BackgroundSporulation of the fission yeast Schizosaccharomyces pombe is a cell differentiation process which accompanies meiosis. The spo6+ gene was identified as a sporulation‐specific gene, whose transcription was regulated by the forkhead family transcription factor Mei4.Results spo6 + encodes a protein with sequence similarity to Saccharomyces cerevisiae Dbf4p, which is required for the initiation of DNA replication. However, doubling time and cell morphology of spo6 deletion mutants and spo6‐cDNA over‐expressing cells were indistinguishable from wild‐type cells. Spliced mature mRNAs of spo6+ appeared when diploid cells committed to meiosis. Spo6p fused to green fluorescent protein (GFP) preferentially localized in a nucleus. Although spo6Δ diploids normally underwent premeiotic DNA replication and meiosis‐I, approximately 80% of cells were blocked at the binucleate stage during meiosis and virtually no asci were formed. Anti‐tubulin staining revealed that only 25% of the binucleate cells assembled spindle microtubules for meiosis‐II. In a small number of tetranucleate cells, sister nuclei insufficiently separated and spindles were frequently fragmented. The meiosis‐II arrest phenotype was exaggerated at low temperature and in the presence of caffeine.ConclusionsThese results indicate that Spo6p is a novel Dbf4‐related nuclear protein, which is expressed during meiosis and is indispensable for normal progression of meiosis‐II and sporulation.