CRISPR/Sc++-mediated genome editing in rice

Streptococcus canis Cas9 (ScCas9) is an RNA-guided endonuclease with NNG protospacer adjacent motif (PAM) specificity whose genome-editing activity in rice is locus-dependent. Here we investigated the performance of a ScCas9 variant named Sc⁺⁺ at different NNG PAM sites in the rice genome; Sc⁺⁺ harbors a T1227K mutation and the substitution of a positively charged loop (residues 367–376). Sc⁺⁺ nuclease achieved broader genome editing compared to the original ScCas9, and its nickase improved targeted base editing in transgenic rice plants. Using the high-efficiency adenine base editor rBE73b, we generated many new OsGS1 alleles suitable for screening of rice germplasm for potential herbicide resistance in the future. The CRISPR/Sc⁺⁺ system expands the genome-editing toolkit for rice.