一个推测的野油菜黄单胞菌Ⅲ型分泌效应子基因XopXccP对寄主植物的致病性分析

XopXccP,a putative type Ⅲ effector gene of Xanthomonas campestris pv. campestris,is required for pathogenicity on host plants

野油菜黄单胞菌野油菜致病变种(Xanthomonas campestris pv.campestris,Xcc)是一种在全球范围内引起十字花科植物黑腐病的重要病原细菌。Xcc中效应蛋白与植物互作机理的研究还不够全面,在已经测序的菌株Xcc 8004中,Xc_2994基因预测编码一个III型分泌效应蛋白XopXccP,其生物学功能尚不清楚。为了探索XopXccP的生物学功能,我们构建了Xcc 8004菌株的XopXccP基因缺失突变体,结果发现XopXccP基因缺失后,病原菌在多个甘蓝、花椰菜以及模式植物拟南芥(Col-0)上的致病性显著下降,甚至几乎不致病。同时,采用农杆菌侵染拟南芥花序的转化方法,获得了转XopXccP基因拟南芥纯系,经过诱导效应蛋白XopXccP在拟南芥中表达,发现转基因拟南芥出现类似病斑的细胞死亡。本研究结果初步证明,XopXccP是一种毒性蛋白,是Xcc 8004对多数十字花科植物致病所必须的。

Xanthomonas campestris pv. campestris （Xcc） is the causal agent of black rot disease in cruciferous plants. Few effectors of Xcc have been characterized genetically and biochemically. In this study, a putative effector coding gene Xc_2994 in Xcc 8004 was characterized. In order to explore the virulence function of XopXccP, a XopXccP deletion mutant was generated by gene knockout. The pathogenicity of △XopXccP was tested on cabbage, cauliflower and Arabidopsis （Col-0）. The results indicated that pathogenicity of △XopXccP was significantly declined. To test the function of XopXccP in vivo, an inducible promoter driven XopXccP was transferred into Arabidopsis. Pathogenicity test indicated that transgenic Arabidopsis appeared lesion mimic cell death after the induced expression of XopXccP. These results suggest that the effector XopXccP is a virulent factor on host plants and is required for pathgenicity on cruciferous plants.