根瘤菌为根际土壤细菌，与豆科植物共生形成固氮根瘤。过氧化物还原酶(Prxs)依靠自身的半胱氨酸进行氧化还原反应，能有效地清除活性氧，在根瘤菌-豆科宿主共生中发挥重要作用，但其作用机制未得到阐明。豌豆根瘤菌3841基因组含有3个过氧化物还原酶编码基因。本项目拟通过基因同源重组和转导技术，构建过氧化物还原酶单、双和三（全）基因突变株。进一步通过突变株和野生株感染豌豆宿主，比较它们在共生表型、prxs相关基因表达、Prxs的时空表达特征、关键作用底物及酶活性等方面的差异，系统研究豌豆根瘤菌过氧化物还原酶在共生固氮中的功能。在此基础上，通过荧光差异双向凝胶电泳（2-D DIGE）筛选过氧化物还原酶全基因突变株形成根瘤类菌体中的差异蛋白质，并利用实时定量RT-PCR、Western blotting以及基因突变技术对差异蛋白质的功能进行确证，研究过氧化物还原酶在根瘤氧化还原体系中的调控机制。

Rhizobia are rhizospheric soil bacteria, can interact symbiotically with legumes to form nitrogen-fixing nodules. Peroxiredoxins (Prxs) reduces peroxides with redox-active cysteine, play an important role in symbiotic nitrogen fixation. Rhizobium leguminosarum bv. viciae 3841 genome contains three peroxiredoxin-encoding genes. In this study, mutations in one, two or all three prx genes will be constructed by homologous recombination and transduction. In order to investigate the function of peroxiredoxins in symbiotic nitrogen fixation, a series of experiments such as symbiotic phenotype, prxs relative gene expression, temporal and spatial expression of Prxs, analysis of key substrates and enzymes will be conducted to test the differences of nodules infected by wild type and prx mutants. To further determine the regulatory mechanism of peroxiredoxins on nodule redox system, the technique of two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) for differential protein expression analysis will be evaluated using R. leguminosarum 3841 prx triple mutant infected pea nodule bacteroids. Real-time quantitative RT-PCR, Western blotting and gene mutation will be conducted to determine the interaction mechanism between the target proteins and Prxs.