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Yeast
Volume 1 (2000), Issue 3, Pages 170-187
http://dx.doi.org/10.1002/1097-0061(20000930)17:3<170::AID-YEA25>3.0.CO;2-V
Research Article

The Dual Origin of the Yeast Mitochondrial Proteome

1Department of Molecular Evolution, Uppsala University, Uppsala 752 34, Sweden
2Department of Molecular Evolution, Evolutionary Biology Center, Norbyvägen 18C, Uppsala 752 34, Sweden

Received 30 May 2000; Accepted 14 July 2000

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We propose a scheme for the origin of mitochondria based on phylogenetic reconstructions with more than 400 yeast nuclear genes that encode mitochondrial proteins. Half of the yeast mitochondrial proteins have no discernable bacterial homologues, while one-tenth are unequivocally of α-proteobacterial origin. These data suggest that the majority of genes encoding yeast mitochondrial proteins are descendants of two different genomic lineages that have evolved in different modes. First, the ancestral free-living α-proteobacterium evolved into an endosymbiont of an anaerobic host. Most of the ancestral bacterial genes were lost, but a small fraction of genes supporting bioenergetic and translational processes were retained and eventually transferred to what became the host nuclear genome. In a second, parallel mode, a larger number of novel mitochondrial genes were recruited from the nuclear genome to complement the remaining genes from the bacterial ancestor. These eukaryotic genes, which are primarily involved in transport and regulatory functions, transformed the endosymbiont into an ATP-exporting organelle.