A unique mechanism for protein processing and degradation in Arabidopsis thaliana.

Precursor protease vesicles are plant-specific compartments containing precursors of enzymes that are thought to participate in the degradation of cellular components in organs undergoing senescence. We report in vivo evidence that the precursor protease vesicle-localized vacuolar processing enzyme-gamma (VPEgamma) is critical for maturation of the plant vacuolar protease AtCPY. We also provide biochemical and functional evidence that VPEgamma is involved in degradation of the vacuolar invertase AtFruct4 in aging tissues. Moreover, a proteomics-based approach identified various proteins found in the vacuoles of aging vpegamma mutants but not in WT plants, suggesting a unique role of VPEgamma in protein processing and degradation in Arabidopsis.