The control of intracellular glycerol in Saccharomyces cerevisiae influences osmotic stress response and resistance to increased temperature

Glycerol has been demonstrated to serve as the major osmolyte of Saccharomy ces cerevisiae. Consistently, mutant strains gpd1gpd2 and gpp1gpp2, which a re devoid of the main glycerol biosynthesis pathway, have been shown to be osmosensitive. In addition, the primary hyperosmotic stress response is aff ected in these strains. Hog1p phosphorylation turned out to be prolonged an d osmostress-induced gene expression is delayed compared with the kinetics observed in wild-type cells. A hog1 deletion strain was previously found to contain lower internal glycerol and therefore displays an osmosensitive ph enotype. Here, we show that the osmosensitivity of hog1 is suppressed by gr owth at 37 degrees C. We reasoned that this temperature-remedial osmoresist ance might be caused by a higher intracellular glycerol level at the elevat ed temperature. This hypothesis was confirmed by measurement of the glycero l concentration, which was shown to be similar for wild type and hog1 cells only at elevated growth temperatures. In agreement with this finding, hog1 cells containing an fps1 allele, encoding a constitutively open glycerol c hannel, have lost their temperature-remedial osmoresistance. Furthermore, g pd1gpd2 and gpp1gpp2 strains were found to be temperature sensitive. The gr owth defect of these strains could be suppressed by adding external glycero l. In conclusion, the ability to control glycerol levels influences proper osmostress-induced signalling and the cellular potential to grow at elevate d temperatures. These data point to an important, as yet unidentified, role of glycerol in cellular functioning.