Induction of petite yeast mutants by membrane-active agents

Area of Science:

• Molecular Biology
• Yeast Genetics
• Mitochondrial DNA Research

Background:

• Ethanol is a potent mutagen affecting Saccharomyces mitochondrial DNA.
• Organic solvents and ergosterol synthesis defects increase petite mutation rates.
• Yeast strains exhibit varying sensitivities to mitochondrial mutagens.

Purpose of the Study:

• To investigate the mutagenic effects of membrane solvents on yeast mitochondrial DNA.
• To explore the role of mitochondrial membrane composition and nuclear genes in petite mutation induction.
• To compare the responses of wine and laboratory yeast strains to these mutagens.

Main Methods:

• Treatment of Saccharomyces cerevisiae with ethanol and other membrane solvents.
• Analysis of petite mutation [rho-] frequency in ergosterol synthesis mutants (erg mutants).
• Mitochondrial transfer experiments between wine and laboratory yeast strains.
• Genetic analysis of wine yeast-laboratory yeast hybrids and meiotic segregation.

Main Results:

• Ethanol and solvents like tert-butanol, isopropanol, and sodium dodecyl sulfate are potent petite mutation inducers.
• Ergosterol-deficient mutants show a high frequency of spontaneous petite cells.
• Wine yeast strains display higher tolerance to alcohol mutagens but increased sensitivity to sodium dodecyl sulfate compared to lab strains.
• Mitochondrial transfer enhanced petite mutation resistance in lab strains.
• Nuclear genes play a crucial role in mitochondrial genome stability, as evidenced by hybrid and segregation analyses.

Conclusions:

• Mitochondrial membrane alterations, induced by solvents or altered composition, increase petite mutant proportion.
• The stability of mitochondrial DNA ([rho+]) is influenced by both mitochondrial DNA nature and nuclear genes.
• Both mitochondrial and nuclear factors contribute to the regulation of mitochondrial genome stability in yeast.