【作者】 王凛；

【导师】 唐纪良； 何勇强；

【作者基本信息】 广西大学 ， 生物化学与分子生物学， 2004， 硕士

【摘要】 σ因子是原核生物RNA聚合酶的一个亚基，是原核基因表达的主要调节因子。细菌利用不同的σ因子控制不同的基因的转录，其中包括与致病相关的基因。野油菜黄单胞菌野油菜致病变种8004菌株（Xcc 8004）基因组测序和注释工作已经完成。在该基因组中，根据注释结果，Xcc 8004中共有13个编码σ因子的ORF，其中XC1143编码的一个σ⁷⁰因子。为了研究该σ因子在Xcc中的作用，我们构建了该基因的Tn5gusA5的插入突变体和pK18mob定点整合突变体并进行了表型分析。该突变体在丰富培养基和基本培养基上的生长状况与野生型没有明显差别，胞外蛋白酶、纤维素酶、淀粉酶的活性也与野生型的一致。这些结果表明，该σ因子与Xcc的生长以及主要胞外酶的产生无关。在寄主植物满身红箩卜上检测了突变体的致病性，该基因的Tn5gusA5插入突变体O69H01致病力下降明显，241C03下降不明显。进一步的定点整合突变体致病性实验结果与野生型是一致的，这表明该基因与Xcc致病性是无关的。更多还原

【Abstract】 In bacteria, the a factor is a separate component of the RNA polymerase, which has a critical role in promoter recognition and gene transcription. The sequencing and annotation of the complete genome sequence of Xcc 8004 revealed that there are 13 ORF encode a factors in Xcc 8004 genome and the ORF XC1143 encode a putative σ70 factor. To study the function of this ORF, we constructed Tn5gusA5 insertional and integrational mutants in the corresponding gene of wild type strain 8004 and analyzed the phenotypes of the mutants. There is no difference between the mutants and wild type strain in growth rates when they grow in rich and minimum medium and in the activities of extracellular protease, amylase, and cellulose. We performed the pathogenecity test on the host plant Chinese radish and the lesion length on the leaf infected by two insertional mutants are significantly different. But in the experiment of integrational mutants, no differences were found in the virulence between the wild type and the mutants. The involvement of XC1143, the gene encoding a putative o factor, is irrelative in the pathogenicity of Xcc.更多还原