Senescence in Podospora anserina: amplification of a mitochondrial DNA sequence.

Senescence in Podospora anserina has long been shown to be under cytoplasmic control. Comparison of DNAs isolated from young and senescent cultures made it possible to detect the presence, in senescent cultures only, of a specific DNA (SEN-DNA). This DNA consists of repeated sequences arranged in a multimeric set of circular molecules. In this study we have examined one particular SEN-DNA whose monomer unit is 6300 bp long. Using the Southern hybridization technique, we have demonstrated that this SEN-DNA results from the amplication of a sequence of the mitochondrial chromosome. This amplification, which resembles the process leading to rho- ("petite") mutations in yeast, is discussed in relation to the determinism of senescence.