Origin of an animal mitochondrial DNA polymerase subunit via lineage-specific acquisition of a glycyl-tRNA synthetase from bacteria of the Thermus-Deinococcus group.

Phylogenetic tree analysis shows that the accessory subunit animal mitochondrial DNA polymerase emerges as a result of horizontal transfer of the gene encoding glycyl-tRNA synthetase from a bacterium of the Thermus-Deinococcus group into the animal nuclear genome. This acquisition by a distinct eukaryotic lineage of a gene encoding a mitochondrial protein from a nonmitochondrial bacterial source underscores the contribution of different types of horizontal transfer event to the evolution of eukaryotes.