Analysis of the mechanism of cytoskeletal reorganisation in plants in response to pathogenic fungi

肌动蛋白细胞骨架是一个有组织的蛋白质丝网络，它控制许多细胞过程，包括细胞内细胞器和囊泡的运动。这些细丝由单个肌动蛋白链组成。重要的是，这个网络是动态的，因为肌动蛋白可以迅速从细胞质中的游离单体（称为g -肌动蛋白）转变为被纳入细丝（f -肌动蛋白），反之亦然。肌动蛋白丝的组装和拆卸受肌动蛋白结合蛋白（ABPs）的控制，而ABPs又受细胞信号通路的控制。细胞环境的变化或发育线索可以刺激信号网络，通过ABP行为的局部改变引起肌动蛋白丝的重组。每个ABP都有一个特定的功能，它们的活动通常在合作和/或竞争的相互作用中交织在一起。其中一些蛋白质形成肌动蛋白丝，另一些通过与g -肌动蛋白和/或f -肌动蛋白结合来调节单体或丝的动力学。肌动蛋白网络在任何时间和任何空间的状态取决于这些蛋白质的活性总和。植物病原体对经济上重要的植物造成破坏性疾病，目前英国约有6%的小麦收成因疾病而损失。肌动蛋白细胞骨架是植物防御病原体的关键元素。在病原体入侵的最初阶段，肌动蛋白网络被刺激重组，从而使含有壁形成物质的囊泡可以被运送到感染威胁的部位，以增厚和加强植物细胞壁。如果肌动蛋白细胞骨架被破坏，成功感染的机会就会大大增加。该项目旨在了解控制肌动蛋白及其相关蛋白对病原体攻击的反应的分子事件。它的工作原理目前尚不清楚，但我们确实有迹象表明ABPs很重要，它们的活性可以保护植物免受疾病的侵害。谷物中少数抗病基因之一是rpg4，它能编码一种小的g -肌动蛋白和f -肌动蛋白调节蛋白，称为肌动蛋白解聚因子（ADF）。ADF只是控制肌动蛋白网络的众多abp中的一种，我们有证据表明至少有一组其他abp参与其中；肌动蛋白成核的双胍蛋白。有趣的是，动物和真菌细胞中的双胍蛋白是通过植物中不存在的信号转导途径来控制的。植物已经适应了它们的形成蛋白来满足植物的特定需求，我们已经发现一种特殊的植物形成蛋白（AtFH4）与一种叫做呼吸爆发氧化酶的酶相互作用，这种酶在植物防御病原体的信号中起着既定的作用，这个项目也旨在了解这种相互作用的功能意义。在我们的实验中，我们使用模型系统，我们在这里使用的植物病原体攻击模型是拟南芥。一个重要的问题是，这个模型是否与英国最重要的作物物种的现实情况有关。在这里，我们将研究植物防御中肌动蛋白重组的类似机制是否发生在谷物对疾病的反应中，我们将以小麦为研究对象。

The actin cytoskeleton is an organised network of protein filaments that controls many cellular processes including the movement of organelles and vesicles within the cell. These filaments consist of chains of individual actin proteins. Importantly, this network is dynamic, as actin proteins can rapidly change from being free monomers in the cell cytoplasm (known as G-actin) to being incorporated into filaments (F-actin) and vice-versa. The assembly and disassembly of actin filaments is under the control of actin binding proteins (ABPs) which are in turn under the control of cell signalling pathways. A change in the environment of the cell or a developmental cue can stimulate signalling networks to cause the re-organisation of actin filaments through localised changes in ABP behaviour. Each ABP has a specific function and their activities are often intertwined in cooperative and/or competitive interactions. Some of these proteins nucleate actin filaments, others modulate monomer or filament dynamics through their binding to G-actin and/or F-actin. The state of the actin network at any given time and in any given space will depend upon the summation of the activities of each of these proteins. Plant pathogens cause damaging diseases of economically important plants, with approximately 6% of the UK wheat harvest currently being lost to disease. The actin cytoskeleton is a key element of plant defence against pathogens. At the earliest stages of pathogen invasion the actin network is stimulated to reorganise so that vesicles containing wall-forming materials can be transported to the site of the infection threat to thicken and reinforce the plant cell wall. If the actin cytoskeleton is broken down the chances of successful infection are greatly increased. This project is designed to understand the molecular events controlling this response of actin and its associated proteins to pathogen attack. How it works is currently unknown, but we do have an indication that ABPs are important and that their activity can protect plants from disease. One of the few disease resistance genes in cereals to a particularly virulent pathogen Puccinia graminis Ug99 is rpg4, and this encodes a small G-actin and F-actin modulating protein called Actin Depolymerising Factor (ADF). ADF is just one of a plethora of ABPs that control the actin network and we have evidence that at least one other group of ABPs is involved; the actin-nucleating formin proteins. Interestingly, formin proteins are controlled in animal and fungal cells by signal transduction pathways that do not exist in plants. Plants have adapted their formins to plant specific needs and we have found that a particular plant formin, (AtFH4), interacts with an enzyme called a respiratory burst oxidase that has an established role in signalling in the defence of plants against pathogens and this programme also aims to understand the functional significance of this interaction. For our experiments we use model systems and the model we use here for plant pathogen attack is Arabidopsis thaliana. An important question is whether this model relates to real-life situations in the UK's most important crop species. Here we will examine whether similar mechanisms of actin reorganisation in plant defence occur in cereals in response to disease, and we will use wheat for this purpose.