Natural selection and the evolution of mtDNA-encoded peptides: evidence for intergenomic co-adaptation

Mitochondrial DNA (mtDNA) variation is an important tool for the investigat ion of the population genetics of animal species. Recently, recognition of the role of mtDNA mutations in human disease has spurred increasing interes t in the function and evolution of mtDNA and the 13 polypeptides it encodes . These proteins interact with a large number of peptides encoded in the nu cleus to form the mitochondrial electron transport system (ETS). As the ETS is the primary energy generation system in aerobic metazoans. natural sele ction would be expected to favor mutations that enhance ETS function. Such mutations could occur in either the mitochondrial or nuclear genes encoding ETS proteins and would lead to positive intergenomic interactions, or co-a daptation, Direct evidence for intergenomic co-adaptation comes from functi onal studies of systems where nuclear-mitochondrial DNA combinations vary n aturally or can be manipulated experimentally.