13 Molecular Genetics of Fission Yeast Cell Type: Mating Type and Mating-type Interconversion

Abstract

I. INTRODUCTION
The combination of well-developed conventional genetics, molecular genetics, and molecular biology has kept the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe in the forefront of biological research. Nowhere have these approaches been better used than in studies of cell-type determination in the two yeasts, in which some of these tools were actually developed and honed. The cell-type studies were developed in parallel, with interesting differences found at each stage. The studies of S. cerevisiae are reviewed by Herskowitz et al. (this volume). The present chapter is limited to the S. pombe system, with emphasis on recent results. The background is covered here only briefly; for a comprehensive treatment, see earlier reviews by Egel et al. (1980), Egel (1989), and Klar (1987c, 1989c, 1992). The genetic and molecular manipulation of the organism has been reviewed by Gutz et al. (1974) and Moreno et al. (1991).

S. pombe is a fairly typical unicellular eukaryote and usually exists in the haploid state in the P (for plus) or M (for minus) mating type. The corresponding heterothallic strains (i.e., those with a stably inherited haploid mating type) are referred to as h⁺ and h⁻, respectively. The genome consists of three chromosomes with a total DNA content similar to that of S. cerevisiae. Division occurs by fission (Schizo for fission) of the rod-shaped cell to generate nearly equal-sized daughter cells. Both budding and fission yeasts are ascomycete fungi. The term yeast is from mycological nomenclature, indicating single-celled fungus, and does...