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["Killer" plasmid in natural strains of Saccharomyces]
Abstract:
Double stranded RNA's of thirteen wine strains of Saccharomyces belonging to different species and exhibiting killing activity were studied. Two strains of Oxford genetic stocks were used for control. All these strains have four different spectra of killer activity and contain two double stranded RNAs, L and M. All strains regardless of the type of killer activity have the same electrophoretic mobility of L. The mobility of M varies in different strains but is not connected with the spectrum of killing activity. All strains can be cured by cycloheximide. Cured variants have no M. Certain cured strains contain small portions of double stranded RNAs with electrophoretical mobility faster than of M.
Insights
This study investigated double-stranded RNAs in Saccharomyces wine strains with killer activity. Results show killer activity is linked to specific RNA types, not their mobility, and can be eliminated by cycloheximide treatment.
Area of Science:
- Microbiology
- Molecular Biology
- Yeast Genetics
Background:
- Killer activity in Saccharomyces strains is a well-documented phenomenon.
- This activity is often associated with the presence of specific RNA viruses within the yeast cells.
- Understanding the genetic and molecular basis of killer activity is crucial for wine fermentation and yeast strain management.
Purpose of the Study:
- To characterize the double-stranded RNAs (dsRNAs) present in thirteen Saccharomyces wine strains exhibiting killer activity.
- To investigate the relationship between the types and electrophoretic mobilities of dsRNAs (L and M) and the killer activity spectra.
- To determine the effect of cycloheximide treatment on dsRNA presence and killer activity.
Main Methods:
- Isolation and analysis of double-stranded RNAs (dsRNAs) from Saccharomyces wine strains.
- Electrophoretic separation of dsRNAs to determine their mobility.
- Phenotypic characterization of killer activity spectra in different strains.
- Treatment of yeast strains with cycloheximide to induce curing of killer activity.
Main Results:
- All thirteen killer Saccharomyces strains contained two dsRNAs, designated L and M.
- The electrophoretic mobility of the L dsRNA was consistent across all strains, irrespective of killer activity spectrum.
- The mobility of the M dsRNA varied among strains but did not correlate with the specific killer activity spectrum.
- Cycloheximide treatment successfully cured killer activity in all strains, and these cured variants lacked the M dsRNA.
- Some cured strains contained novel dsRNA fragments with faster electrophoretic mobility than M.
Conclusions:
- The M dsRNA is essential for conferring killer activity in these Saccharomyces strains.
- While the L dsRNA is consistently present, its specific mobility is not linked to killer phenotype.
- The M dsRNA's variable mobility suggests strain-specific variations or modifications not directly tied to the killer spectrum.
- Cycloheximide-induced curing provides a method to eliminate killer activity and associated M dsRNA, potentially revealing insights into dsRNA replication or degradation.