A transcription activator-like effector is trapped in nonhost plants for immunity.

pv. (), the causal agent of bacterial leaf blight in rice, delivers transcription activator-like effector (TALE) proteins into host cells to activate susceptibility or resistance () genes that promote disease or immunity, respectively. Nonhost plants serve as potential reservoirs of genes; consequently, nonhost genes may trap TALEs to trigger an immune response. In this study, we screened 17 TALEs for their ability to induce a hypersensitive response (HR) in the nonhost plant (); only AvrXa10 elicited an HR when transiently expressed in . The HR generated by AvrXa10 required both the central repeat region and the activation domain, suggesting a specific interaction between AvrXa10 and a potential -like gene in nonhost plants. Evans blue staining and ion leakage measurements confirmed that the AvrXa10-triggered HR was a form of cell death, and the transient expression of AvrXa10 in induced immune responses. Genes targeted by AvrXa10 in the genome were identified by transcriptome profiling and prediction of effector binding sites. Using several approaches ( reporter assays, electrophoretic mobility-shift assays, targeted designer TALEs, and on-spot gene silencing), we confirmed that AvrXa10 targets , a C2H2-type zinc finger protein that resides in the nucleus. Functional analysis indicated that overexpression of and its rice orthologs triggered cell death in rice protoplasts. An NbZnFP1 ortholog was also identified in tomato and was specifically activated by AvrXa10. These results demonstrate that is a nonhost gene that traps AvrXa10 to promote plant immunity in .