Abstract
Growth properties and gene expression profiles by using slide glass-based DNA microarray under high osmotic pressure condition (addition of NaCl) were compared between the two yeast strains, a laboratory strain and a brewing one used for Japanese rice wine (sake) brewing. Growth properties in both strains after addition of 1 M of NaCl revealed that the brewing strain was more tolerant to osmotic stress than the laboratory one. DNA microarray analysis data indicated that the genes encoding the enzymes involved in acetate, glycerol and trehalose synthetic pathways were up-regulated in both strains under the stress conditions. Moreover, genes encoding sodium ion pump and cupper ion-binding proteins were more up-regulated in brewing strain than in the laboratory strain. Up-regulation of these genes might characterize the osmotic stress-tolerance of the brewing strain. We constructed a glycerol-overproducing strain by expressing GPD1 gene encoding glycerol-3-phosphate dehydrogenase constitutively in the laboratory strain and evaluated the osmotic stress tolerance of this strain. This improved strain showed more tolerant to osmotic stress than the parent strain, but glycerol was immediately exported outside of the cells. We are constructing further improved strain by disrupting the gene encoding glycerol exporter protein and we will evaluate again the stress tolerance of this strain.
