A Conserved Basal Transcription Factor Is Required for the Function of Diverse TAL Effectors in Multiple Plant Hosts

Abstract

Many <i>Xanthomonas</i> bacteria use transcription activator-like effector (TALE) proteins to activate plant disease susceptibility (<i>S</i>) genes, and this activation contributes to disease. We recently reported that rice basal transcription factor IIA gamma subunit, OsTFIIAγ5, is hijacked by TALE-carrying <i>Xanthomonas oryzae</i> infecting the plants. However, whether TFIIAγs are also involved in TALE-carrying <i>Xanthomonas</i>-caused diseases in other plants is unknown. Here, molecular and genetic approaches were used to investigate the role of TFIIAγs in other plants. We found that TFIIAγs are also used by TALE-carrying <i>Xanthomonas</i> to cause disease in other plants. The TALEs of <i>Xanthomonas citri</i> pv. <i>citri</i> (<i>Xcc</i>) causing canker in citrus and <i>Xanthomonas campestris</i> pv. <i>vesicatoria</i> (<i>Xcv</i>) causing bacterial spot in pepper and tomato interacted with corresponding host TFIIAγs as in rice. Transcriptionally suppressing <i>TFIIAγ</i> led to resistance to <i>Xcc</i> in citrus and <i>Xcv</i> in pepper and tomato. The 39th residue of OsTFIIAγ5 and citrus CsTFIIAγ is vital for TALE-dependent induction of plant <i>S</i> genes. As mutated OsTFIIAγ5^{V 39E}, CsTFIIAγ^{V 39E}, pepper CaTFIIAγ^{V 39E}, and tomato SlTFIIAγ^{V 39E} also did not interact with TALEs to prevent disease. These results suggest that TALE-carrying bacteria share a common mechanism for infecting plants. Using TFIIAγ^{V 39E}-type mutation could be a general strategy for improving resistance to TALE-carrying pathogens in crops.