title: TOR and RAS pathways regulate desiccation tolerance in Saccharomyces cerevisiae.
abstract: Tolerance to desiccation in cultures of Saccharomyces cerevisiae is inducible; only one in a million cells from an exponential culture survive desiccation compared with one in five cells in stationary phase. Here we exploit the desiccation sensitivity of exponentially dividing cells to understand the stresses imposed by desiccation and their stress response pathways. We found that induction of desiccation tolerance is cell autonomous and that there is an inverse correlation between desiccation tolerance and growth rate in glucose-, ammonia-, or phosphate-limited continuous cultures. A transient heat shock induces a 5000-fold increase in desiccation tolerance, whereas hyper-ionic, -reductive, -oxidative, or -osmotic stress induced much less. Furthermore, we provide evidence that the Sch9p-regulated branch of the TOR and Ras-cAMP pathway inhibits desiccation tolerance by inhibiting the stress response transcription factors Gis1p, Msn2p, and Msn4p and by activating Sfp1p, a ribosome biogenesis transcription factor. Among 41 mutants defective in ribosome biogenesis, a subset defective in 60S showed a dramatic increase in desiccation tolerance independent of growth rate. We suggest that reduction of a specific intermediate in 60S biogenesis, resulting from conditions such as heat shock and nutrient deprivation, increases desiccation tolerance.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: Aaron Z
authors.initials: AZ
authors.lastname: Welch
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Gibney
authors.forename: David
authors.initials: D
authors.lastname: Botstein
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Koshland
mesh_terms: D000222:Adaptation, Physiological; D003470:Culture Media; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003681:Dehydration; D055786:Gene Knockout Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D013312:Stress, Physiological; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D003470:Culture Media; D017868:Cyclic AMP-Dependent Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; D014157:Transcription Factors; D018631:ras Proteins; C561842:TORC1 protein complex, S cerevisiae; C083324:TOR1 protein, S cerevisiae; C489014:RAS1 protein, S cerevisiae; C489015:RAS2 protein, S cerevisiae