title: Auxotrophic Mutations Reduce Tolerance of Saccharomyces cerevisiae to Very High Levels of Ethanol Stress.
abstract: Very high ethanol tolerance is a distinctive trait of the yeast Saccharomyces cerevisiae with notable ecological and industrial importance. Although many genes have been shown to be required for moderate ethanol tolerance (i.e., 6 to 12%) in laboratory strains, little is known of the much higher ethanol tolerance (i.e., 16 to 20%) in natural and industrial strains. We have analyzed the genetic basis of very high ethanol tolerance in a Brazilian bioethanol production strain by genetic mapping with laboratory strains containing artificially inserted oligonucleotide markers. The first locus contained the ura3Δ0 mutation of the laboratory strain as the causative mutation. Analysis of other auxotrophies also revealed significant linkage for LYS2, LEU2, HIS3, and MET15. Tolerance to only very high ethanol concentrations was reduced by auxotrophies, while the effect was reversed at lower concentrations. Evaluation of other stress conditions showed that the link with auxotrophy is dependent on the type of stress and the type of auxotrophy. When the concentration of the auxotrophic nutrient is close to that limiting growth, more stress factors can inhibit growth of an auxotrophic strain. We show that very high ethanol concentrations inhibit the uptake of leucine more than that of uracil, but the 500-fold-lower uracil uptake activity may explain the strong linkage between uracil auxotrophy and ethanol sensitivity compared to leucine auxotrophy. Since very high concentrations of ethanol inhibit the uptake of auxotrophic nutrients, the active uptake of scarce nutrients may be a major limiting factor for growth under conditions of ethanol stress.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Steve
authors.initials: S
authors.lastname: Swinnen
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Goovaerts
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Kristien
authors.initials: K
authors.lastname: Schaerlaekens
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Françoise
authors.initials: F
authors.lastname: Dumortier
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Verdyck
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Kris
authors.initials: K
authors.lastname: Souvereyns
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: Griet
authors.initials: G
authors.lastname: Van Zeebroeck
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium.
authors.forename: María R
authors.initials: MR
authors.lastname: Foulquié-Moreno
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Flanders, Belgium Department of Molecular Microbiology, VIB, Leuven-Heverlee, Flanders, Belgium johan.thevelein@mmbio.vib-kuleuven.be.
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
mesh_terms: D000596:Amino Acids / Q000235:genetics* / Q000378:metabolism; D025141:Drug Resistance, Fungal / Q000235:genetics*; D000431:Ethanol / Q000633:toxicity*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D000596:Amino Acids; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol