CRISPR gene-editing technology enables precise editing of DNA sequences in vivo and it has been widely used in modifying genes in many organisms including crop plants. Compared to gene editing for medical purposes, editing genes in crop plants has unique challenges. One of the most important considerations of gene editing in crop plants is that the edited plants should not contain the transgenes used for the editing process. The removal of the CRISPR construct is a prerequisite for regulatory approval of commercial applications of any edited crops. Moreover, the existence of the CRISPR constructs prevents us from accurately determining heredity patterns and eliminating off target effects. The transgenes can be segregated out if the plants are propagated sexually, but genetic segregation and genotyping are time consuming and labor-intensive. In this presentation, I will present several strategies that can efficiently, quickly, and reliably generate edited, but transgene-free plants. We programmed the CRISPR/Cas9 constructs to undergo self-elimination once the target gene is edited. Our work enables us to generate knockout plants without any transgenes in just a single generation. We also designed strategies to eliminate transgenes in crops such as grapes that are propagated asexually. Another major challenge in editing genes in plants is the inefficient homologous recombination-based gene targeting/replacement (HDR) because of the difficulties in delivering repair templates into plant cells. We have developed strategies that can overcome the main obstacles in HDR.
Gene Editing Technology for Crop Improvement
Professor, Department of Cell and Developmental Biology
University of California, San Diego
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