MitOS forms a complex extended scaffold-like structure on the mitochondrial inner membrane. (A) Cells expressing GFP-tagged versions of MitOS components as indicated and mito-dsRed were visualized by light microscopy. Representative images are shown. The boxes indicate the areas shown in the inset. (B) Cells expressing Fcj1-mCherry and Aim5-yeGFP were visualized by light microscopy. Representative images are shown. The boxes indicate the areas shown in the insets. Arrows indicate Fcj1-mCherry puncta. Double arrowheads indicate areas labeled exclusively by Aim5-yeGFP. (C) Rho0 cells expressing GFP-tagged versions of MitOS components as indicated and mito-dsRed were visualized by light microscopy. Representative images are shown. Boxes indicate the areas shown in the inset. Bar, 2 µm. (D) Schematic representation of MitOS localization in mitochondria and its role as an organizer of inner membrane structure. BR, boundary membrane region; CJ, cristae junction; MIM, inner mitochondrial membrane; MOM, outer mitochondrial membrane. Bars, 2 µm.