Linearization of maize mitochondrial chromosomes by recombination with linear episomes

Cytoplasmic male sterility in maize is determined by the mitochondrial genotype. One strain of cytoplasmically male sterile maize contains, in addition to the usual circular mitochondrial chromosomes, two short linear episomes, S-1 and S-2. We report here that S-1 and S-2 can recombine with homologous sequences present on the circular chromosomes to convert a high proportion of the mitochondrial DNA into linear molecules with S-1 and S-2 covalently linked to one end.