Podospora anserina

Podospora anserina ages and dies with programmed regularity—a defined lifespan that made it an early model for fungal senescence. Unlike S. cerevisiae's indefinite growth potential (mothers age but daughters are rejuvenated), P. anserina cultures inevitably senesce after a predictable number of days. This obligate senescence provided geneticists with a system where aging is the rule rather than the exception, enabling identification of genes that accelerate or delay the inevitable decline.

Mitochondrial dynamics drive P. anserina senescence. Young cultures maintain functional mitochondria through quality control systems that eliminate damaged organelles. As cultures age, these systems fail, damaged mitochondria accumulate, and energy production declines. The specificity is remarkable: P. anserina senescence involves characteristic mitochondrial DNA rearrangements and accumulation of a specific senescence plasmid (pAL2-1). These molecular markers enable precise measurement of senescence progression.

Comparison between P. anserina's obligate senescence and S. cerevisiae's indefinite growth potential reveals the diversity of fungal aging strategies. P. anserina may have evolved programmed death to limit resource competition with offspring—the parent mycelium dies, releasing nutrients for progeny. Alternatively, the mitochondrial rearrangements may simply be unavoidable consequences of aging that P. anserina hasn't evolved to escape. Whatever the evolutionary explanation, P. anserina demonstrates that senescence can be genetically programmed rather than purely stochastic.