Conditional editing of the genome using single transcripts expressing Cas9 and sgRNA.

The CRISPR/Cas9(clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR- associated protein 9) system, a highly efficient, simple, and easy genome editing technology, offers significant potential for genetic engineering and has been commonly applied in gene function studies in . However, when using CRISPR/Cas9 system to edit gene, Cas9 and sgRNA expression elements exist in different individuals, and Cas9 and sgRNA must be integrated into an individual through a complex genetic hybridization process, which has a long and complex operation cycle In this study, on the basis of the CRISPR/Cas9 system, we introduced the tRNA-sgRNA system and triplex elements, used triplex elements to link Cas9 and tRNA-sgRNA genes, stabilized the end of Cas9 mRNA after single transcript cutting, and made the expression of both Cas9 protein and sgRNA with a single transcript a reality. And as we obtained the corresponding phenotypic progeny in one hybridization, genetic manipulation was simplified. We found that conditional knockout of the gene in the eye and the gene in the adult wing disc resulted in corresponding phenotypes that matched expectations using our new conditional gene editing system. So the significant advances in this new conditional gene editing system over the existing CRISPR/Cas9 system are that it is more efficient, extendable, and easy to use.