Effect of auxotrophic starvation of mitochondrial marker transmission in the cdc8 mutant of Saccharomyces cerevisiae.

Abstract

Crosses were made using strains of S. cerevisiae which carried mitochondrial markers conferring resistance to erythromycin and chloramphenicol. The effect of auxotrophic starvation of one parent prior to mating on the transmission of its mitochondrial markers was studied in different crosses relative to the presence of the cdc8 nuclear mutation (a temperature-sensitive DNA replication). In crosses between two cdc8 mutant strains, auxotrophic starvation of one of the haploid parental stains prior to mating caused a marked decrease of its mitochondrial marker transmission to the diploid progeny of the cross. The transmission decreased as a function of the time of starvation. This effect was not observed in the cross between two wild type strains and in crosses of starved cdc8 phenotypic revertants with cdc8 mutant strains. Only a small, if any, effect of starvation on mitochondrial marker transmission was observed when starved cdc8 mutant strains were crossed either with their phenotypic revertants or with the wild-type strains. In one of the haploid parental strains the starvation increased the frequency of petites as a function of starvation time, while in the other this effect was not observed. In the progeny of cdc8 X cdc8 crosses (both in starvation experiments and in control crosses) an increased frequency of diploid petite cells accompanied by a decreased frequency of recombination between mitochondrial markers was noticed. The influence of the cdc8 mutation on the transmission of mitochondrial markers is discussed in terms of high frequency of p- molecule formation in cdc8 strains.