Characterisation of a conserved protein acting as key positive regulator in plant innate immunity

植物缺乏有颌骨脊椎动物的适应性免疫机制，因此它们依靠先天免疫反应进行防御。作为固着生物，它们容易受到不断变化的环境条件的影响，包括不断的病原体攻击。然而，潜在的病原体首先必须遇到结构性的屏障，如蜡层或坚硬的细胞壁。如果病原体能够克服这些障碍，它们就会受到植物细胞的识别。植物缺乏专门识别微生物的循环细胞，如巨噬细胞。相反，每个细胞都能够自主地识别病原体并对其做出反应。此外，系统信号可以被触发以响应微生物刺激，为即将到来的攻击准备幼稚的组织。总体而言，植物的天然免疫是非常有效的，而且大多数植物对大多数微生物都有抵抗力。这一成功的部分原因是所有细胞都编码了令人惊叹的识别特异性。植物最初通过位于细胞表面的模式识别受体(PRRs)感知病原体相关的分子模式(PAMP)来感知微生物。PAMP是保守的、不可或缺的分子，是一整类微生物的特征，因此很难突变或删除。它们也被称为微生物相关分子模式(MAMP)，因为它们并不局限于病原微生物。这种第一级识别被称为PAMP触发免疫(PTI)。为了感染寄主植物，成功的病原体已经进化出策略，要么逃避识别，要么抑制随后的信号步骤。在许多情况下，抑制PTI涉及病原体分泌毒力效应物。在植物和病原体之间的动态协同进化中，一些植物进化出了抗性蛋白(R蛋白)来直接或间接地识别这些效应物。这种所谓的效应器触发免疫(ETI)通常伴随着被称为超敏反应(HR)的局部细胞死亡。反过来，病原体进化出能够抑制ETI的效应器，因此宿主和病原体之间的军备竞赛仍在继续。在这个模型中，PTI是植物主动防御的第一个方面，因此可以被认为是植物-微生物相互作用的主要驱动力。我们需要正确地理解PTI，不仅是因为它的内在兴趣，而且因为许多效应器靶将是PTI的组成部分。尽管PTI很重要，但我们仍然对PAMP的感知和信号转导知之甚少。我们正在使用植物模式物种拟南芥来研究PTI。我们已经确定了一种在植物中保守的蛋白质，也存在于哺乳动物、昆虫和蠕虫中，是PAMP反应和细菌抗病的关键调节因子。我们的初步结果表明，该蛋白是几个PAMP感知系统所必需的。我们将讨论该蛋白是否直接调节PAMP的感知，或在PAMP与其受体结合后作用于下游信号水平。我们还将确定哪些其他PAMP感知系统依赖于该蛋白质。最后，将进行实验以探索该蛋白质的分子功能。

Plants lack the adaptive immunity mechanisms of jawed vertebrates, so rely on innate immune responses for their defence. As sessile organisms they are subject to changing environmental conditions including constant pathogen attack. However, would-be pathogens have first to encounter constitutively present barriers such as wax layers or rigid cell walls. If a pathogen can overcome these barriers, they are then subject to recognition by plant cells. Plants lack circulating cells specialized in microbe recognition, such as macrophages. Instead, each cell is able to recognise and respond to pathogens autonomously. In addition, systemic signalling can be triggered in response to microbial stimuli that prepare naïve tissue for imminent attack. Overall, plant innate immunity is very efficient and most plants are resistant to most microbes. Part of this success is due to an amazing spectrum of recognition specificities encodes by all cells. Plants initially sense microbes via perception of pathogen-associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs) located on the cell surface. PAMPs are conserved, indispensable molecules that are characteristic of a whole class of microbes, therefore are difficult to mutate or delete. They are also referred to as microbe-associated molecular patterns (MAMPs), as they are not limited to pathogenic microbes. This first level of recognition is referred to as PAMP-triggered immunity (PTI). To infect host plants successful pathogens have evolved strategies either to evade recognition, or to suppress the subsequent signalling steps. In many cases, suppression of PTI involves secretion of virulence effectors by the pathogens. In a dynamic co-evolution between plants and pathogens, some plants have evolved resistance proteins (R proteins) to recognise these effectors directly or indirectly. This so-called effector-triggered immunity (ETI) is often accompanied by local cell death known as the hypersensitive response (HR). In turn, pathogens have evolved effectors capable of suppressing ETI, and so the arms-race between host and pathogens continues. In this model, PTI is the first facet of active plant defence and can therefore be considered as the primary driving-force of plant-microbe interactions. We need to understand PTI properly not only because of its intrinsic interest, but because many of the effector targets will be PTI components. Despite the importance of PTI, we still know little about PAMP perception and signalling. We are using the plant model species Arabidopsis thaliana to study PTI. We have identified a protein conserved in plants, but also in mammals, insects and worms, as being a key regulator of PAMP responses and bacterial disease resistance. Our preliminary results indicate that this protein is required for several PAMP perception systems. We will address if this protein directly regulates PAMP perception or acts on the level of downstream signalling following binding of the PAMP to its receptor. We will also determine which other PAMP perception systems are dependent on this protein. Finally, experiments to explore the molecular function of this protein will be performed.