Integrated control of Caulobacter cell physiology by visible light and stress

描述（由申请人提供）：细胞的环境对其生理学、发育和进化具有深远的影响。新月柄杆菌是研究细胞周期调控和发育的细菌模型，为研究环境感知和适应的分子基础提供了一个很好的实验系统。该提案的目标是定义光和应力信号如何被细菌整合以调节细胞包膜和细胞粘附的分子和细胞机制。LOV-组氨酸激酶（LOV-HKs）是一类新发现的蓝光光传感器，在许多原核生物中具有保守性。尽管LOV-HK的调节作用还不清楚，但最近已显示这些信号蛋白控制流产布鲁氏菌的毒力和柄杆菌属响应光的细胞粘附.在这些发现之前，柄杆菌和布鲁氏菌都不知道或假定对可见光有反应。事实上，大多数编码LOV-HK的物种都是化能营养生物，没有预测的光生物学。我们已经发现了柄杆菌中的调节网络，其中LOV-HK、LovK和受体蛋白LovR与CT形成调节反馈回路，CT是一种包膜应力σ因子，对渗透和氧化应激下的细胞存活至关重要。本提案中详述的实验将检验LovK/LovR系统是新型信号传导网络的一部分的假设，其中经典的双组分信号传导和C依赖性转录控制交叉以响应环境中的多种物理和化学线索来调节细胞包膜的组成。我们将使用多种方法的组合来定义化学和光环境之间的相互作用如何影响细胞的应激适应，细胞被膜组成和细胞粘附。具体来说，我们将回答以下问题：（一）如何LovK/LovR双组分系统调节细胞包膜的组成和细胞粘附响应光，（二）什么是调节LovK/LovR光敏网络和CT应力响应网络之间的相互作用，（iii）什么是CT，CU和PhyR，三西格玛因子，似乎是由CT调节的转录靶点？如果时间允许，我们使用遗传和生化筛选来确定LovK/LovR粘附途径中的其他调节剂。我们的实验将推进我们对LOV-HKs光调节的理解，LOV-HKs是影响细菌发病机制的原核生物学的一个重要新领域。更一般地说，这些研究将提供有关细菌在波动环境中感知和整合多种环境刺激的机制的重要数据，这对细菌细胞存活至关重要。

DESCRIPTION (provided by applicant): The environment of a cell has a profound influence on its physiology, development, and evolution. Caulobacter crescentus, a bacterial model for the study of cell cycle control and development, provides an excellent experimental system to investigate the molecular basis of environmental perception and adaptation. The goal of this proposal is to define the molecular and cellular mechanisms of how light and stress signals are integrated by a bacterium to regulate the cell envelope and cell adhesion. LOV-histidine kinases (LOV-HKs), a newly-discovered class of blue-light photosensors, are conserved across a range of prokaryotes. Although the regulatory roles of LOV- HKs are not well understood, these signaling proteins have recently been shown to control virulence in Brucella abortus and cell adhesion in Caulobacter in response to light. Prior to these discoveries, neither Caulobacter nor Brucella were known or presumed to respond to visible light. Indeed, the majority of species encoding LOV-HKs are chemotrophs with no predicted photobiology. We have uncovered a regulatory network in Caulobacter in which the LOV-HK, LovK, and the receiver protein, LovR, form a form a regulatory feedback loop with CT, an envelope stress sigma factor that is critical for cell survival under osmotic and oxidative stress. The experiments detailed in this proposal will test the hypothesis that LovK/LovR system is part of a novel signaling network in which classical two- component signaling and C-dependent control of transcription intersect to regulate the composition of the cell envelope in response to multiple physical and chemical cues in the environment. We will use a combination of methods to define how interaction between the chemical and light environments affect cellular stress adaptation, cell envelope composition, and cell adhesion. Specifically, we will answer the following questions: (i) How does the LovK/LovR two-component system regulate cell envelope composition and cell adhesion in response to light, (ii) What are the regulatory interactions between the LovK/LovR photosensory network and the CT stress-response network, and (iii) What are the transcriptional targets of CT, CU, and PhyR, three sigma factors that appear to be regulated by CT? Time permitting, we use genetic and biochemical screens to identify additional regulators in the LovK/LovR adhesion pathway. Our experiments will advance our understanding of photoregulation by LOV-HKs, an important new area of prokaryotic biology that impacts bacterial pathogenesis. More generally, these studies will provide important data on mechanisms bacteria use to sense and integrate multiple environmental stimuli in a fluctuating environment, which is critical for bacterial cell survival.