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Plasmids controlled exclusion of the K2 killer double-stranded RNA plasmid of yeast

R B Wickner

    Cell
    |August 1, 1980
    PubMed

    Insights

    Killer yeast strains (K1 and K2) secrete toxins, with distinct double-stranded RNA plasmids ([KIL-k1] and [KIL-k2]). New elements [EXL] and [NEX] influence plasmid exclusion and maintenance, revealing complex genetic interactions in Saccharomyces.

    Area of Science:

    • Microbiology
    • Genetics
    • Molecular Biology

    Background:

    • Saccharomyces killer strains (K1, K2) produce protein toxins and possess distinct double-stranded RNA plasmids ([KIL-k1], [KIL-k2]).
    • These plasmids mediate inter-strain killing and exhibit exclusion phenomena during mating.
    • Understanding the genetic elements governing these interactions is crucial for yeast genetics.

    Purpose of the Study:

    • To characterize the genetic interactions of novel non-Mendelian elements ([EXL], [NEX]) with killer plasmids in Saccharomyces.
    • To investigate the role of the chromosomal gene MKT1 in plasmid maintenance.
    • To identify genes required for the replication of [EXL] and [NEX].

    Main Methods:

    • Genetic crosses and analysis of non-Mendelian inheritance patterns.
    • Phenotypic analysis of killer activity and plasmid exclusion.
    • Investigating gene dependencies for plasmid replication and maintenance.

    Main Results:

    • The [KIL-k1] plasmid excludes [KIL-k2].
    • [EXL] excludes [KIL-k2] but not [KIL-k1].
    • [NEX] interferes with [EXL]'s exclusion of [KIL-k2] and its replication depends on MAK3, while [EXL] requires MAK1, MAK3, MAK10, and PET18.
    • MKT1 is essential for [KIL-k2] maintenance only in the presence of [NEX].

    Conclusions:

    • Novel genetic elements [EXL] and [NEX] modulate killer plasmid interactions and replication in Saccharomyces.
    • [NEX] plays a regulatory role in plasmid exclusion and maintenance, influenced by chromosomal genes like MKT1.
    • The study elucidates complex genetic control mechanisms governing dsRNA plasmid behavior in yeast.

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