摘要
野油菜黄单胞菌野油菜致病变种(Xanthomonas campestris pv.Campestris,Xcc)是使十字花科植物产生黑腐病的重要病原细菌。Xcc通过Ⅲ型分泌系统分泌效应蛋白到植物体内帮助Xcc的侵染和繁殖。Hpa A蛋白是一个广泛存在于黄单胞菌中的效应蛋白,在辣椒斑点病菌(Xanthomonas campestris pv.vesicatoria,Xcv)中,Hpa AXcv85-10已经被证明是一个Ⅲ型效应蛋白,并且参与其他效应蛋白的分泌过程,但是在Xcc中,对Hpa A的功能还不是了解得很清楚。本研究以Xcc8004菌株的Hpa A蛋白为研究对象,通过分泌蛋白检测和亚细胞定位分别研究Hpa AXcc8004是否也由Ⅲ型分泌系统分泌以及Hpa AXcc8004在植物细胞的作用部位。结果表明,Hpa AXcc8004的分泌依赖于Xcc8004的Ⅲ型结构基因hrc V,暗示着Hpa AXcc8004也是作为Ⅲ型分泌效应蛋白来发挥功能。在拟南芥原生质体细胞中,将Hpa AXcc8004与GFP蛋白融合表达,发现Hpa AXcc8004定位于植物细胞核中。进一步通过同源重组的方法获得了Xcc8004 Hpa A基因缺失突变体,在寄主甘蓝、萝卜、拟南芥上分别接种野生型Xcc8004和Hpa A基因缺失突变体,发现基因缺失突变体毒性显著降低,表明Hpa AXcc8004在上述寄主植物上对于Xcc8004的完整毒性是必须的。在Hpa A的拟南芥转基因植株上,Hpa AXcc8004还可以减弱假单胞菌DC3000和Xcc8004发黄的表型。
Xanthomonas campestris pv. campestris （Xcc）, a Gram-negative plant pathogenic bacterium, can cause black rot diseases on crucifer plants, including cabbage, radish and Arabidopsis. Xcc secrets effector proteins into plants via the type Ⅲ secretion system to help its infection and reproduction. HpaA protein widely exists in Xan- thomonas, and it has been reported that HpaAxcv85-10 is a type Ⅲ effector and participates in other effector secretion in X. campestris pv. vesicatoria （Xcv）. Xcc contains the HpaA protein homologue. However, it is not clear whether the HpaAXcc protein can be secreted in type Ⅲ secretion system, and the mechanism of hpaAXcc remains un- clear. In this study, secretion assay indicated the HpaAxcc8004 protein secretion was type Ⅲ secretion system de- pendent. Subcellular localization assay indicated that HpaAxcc8004 was located in the plant cell nucleus, which was consistent with HpaAxcv85-10 protein location in plants. In addition, the deletion mutant of HpaA gene was achieved by means of homologous recombination, and the deletion mutant caused reduced symptoms in cabbage, radish and Arabidopsis thanliana, which indicated that HpaAxcc8004 was required for the Xcc8004 complete toxicity in the host plants. Furthermore, in the HpaA transgenic Arabidopsis, HpaAxcc8004 can perform its function to reduce the chloro- sis symptoms caused by Pseudomonas DC3000 and Xcc8004.
出处
《热带生物学报》
2015年第2期119-126,共8页
Journal of Tropical Biology
基金
海南大学青年基金资助项目(qnjj1204)
海南省自然科学基金资助项目(314043)
