Yeast killer mutants with altered double-stranded ribonucleic acid

Area of Science:

• Molecular biology
• Yeast genetics
• Virology

Background:

• Killer strains of Saccharomyces cerevisiae harbor two distinct double-stranded RNA (dsRNA) species, L (2.5 x 10^6) and M (1.4 x 10^6).
• The M dsRNA component is characterized by high adenine content and is implicated in killer phenotypes.

Purpose of the Study:

• To investigate the role of dsRNA components in killer yeast, specifically the M dsRNA, in toxin production and immunity.
• To characterize dsRNA profiles in various killer mutants, including those defective in toxin and/or immunity functions.

Main Methods:

• Analysis of dsRNA profiles in wild-type and mutant killer yeast strains using molecular weight estimations.
• Comparison of dsRNA content and composition across different mutant classes (e.g., toxin-deficient, immunity-deficient, temperature-sensitive, superkiller).

Main Results:

• Mutants lacking both toxin and immunity functions are devoid of M dsRNA, with one mutant exhibiting a novel 5 x 10^5 molecular weight dsRNA.
• Superkiller strains possess 2.5 times more M dsRNA than standard killer strains.
• Immunity-minus mutants contain an additional 2.5 x 10^5 molecular weight dsRNA alongside the standard L and M dsRNAs.

Conclusions:

• The M dsRNA is strongly correlated with and likely controls toxin production in killer yeast.
• The L and M dsRNA species appear to be co-regulated, as M dsRNA absence leads to significant alterations in L dsRNA levels.