Establishment of a visual gene knockout system based on CRISPR/Cas9 for the rare actinomycete Nonomuraea gerenzanensis.

Objectives: To develop a modified CRISPR/Cas9 system with the β-glucuronidase (GusA) reporter and a dual sgRNA cassette for Nonomuraea gerenzanensis (N. gerenzanensis). Results: With the aid of a visual GusA reporter, the complicated and tedious process of cloning and gene identification could be abandoned entirely in the genetic editing of N. gerenzanensis. Moreover, introducing a dual sgRNA cassette into the CRISPR/Cas9 system significantly improved gene deletion efficiency compared to the single sgRNA element. Furthermore, the length of the homologous flanking sequences set to the lowest value of 500 bp in this system could still reach the relatively higher conjugation transfer frequency. Conclusions: The enhanced CRISPR/Cas9 system could efficiently perform genetic manipulation on the rare actinomycete N. gerenzanensis. [ABSTRACT FROM AUTHOR]