title: Osmoregulation of fission yeast: cloning of two distinct genes encoding glycerol-3-phosphate dehydrogenase, one of which is responsible for osmotolerance for growth.
abstract: Many types of microorganisms, including both prokaryotes and eukaryotes, have developed mechanisms to adapt to severe osmotic stress. In this study, we isolated multicopy suppressor genes for a Schizosaccharomyces pombe mutant, which exhibited the clear phenotype of being osmosensitive for growth (Osms) on agar plates containing high concentrations of either non-ionic or ionic osmotic solutes. Two genes were thus identified, and each was suggested to encode an NADH-dependent glycerol-3-phosphate dehydrogenase (GPD), which is required for glycerol synthesis. The nucleotide sequences, determined for these genes (named gpd1+ and gpd2+, respectively), revealed that S. pombe has two distinct GPD isozymes. They are only 60% identical to each other in their amino acid sequences. One such isozyme, GPD1, was shown to be directly involved in osmoregulation, based on the following observations. (i) Expression of gpd1+ was regulated at the mRNA level in response to osmotic upshift. (ii) It was demonstrated that wild-type cells markedly accumulated internal glycerol under high-osmolarity growth conditions. (iii) delta gpd1 mutants, however, failed to do so even in a high-osmolarity medium, and thus exhibited an Osms phenotype. On the other hand, the gpd2+ gene was constitutively expressed at a particular low level, regardless of the osmolarity of the medium.
authors.affiliation: Laboratory of Molecular Microbiology, Nagoya University, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Ohmiya
authors.forename: H
authors.initials: H
authors.lastname: Yamada
authors.forename: K
authors.initials: K
authors.lastname: Nakashima
authors.forename: H
authors.initials: H
authors.lastname: Aiba
authors.forename: T
authors.initials: T
authors.lastname: Mizuno
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005816:Genetic Complementation Test; D005990:Glycerol / Q000378:metabolism; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics*; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D010641:Phenotype; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D017386:Sequence Homology, Amino Acid
chemical_list: D005993:Glycerolphosphate Dehydrogenase; D005990:Glycerol