Proline is considered to be a stress protectant in the yeast Saccharomyces cerevisiae, as is trehalose. In this study, we constructed yeast strains that accumulate proline but not trehalose and that increase proline levels in response to stress. Our results suggest that proline does not complement the function of trehalose, and that moderate expression of the PRO1 gene encoding γ-glutamyl kinase is important to stress tolerance of yeast cells.
