Microaerobic glycerol formation in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae produces large amounts of glycerol as an osmoregulator during hyperosmotic stress and as a redox sink at low oxygen availability. NAD(+)-dependent glycerol-3-phosphate dehydrogenase in S. ce revisiae is present in two isoforms, coded for by two different genes, GPD1 and GPD2. Mutants for either one or both of these genes were investigated under carefully controlled static and dynamic conditions in continuous cult ures at low oxygen transfer rates. Our results show that S. cerevisiae cont rols the production of glycerol in response to hypoxic conditions by regula ting the expression of several genes. At high demand for NADH reoxidation, a strong induction was seen not only of the GPD2 gene, but also of GPP1, en coding one of the molecular forms of glycerol-3-phosphatase. Induction of t he GPP1 gene appears to play a decisive role at elevated growth rates. At l ow demand for NADH reoxidation via glycerol formation, the GPD1, GPD2, GPP1 , and GPP2 genes were all expressed at basal levels. The dynamics of the ge ne induction and the glycerol formation at low demand for NADH reoxidation point to an important role of the Gpd1p; deletion of the GPD1 gene strongly altered the expression patterns of the GPD2 and GPP1 genes under such cond itions. Furthermore, our results indicate that GCY1 and DAK1, tentatively e ncoding glycerol dehydrogenase and dihydroxyacetone kinase, respectively, m ay be involved in the redox regulation of S. cerevisiae. Copyright (C) 2000 John Wiley Br Sons, Ltd.