Gene disruption through base editing‐induced messenger RNA missplicing in plants

Gene knockout tools are highly desirable for basic and applied plant research. Here, we leverage the Cas9‐derived cytosine base editor to introduce precise C‐to‐T mutations to disrupt the highly conserved intron donor site GT or acceptor site AG, thereby inducing messenger RNA (mRNA) missplicing and gene disruption. As proof of concept, we successfully obtained Arabidopsis null mutant of MTA gene in the T₂ generation and rice double null mutant of GL1‐1 and NAL1 genes in the T₀ generation by this strategy. Elimination of the original intron donor site or acceptor site could trigger aberrant splicing at a new specific exonic site, but not at the closest GT or AG site, suggesting cryptic rules governing splice site recognition. The strategy presented expands the applications of base editing technologies in plants by providing a new means for gene inactivation without generating DNA double‐strand breaks, and it can potentially serve as a useful tool for studying the biology of mRNA splicing.