Stimulation of the yeast high osmolarity glycerol (HOG) pathway: evidence for a signal generated by a change in turgor rather than by water stress

The Saccharomyces cerevisiae HOG pathway controls responses to osmotic shoc k such as production of the osmolyte glycerol. Here we show that the HOG pa thway can be stimulated by addition of glycerol. This stimulation was stron gly diminished in cells expressing an unregulated Fps1p glycerol channel, p resumably because glycerol rapidly equilibrated across the plasma membrane. Ethanol, which passes the plasma membrane readily and causes mater stress by disturbing the hydration of biomolecules, did not activate the HOG pathw ay. These observations suggest that stimulation of the HOG pathway is media ted by a turgor change and not by water stress per se. (C) 2000 Federation of European Biochemical Societies.