katExoo基因缺失突变对水稻白叶枯病菌H2O2抗性和致病性的影响

Effects of gene deletion of katExoo encoding putative catalase on resistance to hydrogen peroxide and pathogenicity of Xanthomonas oryzae pv. oryzae

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。

To reveal the role of katExoo encoding putative catalase （CAT） in H202 resistance and pathogenicity of Xanthomonas oryzae pv. oryzae, the gene deletion and assays for H2 O2 resistance, CAT activity, in vitro growth, and virulence on rice of the AkatExoo mutant were performed in this study. The mutant was generated from Xoo wild-type strain PXO99A through marker exchange, in which the conserved domain of CAT （ GATasel _catalase and catalase clade_2） was replaced by GmR. Significant changes in increased H2O2 resistance and high- er CAT activity were found in the mutant compared to PXO99A. Moreover, remarkable decreases in bacterial growth rate in vitro and in planta of AkatExoo and diseased leaf lesion of rice were observed. Therefore, katE- xoo has been shown to play a critical role in bacterial growth, colonization and pathogenicity on rice. This work partially provides first genetic evidence to support the hypothesis that KatExoo might function as a viru- lence factor in Xoo.