Abstract: Xanthomonas bacteria secrete transcription activator-like effector (TALE) proteins into host cells to activate plant disease susceptibility genes to cause disease, and the process is dependent on interaction between bacteria TFB domain of TALEs and host plant basal transcription factor IIA gamma subunit (TFIIAγ). The key domain or residues of plant TFIIAγ and core residues of bacteria TFB domain that are indispensable for TFIIAγ-TALEs interaction in the process of TALE-carrying Xanthomonas invasion plants are unknown. Here, we showed that the third α-helix domain of OsTFIIAγ5/Xa5, especially the 38th, 39th, 40th and 42th residues were key sites for capturing by TALEs of Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of rice bacterial blight disease. The latter segment of Xoo TFB domain harboring seventy-two amino acid residues was vital for TALE specific binding with host plant OsTFIIAγ5/Xa5. Substitution of some residues in this core region of TFB domain completely compromised capacity of TALEs capturing rice OsTFIIAγ5/Xa5. The rich and conserved arginine residues in this core region of TFB domain were responsible for TALE-dependent plant susceptibility gene activation and virulence of Xoo. These results provide a potential strategy for improving resistance to TALE-carrying pathogens in plants by site-specific modification of key residues of host plant TFIIAγ. 

Key words: Xanthomonas ,  transcription activator-like effector ,  PthXo1 ,  TFB ,  rice