Yeast cell viability under conditions of high temperature and ethanol concentrations depends on the mitochondrial genome

Abstract

Wine yeasts manifest simultaneously a high tolerance to ethanol, thermotolerance, and a high resistance to the mutagenic effects of ethanol on the mitochondrial genome. The transfer of mitochondria from these strains to laboratory yeasts demonstrate that this genome influences the above parameters, since thermotolerance, ethanol-growth tolerance, and the frequency of rho- mutants were either totally or partially modified in the laboratory recipient strain. When the death rate and the rate of formation of rho- mutants were measured under extreme conditions of inhibitory ethanol concentrations and high temperature, a perfect correlation was found between these parameters, and both of them were dependent on the strain of mitochondrial genome. Thus, the transfer of wine yeast mitochondria leads to a lower death rate, and a simultaneous increase in thermotolerance and ethanol tolerance in the recipient strain. These results demonstrate the role that viability plays under conditions of high temperatures and high ethanol concentrations. The greater stability of the rho+ phenotype shown by the wine yeast mitochondrial genome may be responsible for the increased viability conferred by these mitochondria.

Genome-Wide Identification of S accharomyces cerevisiae Genes Required for Maximal Tolerance to Ethanol

“…Moreover, 30 genes encoding mitochondrial proteins (see Table S1 in the supplemental material) are determinants of yeast resistance to high concentrations of ethanol, suggesting that, even in the presence of glucose, mitochondrial functions are essential for ethanol tolerance. These results are in agreement with the notion that ethanol tolerance depends on the stability of the mitochondrial genome (18). A high proportion of the mitochondrion-related genes required for ethanol stress resistance are involved in mitochondrial protein synthesis, respiration, and mitochondrial DNA maintenance (see Table S1 in the supplemental material).…”

“…In response to this effect, yeast exhibits increased plasma membrane H ϩ -ATPase activity, which is important to maintain the intracellular pH and secondary transport mechanisms, which are dependent on the proton gradient across the plasma membrane (1,29,31,34). Ethanol has also been shown to inhibit crucial glycolytic enzymes (5) and to induce the generation of reactive oxygen species (7,11); yeast tolerance is dependent on the stability of the mitochondrial genome (18) and on the activity of the mitochondrial superoxide dismutase, encoded by SOD2 (7). Another factor contributing to the protection of yeast cells is cell wall composition and structure (31), although the exact changes occurring at this level are not well characterized.…”

Programmed Death in Bacteria

“…I am not aware of similar experiments with yeast cells, but analyzing what we know about yeast mutation rates suggests that the function of high-fidelity repair of chromosomal DNA requires an explanation. In S. cerevisiae, mutations that lead to mitochondria with defective oxidative phosphorylation are found in approximately 1% of cells growing on a medium with sugars (16,44,47). These are essentially lethal mutations in vivo, since yeast strains lacking oxidative phosphorylation have not been isolated from the environment.…”

Genetic Differentiation of the Sherry Yeasts Saccharomyces cerevisiae

“…Molecular studies of sherry yeasts commenced in the late 1980s [9]. Restriction analysis of the amplified ribosomal DNA fragment containing the 5.8S RNA gene and the internal transcribed spacers ITS1 and ITS2 (the 5.8S-ITS fragment) demonstrated that the corresponding profiles of sherry yeasts were unique [10].…”