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首页> 外文期刊>Applied Microbiology >The Sinorhizobium melilotintrX Gene Is Involved in Succinoglycan Production, Motility, and Symbiotic Nodulation on Alfalfa
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The Sinorhizobium melilotintrX Gene Is Involved in Succinoglycan Production, Motility, and Symbiotic Nodulation on Alfalfa

机译：Sinorhizobium melilotintrX基因参与苜蓿的琥珀酸聚糖生产，运动性和共生结瘤。

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Rhizobia establish a symbiotic relationship with their host legumes to induce the formation of nitrogen-fixing nodules. This process is regulated by many rhizobium regulators, including some two-component regulatory systems (TCSs). NtrY/NtrX, a TCS that was first identified in Azorhizobium caulinodans , is required for free-living nitrogen metabolism and symbiotic nodulation on Sesbania rostrata . However, its functions in a typical rhizobium such as Sinorhizobium meliloti remain unclear. Here we found that the S. meliloti response regulator NtrX but not the histidine kinase NtrY is involved in the regulation of exopolysaccharide production, motility, and symbiosis with alfalfa. A plasmid insertion mutant of ntrX formed mucous colonies, which overproduced succinoglycan, an exopolysaccharide, by upregulating its biosynthesis genes. This mutant also exhibited motility defects due to reduced flagella and decreased expression of flagellins and regulatory genes. The regulation is independent of the known regulatory systems of ExoR/ExoS/ChvI, EmmABC, and ExpR. Alfalfa plants inoculated with the ntrX mutant were small and displayed symptoms of nitrogen starvation. Interestingly, the deletion mutant of ntrY showed a phenotype similar to that of the parent strain. These findings demonstrate that the S. meliloti NtrX is a new regulator of succinoglycan production and motility that is not genetically coupled with NtrY.
机译：根瘤菌与其宿主豆类建立共生关系，以诱导固氮根瘤的形成。此过程由许多根瘤菌调节剂调节，包括一些两组分调节系统（TCS）。 NtrY / NtrX是一种首先在菜足类固氮菌中鉴定出的TCS，它是Sesbania rostrata上自由生活的氮代谢和共生结瘤所必需的。然而，其在典型的根瘤菌如苜蓿中华根瘤菌中的功能仍不清楚。在这里，我们发现苜蓿链球菌响应调节剂NtrX而不参与组氨酸激酶NtrY参与苜蓿的胞外多糖产生，运动和共生的调节。 ntrX的质粒插入突变体形成粘液菌落，通过上调其生物合成基因而过量产生琥珀聚糖（一种外多糖）。该突变体还由于鞭毛减少以及鞭毛蛋白和调节基因的表达降低而表现出运动缺陷。该法规独立于ExoR / ExoS / ChvI，EmmABC和ExpR的已知法规体系。接种了ntrX突变体的苜蓿植株很小，并表现出氮饥饿的症状。有趣的是，ntrY的缺失突变体表现出与亲本菌株相似的表型。这些发现表明，苜蓿链球菌NtrX是琥珀糖生产和运动的新调节剂，其与NtrY没有遗传耦合。

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