FIGURE 1.

A model of peroxisomal protein degradation in plant cells. (A) When autophagy occurs at a basal level or when a core ATG gene is missing, degradation of matrix proteins like ICL and MLS may depend on intraperoxisomal degradation (IPD) or peroxisome-associated protein degradation (PexAD). (B) Pexophagy may be induced by loss of LON2, inactivation of IPD and PexAD, or a developmental process in which peroxisomes are past a critical level of oxidative stress (for example, intensive fatty acid β-oxidation during early seedling growth). Under pexophagy-inducing conditions, phagophore initiates, expands, and forms the autophagosome to sequester and target the peroxisome to the vacuole for degradation. In this model, hydrogen peroxide (H₂O₂) is shown as a sole matrix-derived induction signal for pexophagy, although we cannot exclude the possibility of additional induction signals. Refer to the main text for possible contributions of PEX4, PEX14, NBR1, and ATG8 proteins to target recognition. Broken arrows indicate highly speculative steps.