Synthetic gene expression circuits regulating sexual reproduction

The budding yeast Saccharomyces cerevisiae has been widely utilized in fermentative production since ancient times. Several approaches for modification of yeast traits have been developed, including mutagenesis, protoplast fusion, and genetic modification. Crossbreeding provides an attractive means to improve and combine strain traits based on sexual reproduction. Common crossbreeding strategies require the isolation of MATa and MATα haploids via sporulation, as most of parental yeasts are MATa/α diploids and unable to mate directly. Unfortunately, many yeast strains used in industry exhibit low sporulation rates resulting in limited crossbreeding efficiency and numerous technical challenges. Here, we review the construction of synthetic gene expression circuits as a means to provide alternative methods for sporulation for yeast crossbreeding. These methods enable researchers to convert the sequence of the MAT locus and subsequently acquire crossbreds via mating of isolated yeast strains. The purpose of this chapter is to provide a basic guide for researchers who are attempting to expand the variety of yeast resources using the sexual reproduction machinery of yeast.