Review Review ATGs are only Partially Conserved in Protists

Macroautophagy (hereafter referred to as autophagy) is a major intracellular degradation system that, in eukaryotes, is mediated by a special organelle, the autophagosome.1,2 Upon autophagy induction, small pieces of the cytoplasm are enclosed by phagophores, which mature into autophagosomes. Then, completed autophagosomes fuse with the lysosome, and the cyto-plasm-derived materials inside the autophagosomes are degraded by lysosomal hydrolases. These degrading structures, called autolysosomes, undergo autolysosomal reformation to terminate autophagy.3 Thus, the autophagosome is a transient structure. Autophagy is important for many physiological and pathological processes: for example, production of amino acids during starva-tion, development, quality control of intracellular proteins and organelles, and degradation of intracellular bacteria.4-6 Autophagosome formation requires autophagy-related (Atg