title: Transcriptional changes associated with ethanol tolerance in Saccharomyces cerevisiae.
abstract: Saccharomyces spp. are widely used for ethanol production; however, fermentation productivity is negatively affected by the impact of ethanol accumulation on yeast metabolic rate and viability. This study used microarray and statistical two-way ANOVA analysis to compare and evaluate gene expression profiles of two previously generated ethanol-tolerant mutants, CM1 and SM1, with their parent, Saccharomyces cerevisiae W303-1A, in the presence and absence of ethanol stress. Although sharing the same parentage, the mutants were created differently: SM1 by adaptive evolution involving long-term exposure to ethanol stress and CM1 using chemical mutagenesis followed by adaptive evolution-based screening. Compared to the parent, differences in the expression levels of genes associated with a number of gene ontology categories in the mutants suggest that their improved ethanol stress response is a consequence of increased mitochondrial and NADH oxidation activities, stimulating glycolysis and other energy-yielding pathways. This leads to increased activity of energy-demanding processes associated with the production of proteins and plasma membrane components, which are necessary for acclimation to ethanol stress. It is suggested that a key function of the ethanol stress response is restoration of the NAD(+)/NADH redox balance, which increases glyceraldehyde-3-phosphate dehydrogenase activity, and higher glycolytic flux in the ethanol-stressed cell. Both mutants achieved this by a constitutive increase in carbon flux in the glycerol pathway as a means of increasing NADH oxidation.
authors.affiliation: School of Engineering and Science, Victoria University, PO Box 14428, Melbourne, Australia. Dana.Stanley@csiro.au
authors.forename: Dragana
authors.initials: D
authors.lastname: Stanley
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Chambers
authors.forename: Grant A
authors.initials: GA
authors.lastname: Stanley
authors.forename: Anthony
authors.initials: A
authors.lastname: Borneman
authors.forename: Sarah
authors.initials: S
authors.lastname: Fraser
mesh_terms: D002244:Carbon / Q000378:metabolism; D004361:Drug Tolerance; D000431:Ethanol / Q000633:toxicity*; D020869:Gene Expression Profiling; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006019:Glycolysis; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism
chemical_list: D009243:NAD; D000431:Ethanol; D002244:Carbon; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); D005990:Glycerol