Mitochondrial superoxide dismutase is essential for ethanol tolerance of Saccharomyces cerevisiae in the post-diauxic phase.
This work reports the role of both superoxide dismutases-CuZnSOD (encoded by SOD1) and MnSOD (encoded by SOD2)-in the build-up of tolerance to ethanol during growth of Saccharomyces cerevisiae from exponential to post-diauxic phase. Both enzyme activities increase from the exponential phase to the diauxic shift and from the diauxic shift to the post-diauxic phase. The levels of mRNA-SOD1 and mRNA-SOD2 increase from the exponential phase to the diauxic shift; however, during the post-diauxic phase mRNA-SOD1 levels decrease while mRNA-SOD2 levels remain unchanged. These data indicate the existence of two regulatory mechanisms involved in the induction of SOD activity during growth: synthesis de novo of the proteins (until the diauxic shift), and post-transcriptional or post-translational regulation (during the post-diauxic phase). Ethanol does not alter the activities of either enzyme in cells from the diauxic shift or post-diauxic-phases, although the respective mRNA levels decrease in post-diauxic-phase cells treated with ethanol (14% or 20%). Results of experiments with sod1 and sod2 mutants show that MnSOD, but not CuZnSOD, is essential for ethanol tolerance of diauxic-shift and post-diauxic-phase cells. Evidence that ethanol toxicity is correlated with the production of reactive oxygen species in the mitochondria is obtained from results with respiration-deficient mutants. In these cells, the induction of superoxide dismutase activity by ethanol is low; also, the respiratory deficiency restores the capacity of sod2 cells to acquire ethanol tolerance.
Costa
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Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal.
Amorim
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MA
Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal.
Reis
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E
Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal.
Quintanilha
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A
Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal.
Moradas-Ferreira
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P
Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal.
D004790:Enzyme Induction; D000431:Ethanol / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology*; D008928:Mitochondria / Q000201:enzymology*; D010101:Oxygen Consumption; D012331:RNA, Fungal / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013482:Superoxide Dismutase / Q000235:genetics / Q000502:physiology*
D005656:Fungal Proteins; D007527:Isoenzymes; D012331:RNA, Fungal; D012333:RNA, Messenger; D000431:Ethanol; D013482:Superoxide Dismutase