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为了揭示过氧化氢酶基因katExoo在水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)过氧化氢(H2O2)抗性和致病性中的功能,本研究构建了基因缺失突变体ΔkatExoo,测定了突变体的H2O2抗性、过氧化氢酶(CAT)活性、在离体培养条件下的生长速率以及对水稻的致病性。用标记基因置换法获得了ΔkatExoo突变体,其保守的CAT结构域(GATase1_catalase和catalase_clade_2)被GmR片段所替换。katExoo基因缺失突变并不导致病菌的H2O2抗性和CAT活性降低或丧失,反而在一定程度上使之增强和升高。ΔkatExoo离体生长量显著降低,水稻接种叶片病斑明显缩短、在叶组织内的种群量下降。表明基因缺失突变显著地影响了病菌的生长、定殖和致病性。本研究结果为“KatExoo可能是Xoo的一个毒性因子”的假设提供了遗传学证据。
In order to reveal the function of catalase gene catalase in the resistance and pathogenicity of hydrogen peroxide (H2O2) in Xanthomonas oryzae pv. Oryzae (Xoo), the gene deletion mutant ΔkatExoo was constructed in this study The H2O2 resistance, the activity of catalase (CAT), the growth rate of in vitro culture and the pathogenicity to rice were studied. The katExoo mutant was obtained by marker gene replacement and its conserved CAT domains (GATase1_catalase and catalase_clade_2) were replaced with GmR fragments. The deletion of katExoo gene does not result in the reduction or loss of H2O2 resistance and CAT activity of the bacteria, but to a certain extent, it is enhanced and increased. ΔkatExoo significantly decreased in vitro growth, significantly lessened the diseased plaque in inoculated leaves of rice, and decreased the population in leaf tissue. The results showed that gene deletion mutation significantly affected the growth, colonization and pathogenicity of pathogenic bacteria. The results of this study provide genetic evidence for the hypothesis that “KatExoo may be a virulence factor for Xoo.”