Genomic Recombination of the Mitochondrial atp6 Gene in Arabidopsis thaliana at the Protein Processing Site Creates Two Different Presequences

In the mitochondrial genome of the flowering plant Arabidopsisthaliana the atp6 open reading frame is located on the borderof one of the repeats resulting in two copies with differentpresequence extensions. The two presequences of 135 and 97 aminoacids respectively show no similarity to each other, while themature protein sequences are identical. Both preproteins aremost likely synthesized in Arabidopsis mitochondria from promoterelements upstream of each copy. The presence of two arrangementsin the mitochondrial genome of fertile Arabidopsis plants suggeststhis recombination to be unrelated to a cytoplasmic male sterilephenotype. This recombination precisely at the mature proteinterminus is reminiscent of the domain shuffling model in proteinevolution.