Dynamics of the mitochondrial genome during Podospora anserina aging.

Senescence in Podospora anserina is always correlated with extrachromosomal mitochondrial DNA amplification (senDNA). Here we report a quantitative kinetic analysis of the molecular events that occur in the mitochondrial DNA of several wild-type cultures during aging. For each culture, the amplification of senDNA molecules and the modifications of the mitochondrial chromosome are analyzed at different ages and in relation with two age-related parameters: growth rate and fertility. We find senDNAs exponentially amplified from the germination state and particular regions of the mitochondrial chromosome preferentially lost only in the pre-senescent state, i.e. a few centimeters before the growth arrest of the mycelium. This late loss of information, concomitant with the first phenotypic expression of senescence (loss of fertility), begins in the regions from which the senDNAs originate and culminates with the growth arrest of the mycelium.