A simple and efficient method for CRISPR/Cas9-induced mutant screening

The clustered regularly interspaced short palindromic repeats（CRISPR）/CRISPR-associated protein 9（Cas9） system provides a technological breakthrough in mutant generation. Several methods such as the polymerase chain reaction（PCR）/restriction enzyme（RE） assay, T7 endonuclease I（T7EI） assay, Surveyor nuclease assay, PAGE-based genotyping assay, and high-resolution melting（HRM） analysis-based assay have been developed for screening CRISPR/Cas9-induced mutants. However, these methods are timeand labour-intensive and may also be sequence-limited or require very expensive equipment. Here, we described a cost-effective and sensitive screening technique based on conventional PCR, annealing at critical temperature PCR（ACT-PCR）, for identifying mutants. ACT-PCR requires only a single PCR step followed by agarose gel electrophoresis. We demonstrated that ACT-PCR accurately distinguished CRISPR/Cas9-induced mutants from wild type in both rice and zebrafish. Moreover, the method can be adapted for accurately determining mutation frequency in cultured cells. The simplicity of ACT-PCR makes it particularly suitable for rapid, large-scale screening of CRISPR/Cas9-induced mutants in both plants and animals.