Induction of longevity by cytoplasmic transfer of a linear plasmid in Podospora anserina

In Podospora anserina the longevity inducing linear plasmid pAL2-1 was transferred from the extrachromosomal long-lived mutant AL2 to the short-lived wild-type strain A. The resulting strain, AL2-IV, exhibited the long-lived phenotype. In the short-lived progeny of crosses between this strain and wild-type strain A, the plasmid was absent. In contrast, all long-lived progeny contained both the autonomous plasmid as well as copies of it integrated in the mitochondrial DNA (mtDNA). Molecular analysis revealed that the integrated plasmid copies most likely resulted from a de novo integration of the autonomous element and the generation of AT-linker sequences at the integration site. We conclude that once the plasmid is present in mitochondria of a particular genetic background, it is able to integrate into the mtDNA and to induce longevity.