{"title":"RNA polymerase II-driven CRISPR-Cas9 system for efficient non-growth-biased metabolic engineering of Kluyveromyces marxianus","authors":"Danielle Bever , Ian Wheeldon , Nancy Da Silva","doi":"10.1016/j.mec.2022.e00208","DOIUrl":null,"url":null,"abstract":"<div><p>The thermotolerant yeast <em>Kluyveromyces marxianus</em> has gained significant attention in recent years as a promising microbial candidate for industrial biomanufacturing. Despite several contributions to the expanding molecular toolbox for gene expression and metabolic engineering of <em>K. marxianus</em>, there remains a need for a more efficient and versatile genome editing platform. To address this, we developed a CRISPR-based editing system that enables high efficiency marker-less gene disruptions and integrations using only 40 bp homology arms in NHEJ functional and non-functional <em>K. marxianus</em> strains. The use of a strong RNA polymerase II promoter allows efficient expression of gRNAs flanked by the self-cleaving RNA structures, tRNA and HDV ribozyme, from a single plasmid co-expressing a codon optimized Cas9. Implementing this system resulted in nearly 100% efficiency of gene disruptions in both NHEJ-functional and NHEJ-deficient <em>K. marxianus</em> strains, with donor integration efficiencies reaching 50% and 100% in the two strains, respectively. The high gRNA targeting performance also proved instrumental for selection of engineered strains with lower growth rate but improved polyketide biosynthesis by avoiding an extended outgrowth period, a common method used to enrich for edited cells but that fails to recover advantageous mutants with even slightly impaired fitness. Finally, we provide the first demonstration of simultaneous, markerless integrations at multiple loci in <em>K. marxianus</em> using a 2.6 kb and a 7.6 kb donor, achieving a dual integration efficiency of 25.5% in a NHEJ-deficient strain. These results highlight both the ease of use and general robustness of this system for rapid and flexible metabolic engineering in this non-conventional yeast.</p></div>","PeriodicalId":18695,"journal":{"name":"Metabolic Engineering Communications","volume":null,"pages":null},"PeriodicalIF":3.7000,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2214030122000177/pdfft?md5=f6be45d36815b9de356945d06bf05598&pid=1-s2.0-S2214030122000177-main.pdf","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Metabolic Engineering Communications","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2214030122000177","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"BIOTECHNOLOGY & APPLIED MICROBIOLOGY","Score":null,"Total":0}
引用次数: 2
Abstract
The thermotolerant yeast Kluyveromyces marxianus has gained significant attention in recent years as a promising microbial candidate for industrial biomanufacturing. Despite several contributions to the expanding molecular toolbox for gene expression and metabolic engineering of K. marxianus, there remains a need for a more efficient and versatile genome editing platform. To address this, we developed a CRISPR-based editing system that enables high efficiency marker-less gene disruptions and integrations using only 40 bp homology arms in NHEJ functional and non-functional K. marxianus strains. The use of a strong RNA polymerase II promoter allows efficient expression of gRNAs flanked by the self-cleaving RNA structures, tRNA and HDV ribozyme, from a single plasmid co-expressing a codon optimized Cas9. Implementing this system resulted in nearly 100% efficiency of gene disruptions in both NHEJ-functional and NHEJ-deficient K. marxianus strains, with donor integration efficiencies reaching 50% and 100% in the two strains, respectively. The high gRNA targeting performance also proved instrumental for selection of engineered strains with lower growth rate but improved polyketide biosynthesis by avoiding an extended outgrowth period, a common method used to enrich for edited cells but that fails to recover advantageous mutants with even slightly impaired fitness. Finally, we provide the first demonstration of simultaneous, markerless integrations at multiple loci in K. marxianus using a 2.6 kb and a 7.6 kb donor, achieving a dual integration efficiency of 25.5% in a NHEJ-deficient strain. These results highlight both the ease of use and general robustness of this system for rapid and flexible metabolic engineering in this non-conventional yeast.
期刊介绍:
Metabolic Engineering Communications, a companion title to Metabolic Engineering (MBE), is devoted to publishing original research in the areas of metabolic engineering, synthetic biology, computational biology and systems biology for problems related to metabolism and the engineering of metabolism for the production of fuels, chemicals, and pharmaceuticals. The journal will carry articles on the design, construction, and analysis of biological systems ranging from pathway components to biological complexes and genomes (including genomic, analytical and bioinformatics methods) in suitable host cells to allow them to produce novel compounds of industrial and medical interest. Demonstrations of regulatory designs and synthetic circuits that alter the performance of biochemical pathways and cellular processes will also be presented. Metabolic Engineering Communications complements MBE by publishing articles that are either shorter than those published in the full journal, or which describe key elements of larger metabolic engineering efforts.