title: The role of the SPO11 gene in meiotic recombination in yeast.
abstract: Several complementary experimental approaches were used to demonstrate that the SPO11 gene is specifically required for meiotic recombination. First, sporulating cultures of spo11-1 mutant diploids were examined for landmark biochemical, cytological and genetic events of meiosis and ascosporogenesis. Cells entered sporulation with high efficiency and showed a near-doubling of DNA content. Synaptonemal complexes, hallmarks of intimate homologous pairing, and polycomplex structures appeared during meiotic prophase. Although spontaneous mitotic intra- and intergenic recombination occurred at normal levels, no meiotic recombination was observed. Whereas greater than 50% of cells completed both meiotic divisions, packaging of the four meiotic products into mature ascospores took place in only a small subset of asci. Haploidization occurred in less than 1% of viable colony-forming units. Second, the Rec- meiotic defect conferred by spo11-1 was confirmed by dyad analysis of spores derived from spo13-1 single-division meiosis in which recombination is not a requirement for viable ascospore production. Diploids homozygous for the spo13-1 mutation undergo meiotic levels of exchange followed by a single predominantly equational division and form asci containing two near-diploid spores. With the introduction of the spo11-1 mutation, high spore viability was retained, whereas intergenic recombination was reduced by more than 100-fold.
mesh_terms: D000483:Alleles; D002467:Cell Nucleus / Q000648:ultrastructure; D002874:Chromosome Mapping; D004171:Diploidy; D005800:Genes, Fungal; D008540:Meiosis; D008854:Microscopy, Electron; D008938:Mitosis; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D013172:Spores, Fungal / Q000648:ultrastructure