Influence of genotype and nutrition on survival and metabolism of starving yeast

Abstract

Starvation of yeast cultures limited by auxotrophic requirements results in glucose wasting and failure to achieve prompt cell-cycle arrest when compared with starvation for basic natural nutrients like phosphate or sulfate. We measured the survival of yeast auxotrophs upon starvation for different nutrients and found substantial differences: When deprived of leucine or uracil, viability declined exponentially with a half-life of <2 days, whereas when the same strains were deprived of phosphate or sulfate, the half-life was Ϸ10 days. The survival rates of nongrowing auxotrophs deprived of uracil or leucine depended on the carbon source available during starvation, but were independent of the carbon source during prior growth. We performed an enrichment procedure for mutants that suppress lethality during auxotrophy starvation. We repeatedly found loss-of-function mutations in a number of functionally related genes. Mutations in PPM1, which methylates protein phosphatase 2A, and target of rapamycin (TOR1) were characterized further. Deletion of PPM1 almost completely suppressed the rapid lethality and substantially suppressed glucose wasting during starvation for leucine or uracil. Suppression by a deletion of TOR1 was less complete. We suggest that, similar to the Warburg effect observed in tumor cells, starving yeast auxotrophs wastes glucose as a consequence of the failure of conserved growth control pathways. Furthermore, we suggest that our results on condition-dependent chronological lifespan have important implications for the interpretation and design of studies on chronological aging. auxotrophy starvation ͉ chronological aging ͉ Warburg effect

Yeast metabolic and signaling genes are required for heat-shock survival and have little overlap with the heat-induced genes

“…Auxotrophic markers were included in the original yeast deletion collection to allow further genetic manipulation of the deletion collection strains (5). These auxotrophic mutations sometimes have unexpected phenotypes that can interfere with experiments, notably those involving nutrient starvation and potentially other stresses also (7,15). To produce a prototrophic deletion resource without this drawback, we generated a prototrophic deletion collection consisting of 4,783 viable deletion strains (see Materials and Methods for details).…”

Metabolic cycling without cell division cycling in respiring yeast

“…A related inference based on our data is that metabolic cycling does not require continuous influx of fresh media and fluctuations in nutrient concentrations that may arise in continuous cultures, such as oscillation in the glucose concentration in the media of glucose-limited YMC cultures. In our experimental system of a culture cycling in batch, all essential nutrients are likely to decrease as the cells cycle metabolically but not to increase, because the only source of nutrients could be the lysing of starved cells, which is very unlikely to occur at a significant rate a few hours after the exponential growth of a prototrophic culture (23,24).…”

Budding YeastSSD1-VRegulates Transcript Levels of Many Longevity Genes and Extends Chronological Life Span in Purified Quiescent Cells

“…Moreover, these assays of SP cultures are typically carried out with auxotrophic strains. Starved auxotrophs have short but variable life spans, depending on the limiting nutrient (Henry, 1973;Boer et al, 2008). They also have a nonuniform arrest (Saldanha et al, 2004), accumulate more reactive oxygen species and DNA fragmentation (Gomes et al, 2007)¤ and exhaust their …”