转录调控因子OxyRxoo对水稻白叶枯病菌H2O2降解途径的调控作用

Roles of OxyRxoo,a transcriptional regulator of Xanthomonas oryzae pv.oryzae in regulation of detoxification of hydrogen peroxide

【目的】为了阐明水稻白叶枯病菌(Xanthomonas oryzaepv.oryzae,简称Xoo)转录调控因子OxyRxoo对过氧化氢(H2O2)降解途径的调控作用。【方法】本研究对推导的H2O2识别调控基因oxyRxoo进行了基因克隆、序列分析、缺失突变和互补试验及其相关表型的鉴定。【结果】克隆的oxyRxoo基因序列与其它几种病原黄单胞菌的同源序列高度保守。OxyRxoo是LysR家族成员之一,具有PBPb结构域和DNA结合保守结构域(HTH)。用标记交换法构建了△oxyRxoo基因缺失突变体。与野生型菌株PXO99A相比,尽管△oxyRxoo在离体培养条件下的生长无明显变化,但H2O2抗性显著地降低,过氧化物酶(CAT)活性明显下降,基因互补可以使之恢复;过氧化物酶基因表达下调,oxyRxoo自身表达显著上调。【结论】OxyRxoo作为一个重要转录调控因子,调控了Xoo的H2O2降解途径。

[ Objective] OxyRxoo is a homologue of OxyR from Xanthomonas oryzae pv. oryzae （Xoo） ,the pathogen of bacterial blight of rice. To elucidate the role of OxyRxoo in detoxification of hydrogen peroxide. [Methods] OxyRxoo was studied by gene cloning, sequencing, deletion, complement and phenotype analysis. [ Result] Compared to those of the wild-type strain PX099A, there was no difference in bacterial growth in vitro of A oxyRxoo, but A oxyRxoo is more sensitive to H2O2 with reduced catalase activity. In the presence of H2O2, the expression of catalase genes （ ahpCxoo, catBxoo, katExoo and srpAxoo ） was significantly down-regulated, while the expression of oxyRxoo was up-regulated in A oxyRxoo. [ Conclusion] OxyRxoo functions as a transcription regulator in mediating and controlling H2O2 detoxification in Xoo.