CRISPR-Cas9 systems have been widely used in animals and plants for genome editing, epigenetic modification, etc. (Cong et al., 2013, Hilton et al., 2015). However, the accurate recognition of target sites of CRISPR/Cas9 systems depends on the single-guide RNA (sgRNA) corresponding to each target site and protospacer adjacent motifs (PAMs) around these sites (Anders et al., 2014). Cas9-sgRNA complexes will directly eject the DNA template if no PAMs are recognized before base pairing between target sites and sgRNA (Sternberg et al., 2014).