Analysis of Meiotic Recombination Pathways in the Yeast Saccharomyces cerevisiae

Abstract

Abstract In the yeast, Saccharomyces cerevisiae, several genes appear to act early in meiotic recombination. HOPl and REDl have been classified as such early genes. The data in this paper demonstrate that neither a redl nor a hopl mutation can rescue the inviable spores produced by a rad52 spol3 strain; this phenotype helps to distinguish these two genes from other early meiotic recombination genes such as SPOll, REC104, or A4EI4. In contrast, either a redl or a hopl mutation can rescue a rad50S spol3 strain; this phenotype is similar to that conferred by mutations in the other early recombination genes (e.g., REC104). These two different results can be explained because the data presented here indicate that a rad50S mutation does not diminish meiotic intrachromosomal recombination, similar to the mutant phenotypes conferred by redl or hopl. Of course, REDl and HOPl do act in the normal meiotic interchromosomal recombination pathway; they reduce interchromosomal recombination to ~10% of normal levels. We demonstrate that a mutation in a gene (REC104) required for initiation of exchange is completely epistatic to a mutation in REDl. Finally, mutations in either HOPl or RED1 reduce the number of doublestrand breaks observed at the HIS2 meiotic recombination hotspot.