Short-homology-mediated PCR-based method for gene introduction in the fission yeast Schizosaccharomyces pombe

Schizosaccharomyces pombe is a commonly utilized model organism for studying various aspects of eukaryotic cell physiology. One reason for its widespread use as an experimental system is the ease of genetic manipulations, leveraging the natural homology-targeted repair mechanism to accurately modify the genome. We conducted a study to assess the feasibility and efficiency of directly introducing exogenous genes into the fission yeast S. pombe using Polymerase Chain Reaction (PCR) with short-homology flanking sequences. Specifically, we amplified the NatMX6 gene (which provides resistance to nourseothricin) using PCR with oligonucleotides that had short flanking regions of 20 bp, 40 bp, 60 bp and 80 bp to the target gene. By using this purified PCR product, we successfully introduced the NatMX6 gene at position 171 385 on chromosome III in S. pombe. We have made a simple modification to the transformation procedure, resulting in a significant increase in transformation efficiency by at least 5-fold. The success rate of gene integration at the target position varied between 20% and 50% depending on the length of the flanking regions. Additionally, we discovered that the addition of dimethyl sulfoxide and boiled carrier DNA increased the number of transformants by ~60- and 3-fold, respectively. Furthermore, we found that the removal of the pku70+ gene improved the transformation efficiency to ~5% and reduced the formation of small background colonies. Overall, our results demonstrate that with this modified method, even very short stretches of homologous regions (as short as 20 bp) can be used to effectively target genes at a high frequency in S. pombe. This finding greatly facilitates the introduction of exogenous genes in this organism.