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【目的】细菌中过氧化物/过氧化氢酶Kat G参与活性氧(ROS)的解毒过程,从而防止其对细菌生长伤害,本文研究根瘤菌中kat G基因的抗氧化功能对豌豆根瘤菌3841生长及共生固氮的影响。【方法】通过基因敲除、遗传互补和对菌株的抗氧化和共生能力分析,系统地探究了根瘤菌中kat G基因的功能。【结果】kat G基因突变不影响菌株在自生培养条件下生长状况,但H2O2短时间处理导致突变株的存活率显著下降。实时荧光定量RT-PCR结果显示,H2O2不能诱导豌豆根瘤菌3841kat G基因的表达。进一步研究发现突变体中kat G基因缺失能显著提高抗氧化基因ohr B的表达,而降低grx C基因的表达。植物盆栽实验发现,kat G突变虽然对根瘤菌共生固氮能力和竞争结瘤能力均无影响,但kat G在类菌体中表达显著下调。同时,kat G突变显著影响了根瘤菌在植物根圈中的定殖能力。【结论】研究表明kat G虽对豌豆根瘤菌自生和共生固氮无明显影响,但在抗氧化和根圈定殖中起重要作用,外源H2O2对kat G的表达无诱导作用,但kat G调节ohr B和grx C等抗氧化基因的表达,从而在抗氧化和共生中发挥作用。
【Objective】 Kat G, a peroxide / catalase in bacteria, is involved in the detoxification of reactive oxygen species (ROS), thus preventing its damage to bacterial growth. In this paper, the antioxidant activity of kat G gene in Rhizobium was studied. Growth and Symbiotic Nitrogen Fixation. 【Method】 The function of kat G gene in rhizobium was systematically investigated by gene knockout, genetic complementation and anti-oxidative and symbiotic ability analysis. 【Result】 The mutation of kat G gene did not affect the growth of the strain under autogenous culture conditions. However, the short-term treatment of H2O2 resulted in a significant decrease in the survival rate of the mutant strain. Real-time fluorescent quantitative RT-PCR results showed that H2O2 could not induce the expression of 3841kat G gene of pea Rhizobium. Further study found that deletion of kat G gene in mutant could significantly increase the expression of ohr B, an antioxidant gene, and decrease the expression of grx C gene. Plant pot experiments found that although the kat G mutation had no effect on symbiotic nitrogen fixation ability and competitive nodulation ability, kat G was significantly down-regulated in the mycobacteria. At the same time, the kat G mutation significantly affected rhizobia colonization in plant rhizosphere. 【Conclusion】 The results showed that although kat G had no significant effect on autotrophic and symbiotic nitrogen fixation of pea Rhizobium, it played an important role in antioxidation and root colonization. Exogenous H2O2 had no effect on the expression of kat G, but kat G regulated ohr B and grx C and other antioxidant gene expression, which play a role in antioxidant and symbiotic.