INDUCTION OF LONGEVITY BY CYTOPLASMIC TRANSFER OF A LINEAR PLASMID INPODOSPORA-ANSERINA

In Podospora anserina the longevity inducing linear plasmid pAL2-1 was transferred from the extrachromosomal long-lived mutant AL2 to the sh ort-lived wild-type strain A. The resulting strain, AL2-IV, exhibited the long-lived phenotype. In the short-lived progeny of crosses betwee n this strain and wild-type strain A, the plasmid was absent. In contr ast, all long-lived progeny contained both the autonomous plasmid as w ell as copies of it integrated in the mitochondrial DNA (mtDNA). Molec ular 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 gene tic background, it is able to integrate into the mtDNA and to induce l ongevity.