Single-membrane-bound organelles: Division and inheritance

C. merolae cells contain four types of single-membrane-bound organelles-the ER, Golgi bodies, vacuoles/lysosomes, and peroxisomes-the dynamics of which have been studied during the cell cycle by fluorescence microscopy and electron microscopy. The ER retains some integrity throughout the cell cycle and is apportioned to daughter cells by spindle elongation. Golgi bodies proliferate prior to M phase and lie close to the spindle poles, with which they are inherited. Vacuoles proliferate and migrate toward mitochondria before M phase, and by binding to the mitochondria, they become inherited by daughter cells. This binding requires a coiled-coil protein, vacuole inheritance gene 1 (VIG1). Peroxisomes associate with the division planes of mitochondria before mitochondrial division, after which they divide-a process that is dependent on dynamin and peroxisomedividing (POD) machinery-and are inherited with the divided mitochondria. The inheritance of vacuoles and peroxisomes relies on the spindle, because it is required for mitochondrial inheritance. Because the spindle segregates chromosomes, the inheritance of all single-membrane-bound organelles is coupled to chromosomalinheritance via the spindle. This coupling allows cells to retain organelles and remain functional after cell division.