Precise Genome Modification In Tomato Using An Improved Prime Editing System

The CRISPR/Cas-mediated genome editing technology has been widely applied to create knock-out alleles of genes by generating short insertions or deletions (indel) in various plant species. Due to the low efficiency of homology-directed repair (HDR) and difficulties in the delivery of DNA template for HDR, precise genome editing remains challenging in plants (Mao et al., 2019). A tandem repeat-HDR method was developed very recently for sequence replacement in rice, which is most useful for monocots (Lu et al., 2020). Base editors developed from Cas9 nickase fusion with cytosine and adenine deaminases enable targeted C-to-T or A-to-G substitutions, but are restricted to specific types of base replacements and target site selections (Mao et al., 2019).