Figure 1

Morphology of autophagy pathways in yeast. Autophagy is the membrane-trafficking pathway that delivers cytoplasmic material to the vacuole for degradation and recycling. Macroautophagy involves the formation of a cytosolic double-membrane vesicle, an autophagosome, which sequesters bulk cytoplasm. Upon completion, autophagosomes fuse with the vacuole membrane releasing a single membrane autophagic body inside the vacuole lumen. The autophagic body is degraded by vacuolar hydrolases. During microautophagy, the sequestration event occurs directly at the vacuole surface. The process also results in a single-membrane vesicle that is ultimately degraded inside the vacuole. Peroxisomes can be selectively taken into the vacuole for degradation by the pexophagy pathway, a specific type of autophagy. Whereas macropexophagy requires the formation of a sequestering vesicle in the cytosol, micropexophagy occurs directly at the vacuole surface.