Fig. 2. Examples of the potential applications of CRISPR/Cas-mediated cis-engineering in horticultural crops.

a CRISPR/Cas-mediated point mutations can be achieved by base editor or HDR-mediated CRE swapping. In some Capsicum species, a mutated W-box in the MYB31 promoter is not recognized by the activator WRKY9. Base editor and CRE swapping can change the motif TTGGC to W-box (TTGAC), which can be bound by WRKY9, resulting in increased expression of MYB31 and higher pungency level. b The R6 motif insertion mediated by HDR confers trans-regulation by flavonoid-related MYBs, which can bind the R6-containing promoters of the genes encoding enzymes of the anthocyanin biosynthetic pathway, resulting in enhanced expression of these genes and higher anthocyanin levels. CRE, cis-regulatory element; F3′5′H, flavonoid 3′5′-hydroxylase.