Increasing fidelity and efficiency by modifying cytidine base-editing systems in rice

The efficiency of plant cytidine base-editing systems is limited, and unwanted mutations frequently occur in transgenic plants. We increased the cytidine editing frequency and fidelity of the plant base editor 3 (BE3) and targeted activation-induced cytidine deaminase (CDA) (target-AID) systems by coexpressing three copies of free uracil-DNA glycosylase (UDG) inhibitor (UGI). The editing efficiency of the improved BE3 and CDA systems reached as high as 88.9% and 85.7%, respectively, in regenerated rice plants, with a very low frequency of unwanted mutations. The low editing frequency of the BE3 system in the GC context could be overcome by the modified CDA system. These results provide a high-fidelity and high-efficiency solution for rice genomic base editing. (C) 2019 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.