Advances in gene editing without residual transgenes in plants

Transgene residuals in edited plants affect genetic analysis, pose off-target risks, and cause regulatory concerns. Several strategies have been developed to efficiently edit target genes without leaving any transgenes in plants. Some approaches directly address this issue by editing plant genomes with DNA-free reagents. On the other hand, DNA-based techniques require another step for ensuring plants are transgene-free. Fluorescent markers, pigments, and chemical treatments have all been employed as tools to distinguish transgenic plants from transgene-free plants quickly and easily. Moreover, suicide genes have been used to trigger self-elimination of transgenic plants, greatly improving the efficiency of isolating the desired transgene-free plants. Transgenes can also be excised from plant genomes using site-specific recombination, transposition or gene editing nucleases, providing a strategy for editing asexually produced plants. Finally, haploid induction coupled with gene editing may make it feasible to edit plants that are recalcitrant to transformation. Here, we evaluate the strengths and weaknesses of recently developed approaches for obtaining edited plants without transgene residuals. New technologies enable efficient isolation of target gene-edited plants without any transgene residuals.

Automated summary

This article introduces several strategies to eliminate transgene residuals in edited plants, including direct editing of plant genomes with DNA-free reagents, using fluorescent markers, pigments, and chemical treatments to distinguish transgenic plants from transgene-free plants, and triggering self-elimination of transgenic plants through suicide genes. Additionally, it discusses the methods of excising transgenes from plant genomes using site-specific recombination, transposition, or gene editing nucleases, as well as the combination of haploid induction and gene editing for editing recalcitrant plants.