Entamoeba mitosomes play an important role in encystation by association with cholesteryl sulfate synthesis

Evolution and diversification of organelles is a central topic in biology. Mitochondrion-related organelles (MROs) are highly modified forms of mitochondria found in anaerobic eukaryotes. MROs show a spectrum of functions that are either reduced or modified from those of canonical mitochondria by environmental constraints and evolutionary selection. Hence, elucidation of MRO functions will improve our understanding of organelle evolution and the speciation of eukaryotes. Here, we substantiate a role of the Entamoeba mitosome, a type of MRO, by showing that cholesteryl sulfate synthesized through a mitosomal pathway regulates differentiation that is essential for the parasite's life cycle. These findings support the contribution of an endosymbiont-derived organelle to parasitism, a previously unrecognized concept that casts new light on organelle evolution.