Adaptation of Saccharomyces cerevisiae to high hydrostatic pressure causing growth inhibition.

Genome-wide mRNA expression profiles of Saccharomyces cerevisiae growing under hydrostatic pressure were characterized. We selected a hydrostatic pressure of 30 MPa at 25 degrees C because yeast cells were able to grow under these conditions, while cell size and complexity were increased after decompression. Functional characterization of pressure-induced genes suggests that genes involved in protein metabolism and membrane metabolism were induced. The response to 30 MPa was significantly different from that observed under lethal conditions because protein degradation was not activated under 30 MPa pressure. Strongly induced genes those that contribute to membrane metabolism and which are also induced by detergents, oils, and membrane stabilizers.

Genome-wide expression analysis of yeast response during exposure to 4 degrees C.

Adaptation to temperature fluctuation is essential for the survival of all living organisms. Although extensive research has been done on heat and cold shock responses, there have been no reports on global responses to cold shock below 10 degrees C or near-freezing. We examined the genome-wide expression in Saccharomyces cerevisiae, following exposure to 4 degrees C. Hierarchical cluster analysis showed that the gene expression profile following 4 degrees C exposure from 6 to 48 h was different from that at continuous 4 degrees C culture. Under 4 degrees C exposure, the genes involved in trehalose and glycogen synthesis were induced, suggesting that biosynthesis and accumulation of those reserve carbohydrates might be necessary for cold tolerance and energy preservation. The observed increased expression of phospholipids, mannoproteins, and cold shock proteins (e.g., TIP1) is consistent with membrane maintenance and increased permeability of the cell wall at 4 degrees C. The induction of heat shock proteins and glutathione at 4 degrees C may be required for revitalization of enzyme activity, and for detoxification of active oxygen species, respectively. The genes with these functions may provide the ability of cold tolerance and adaptation to yeast cells.

Screening of genes that respond to cryopreservation stress using yeast DNA microarray.

We studied the response of yeast cells after cryopreservation treatment using DNA microarray technology. Genes that contribute to "Cell rescue, defense and virulence," "energy," and "metabolism," were significantly induced. These genes were classified as encoding heat shock proteins, oxidative stress scavenger, and enzymes involved in glucose metabolism. The expression profile of mRNA after cryopreservation treatment was calculated to be closer to that following treatment with detergent or plant oils rather than by other stress factors such as heavy metals and agricultural chemicals. These results suggest that the cryopreservation treatment caused damage to the structure of the cell wall and cellular organelles. This was supported by the localization of the products of the induced genes at the cell wall and within cellular organelles.

Piezophysiology of genome wide gene expression levels in the yeast Saccharomyces cerevisiae.

Hydrostatic pressure is one of the physical factors affecting cellular physiology. Hydrostatic pressure of a few hundred MPa decreases the viability of yeast cells, and pressure of a few tens MPa decreases the growth rate. To understand the effect of hydrostatic pressure, we employed yeast DNA microarrays and analyzed genome-wide gene-expression levels after the pressure treatment with 180 MPa (immediate) at 4 degrees C and recovery incubation for 1 h and 40 MPa (16 h) at 4 degrees C and recovery incubation for 1 h. The transcription of genes involved in energy metabolism, cell defense, and protein metabolism was significantly induced by the pressure treatment. Genome-wide expression profiles suggested that high pressure caused damage to cellular organelles, since the induced gene products were localized in the membrane structure and/or cellular organelles. Hierarchical clustering analysis suggested that the damage caused by the pressure was similar to that caused by detergents, oils, and freezing/thawing. We also estimated the contribution of induced genes to barotolerance using some strains that have the deletion in the corresponding genes.