Endosymbiosis before eukaryotes: mitochondrial establishment in protoeukaryotes
- PDF / 2,699,869 Bytes
- 21 Pages / 595.276 x 790.866 pts Page_size
- 60 Downloads / 151 Views
Cellular and Molecular Life Sciences
REVIEW
Endosymbiosis before eukaryotes: mitochondrial establishment in protoeukaryotes István Zachar1,2,3 · Gergely Boza1,4 Received: 29 June 2019 / Revised: 25 December 2019 / Accepted: 14 January 2020 © The Author(s) 2020
Abstract Endosymbiosis and organellogenesis are virtually unknown among prokaryotes. The single presumed example is the endosymbiogenetic origin of mitochondria, which is hidden behind the event horizon of the last eukaryotic common ancestor. While eukaryotes are monophyletic, it is unlikely that during billions of years, there were no other prokaryote–prokaryote endosymbioses as symbiosis is extremely common among prokaryotes, e.g., in biofilms. Therefore, it is even more precarious to draw conclusions about potentially existing (or once existing) prokaryotic endosymbioses based on a single example. It is yet unknown if the bacterial endosymbiont was captured by a prokaryote or by a (proto-)eukaryote, and if the process of internalization was parasitic infection, slow engulfment, or phagocytosis. In this review, we accordingly explore multiple mechanisms and processes that could drive the evolution of unicellular microbial symbioses with a special attention to prokaryote–prokaryote interactions and to the mitochondrion, possibly the single prokaryotic endosymbiosis that turned out to be a major evolutionary transition. We investigate the ecology and evolutionary stability of inter-species microbial interactions based on dependence, physical proximity, cost–benefit budget, and the types of benefits, investments, and controls. We identify challenges that had to be conquered for the mitochondrial host to establish a stable eukaryotic lineage. Any assumption about the initial interaction of the mitochondrial ancestor and its contemporary host based solely on their modern relationship is rather perilous. As a result, we warn against assuming an initial mutually beneficial interaction based on modern mitochondria–host cooperation. This assumption is twice fallacious: (i) endosymbioses are known to evolve from exploitative interactions and (ii) cooperativity does not necessarily lead to stable mutualism. We point out that the lack of evidence so far on the evolution of endosymbiosis from mutual syntrophy supports the idea that mitochondria emerged from an exploitative (parasitic or phagotrophic) interaction rather than from syntrophy. Keywords Mutualism · Endosymbiosis · Prokaryotes · Mitochondria · Eukaryogenesis
Introduction * István Zachar [email protected] 1
Evolutionary Systems Research Group, Institute of Evolution, Centre for Ecological Research, Klebelsberg Kunó str. 3., Tihany 8237, Hungary
2
MTA‑ELTE Theoretical Biology and Evolutionary Ecology Research Group, Department of Plant Taxonomy and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/c, Budapest 1117, Hungary
3
Center for the Conceptual Foundations of Science, Parmenides Foundation, Kirchplatz 1, 82049 Munich, Germany
4
Evolution and Ecology Program, Internation
Data Loading...
