Most Sinorhizobium meliloti Extracytoplasmic Function Sigma Factors Control Accessory Functions.
Most Sinorhizobium meliloti Extracytoplasmic Function Sigma Factors Control Accessory Functions.
复制标题
DOI：
10.1128/mspheredirect.00454-18
复制
发表时间：
2018-10-10
期刊：
影响因子：
4.8
通讯作者：
Long SR
中科院分区：
文献类型：
--
作者：
Lang C;Barnett MJ;Fisher RF;Smith LS;Diodati ME;Long SR
固定（还原）土壤氮在土壤肥力和成功的食物生长中起着关键作用。许多土壤肥力依赖于共生固氮：细菌伴侣感染宿主植物根部，减少大气中的二氮，以换取宿主代谢燃料，这一过程涉及伴侣之间复杂的相互作用，由每个伴侣中基因表达的变化介导。在这里，我们测试了一个家族的11个细胞质外功能（ECF）基因调控蛋白（σ因子[σs]）与RNA聚合酶相互作用，以确定他们是否发挥了重要作用，在建立一个固氮共生或在响应各种压力，包括细胞包膜压力的作用。我们发现，共生固氮发生，即使当所有11个这些调控基因被删除，大多数ECF σ因子控制辅助功能，并没有ECF σ因子是必需的，以生存信封压力。细菌必须感知环境的变化，并对功能和/或结构的变化做出反应，以科普。细胞质外功能σ因子（ECF σs）响应细胞和环境信号调节转录。苜蓿中华根瘤菌（Sinorhizobium meliloti）是一种共生固氮α-变形杆菌，携带11个ECF样σs（RpoE 1 ~-E10和FecI）基因。我们假设其中一些在介导细菌与其植物共生伙伴之间的相互作用中发挥作用。当细菌与植物根建立接触时，细菌感觉到其直接环境的变化，当根瘤形成时开始侵入植物，穿过几个根细胞层，并通过内吞作用进入植物皮层细胞。我们使用遗传学、转录组学和功能性来表征整个S。苜蓿草群的ECF σs。我们发现了单个σs的新靶点，通过过表达单个ECF σs确认了其他靶点，并鉴定或确认了其中9个的推定启动子基序。我们构建了每个ECF σ基因及其已证实或推定的抗σ基因的精确缺失株以及11个ECF σ和抗σ基因全部缺失的菌株。该全ECF σ缺失菌株在自由生长、Biolog表型微阵列测定或对多种应激的响应中未显示出重大缺陷。没有ECF σs是在寄主植物紫花苜蓿和蒺藜苜蓿上共生所必需的：所有ECF σ和抗σ基因缺失的菌株是共生正常的。重要性固定（还原）土壤氮在土壤肥力和成功的食物生长中起着关键作用。土壤肥力很大程度上依赖于共生固氮：细菌伴侣感染宿主植物根部并减少大气中的双氮以换取宿主代谢燃料，这一过程涉及伴侣之间复杂的相互作用，由每个伴侣中基因表达的变化介导。在这里，我们测试了一个家族的11个细胞质外功能（ECF）基因调控蛋白（σ因子[σs]）与RNA聚合酶相互作用，以确定他们是否发挥了重要作用，在建立一个固氮共生或在响应各种压力，包括细胞包膜压力的作用。我们发现，共生固氮发生，即使当所有11个这些调控基因被删除，大多数ECF σ因子控制辅助功能，并没有ECF σ因子是必需的，以生存信封压力。
Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress. Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner. The bacterium senses changes in its immediate environment as it establishes contact with the plant root, initiates invasion of the plant as the root nodule is formed, traverses several root cell layers, and enters plant cortical cells via endocytosis. We used genetics, transcriptomics, and functionality to characterize the entire S. meliloti cohort of ECF σs. We discovered new targets for individual σs, confirmed others by overexpressing individual ECF σs, and identified or confirmed putative promoter motifs for nine of them. We constructed precise deletions of each ECF σ gene and its demonstrated or putative anti-σ gene and also a strain in which all 11 ECF σ and anti-σ genes were deleted. This all-ECF σ deletion strain showed no major defects in free-living growth, in Biolog Phenotype MicroArray assays, or in response to multiple stresses. None of the ECF σs were required for symbiosis on the host plants Medicago sativa and Medicago truncatula: the strain deleted for all ECF σ and anti-σ genes was symbiotically normal. IMPORTANCE Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress.