A New Scheme To Artificially Alter Yeast Mating-Types Without Autodiploidization

Sexual hybridization can drive dramatic yeast evolution through the inheritance of genomic information from each parental cell. Unfortunately, however, a pair of strains, MATa and MAT alpha mating-types, is absolutely quired for sexual hybridization of budding yeasts, which restricts the combining possibilities of previously isolated and engineered strains. While the Ho endonuclease has been used to artificially convert yeast mating types, "stuck" mutations are often hindrances to mating-type conversion due to extremely low efficiency of DNA digestion. An alternative and powerful approach to generate mating strains with specific properties and desired mating-type from existing strains is needed, to accelerate progress in yeast breeding technology and strain engineering. I established an approach for generating MATa and MAT alpha mating-types from those of the opposite mating-type using synthetic DNA substitution of the MAT gene. I used previously constructed episomal vectors that suppress the mating ability of existing cells and produce opposite mating-type derivatives with antibiotic resistance for target cell isolation. I demonstrated that the mating-type-altered cells exhibited the same phenotype as those separately generated without MAT gene substitution. This approach can facilitate yeast-strain development and sexual hybridization using available resources with less efforts.