Abstract
Summary 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 OsTFIIAγ5 (Xa5) and activates the transcription of host genes. However, how OsTFIIAγ1, the other OsTFIIAγ protein, functions in the presence of TALEs remains unclear. In this study, we show that OsTFIIAγ1 plays a compensatory role in the absence of Xa5. The expression of OsTFIIAγ1, which is activated by TALE PthXo7, increases the expression of host genes targeted by avirulent and virulent TALEs. Defective OsTFIIAγ1 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 OsTFIIAγ1, 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 OsTFIIAγ1 with a stronger affinity than xa5. These results provide insights into the complex roles of OsTFIIAγ1 and OsTFIIAγ5 in TALE‐mediated host gene transcription.
Highlights
Bacterial plant pathogens reduce the yield of many important crops of global importance, including rice, tomatoes, peppers and citrus
transcription activator-like effectors (TALEs) are translocated to the nucleus where they bind to specific promoter sequences in host genes, which are designated as TAL effector-binding elements (EBEs) (Chen et al, 2010; Mak et al, 2013)
To investigate whether naturally occurring X. oryzae pv. oryzae (Xoo) strains isolated from the environment have the ability to evade xa5-mediated resistance, we examined the virulence of 65 Xoo strains isolated from 13 rice-planting provinces in China
Summary
Bacterial plant pathogens reduce the yield of many important crops of global importance, including rice, tomatoes, peppers and citrus. Xanthomonas is a widespread bacterial genus that contains approximately 30 pathogenic species known to cause disease in over 300 plant hosts (Boch et al, 2014; Schornack et al, 2013). TALE-like proteins are not restricted to the genus Xanthomonas, as they are found in other plant pathogens and endosymbionts, including Ralstonia solanacearum and Burkholderia rhizoxinica, respectively (de Lange et al, 2014). Apart from their EBE-binding ability, it remains unclear how TALEs function to promote the transcription of target genes cooperatively with other transcriptional factors
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