The role of trehalose synthesis for the acquisition of thermotolerance in yeast

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Abstract
In the yeast Saccharomyces cerevisiae, accumulation of the non‐reducing disaccharide trehalose is triggered by various stimuli that activate the heat‐schock response. Several studies have shown a close correlation between trehalose levels and tolerance to heat stress, suggesting that trehalose may be a protectant which contributes to thermotolerance. In this study, we have examined mutants defective in genes coding for key enzymes involved in trehalose metabolism with respect to the heat‐induced and stationary‐phase‐induced accumulation of trehalose and the acquisition of thermotolerance. Inactivation of either TPS1 or TPS2, encoding subunits of the trehalose‐6‐phosphate synthase/phosphatase complex, caused an inability to accumulate trehalose upon a mild heat‐shock or upon initiation of the stationary phase and significantly reduced the levels of heat‐induced and stationary‐phase‐induced thermotolerance. Deletion of NTH1, the gene coding for the neutral trehalase, resulted in a defect in trehalose mobilization during recovery from a heat shock which was paralleled by an abnormally slow decrease of thermotolerance. Our results provide strong genetic evidence that heat‐induced synthesis of trehalose is an important factor for thermotolerance induction. In an accompanying study [Hottiger, T., De Virgilio, C., Hall, M. N., Boller, T. & Wiemken, A. (1993) Eur. J. Biochem. 219, 187–193], we present evidence that the function of heat‐induced trehalose accumulation may be to increase the thermal stability of proteins.