A novel plant pathogenesis regulatory system in Erwinia: functional analysis of a new post-transcriptional input to bacterial quorum sensing control.

这项拟议的研究涉及植物细菌病原体中的一种新基因的研究。马铃薯腐烂病的病原菌欧文氏杆菌(Erwinia)在马铃薯生产中占有重要地位。这种细菌通过产生一系列酶来攻击植物，这些酶可以降解植物的细胞壁，导致商业上重要的腐烂疾病症状。细菌产生这些植物细胞壁降解酶的能力受到细菌细胞密度的影响；只有当细菌密度较高时，这些酶才会大量产生。细菌产生一种名为OHHL的可扩散的小化学信号，这种分子的浓度直接反映了细菌的密度。在这个过程中(群体感应)，细菌使用化学信号相互交流，从而将细胞密度与侵略性腐烂植物的能力联系起来。如果制定群体感应过程的能力被阻止，那么细菌就不再能够致病。因此，深入了解这种马铃薯病原菌的群体感应作用模式，对于我们从根本上了解细菌病原体如何相互沟通，以及如果我们能够理解这一过程，我们可能如何干预疾病具有重要意义。目前还没有针对欧文氏杆菌引起的马铃薯疾病的化学控制系统，因此，从根本上了解它是如何导致感染的，是最终合理治疗的唯一途径。在这项提案中，我们将研究一个新基因(ECA2020)的作用，我们最近发现该基因参与了群体感应过程。该基因的产物影响参与群体感应的关键蛋白之一(VirR)的表达/功能。我们将通过调查ECA2020与其他蛋白质的相互作用来研究ECA2020的运作方式，并检验这样的假设，即它可能具有一些类似于参与信使RNA加工的高等生物蛋白质的功能。我们将寻找能够绕过它们对ECA2020系统的依赖的细菌突变体，并研究对完全活性的VirR蛋白生产的确切影响。我们还将测试连续基因(ECA2019)可能参与相关过程的可能性，并调查ECA2020基因本身是如何调控的。总体目标是试图找出这种新基因如何在植物感染和疾病发生过程中调节群体感应系统的功能，因为这可能是控制欧文氏菌引起的马铃薯腐烂病的长期目标。

This proposed research involves the study of a new gene in a bacterial pathogen of plants. The bacterial pathogen (Erwinia) causes rotting diseases of potato and other plants and is important in potato crop production. The bacteria attack the plant by producing a spectrum of enzymes that can degrade the cell walls of the plant leading to the commercially-significant rotting disease symptoms. The ability of the bacteria to make these plant cell wall degrading enzymes is affected by the cell population density of the bacteria; the enzymes are only made in abundance when the bacterial density if high. The bacteria make a small diffusible chemical signal called OHHL and the concentration of this molecule is a direct reflection of bacterial density. In this process (quorum sensing) the bacteria use the chemical signal to communicate with each other and thereby link cell density to the ability to aggressively rot the plant. If the ability to enact the process of quorum sensing is blocked then the bacteria are no longer capable of causing disease. Consequently, a deeper understanding of the mode of action of quorum sensing in this potato pathogen is important for our fundamental appreciation of how bacterial pathogens communicate with each other and, if we can understand the process, how we might intervene in the disease. There are no chemical control systems available for potato diseases caused by Erwinia and so fundamental understanding of how it causes infection is the only route to an eventual rational therapy. In this proposal we will investigate the role of a new gene (ECA2020) that we have shown recently to be involved in the process of quorum sensing. The product of this gene affects the expression/functionality of one of the key proteins (VirR) involved in quorum sensing. We will study the way ECA2020 operates by investigating which other proteins it interacts with and we will test the hypothesis that it may have some functions similar to proteins from higher organisms that are involved in messenger RNA processing. We will look for bacterial mutants that can bypass their dependence on the ECA2020 system and we will study the precise impact on production of the fully active VirR protein. We will also test the possibility that the contiguous gene (ECA2019) might be involved in a related process and we will investigate how the ECA2020 gene is itself regulated. The overall aim is to try to work out how this new gene modulates the function of the quorum sensing system during plant infection and disease initiation because this might be a target in the longer term for control of potato rotting diseases caused by Erwinia.