Fig. 9.

Hypothetical model proposing peroxisomal H₂O₂ retrograde signalling after APX4 knockdown followed by catalase (CAT) inhibition in rice leaves. Differential H₂O₂ accumulation in peroxisomes of APX-silenced and non-transformed leaves could induce different H₂O₂ fluxes towards the cytosol and other compartments, triggering distinct signalling mechanisms. In these cellular compartments (cytosol, chloroplasts, and nucleus), H₂O₂ could trigger signalling for increasing synthesis/degradation of several different proteins. It is postulated that the proteins of primary importance for mitigation of the adverse effects induced by CAT inhibition are those belonging to the cytosolic and chloroplast ASC–GSH cycle and other important antioxidant and protective proteins.