticle, plants switch to a primed state that includes enhanced OG-mediated defenses. (B) In ABA-deficient plants (aba2-1), the ABA-mediated removal of ROS is lost. This allows for an enhanced accumulation of peroxidase- and probably other enzyme-derived ROS, which subsequently represses the expression of cutin-biosynthetic genes and thereby leads to an increase in the permeability of the cuticle. This increased permeability is positively correlated with defense priming and induced resistance.