State-of-the-art strain engineering techniques for the methylotrophic yeast Pichia pastoris (syn. Komagataella spp.) include overexpression of endogenous and heterologous genes and deletion of host genes. For efficient gene deletion, methods such as the split-marker technique have been established. However, synthetic biology trends move toward building up large and complex reaction networks, which often require endogenous gene knockouts and simultaneous overexpression of individual genes or whole pathways. Realization of such engineering tasks by conventional approaches employing subsequent steps of transformations and marker recycling is very time- and labor-consuming. Other applications require tagging of certain genes/proteins or promoter exchange approaches, which are hard to design and construct with conventional methods. Therefore, efficient systems are required that allow precise manipulations of the P. pastoris genome, including simultaneous overexpression of multiple genes. To meet this challenge, we have developed a CRISPR/Cas9-based kit for gene insertions, deletions, and replacements, which paves the way for precise genomic modifications in P. pastoris. In this chapter, the versatile method for performing these modifications without the integration of a selection marker is described. A ready-to-use plasmid kit for performing CRISPR/Cas9-mediated genome editing in P. pastoris based on the GoldenPiCS modular cloning vectors is available at Addgene as CRISPi kit (#1000000136).
Keywords: CRISPR/Cas9; Genome editing; GoldenPiCS; Pichia pastoris; Synthetic biology.