Genetic Studies of Effect of Paromomycin on Growth in Saccharomyces cerevisiae Ⅱ Non-mitochondrial cytoplasmic and chromosomal genes control paromomycin resistance

A high concentration of paromomycin (lOmg/ml) inhibited the growth on glucose medium of various strains of S. cerevisiae by various degrees. A strain, KL14-4A, resistant to the drug was crossed with a strain, C814-36B, which could not grow under the same conditions. The resultant zygote progeny were examined for the degree of growth on glucose plates containing the drug. The results showed that most diploid clones could grow but by various degrees. A petite matant harboring no mitochondrial DNA was obtained from KL14-4A by treatment with ethidium bromide. The petite mutant was crossed to C814-36B and the zygote progeny showed nearly the same pattern of degrees of growth as the above zygotes. Subclone analysis of the zygote progeny indicated that the trait of each diploid clone on the drug plate was fairly inherent. A stable diploid clone obtained after successive growth on glucose medium was sporulated and the ascospores were examined. The results indicated that the genetic traits including mitochondrial paromomycin resistance were irregularly distriduted in the tetrads. Subclones from each spore clone were also fairly inherent for the degrees of growth on media containing paromomycin. These results strongly suggest that non-mitochondnal cytoplasmic genes together with chromosomal genes would participate in control of the growth in S. cerevisiae at the presence of paromomycin and that the chromosomal genes would also affect the mitochondrial paromomycin-resistance gene expresion