Xanthomonas TAL effectors hijack host basal transcription factor IIA α and γ subunits for invasion

The Xanthomonas genus includes Gram-negative plant-pathogenic bacteria, which infect a broad range of crops and wild plant species, cause symptoms with leaf blights, streaks, spots, stripes, necrosis, wilt, cankers and gummosis on leaves, stems and fruits in a wide variety of plants via injecting their effector proteins into the host cell during infection. Among these virulent effectors, transcription activator-like effectors (TALEs) interact with the gamma subunit of host transcription factor (THIA gamma) to activate the transcription of host disease susceptibility genes. Functional TFIIA is a ternary complex comprising alpha, beta and gamma subunits. However, whether TALEs recruit TFIIA alpha, TFIIA beta, or both remains unknown. The underlying molecular mechanisms by which TALEs mediate host susceptibility gene activation require full elucidation. Here, we show that TALEs interact with the alpha+gamma binary subcomplex but not the alpha+beta+gamma ternary complex of rice TFIIA (holo-OsTFIIA). The transcription factor binding (TFB) regions of TALEs, which are highly conserved in Xanthomonas species, have a dominant role in these interactions. Furthermore, the interaction between TALEs and the alpha+gamma complex exhibits robust DNA binding activity in vitro. These results collectively demonstrate that TALE-carrying pathogens hijack the host basal transcription factors TFIlA alpha and TFIIA gamma, but not TFIIA beta to enhance host susceptibility during pathogen infection. The uncovered mechanism widens new insights on host-microbe interaction and provide an applicable strategy to breed high-resistance crop varieties. (C) 2018 Elsevier Inc. All rights reserved.