The quorum sensing regulator CinR hierarchically regulates two other quorum sensing pathways in ligand-dependent and -independent fashions in Rhizobium etli.
The quorum sensing regulator CinR hierarchically regulates two other quorum sensing pathways in ligand-dependent and -independent fashions in Rhizobium etli.
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群体感应调节器 CinR 在根瘤菌 etli 中以配体依赖和独立的方式分层调节另外两个群体感应途径
DOI：
10.1128/jb.00003-15
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发表时间：
2015
影响因子：
3.2
通讯作者：
Zhu Jun
中科院分区：
文献类型：
--
作者：
Zheng Huiming;Mao Yiling;Zhu Qingcheng;Ling Jun;Zhang Na;Naseer Nawar;Zhong Zengtao;Zhu Jun
摘要 许多根瘤菌物种使用复杂的基于 N-酰基高丝氨酸内酯 (AHL) 的群体感应 (QS) 系统来监测其种群密度并调节其与植物宿主的共生相互作用。根瘤菌 CFN42 中至少存在三种 LuxRI 型调控系统：CinRI、RaiRI 和 TraRI。在这项研究中，我们表明 CinI、RaiI 和 TraI 负责在测试条件下合成所有 AHL。这些 AHL 合酶基因的激活需要其相应的 LuxR 型对应物。我们进一步证明 CinRI 位于激活 RaiRI 和 TraRI QS 系统的监管级联的顶部。此外，我们发现CinR在其同源AHL配体不存在的情况下具有结合cinI启动子的特异性亲和力，从而激活cinI转录。添加 AHL 可改善与 cinI 启动子的结合并增强 cinI 表达。此外，我们发现与野生型相比，cinR突变体的根瘤形成减少，并且cinR、raiR和traI突变体的固氮活性水平显着低于野生型。这些结果表明，R. etli 中复杂的 QS 调节系统在其与豆科植物宿主的共生中发挥着重要作用。重要性 许多细菌利用群体感应 (QS) 来监测其细胞密度并协调调节许多生理功能。根瘤菌通常具有多样且复杂的 LuxR/LuxI 型群体感应系统，可能参与共生和 N2 固定。在这项研究中，我们在根瘤菌 CFN42 中鉴定了三个 LuxR/LuxI 型 QS 系统：CinRI、RaiRI 和 TraRI。我们在这些 QS 组件之间建立了一个复杂的调节网络，发现这些 QS 系统在共生过程中发挥着重要作用。
ABSTRACT Many rhizobial species use complex N-acyl-homoserine lactone (AHL)-based quorum sensing (QS) systems to monitor their population density and regulate their symbiotic interactions with their plant hosts. There are at least three LuxRI-type regulatory systems in Rhizobium etli CFN42: CinRI, RaiRI, and TraRI. In this study, we show that CinI, RaiI, and TraI are responsible for synthesizing all AHLs under the tested conditions. The activation of these AHL synthase genes requires their corresponding LuxR-type counterparts. We further demonstrate that CinRI is at the top of the regulatory cascade that activates RaiRI and TraRI QS systems. Moreover, we discovered that CinR possesses a specific affinity to bind cinI promoter in the absence of its cognate AHL ligand, thereby activating cinI transcription. Addition of AHLs leads to improved binding to the cinI promoter and enhanced cinI expression. Furthermore, we found that compared to the wild type, the cinR mutation displayed reduced nodule formation, and cinR, raiR, and traI mutants show significantly lower levels of nitrogen fixation activity than the wild type. These results suggest that the complex QS regulatory systems in R. etli play an important role in its symbiosis with legume hosts. IMPORTANCE Many bacteria use quorum sensing (QS) to monitor their cell densities and coordinately regulate a number of physiological functions. Rhizobia often have diverse and complex LuxR/LuxI-type quorum sensing systems that may be involved in symbiosis and N2 fixation. In this study, we identified three LuxR/LuxI-type QS systems in Rhizobium etli CFN42: CinRI, RaiRI, and TraRI. We established a complex network of regulation between these QS components and found that these QS systems played important roles in symbiosis processes.