Ageing transcriptomes of selected mutants on different carbon sources

Here we show that an unrestricted galactose diet in early life minimises pathology during replicative ageing in budding yeast, irrespective of diet later in life. Lifespan and average mother cell division rate are comparable between glucose and galactose diets, but markers of senescence and the progressive dysregulation of gene expression observed on glucose are minimal on galactose, showing these to be facets of ageing pathology rather than intrinsic parts of the replicative ageing process. Respiration on galactose is critical for minimising ageing pathology, and forced respiration during ageing on glucose by over-expression of Hap4 also has the same effect though only in a fraction of cells. This fraction maintains Hap4 activity to advanced age with low senescence and a youthful gene expression profile, whereas other cells in the same population that lose Hap4 activity undergo dramatic dysregulation of gene expression and accumulate aneuploid fragments of chromosome XII aneuploidy (ChrXIIr), which are tightly associated with ageing pathology. Overall design: Mother Enrichment Project (MEP) yeast were harvested at log phase or aged for 24 or 48 hours in YP with indicated carbon sources at 2%. Mother cells were purified, total RNA extracted and libraries processed using a NEBNext Ultra II directional RNAseq kit with poly(A)+ selection module.