katG基因在豌豆根瘤菌抗氧化中的功能  

Antioxidative function of katG gene in Rhizobium leguminosarum

作　　者：周艳琳[1] 何冬兰[1] 李晓华[1] 曾小波[1] 田梦洋[1] 程国军[1] 

机构地区：[1]中南民族大学生命科学学院,湖北武汉430074

出　　处：《微生物学报》2015年第7期843-850,共8页Acta Microbiologica Sinica

基　　金：湖北省自然科学基金项目(2014CFB914);中南民族大学中央高校基本科研业务费专项资金自科重点项目(CZZ12005;CZW14001)~~

摘　　要：【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] Catalase-peroxidase Kat G can protect bacteria from damage of reactive oxygen species. This study investigated the antioxidative function of catalase- peroxidase gene kat G in Rhizobium leguminosarum 3841. [Methods]kat G mutant strain of R. leguminosarum was constructed by homologous recombination. The wild type,kat G mutant and complementary strain were challenged by oxidative stress and symbiotic ability. [Results]Under free- living conditions,the kat G mutant exhibited no generation time extension. However,cells of the kat G strain were deficient in consumption of high concentrations of H2O2 and were vulnerable after aquick exposure to H2O2. The real-time qRT-PCR results showed that kat G was expressed independently of exogenous H2O2. In contrast,the kat G mutant strain displayed higher express level of ohr B gene and lower expression level of grx C than the wild type. With regard to symbiotic capacities with Pisum sativum,the kat G mutant was indistinguishable in root nodule nitrogenase activity and competition nodule ability from the wild type. However,kat G gene was expressed significantly lower in bacteroids than that in free-living strains. Besides,the colonization of the pea rhizosphere by the kat G mutant was impaired compared to that of the wild type. [Conclusion]The deletion of kat G had nosignificant effect in 3841 under the free-living and symbiosis condition but was essential in antioxidation and colonization of the pea rhizosphere. Although kat G could not be induced by H2O2,it still played acentral role in antioxidation and symbiotic nitrogen fixation by regulating the antioxidant genes such as ohr B and grx C.

关 键 词：豌豆根瘤菌 KATG基因 实时荧光定量RT-PCR 抗氧化功能 共生固氮 

分 类 号：S643.3[农业科学—蔬菜学] Q939.114[农业科学—园艺学]