A GRFGIF chimeric protein improves the regeneration efficiency of transgenic plants

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The potential of genome editing to improve the agronomic performance of crops is often limited by low plant regeneration efficiencies and few transformable genotypes. Here, we show that expression of a fusion protein combining wheat GROWTH-REGULATING FACTOR 4 (GRF4) and its cofactor GRF-INTERACTING FACTOR 1 (GIF1) substantially increases the efficiency and speed of regeneration in wheat, triticale and rice and increases the number of transformable wheat genotypes. GRF4GIF1 transgenic plants were fertile and without obvious developmental defects. Moreover, GRF4GIF1 induced efficient wheat regeneration in the absence of exogenous cytokinins, which facilitates selection of transgenic plants without selectable markers. We also combined GRF4GIF1 with CRISPRCas9 genome editing and generated 30 edited wheat plants with disruptions in the gene Q (AP2L-A5). Finally, we show that a dicot GRFGIF chimera improves regeneration efficiency in citrus, suggesting that this strategy can be applied to dicot crops.