Plasticity of the mitochondrial genome in Podospora. Polymorphism for 15 optional sequences: group-I, group-II introns, intronic ORFs and an intergenic region.

The mitochondrial chromosome of 15 Podospora anserina and one Podospora comata wild-type strains have been extensively examined for the presence of optional elements and for sequence divergence. Among the P. anserina strains, nine optional sequences were found. By comparing P. anserina with the closely related and weakly interfertile P. comata species, six additional optional sequences were detected. These optional elements correspond to mitochondrial introns belonging to different groups and subgroups (11 cases), intronic open reading frames (two cases), a complex insert and an intergenic region. Although difficult to explain, the distribution of optional mitochondrial sequences among the 15 wild-type isolates of P. anserina is far from random.