Increased peroxisome proliferation is associated with early yeast replicative ageing.

Peroxisomes are single membrane-bound organelles ubiquitously present in several cell types and are associated with cell and tissue-specific functions. Their role in cellular ageing is under investigation in various model systems. Metabolism of cellular reactive oxygen species is a universal function performed by these organelles. In this study, we investigated alterations in peroxisome number upon early replicative ageing of yeast cells. Increase in the number of peroxisomes in replicatively aged mother cells of wild-type yeast was observed when cultured in both peroxisome-inducing and non-inducing medium. Further, we investigated if this increase in peroxisome number in replicatively aged cells is due to enhanced peroxisome proliferation. For this, the number of peroxisomes in replicatively aged mother cells of pex11, pex25 and pex11pex25 was analysed. Increased percentage of aged cells was observed in pex25 and pex11pex25 cells cultured in peroxisome-inducing oleic acid medium. Interestingly, when cultured in oleic acid, young mother cells devoid of Pex11 showed reduced peroxisome proliferation compared to old mother cells. Induced activity of the antioxidant enzyme catalase and reduced accumulation of reactive oxygen species were reported in all studied strains when cultured in oleic acid medium. Further, our data also suggest that replicatively aged cells with increased peroxisome number also display mitochondrial dysfunction and fragmentation in all the strains studied. In conclusion, our data suggests a correlation between increase in peroxisome number and replicative age of yeast cells and interestingly this increase seems to be partly dependent on the fission proteins.