A Mutation In A Putative σ Factor Gene Of Xanthomonas Campestris Pv. Campestris And Its Phenotypic Analysis

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.