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J Bacteriol. 1974 February; 117(2): 681-686
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Yeast Killer Mutants with Altered Double-Stranded Ribonucleic Acid

Department of Biology, University of South Carolina, Columbia, South Carolina 29208
² Department of Plant Genetics, University of Arizona, Tucson, Arizona 85721
Department of Genetics, Development and Physiology, Cornell University, Ithaca, New York 14850

ABSTRACT

Killer strains of Saccharomyces cerevisiae contain two species of double-stranded ribonucleic acid (dsRNA) with molecular weights estimated at 2.5 x 10⁶ (L) and 1.4 x 10⁶ (M). The M component appears to have a high adenine content. All mutants of killer which are defective for both the toxin and immunity functions lack the M dsRNA. One of these mutants has a novel dsRNA with a molecular weight of 5 x 10⁵. Another class of killer mutants contains strains which are defective for either the toxin or the immunity function. They include temperature-sensitive killers, superkillers, and immunity-minus strains. The dsRNA profile of temperature-sensitive killers resembles that of the standard killer. The superkiller has 2.5 times more of the M dsRNA (1.4 x 10⁶ daltons) than does the standard killer. Immunity-minus killers have, in addition to the two dsRNAs species of standard killer, a novel dsRNA with a molecular weight of 2.5 x 10⁵. The data are consistent with the hypothesis that the M RNA controls toxin production. In addition, the two RNAs, L and M, seem to be regulated together. When the M RNA is missing, the amount of L is either greatly elevated or greatly reduced.