Microstructure and ultrastructure observasion of primary root development in Arabidopsis thaliana with MG132 treatment were carried out using optical and electron microscope.(1)The differential interference contrast (DIC) observation indicated that MG132 induced cytosolic vacuolization in root cells in a dose-dependent manner.(2)Coomassie Brilliant Blue staining indicated that MG132-induced vacuoles were filled with proteins.(3)Immunofluorescence labeling with anti-ubiquitin antibody reveled the accumulation of the ubiquitinated proteins in vacuoles,suggesting a promotion of autophagic vacuolization in response to proteasome malfunction.(4)TEM observation confirmed the formation of autolysosomes in root cells.In summary,our result revealed the promotion of autophagy-derived vacuolization in response to proteasome malfunction,thus provide a new evidences of the functional link between the ubiquitin/proteasome pathway and autophagic vacuolization.