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水稻条斑病菌(Xanthomonas oryzaepv.oryzicola,Xoc)的hrp基因决定了病原菌在非寄主植物上的过敏反应(hypersensitive response,HR)和在寄主植物上的致病性(pathogenicity),基因产物形成Ⅲ型分泌系统(type-Ⅲ secretion system,T3SS)将致病性效应分子注入寄主细胞从而引起水稻产生抗病性或者感病性反应。以位于hrpB操纵单元的首个hr-pB1基因为对象,通过基因敲除方式对其进行了突变,发现hrpB1突变体丧失了在水稻上的致病性和在烟草上激发HR的能力,并且在水稻组织中的生长能力显著降低。RT-PCR测定结果表明,hrpB1的转录表达受HrpG和HrpX的正调控。免疫杂交结果显示,HrpB1蛋白可通过T3SS进行分泌。这些结果不仅明确了hrpB1基因在病原菌致病性中的功能,而且提示了hrp结构基因不仅仅局限于形成Ⅲ型分泌系统,部分hrp基因产物本身也通过Ⅲ型系统分泌到胞外,并且可能起到效应分子的功能。
The hrp gene of Xanthomonas oryzaev.oryzicola (Xoc) determines the hypersensitive response (HR) of pathogens to non-host plants and the pathogenicity of host plants. The gene products form type III The secretion of type-III secretion system (T3SS) injects pathogenic effector molecules into host cells to cause resistance or susceptibility to rice. The first hr-pB1 gene located in the hrpB manipulation unit was mutated by gene knockout and found that the hrpB1 mutant lost its pathogenicity on rice and its ability to stimulate HR on tobacco Growth capacity in rice tissues was significantly reduced. RT-PCR results showed that the transcriptional expression of hrpB1 was positively regulated by HrpG and HrpX. Immunoblotting results showed that HrpB1 protein can be secreted by T3SS. These results not only clarified the function of hrpB1 gene in the pathogenicity of pathogens, but also suggested that the hrp structural gene is not limited to the formation of the type III secretion system. Some hrp gene products themselves are also secreted by the type III system to the outside of the cell and may play To the effect of molecular function.