A design optimized prime editor with expanded scope and capability in plants.

The ability to manipulate the genome in a programmable manner has illuminated biology and shown promise in plant breeding. Prime editing, a versatile gene-editing approach that directly writes new genetic information into a specified DNA site without requiring double-strand DNA breaks, suffers from low efficiency in plants. In this study, N-terminal reverse transcriptase-Cas9 nickase fusion performed better in rice than the commonly applied C-terminal fusion. In addition, introduction of multiple-nucleotide substitutions in the reverse transcriptase template stimulated prime editing with enhanced efficiency. By using these two methods synergistically, prime editing with an average editing frequency as high as 24.3% at 13 endogenous targets in rice transgenic plants, 6.2% at four targets in maize protoplasts and 12.5% in human cells was achieved, which is two- to threefold higher than the original editor, Prime Editor 3. Therefore, our optimized approach has potential to make more formerly non-editable target sites editable, and expands the scope and capabilities of prime editing in the future.