水稻转录因子WRKY68在Xa21介导的抗白叶枯病反应中发挥正调控作用

Rice transcription factor WRKY68 plays a positive role in Xa21-mediated resistance to Xanthomonas oryzae pv.oryzae

白叶枯病是一种严重影响水稻产量的细菌性病害。Xa21是第一个克隆的抗白叶枯病基因,具有广谱抗性,在水稻抗病育种中被广泛应用。转录因子的鉴定对解析Xa21介导的水稻抗白叶枯病分子机制具有重要意义。本研究构建了Xa21背景下的WRKY68-RNAi转基因水稻。与受体材料4021相比,转基因水稻中WRKY68蛋白质丰度下调,接种白叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)后抗病性下降,证明WRKY68基因在Xa21介导的抗白叶枯病反应中发挥正调控作用。此外,转基因受体材料4021和感病对照TP309接种后不同时期和部位叶片中WRKY68的蛋白质丰度没有显著差异,表明WRKY68蛋白质的表达不受抗病基因Xa21和病原物Xoo诱导,推测其功能主要是调控下游基因的表达。WRKY68-RNAi转基因水稻接种后,PR1A、PR5、PR10A、PR-pha和PAL1等病程相关蛋白质表达丰度发生变化,表明相关基因可能在WRKY68基因的调控下参与下游抗病反应。

Leaf blight is a bacterial disease of rice which leads to heavy yield losses.Xa21 which harbors broad spectrum resis-tance to leaf blight is the first resistant gene cloned in rice and is widely used in rice breeding program.The identification of tran-scription factor involved in Xa21-mediated resistance to bacterial leaf blight is of great significance.In this study,transgenic WRKY68-RNAi lines with reduced expression level of WRKY68 protein in the background of Xa21 were generated.The WRKY68-RNAi transgenic lines showed reduced resistance to Xanthomonas oryzae pv.oryzae(Xoo),indicating that WRKY68 played a positive role in Xa21-mediated resistance in rice.No detectable changes of WRKY68 protein abundance in leaves at different stages and positions after inoculation were identified by Western blot,indicating that the expression of WRKY68 protein were independent of Xa21 and Xoo,and thus WRKY68 gene may function as a transcription factor to regulate downstream genes.It was further found that the abundance of a number of pathogenesis-related proteins,including PR1A,PR5,PR10A,PR-pha,and PAL1 were dramatically changed in WRKY68-RNAi transgenic lines when inoculated with Xoo,suggested that these pathogene-sis-related proteins were regulated by WRKY68 and the corresponding genes were involved in the downstream defenses responses.