Late acquisition of mitochondria by a host with chimaeric prokaryotic ancestry
Authors: Alexandros A Pittis
Toni Gabaldón
Journal: Nature (2016)
Discipline: Multidisciplinary
Keywords: Eukaryotes; Mitochondria; Endosymbiosis; Phylogenomics; Evolution
Affiliations: Bioinformatics and Genomics Programme, Centre for Genomic Regulation (CRG), Carrer del Dr Aiguader, 88, 08003 Barcelona, Spain., Departament of Ciències Experimentals I de La Salut, Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain., Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig de Lluís Companys 23, 08010 Barcelona, Spain.

Abstract:  The origin of eukaryotes stands as a major conundrum in biology. Current evidence indicates that the last eukaryotic common ancestor already possessed many eukaryotic hallmarks, including a complex subcellular organization. In addition, the lack of evolutionary intermediates challenges the elucidation of the relative order of emergence of eukaryotic traits. Mitochondria are ubiquitous organelles derived from an alphaproteobacterial endosymbiont. Different hypotheses disagree on whether mitochondria were acquired early or late during eukaryogenesis. Similarly, the nature and complexity of the receiving host are debated, with models ranging from a simple prokaryotic host to an already complex proto-eukaryote. Most competing scenarios can be roughly grouped into either mito-early, which consider the driving force of eukaryogenesis to be mitochondrial endosymbiosis into a simple host, or mito-late, which postulate that a significant complexity predated mitochondrial endosymbiosis. Here we provide evidence for late mitochondrial endosymbiosis. We use phylogenomics to directly test whether proto-mitochondrial proteins were acquired earlier or later than other proteins of the last eukaryotic common ancestor. We find that last eukaryotic common ancestor protein families of alphaproteobacterial ancestry and of mitochondrial localization show the shortest phylogenetic distances to their closest prokaryotic relatives, compared with proteins of different prokaryotic origin or cellular localization. Altogether, our results shed new light on a long-standing question and provide compelling support for the late acquisition of mitochondria into a host that already had a proteome of chimaeric phylogenetic origin. We argue that mitochondrial endosymbiosis was one of the ultimate steps in eukaryogenesis and that it provided the definitive selective advantage to mitochondria-bearing eukaryotes over less complex forms. 

Retracted: No

PubPeer comments:
 Readers should become aware of a peer-reviewed study that calls into question the conclusions by Pittis Gabaldu00f3n 2016 paper entitled  Late Mitochondrial Origin Is an Artifact , originally published as a preprint . From the Abstract:  The origin of mitochondria was a crucial event in eukaryote evolution. A recent report claimed to provide evidence, based on branch length variation in phylogenetic trees, that the mitochondrion came late in eukaryotic evolution. Here, we reinvestigate their claim with a reanalysis of the published data. We show that the analyses underpinning a late mitochondrial origin suffer from multiple fatal flaws founded in inappropriate statistical methods and analyses, in addition to erroneous interpretations Authors also published a reply: https: www.biorxiv.org content 10.1101 064873v1 ,