Mitochondrial membrane potential and ageing in Podospora anserina

Abstract

Some filamentous fungi exhibit a limited vegetative growth with modifications in the mitochondria, suggesting the involvement of mitochondria in the process of ageing. Nevertheless, the relationship between the ability to grow or the fate of these cells relative to their mitochondrial membrane potential (Ψmt) level has not been investigated. Using flow cytometric analysis, we have assessed Ψmt in young and senescent cultures of wild type strains and mitochondrial or nuclear mutant strains of Podosporaanserina that present very long or brief life span. When we compared two distinct populations of cells obtained from the same strain, we can show a correlation not only between Ψmt and ageing, but also between Ψmt and the frequency of regeneration and/or the life span. However, this relationship is not observed when we compared the cells obtained from different physiological states or mutants strains. These results allow us to suggest that the Ψmt modifications during senescence could be only one of the possible consequences of the process and are not the factor driving towards death. We also show that the driving force of Ψmt is principally maintained by the alternative pathway during ageing, suggesting a role of the alternative oxidase pathway.