| Summary: | <i>Xanthomonas campestris</i> is one of bacteria carrying a type III secretion system which transports their effector proteins into host plant cells to disturb host defense system for their infection. To establish a genome editing system without introducing any foreign gene, we attempted to introduce genome editing enzymes through the type III secretion system. In a test of protein transfer, <i>X. campestris</i> pv. <i>campestris</i> (<i>Xcc</i>) transported a considerable amount of a reporter protein sGFP-CyaA into tobacco plant cells under the control of the type III secretion system while maintaining cell viability. For proof of concept for genome editing, we used a reporter tobacco plant containing a luciferase (LUC) gene interrupted by a meganuclease I-<i>Sce</i>I recognition sequence; this plant exhibits chemiluminescence of LUC only when a frameshift mutation is introduced at the I-<i>Sce</i>I recognition site. Luciferase signal was observed in tobacco leaves infected by <i>Xcc</i> carrying an <i>I-SceI</i> gene which secretes I-<i>Sce</i>I protein through the type III system, but not leaves infected by <i>Xcc</i> carrying a vector control. Genome-edited tobacco plant could be regenerated from a piece of infected leaf piece by repeated selection of LUC positive calli. Sequence analysis revealed that the regenerated tobacco plant possessed a base deletion in the I-<i>Sce</i>I recognition sequence that activated the <i>LUC</i> gene, indicating genome editing by I-<i>Sce</i>I protein transferred through the type III secretion system of <i>Xcc</i>.
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