Targeted deletion and inversion of tandemly arrayed genes in Arabidopsis thaliana using zinc finger nucleases

Tandemly arrayed genes (TAGs) or gene clusters are prevalent in higher eukaryotic genomes. For example, approximately 17% of genes are organized in tandem in the model plant Arabidopsis thaliana. The genetic redundancy created by TAGs presents a challenge for reverse genetics. As molecular scissors, engineered zinc finger nucleases (ZFNs) make DNA double-strand breaks in a sequence-specific manner. ZFNs thus provide a means to delete TAGs by creating two double-strand breaks in the gene cluster. Using engineered ZFNs, we successfully targeted seven genes from three TAGs on two Arabidopsis chromosomes, including the well-known RPP4 gene cluster, which contains eight resistance (R) genes. The resulting gene cluster deletions ranged from a few kb to 55 kb with frequencies approximating 1% in somatic cells. We also obtained large chromosomal deletions of ~9 Mb at approximately one tenth the frequency, and gene cluster inversions and duplications also were achieved. This study demonstrates the ability to use sequence-specific nucleases in plants to make targeted chromosome rearrangements and create novel chimeric genes for reverse genetics and biotechnology.