Mitochondrion lifecycle

Mitochondria are never made de novo: they grow by importing nuclear-encoded proteins and lipids into pre-existing organelles, divide, fuse, carry out their metabolic functions, are kept in check by quality-control pathways, and are removed by selective autophagy. This umbrella module composes the modules for each of those stages by reference. Protein import and iron-sulfur cluster assembly are required in every eukaryote with a mitochondrion-related organelle, including anaerobic hydrogenosomes and mitosomes that have lost respiration; the other stages vary between lineages.

Stage skeleton shared by organelle lifecycle umbrellas (part roles): biogenesis and protein supply, division, fusion, function, quality control, turnover. Read as a satisfiability rule, the umbrella is satisfied when its required stages are, so only stages that are both universal and modelled as rules are required: protein import and iron-sulfur cluster assembly. Division, fusion, quality control and turnover are optional because the referenced modules are not yet written as eukaryote-wide rules: the dynamin-related fission node also requires the metazoan MFF adaptor, mitofusin fusion is absent from plants, and the mitochondrial UPR module is metazoan. Division should become required once its module carries lineage variants (Mff, Mdv1/Fis1, and FtsZ-based division in some algae and protists). Respiration is optional because hydrogenosomes and mitosomes lack it, and complex I is optional within it because Saccharomyces respires without one, using single-subunit NADH dehydrogenases instead. Both required stages are rule candidates, with a named exception not yet modelled as a variant: kinetoplastids for protein import, and Archamoebae such as Entamoeba, whose bacterial-type NIF system replaces NFS1 and ISCU, for iron-sulfur cluster assembly. Those genomes report a gap at the step concerned; the Fe-S module's notes list further lineages to check. Not yet modelled, because no eukaryote-wide module exists to reference: mitochondrial DNA maintenance and gene expression, membrane lipid supply (cardiolipin synthesis, ER contact sites), cristae organization (MICOS), and alpha-helical outer-membrane protein insertion. Drosophila-scoped modules exist for the first three (dmel_mitochondrial_dna_replisome, dmel_mitochondrial_ribosome, dmel_cardiolipin_biosynthesis_remodeling, dmel_micos_complex) but cannot serve as eukaryote-wide stages.