The Caulobacter NtrB-NtrC two-component system bridges nitrogen assimilation and cell development.
The Caulobacter NtrB-NtrC two-component system bridges nitrogen assimilation and cell development.
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Caulobacter NtrB-NtrC 双组分系统连接氮同化和细胞发育。
DOI：
10.1101/2023.06.06.543975
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Crosson,Sean
中科院分区：
文献类型：
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作者：
North,Hunter;McLaughlin,Maeve;Fiebig,Aretha;Crosson,Sean
一套分子感觉系统使柄杆菌能够控制生长、发育和繁殖，以响应必需元素的水平。细菌增强子结合蛋白（bEBP）NtrC及其同源传感器组氨酸激酶（NtrB）是许多细菌中氮同化的关键调节因子，但它们在柄杆菌代谢和发育中的作用尚不清楚。值得注意的是，柄杆菌NtrC是一种非常规的bEBP，其缺乏通常称为GAFTGA基序的σ54相互作用环。在这里，我们表明，删除新月柄杆菌ntrC减缓细胞生长在复杂的培养基和ntrBandntrCare必不可少的氨是唯一的氮源时，由于他们的要求谷氨酰胺合成酶的表达。一个保守的IS 3家族移动的遗传元件的随机转座经常通过恢复glnBA操纵子的转录来挽救ntrC突变株的生长缺陷，揭示了IS 3转座在营养限制期间塑造柄杆菌种群进化中的可能作用。我们进一步确定了几十个直接的NtrC结合位点的C。crescentuschromosome，与大部分位于附近的基因参与多糖的生物合成。大多数结合位点与必需的核苷相关蛋白GapR或细胞周期调节因子MucR 1的结合位点一致。因此，预测NtrC直接影响细胞周期和细胞发育的调节。事实上，NtrC功能的丧失导致延长的极柄和细胞被膜多糖的合成增加。这项研究建立了NtrC，氮代谢，极性形态发生，和包膜多糖合成inCaulobacter.IMPORTANCEBacteria平衡细胞过程与其环境中的营养物质的可用性之间的监管连接。NtrB-NtrC双组分信号系统负责控制许多细菌中的氮同化。我们已经描述了ntrC缺失对柄杆菌生长和发育的影响，并揭示了自发IS元件转座在拯救ntrC突变引起的转录和营养缺陷中的作用。我们进一步定义了调节子ofCaulobacterNtrC，细菌增强子结合蛋白，并证明它与参与细胞周期调控和染色体组织的必需蛋白质共享特异性结合位点。我们的工作提供了一个全面的看法，转录调控介导的一个独特的NtrC蛋白，建立其连接到氮同化和发育过程inCaulobacter。
A suite of molecular sensory systems enablesCaulobacterto control growth, development, and reproduction in response to levels of essential elements. The bacterial enhancer-binding protein (bEBP) NtrC and its cognate sensor histidine kinase, NtrB, are key regulators of nitrogen assimilation in many bacteria, but their roles inCaulobactermetabolism and development are not well defined. Notably,CaulobacterNtrC is an unconventional bEBP that lacks the σ54-interacting loop commonly known as the GAFTGA motif. Here we show that deletion ofCaulobacter crescentus ntrCslows cell growth in complex medium and thatntrBandntrCare essential when ammonium is the sole nitrogen source due to their requirement for glutamine synthetase expression. Random transposition of a conserved IS3-family mobile genetic element frequently rescued the growth defect ofntrCmutant strains by restoring transcription of theglnBAoperon, revealing a possible role for IS3 transposition in shaping the evolution ofCaulobacterpopulations during nutrient limitation. We further identified dozens of direct NtrC-binding sites on theC. crescentuschromosome, with a large fraction located near genes involved in polysaccharide biosynthesis. The majority of binding sites align with those of the essential nucleoid-associated protein, GapR, or the cell cycle regulator, MucR1. NtrC is therefore predicted to directly impact the regulation of cell cycle and cell development. Indeed, loss of NtrC function led to elongated polar stalks and elevated synthesis of cell envelope polysaccharides. This study establishes regulatory connections between NtrC, nitrogen metabolism, polar morphogenesis, and envelope polysaccharide synthesis inCaulobacter.IMPORTANCEBacteria balance cellular processes with the availability of nutrients in their environment. The NtrB-NtrC two-component signaling system is responsible for controlling nitrogen assimilation in many bacteria. We have characterized the effect ofntrBandntrCdeletion onCaulobactergrowth and development and uncovered a role for spontaneous IS element transposition in the rescue of transcriptional and nutritional deficiencies caused byntrCmutation. We further defined the regulon ofCaulobacterNtrC, a bacterial enhancer-binding protein, and demonstrate that it shares specific binding sites with essential proteins involved in cell cycle regulation and chromosome organization. Our work provides a comprehensive view of transcriptional regulation mediated by a distinctive NtrC protein, establishing its connection to nitrogen assimilation and developmental processes inCaulobacter.