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Extrachromosomal inheritance in Schizosaccharomyces pombe. III. Isolation and characterization of
Abstract:
In the antimycin--resistant mutant anar-8 of the fission yeast Schizosaccharomyces pombe (Sch.p.) spontaneous mutants were isolated showing high resistance to the aminoglycoside antibiotic paromomycin. All mutants were resistant to the structurally related antibiotic neomycin. Tetrad analysis, mitotic segregation analysis, and mitotic haploidization revealed extrachromosomal, very likely mitochondrial inheritance. In contrast to the rapid segregation of mitochondrial markers in zygotic clones of Saccharomyces cerevisiae (S.c.) the heteroplasmic state of diploids proved to persist for at least 50 generations after zygote formation. Stationary cultures of the paromomycin-resistant mutants parr-106 and parr-112 contain up to 6% respiratory-deficient mutants, but no reversion to paromomycin-sensitivity was observed among 1700-1800 colonies tested. The ability of mutant anar-8 to produce spontaneously respiratory-deficient mutants could be separated from the antimycin-resistant phenotype of anar-8.
Insights
New fission yeast mutants exhibit resistance to paromomycin and neomycin antibiotics, with inheritance patterns suggesting mitochondrial DNA. These mutants maintain a stable heteroplasmic state for extended generations.
Area of Science:
- * Molecular genetics
- * Yeast biology
- * Antibiotic resistance mechanisms
Background:
- * Antimycin-resistant mutant anar-8 in *Schizosaccharomyces pombe* was used as a starting point.
- * Aminoglycoside antibiotics like paromomycin and neomycin are crucial in medicine.
Purpose of the Study:
- * To isolate and characterize spontaneous mutants resistant to paromomycin in *Schizosaccharomyces pombe*.
- * To investigate the inheritance pattern of paromomycin resistance.
- * To analyze the relationship between paromomycin resistance and respiratory deficiency.
Main Methods:
- * Isolation of spontaneous mutants from *Schizosaccharomyces pombe* anar-8.
- * Phenotypic characterization of antibiotic resistance (paromomycin, neomycin).
- * Genetic analysis: Tetrad analysis, mitotic segregation, and mitotic haploidization.
- * Assessment of respiratory-deficient mutants and reversion rates.
Main Results:
- * Isolated mutants resistant to paromomycin and neomycin, indicating extrachromosomal, likely mitochondrial inheritance.
- * Observed stable heteroplasmy in diploids persisting over 50 generations, unlike in *Saccharomyces cerevisiae*.
- * Stationary cultures showed up to 6% respiratory-deficient mutants, with no observed reversion to paromomycin sensitivity.
- * The ability of mutant anar-8 to produce respiratory-deficient mutants was separable from its antimycin resistance.
Conclusions:
- * Paromomycin resistance in *Schizosaccharomyces pombe* is linked to mitochondrial genetics.
- * The persistence of heteroplasmy in *Schizosaccharomyces pombe* differs significantly from *Saccharomyces cerevisiae*.
- * Paromomycin resistance and respiratory deficiency are distinct phenotypes in this yeast model.