title: Two-step activation of meiosis by the mat1 locus in Schizosaccharomyces pombe.
abstract: The mat1 locus is a key regulator of both conjugation and meiosis in the fission yeast Schizosaccharomyces pombe. Two alternative DNA segments of this locus, mat1-P and mat1-M, specify the haploid cell types (Plus and Minus). Each segment includes two genes: mat1-P includes mat1-Pc and mat1-Pm, while mat1-M includes mat1-Mc and mat1-Mm. The mat1-Pc and mat1-Mc genes are responsible for establishing the pheromone communication system that mediates conjugation between P and M cells, while all four mat1 genes are required for meiosis in diploid P/M cells. Our understanding of the initiation of meiosis is based largely on indirect observations, and a more precise investigation of these events was required to define the interaction between the mat1 genes. Here we resolve this issue using synthetic pheromones and P/M strains with mutations in either mat1-Pc or mat1-Mc. Our results suggest a model in which the mat1 locus plays two roles in controlling meiosis. In the first instance, the mat1-Pc and mat1-Mc functions are required to produce the mating pheromones and receptors that allow the generation of a pheromone signal. This signal is required to induce the expression of mat1-Pm and mat1-Mm. This appears to be the major pheromone-dependent step in controlling meiosis since ectopic expression of these genes allows meiosis in the absence of mat1-Pc and mat1-Mc. The mat1-Pm and mat1-Mm products complete the initiation of meiosis by activating transcription of the mei3 gene.
authors.affiliation: Department of Genetics, University of Copenhagen, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Willer
authors.forename: L
authors.initials: L
authors.lastname: Hoffmann
authors.forename: U
authors.initials: U
authors.lastname: Styrkársdóttir
authors.forename: R
authors.initials: R
authors.lastname: Egel
authors.forename: J
authors.initials: J
authors.lastname: Davey
authors.forename: O
authors.initials: O
authors.lastname: Nielsen
mesh_terms: D001483:Base Sequence; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D036341:Intercellular Signaling Peptides and Proteins; D008540:Meiosis / Q000235:genetics*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics*; D010675:Pheromones / Q000378:metabolism; D012098:Reproduction / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D036341:Intercellular Signaling Peptides and Proteins; C089516:Mating Factor, S pombe; D010455:Peptides; D010675:Pheromones; D029702:Schizosaccharomyces pombe Proteins; C490320:mfm1 protein, S pombe