Xanthomonas oryzae pv. oryzae strain PXO99A induces the expression of the host gene Os8N3, which results in increased host susceptibility to bacterial blight of rice. Here, we show that PXO99A affects the expression of two additional genes in a type III secretion system-dependent manner, one encoding a bZIP transcription factor (OsTFX1) and the other the small subunit of the transcription factor IIA located on chromosome 1 (OsTFIIAγ1). Induction of OsTFX1 and OsTFIIAγ1 depended on the type III effector genes pthXo6 and pthXo7, respectively, both encoding two previously undescribed members of the transcription activator-like (TAL) effector family. pthXo7 is strain-specific and may reflect adaptation to the resistance mediated by xa5, an allele of OsTFIIAγ5 encoding a second form of the TFIIA small subunit on chromosome 5 of rice. The loss of pthXo6 resulted in reduced pathogen virulence, and ectopic expression of OsTFX1 abrogated the requirement for pthXo6 for full virulence. X. oryzae pv. oryzae therefore modulates the expression of multiple host genes using multiple TAL effectors from a single strain, and evidence supports the hypothesis that expression of the associated host genes contributes to host susceptibility to disease.
水稻白葉枯病菌小種PXO99A誘導(dǎo)寄主基因Os8N3的表達(dá)，導(dǎo)致水稻對(duì)白葉枯病的易感性增加。本研究我們發(fā)現(xiàn)PXO99A以Ⅲ型分泌系統(tǒng)依賴的方式影響另外兩個(gè)基因的表達(dá)，一個(gè)是bZIP轉(zhuǎn)錄因子編碼基因OsTFX1，另一個(gè)是位于1號(hào)染色體上的轉(zhuǎn)錄因子ⅡA小亞基編碼基因OsTFIIAγ1。OsTFX1和OsTFIIAγ1的誘導(dǎo)分別依賴于Ⅲ型效應(yīng)基因pthXo6和pthXo7，這兩個(gè)基因都編碼兩個(gè)以前未鑒定的轉(zhuǎn)錄激活因子樣（TAL）效應(yīng)子家族成員。pthXo7具有小種特異性，可能反映了對(duì)xa5介導(dǎo)的抗性的適應(yīng)，xa5是水稻5號(hào)染色體上編碼TFIIA小亞基第二形式的OsTFIIAγ5等位基因。pthXo6的缺失導(dǎo)致病原體的毒力降低，OsTFX1的異位表達(dá)取消了pthXo6對(duì)完全毒力的要求。因此，白葉枯病菌利用來自單一菌株的多個(gè)TAL效應(yīng)子調(diào)節(jié)多個(gè)宿主基因的表達(dá)，并且證據(jù)支持相關(guān)宿主基因的表達(dá)有助于宿主對(duì)疾病易感性的假設(shè)。