te TAL effectors function as specific transcriptional activators in the plant cell nucleus. The specificity of DNA recognition by the TAL effector is determined by the variable amino acids at residues 12 and 13 of each repeat. However, some TAL effectors have been identified as avirulence (Avr) proteins in disease resistance (R) gene-mediated Xoo resistance (Boch and Bonas 2010).