Wenxue Wang, Lei Yan, Jingying Li, Chen Zhang, Yubing He, Shaoya Li, Lanqin Xia

Plant Biotechnology Journal; 2024; IF:11.2

DOI: 10.1111/pbi.14544

Abstract

Wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) is one of the most important food crops in the world. CRISPR/Cas12i3, which belongs to type V-I Cas system, has attracted extensive attentions recently due to its smaller protein size and its less-restricted canonical ‘TTN’ protospacer adjacent motif (PAM). However, due to its relatively lower editing efficacy in plants and the hexaploidy complex nature of wheat, Cas12i3/Cas12i3-5M-mediated genome editing in wheat has not been documented yet. Here, we report engineering of a robust Cas12i3-5M mediated genome editing system in wheat through fusion of T5 exonuclease (T5E) in combination with an optimized crRNA expression strategy (Opt). We first showed that fusion of T5E, rather than ExoI, to Cas12i3-5M increased the gene editing efficiencies by up to 1.34-fold and 3.87-fold, compared to Cas12i3-5M and Cas12i3 in HEK293T cells, respectively. However, its editing efficiency remains low in wheat. We then optimized the crRNA expression strategy and demonstrated that Opt-T5E-Cas12i3-5M could enhance the editing efficiency by 1.20- to 1.33-fold and 4.05- to 7.95-fold in wheat stable lines compared to Opt-Cas12i3-5M and Opt-Cas12i3, respectively, due to progressive 5’-end resection of DNA strand at the cleavage site with increased deletion size. The Opt-T5E-Cas12i3-5M enabled an editing efficiency ranging from 60.71% to 90.00% across four endogenous target genes in stable lines of three elite Chinese wheat varieties. Together, the developed robust Opt-T5E-Cas12i3-5M system enriches wheat genome editing toolkits for either biological research or genetic improvement, and may be extended to other important polyploidy crop species.