CLONING, SEQUENCE, AND DISRUPTION OF THE SACCHAROMYCES-DIASTATICUS DAR1 GENE ENCODING A GLYCEROL-3-PHOSPHATE DEHYDROGENASE

The Saccharomyces diastaticus DAR1 gene was cloned by complementation in an Escherichia coli strain auxotrophic for glycerol-3-phosphate. DA R1 encodes an NADH-dependent dihydroxyacetone phosphate reductase (sn- glycerol-3-phosphate dehydrogenase [G3PDase; EC 1.1.1.8]) homologous t o several other eukaryotic G3PDases. DAR1 is distinct from GUT2, which encodes a glucose-repressed mitochondrial G3PDase, but is identical t o GPD1 from S. cerevisiae, a close relative of S. diastaticus. The lev el of DAR1-encoded G3PDase was increased about threefold in a medium o f high osmolarity. Disruption of DAR1 in a haploid S. cerevisiae was n ot lethal but led to a decrease in cytoplasmic NADH-dependent G3PDase activity, an increase in osmotic sensitivity, and a 25% reduction in g lycerol secretion from cells grown anaerobically on glucose.