Critical protective role of bacterial superoxide dismutase in Rhizobium-legume symbiosis
Critical protective role of bacterial superoxide dismutase in Rhizobium-legume symbiosis
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DOI：
10.1046/j.1365-2958.2000.02178.x
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发表时间：
2000-11-01
影响因子：
3.6
通讯作者：
Touati, D
中科院分区：
文献类型：
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作者：
Santos, R;Hérouart, D;Touati, D
在缺氮的土壤中，根瘤菌在豆科植物的根上形成根瘤，在根瘤内分化为固定大气氮的类细菌。由于氮酶对氧非常敏感，因此对活性氧的保护在根瘤菌-豆科植物共生中起着重要的作用。我们删除了Sinorhizobium meliloti唯一胞质超氧化物歧化酶（SOD）的sodA基因。由此产生的突变体，缺乏超氧化物歧化酶，生长几乎正常，在自由生活时对氧化应激只有适度敏感。相反，其在紫花苜蓿中的共生特性受到严重影响。固氮能力严重受损。更引人注目的是，大多数缺乏sod的细菌并没有进入固氮类细菌的分化阶段。缺乏sod的突变体结瘤不良，并表现出异常感染。释放到植物细胞后，大量细菌不能分化为类细菌，迅速衰老。因此，细菌SOD在共生过程中起着关键的保护作用。
In nitrogen-poor soils, rhizobia elicit nodule formation on legume roots, within which they differentiate into bacteroids that fix atmospheric nitrogen. Protection against reactive oxygen species (ROS) was anticipated to play an important role in Rhizobium-legume symbiosis because nitrogenase is extremely oxygen sensitive. We deleted the sodA gene encoding the sole cytoplasmic superoxide dismutase (SOD) of Sinorhizobium meliloti. The resulting mutant, deficient in superoxide dismutase, grew almost normally and was only moderately sensitive to oxidative stress when free living. In contrast, its symbiotic properties in alfalfa were drastically affected. Nitrogen-fixing ability was severely impaired. More strikingly, most SOD-deficient bacteria did not teach the differentiation stage of nitrogen-fixing bacteroids. The SOD-deficient mutant nodulated poorly and displayed abnormal infection. After release into plant cells, a targe number of bacteria failed to differentiate into bacteroids and rapidly underwent senescence. Thus, bacterial SOD plays a key protective role in the symbiotic process.