The architecture of base editors. A, Schematic view of cytosine base editor and glycosylase base editor. The cytosine base editor contains an UGI at the C-terminus, whereas the glycosylase base editor has an UNG at the C-terminus. The chemical structures of cytosine and uracil are shown and the deaminated amino group is highlighted in red. B, Schematic view of adenine base editor. The chemical structures of adenine and inosine are shown and the deaminated amino group is highlighted in green. C, Architecture of the DddA_tox-derived cytosine base editor targeting to plant organelles. DddA deaminase, a dsDNA cytidine deaminase from Burkholderia cenocepacia; MTP, mitochondrion transit peptide; CTP, chloroplast transit peptide.