title: Ancient homology of the mitochondrial contact site and cristae organizing system points to an endosymbiotic origin of mitochondrial cristae.
abstract: Mitochondria are eukaryotic organelles that originated from an endosymbiotic α-proteobacterium. As an adaptation to maximize ATP production through oxidative phosphorylation, mitochondria contain inner membrane invaginations called cristae. Recent work has characterized a multi-protein complex in yeast and animal mitochondria called MICOS (mitochondrial contact site and cristae organizing system), responsible for the determination and maintenance of cristae [1-4]. However, the origin and evolution of these characteristic mitochondrial features remain obscure. We therefore conducted a comprehensive search for MICOS components across the major groups that encompass eukaryotic diversity to determine the extent of conservation of this complex. We detected homologs for the majority of MICOS components among opisthokonts (the group containing animals and fungi), but only Mic60 and Mic10 were consistently identified outside this group. The conservation of Mic60 and Mic10 in eukaryotes is consistent with their central role in MICOS function [5-7], indicating that the basic mechanism for cristae determination arose early in evolution and has remained relatively unchanged. We found that eukaryotes with ultrastructurally simplified anaerobic mitochondria that lack cristae have also lost MICOS. We then searched for a prokaryotic MICOS and identified a homolog of Mic60 present only in α-proteobacteria, providing evidence for the endosymbiotic origin of mitochondrial cristae. Our study clarifies the origins of mitochondrial cristae and their subsequent evolutionary history, provides evidence for a general mechanism of cristae formation and maintenance in eukaryotes, and points to a new potential factor involved in membrane differentiation in prokaryotes.
authors.affiliation: Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada.
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Muñoz-Gómez
authors.affiliation: Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada; Canadian Institute for Advanced Research, Halifax, NS B3H 4R2, Canada.
authors.forename: Claudio H
authors.initials: CH
authors.lastname: Slamovits
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
authors.forename: Joel B
authors.initials: JB
authors.lastname: Dacks
authors.affiliation: Department of Science, Augustana Faculty, University of Alberta, Camrose, AB T4V 2R3, Canada.
authors.forename: Kaitlyn A
authors.initials: KA
authors.lastname: Baier
authors.affiliation: Department of Science, Augustana Faculty, University of Alberta, Camrose, AB T4V 2R3, Canada.
authors.forename: Katelyn D
authors.initials: KD
authors.lastname: Spencer
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada; Department of Science, Augustana Faculty, University of Alberta, Camrose, AB T4V 2R3, Canada. Electronic address: jeremy.grant.wideman@gmail.com.
authors.forename: Jeremy G
authors.initials: JG
authors.lastname: Wideman
mesh_terms: D019143:Evolution, Molecular; D008928:Mitochondria / Q000502:physiology*; D046912:Multiprotein Complexes / Q000235:genetics*; D040681:Structural Homology, Protein; D013559:Symbiosis
chemical_list: D046912:Multiprotein Complexes