Enhancing resistance to bacterial blight in rice using CRISPR-based base editing technology

Bacterial blight (BB), caused by Xanthomonas oryzae pathovar oryzae ( Xoo ), poses a significant threat to rice production, particularly in Asia and West Africa. Breeding resistance against BB in elite rice varieties is crucial to advancing rice breeding program and supporting smallholder farmers. Transcription Activator-Like effectors (TALes) are key virulence factors in Xoo, with some targeting the susceptibility ( S ) genes such as the sugar transporter SWEET genes in rice. Among these, SWEET14 is an important S gene, with its promoter bound by the TALe TalC which exists across all sequenced African Xoo isolates. In the present study, we utilized CRISPR/Cas9-based cytidine and adenine base editors to alter the effector binding element (EBE) of TalC in the promoter of SWEET14 in rice cultivars Kitaake, IR24, and Zhonghua 11. Mutations with C to T changes in EBE led to reduced SWEET14 induction by TalC-containing Xoo strains, resulting in resistance to African Xoo isolates reliant on TalC for virulence. Conversely, A to G changes retained SWEET14 inducibility and susceptibility to Xoo in edited lines. Importantly, no off-target mutations were detected at predicted sites, and the edited lines exhibited no obvious defects in major agronomic traits in Kitaake. These results underscore the effectiveness of base editing systems for both molecular biology research and crop improvement endeavors.