Mitochondrial DNA sequences in the nuclear genome of a locust

The endosymbiotic theory1 of the origin of mitochondria is widely accepted, and implies that loss of genes from the mitochondria to the nucleus of eukaryotic cells has occurred over evolutionary time2,3. However, evidence at the DNA sequence level for gene transfer between these organelles has so far been limited to a single example, the demonstration that a mitochondrial ATPase subunit gene of Neurospora crassa has an homologous partner in the nuclear genome4. From a gene library of the insect, Locusta migratoria, we have now isolated two clones, representing separate fragments of nuclear DNA, which contain sequences homologous to the mitochondrial genes for ribosomal RNA, as well as regions of homology with highly repeated nuclear sequences. The results suggest the transfer of sequences between mitochondrial and nuclear genomes, followed by evolutionary divergence.