Evaluation of the efficiency of sexual reproduction in restoring Podospora anserina mitochondrial DNA to wild-type.

A Podospora anserina mitochondrial DNA (mtDNA) rearrangement mutant, Mn19, was crossed with a deletion mutant, alphaDelta5. Ascospores (212) from random asci were tested for viability, growth and life-span phenotypes, and mtDNA inheritance. Some spore inviability was detected along with early growth arrest (at the time of spore germination) from which some isolates recovered. However, the majority had wild-type growth and life-span phenotypes. All isolates tested at the DNA level (102) had wild-type mtDNA hybridization patterns with probes that detected defects in the parents. About 20% also inherited low levels of mtDNA molecules with the rearrangement characteristic of the Mn19 parent. These results demonstrate that P. anserina has a remarkable ability, through sexual reproduction, to restore its mtDNA to wild-type, even when the parents are predominately mutant.