A Versatile tRNA-gRNA Array-Based CRISPR/Cas9 Platform Enabling Multiplex Genome Editing and Large-Fragment...

Cephalosporin C (CPC)-derived antibiotics have played a vital role in improving human health and extending life expectancy. Acremonium chrysogenum remains the only microorganism capable of industrial-scale CPC production to date. However, the lack of efficient multiplex genome-editing tools has limited studies on its gene function, high-yield mechanisms as well as metabolic engineering. To overcome this limitation, a rapid and efficient CRISPR/Cas9-based multiplex genome-editing system was developed, driven by endogenous tRNA promoters, enabling one-step multilocus knockout, large-fragment DNA deletion, and gene overexpression in A. chrysogenum. Given that many strains lack visible phenotypes associated with specific genes, we introduced a visually distinguishable red phenotype by expressing the heterologous protein mCherry under a strong promoter. In the wild-type strain, 20 endogenous tRNA promoters were evaluated and compared to the heterologous Aspergillus nidulans PgpdA and Aspergillus fumigatus U6 promoters. The endogenous tRNA^Val promoter showed the highest knockout efficiency (95.5%). The tRNA-gRNA array-based CRISPR/Cas9 system enabled double- and triple-site knockouts without donor DNA in industrial strain, with efficiencies of 50.0-83.3% and 14.3%, respectively. This is the first demonstration of simultaneous triple-site knockout in A. chrysogenum, especially in industrial strain. Using this system, we successfully deleted a 50.7-kb DNA fragment containing the sorbicillinoids biosynthetic gene cluster with nearly 100% efficiency and achieved overexpression of the key gene pcbAB involved in CPC biosynthesis in high-yield strain, increasing CPC titer from 5.59 g/L to 6.92 g/L with an improvement of 23.8%. Overall, this tRNA-gRNA array-based CRISPR/Cas9 multiplex gene-editing system provides an efficient and versatile platform for functional genomics and industrial strain engineering in A. chrysogenum.