Functional genomics of commercial baker's yeasts that have different abilities for sugar utilization and high‐sucrose tolerance under different sugar conditions

Abstract

In the modern baking industry, high-sucrose-tolerant (HS) and maltose-utilizing (LS) yeast were developed using breeding techniques and are now used commercially. Sugar utilization and high-sucrose tolerance differ significantly between HS and LS yeasts. We analysed the gene expression profiles of HS and LS yeasts under different sucrose conditions in order to determine their basic physiology. Twoway hierarchical clustering was performed to obtain the overall patterns of gene expression. The clustering clearly showed that the gene expression patterns of LS yeast differed from those of HS yeast. Quality threshold clustering was used to identify the gene clusters containing upregulated genes (cluster 1) and downregulated genes (cluster 2) under high-sucrose conditions. Clusters 1 and 2 contained numerous genes involved in carbon and nitrogen metabolism, respectively. The expression level of the genes involved in the metabolism of glycerol and trehalose, which are known to be osmoprotectants, in LS yeast was higher than that in HS yeast under sucrose concentrations of 5-40%. No clear correlation was found between the expression level of the genes involved in the biosynthesis of the osmoprotectants and the intracellular contents of the osmoprotectants. The present gene expression data were compared with data previously reported in a comprehensive analysis of a gene deletion strain collection. Welch's t-test for this comparison showed that the relative growth rates of the deletion strains whose deletion occurred in genes belonging to cluster 1 were significantly higher than the average growth rates of all deletion strains.

Stress‐tolerance of baker's‐yeast (Saccharomyces cerevisiae) cells: stress‐protective molecules and genes involved in stress tolerance

“…It is known that sugar utilization and high‐sucrose tolerance differ significantly between HS and LS yeasts [3]. The gene‐expression profiles of HS and LS yeasts were analysed under different sucrose conditions to determine their basic physiology [87]. The clustering analysis clearly showed that the gene‐expression patterns of LS yeast differed from those of HS yeast.…”

“…The expression level of the genes involved in the metabolism of glycerol and trehalose, which are known to be osmoprotectants, was higher in LS yeast than in HS yeast under sucrose concentrations of 5–40%. No clear correlation between the expression level of the genes involved in the biosynthesis of such osmoprotectants and the intracellular contents of the osmoprotectants was found [87].…”

Involvement of ergosterol in tolerance to vanillin, a potential inhibitor of bioethanol fermentation, inSaccharomyces cerevisiae

“…and harvested at the log phase (OD 600 nm =1.0). The experimental procedures of RNA extraction and DNA microarray analysis have been described previously (Tanaka‐Tsuno et al , 2007). Affymetrix Yeast Genome 2.0 arrays (Affymetrix, Santa Clara, CA) were used as the DNA microarrays.…”

Insufficiency of Copper Ion Homeostasis Causes Freeze-Thaw Injury of Yeast Cells as Revealed by Indirect Gene Expression Analysis

“…The yeast cells were exposed to freeze-thaw treatment for 0, 24, or 48 h, and then the cells were subjected to postthaw incubation for 60 min at 30°C in YPD medium. The RNA samples used for DNA microarray analysis were extracted from the cells after postthaw incubation by a method described previously (23). Affymetrix Yeast Genome 2.0 arrays (Affymetrix, Santa Clara, CA) were used as the DNA microarrays.…”