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This site aims to offer an autogenic explanation for the origin of mitochondria, in the sense that the mitochondrial system evolved from existing eukaryotic endomembrane components. This in contrast to the endosymbiotic theory that assumes that mitochondria originated from bacteria that took residence in an unidentified other cell and became enslaved by an unknown mechanism. You can read my critique on the endosymbiotic theory here. The alternative ‘eukaryotic origin for mitochondria’ presents a gradualistic scenario where small genetic changes to the existing endomembrane system lead to generation of a more-or-less independent organelle. Driving forces for such a scenario would be the advantages that a compartmentalization of metabolic function into specialized organelles offers to flexibity and robustness of the cell.

Below (larger picture here) the general steps that would support an autogenic origin of mitochondria: 

origin of mitochondria small

Below, I looked at the evolution of the main metabolic pathways in mitochondria and proposed a gradual evolution (larger picture here.

origin of electron transport chain mitochondria 

 

And below (larger picture here) in its context of the evolution of the eukaryotic cell and its endomembrane system (zie ook de Roos 2006):

origin of endomembranes small

I will try to base my research on the origin of mitochondria based on a model that sees evolution as an expanding system of functional modules that communicate through strictly defined interfaces. In such a system that grows by functional extensions, existing interfaces cannot be changed anymore because of the dependencies of downstream functions on this interface. By analyzing the functional modules, their conserved interfaces and its dependants, it then becomes possible to determine the logical sequence of events that occurred in evolution. I will look specifically to genetic control, protein import mechanisms, metabolic function and its relation with the cell cycle. I believe that these subsystems that are involved in the origin of mitochondria point to a eukaryotic origin as a functional extension of the endomembrane system.

I will incorporate the evolution of the subsystems in a complete gradual scenario for the origin of mitochondria. I will focus on the gradual specialization of the endomembrane system leading to increasingly complex organelles. Diversification of an existing protein targeting to the ER, could lead to specialized ER-derived compartments such as mitosomes and hydrogenosomes and in a seperate line from the ER, the mitochondria. The specific extra functionality that is gained in each step will be related to metabolic activity based on core functionality of an ATP synthase driven by a proton gradient. The presence of introns in some genes suggest an origin from the nuclear genome, although lateral gene transfer using a plasmid or viral vector cannot be excluded. All the intermediates can be found in the organelles of amitochondriate organisms and in mitochondrial genomes without (e.g. Cryptosporidium) or with a very small genome (e.g. Amphidinium). 

A detailed discussion about the eukaryotic origin of mitochondria can be found here.

At the moment comments are more than welcome although the site is in a dynamic state. It’s my intention to incorporate criticism, objections, alternative views etc, so that it will be a dynamic site. On my personal website you can find more of my scientific background and my views on design and evolution. Based on a similar evolutionary framework, I also have proposed gradual scenarios for the origin of life, the origin of introns and genes, the origin of the nucleus and the origin of insect metamorphosis