A large-scale screen in S. pombe identifies seven novel genes required for critical meiotic events.

Meiosis is a specialized form of cell division by which sexually reproducing diploid organisms generate haploid gametes. During a long prophase, telomeres cluster into the bouquet configuration to aid chromosome pairing, and DNA replication is followed by high levels of recombination between homologous chromosomes (homologs). This recombination is important for the reductional segregation of homologs at the first meiotic division; without further replication, a second meiotic division yields haploid nuclei. In the fission yeast Schizosaccharomyces pombe, we have deleted 175 meiotically upregulated genes and found seven genes not previously reported to be critical for meiotic events. Three mutants (rec24, rec25, and rec27) had strongly reduced meiosis-specific DNA double-strand breakage and recombination. One mutant (tht2) was deficient in karyogamy, and two (bqt1 and bqt2) were deficient in telomere clustering, explaining their defects in recombination and segregation. The moa1 mutant was delayed in premeiotic S phase progression and nuclear divisions. Further analysis of these mutants will help elucidate the complex machinery governing the special behavior of meiotic chromosomes.