CRISPR/Cas system-mediated transgene-free or DNA-free genome editing in plants

CRISPR/Cas-based genome-editing technology serves as a powerful and versatile tool for genome modification. It has been broadly utilized in crop breeding to enhance traits such as yield, various quality attributes, and biotic and abiotic stress tolerance. Because of public safety concerns over genetically modified organisms (GMOs), many countries have established stringent regulatory policies for genetically modified plants, dramatically limiting the application of related products. However, genome editing in stably transformed plants can result in transgene-free progeny through self-pollination or hybridization or yield DNA-free gene-edited plants via transient transformation. These edited plants materially differ from GMOs and are referred to as genome-edited organisms (GEOs). GEOs have the potential to alleviate regulatory burdens and aid in commercialization. Various methods have been developed to expedite the creation of transgene-free or DNA-free GEOs. This review summarizes the various strategies for creating these types of GEOs based on the CRISPR/Cas systems. It also covers the advantages and drawbacks of these strategies. Additionally, we examine off-target effects and mitigation strategies for plant genome editing and outline regulatory policies for gene-edited crops in selected countries and regions. We hope this review offers valuable references for the advancement of transgene-free and DNA-free GEOs.