Dear Editor,Precise modification of eukaryotic genomes has been accomplished mainly through homology-directed repair (HDR) of DNA double-strand breaks (DSBs) (Hess et al.,2017).However,the inherent low efficiency of homologous recombination and poor availability of exogenous donor DNA as repair templates strongly impede the use of HDR for precise genome editing in many species (Komor et al.,2017a).To complement the HDR method and circumvent some of its limitations,the recently developed base editing approach has enabled irreversible conversion of cytidine (C) to thymidine (T) (or guanine [G] to adenine [A]) at target loci without requiring DSB formation and HDR (Komor et al.,2016;Nishida et al.,2016).