# Validation of a Modular Base Editing Strategy, Free-BE, in Physcomitrium patens, Maize, and Wheat Article · Guyon-Debast A, Javelle M, Perroud PF, Pichon JP, Paul W, Nogué F - Archive id: doi:10.1002/pld3.70196 - Published: 2026-10-15 - Venue: Plant direct - DOI: https://doi.org/10.1002/pld3.70196 - PMID: 42889475 - Citations: 0 - Source URL: https://doi.org/10.1002/pld3.70196 - Provenance: europepmc ## Abstract Base editing (BE) technologies enable precise genome modification but often generate undesired editing outcomes, including indels, bystander edits, and editing outside the optimal activity windows. Here, we report a modular BE strategy, termed Free-BE, where the cytidine deaminase and Cas9 nickase are delivered as separate components rather than as a single fusion protein. In the moss Physcomitrium patens , Free-BE showed lower editing efficiency than the conventional fused system (Fused-BE). However, it generated fewer indels, a higher proportion of single-nucleotide edits, and reduced out-of-window editing. Free-BE also altered the spectrum of base substitutions, producing a higher proportion of C-to-G and C-to-A transversions than Fused-BE in P. patens . No mutations were detected at four predicted off-target loci examined in P. patens . We further validated Free-BE in crop systems. In a transient maize protoplast reporter assay, Free-BE achieved targeted base conversions, whereas stable transformation of wheat demonstrated successful editing of endogenous loci, although with lower efficiency than Fused-BE. In wheat, Free-BE similarly reduced multicytidine editing and by-products. Together, these results establish Free-BE as a functional modular BE strategy that broadens the plant genome-editing toolbox and may be advantageous for applications requiring greater control over editing outcomes, despite lower overall editing efficiency. _Abstract reproduced under CC-BY (article license as recorded by Europe PMC; abstract reproduced unmodified apart from markup removal)._ Topics: [CRISPR & Gene-Editing Therapies](https://space-kitty.com/topics/gene-editing-therapies) --- Space Kitty Archive · https://space-kitty.com · API: https://space-kitty.com/api/v1 · MCP: https://space-kitty.com/mcp · Premium: $0.20/request via x402 (Base Sepolia (testnet)). Metadata: arXiv (CC0), OpenAlex (CC0), Europe PMC (CC BY/CC0 works), ClinicalTrials.gov.