Xanthomonas oryzae pv. oryzae TALE proteins recruit OsTFIIAγ1 to compensate for the absence of OsTFIIAγ5 in bacterial blight in rice

Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight (BB) of rice, uses transcription activator-like effectors (TALEs) to interact with the basal transcription factor gamma subunit OsTFIIA gamma 5 (Xa5) and activates the transcription of host genes. However, how OsTFIIA gamma 1, the other OsTFIIA gamma protein, functions in the presence of TALEs remains unclear. In this study, we show that OsTFIIA gamma 1 plays a compensatory role in the absence of Xa5. The expression of OsTFIIA gamma 1, which is activated by TALE PthXo7, increases the expression of host genes targeted by avirulent and virulent TALEs. Defective OsTFIIA gamma 1 rice lines show reduced expression of the TALE-targeted susceptibility (S) genes, OsSWEET11 and OsSWEET14, which results in increased BB resistance. Selected TALEs (PthXo1, AvrXa7 and AvrXa27) were evaluated for interactions with OsTFIIA gamma 1, Xa5 and xa5 (naturally occurring mutant form of Xa5) using biomolecular fluorescence complementation (BiFC) and microscale thermophoresis (MST). BiFC and MST demonstrated that the three TALEs bind Xa5 and OsTFIIA gamma 1 with a stronger affinity than xa5. These results provide insights into the complex roles of OsTFIIA gamma 1 and OsTFIIA gamma 5 in TALE-mediated host gene transcription.