Welch AZ, Gibney PA, Botstein D, Koshland DE

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 ...

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stress response pathways. We found that induction of desiccation tolerance is cell autonomous and 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 five thousand- fold increase in desiccation tolerance while hyper- ionic, reductive, oxidative, or hyperosmotic 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.

Date: Nov. 21, 2012

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