Highly Efficient A·T to G·C Base Editing by Cas9n-Guided tRNA Adenosine Deaminase in Rice

The newly developed CRISPR/Cas9-mediated base editing technology with cytosine deaminase is capable of precisely and efficiently introducing point mutations at the target genomic locus, which does not require double-stranded DNA breaks or any donor templates and thus exhibit a great potential for gene correction and genetic diversification in yeasts, plants, and mammalian and human cells (Komor et al., 2016; Nishida et al., 2016; Lu and Zhu, 2017; Ren et al., 2017). However, compared with AID/APOBEC1 members of the cytosine deaminase family that are widely utilized in base editing to induce cytidine (C) to thymine (T) conversion, adenosine deaminase is far from being applicable since TadA/ADAR members act strictly on duplex RNA, or DNA/RNA hybrids with mismatches, instead of single-stranded DNA (Zheng et al., 2017).