Direct evidence for homologous recombination in mussel (Mytilus galloprovincialis) mitochondrial DNA

The: assumption that animal mitochondrial DNA (mtDNA) does not undergo homo logous recombination is based on indirect evidence, yet it has had an impor tant influence on our understanding of mtDNA repair and mutation accumulati on land thus mitochondrial disease and aging) and on biohistorical inferenc es made from population data. Recently, several studies have suggested reco mbination in primate mtDNA on the basis of patterns of frequency distributi on and linkage associations of mtDNA mutations in human populations, but ot hers have failed to produce similar evidence, Here, we provide direct evide nce for homologous mtDNA recombination in mussels, where heteroplasmy is th e rule in males. Our results indicate a high rate of mtDNA recombination. C oupled with the observation that mammalian mitochondria contain the enzymes needed for the catalysis of homologous recombination, these, findings sugg est that animal mtDNA molecules may recombine regularly and that the extent to which. this generates: new haplotypes may depend only on the frequency of biparental inheritance of the mitochondrial genome. This, generalization must, however, await evidence from animal species with typical maternal mt DNA inheritance.