Engineering heterothallic strains in fission yeast

In poor nitrogen conditions, fission yeast cells mate, undergo meiosis and form spores that are resistant to deleterious environments. Natural isolates of Schizosaccharomyces pombe are homothallic. This allows them to naturally switch between the two h- and h+ mating types with a high frequency, thereby ensuring the presence of both mating partners in a population of cells. However, alteration of the mating type locus can abolish mating type switching or reduce it to a very low frequency. Such heterothallic strains have been isolated and are common in research laboratories due to the simplicity of their use for Mendelian genetics. In addition to the standard laboratory strains, a large collection of natural S. pombe isolates is now available, representing a powerful resource for investigating the genetic diversity and biology of fission yeast. However, most of these strains are homothallic, and only tedious or mutagenic strategies have been described to obtain heterothallic cells from a homothallic parent. Here, we describe a simple approach to generate heterothallic strains. It takes advantage of an alteration of the mating type locus that was previously identified in a mating type switching-deficient strain and the CRISPR-Cas9 editing tool, allowing for a one-step engineering of heterothallic cells with high efficiency. A CRISPR-based method for generating heterothallic fission yeast strains from homothallic cells. This approach is not only compatible with laboratory strains but also with natural isolates of Schizosaccharomyces pombe.image Conventional methods for obtaining heterothallic fission yeast strains are inefficient.We implemented a streamlined genetic editing approach to engineer heterothallism.All fission yeast isolates reported in Jeffares et al. can be engineered.This method enhances the exploration of genetic diversity in wild fission yeast.

Automated summary

Schizosaccharomyces pombe is a fission yeast that can mate and form spores in poor nitrogen conditions. Most natural isolates of S. pombe are homothallic, but heterothallic strains are commonly used in research labs. This article describes a simple method to generate heterothallic strains using the CRISPR-Cas9 editing tool.