Fig. 2. Deletion of UGT51 leads to impaired degradation of the peroxisomal marker enzyme Aox. (A) Pichia pastoris cells were grown in methanol medium for 2 days and replica-plated to either a nylon membrane filter attached on a glucose medium plate or to an ethanol medium plate. Purple represents the persistence of the peroxisomal protein Aox detected by its activity staining. In wild-type cells, Aox was degraded following the carbon source shift to glucose (micropexophagy) or ethanol (macropexophagy). In contrast, both mechanisms were impaired in the ugt51Δ mutant (second line). Re-introduction of the UGT51 gene with its original promoter in the ugt51Δ strain restored peroxisome degradation (PoUGT51) (third line). (B) Wild-type and ugt51Δ cells were transferred to glucose medium, and harvested after the indicated times. Protein extracts were then subjected to immunoblot analysis using anti-Aox antibody. The decrease in the intensity of the Aox band was blocked in the ugt51Δ strain.