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Using TAL effector nucleases for targeted genetic modification.
B. YANG (1). (1) Iowa State University, Ames, IA, U.S.A.

TAL (transcription activator-like) effectors of <i>Xanthomonas</i> <i>oryzae</i> pv. <i>oryzae</i> (Xoo) contribute to pathogen virulence by transcriptionally activating specific rice disease susceptibility (S) genes. TAL effector nucleases (TALENs) are fusion proteins of TAL effectors and the DNA cleavage domain of FokI nuclease. TALENs are capable of inducing chromosomal DNA double-strand breaks (DBSs) at specific sites. DBS repair can lead to efficient introduction of sequence modifications or insertions through homology recombination or mutagenic insertions/deletions through nonhomologous end-joining at the site of the break, making TALEN technology a powerful genetic tool. We exploit TALEN technology to edit the specific S genes in rice to thwart the virulence strategy of <i>Xanthomonas</i> <i>oryzae</i> and, thereby, engineer heritable genome modifications for resistance to bacterial blight. Multiple designer TALENs are custom-engineered to precisely edit the effector binding elements within the promoters of two S genes targeted by three TAL effectors of essential virulence of Xoo. The resulting promoter modifications in transgenic plants result in loss of inducibility of S gene by the cognate TAL effectors and concomitantly loss of disease susceptibility (or gain of resistance) to pathogenic Xoo. The TALEN gene constructs can be genetically segregated out in some modified plants. The results demonstrate the feasibility of using TALENs for targeted editing of important genes for crop improvement and also raise the prospect of producing genetically modified plants without a trace of “foreign” DNA left in the genome.<p><p>Keywords:

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