Bacterial division initiates at the site of a contractile Z-ring composed of polymerized FtsZ. The location of the Z-ring in the cell is controlled by a system of three mutually antagonistic proteins, MinC, MinD, and MinE. Plastid division is also known to be dependent on homologs of these proteins, derived from the ancestral cyanobacterial endosymbiont that gave rise to plastids. In contrast, the mitochondria of model systems such as Saccharomyces cerevisiae, mammals, and Arabidopsis thaliana seem to have replaced the ancestral α-proteobacterial Min-based division machinery with host-derived dynamin-related proteins that form outer contractile rings. Here, we show that the mitochondrial division system of these model organisms is the exception, rather than the rule, for eukaryotes. We describe endosymbiont-derived, bacterial-like division systems comprising FtsZ and Min proteins in diverse less-studied eukaryote protistan lineages, including jakobid and heterolobosean excavates, a malawimonad, stramenopiles, amoebozoans, a breviate, and an apusomonad. For two of these taxa, the amoebozoan Dictyostelium purpureum and the jakobid Andalucia incarcerata, we confirm a mitochondrial localization of these proteins by their heterologous expression in Saccharomyces cerevisiae. The discovery of a proteobacterial-like division system in mitochondria of diverse eukaryotic lineages suggests that it was the ancestral feature of all eukaryotic mitochondria and has been supplanted by a host-derived system multiple times in distinct eukaryote lineages.

Biotechnology and Biomedicine Centre of the Academy of Sciences and Charles University in Vestec Group Department of Parasitology Faculty of Science Charles University Prague 128 44 Prague Czech Republic

Centre for Comparative Genomics and Evolutionary Bioinformatics Department of Biochemistry and Molecular Biology Dalhousie University Halifax NS Canada B3H 4R2

Department of Biology and Ecology Faculty of Science University of Ostrava 710 00 Ostrava Czech Republic

Laboratory of Genomics and Bioinformatics Institute of Molecular Genetics Academy of Sciences of the Czech Republic 142 20 Prague 4 Czech Republic

Robert Cedergren Centre for Bioinformatics and Genomics Département de Biochimie Université de Montréal Montreal QC Canada H3T 1J4

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