Defining the signalling network linking pathogen infection and asparagine accumulation in wheat grain

这个项目源于一项发现，一种叫做天冬酰胺的氨基酸在小麦籽粒中积累，以应对疾病，而植物对一种叫做镰镰菌（Fusarium graminearum, Fg）的致病真菌的花感染的反应涉及一种叫做SnRK1的蛋白质。SnRK1是植物代谢的主要调节器，它控制编码一种叫做天冬酰胺合成酶的基因的活性，这种酶负责制造天冬酰胺。该项目将涉及来自洛桑研究所的一个多学科团队，并与来自都柏林大学学院的一个团队合作（没有资格获得BBSRC资助，但通过共享资源，专业知识和数据分析全面参与该项目）。它将定义我们所谓的信号中枢（网络中的控制点），涉及SnRK1和伙伴蛋白，将病原体感染与小麦籽粒中天冬酰胺的合成和积累联系起来。我们认为，通过在Fg感染时激活该中心诱导的天冬酰胺浓度的增加是植物在受到致病生物攻击时如何防御自己的重要组成部分。赤霉病引起赤霉病，从而降低产量和粮食质量，并用一种称为真菌毒素的有毒化合物污染粮食，其中最常见的是脱氧雪腐镰刀菌醇（DON）。当小麦被Fg感染时，SnRK1参与了防御机制的调节，与SnRK1结合的一种名为TaFROG的蛋白质也被证明有助于抵抗Fg和DON。最近的研究表明，Fg感染和DON治疗都以不同的方式影响SnRK1， Fg感染导致SnRK1蛋白分裂成更小的蛋白，这种方式在DON本身中是看不到的。随后，一种由真菌分泌的名为OSP24的蛋白质被证明与SnRK1合作，并导致SnRK1被分解。另一方面，TaFROG与OSP24竞争与SnRK1结合，并保护SnRK1免受降解。这些令人着迷的发现意味着该项目可以直接关注信号中枢及其与SnRK1更广泛网络中其他蛋白质的关系。该网络可能包括几种称为bZIP转录因子的蛋白质。这些蛋白控制一些靶基因的活性，可能包括参与天冬酰胺合成的天冬酰胺合成酶基因，并且具有可能由SnRK1控制的特征。我们的目标是确定连接Fg感染与小麦籽粒天冬酰胺积累的信号中枢的所有组成部分。我们将使用不同的Fg菌株，例如不产生DON和/或OSP24蛋白的菌株，在不同类型的小麦中解剖轮毂。我们将使用一种叫做RNA-seq的技术，它将使我们能够识别受Fg感染或DON治疗影响的所有基因，特别是那些可能参与合成或分解天冬酰胺的基因。我们将使用基于蛋白质的研究来确定额外的枢纽成分，并找出我们感兴趣的bZIP转录因子是否确实控制天冬酰胺合成酶基因的活性。最后，我们将看到不同的Fg菌株引起疾病的能力是否与它们对信号中枢和天冬酰胺的影响有关。这些实验将使我们能够对信号中枢进行建模，并针对中枢中涉及的基因进行进一步的实验，以便我们可以测试我们的模型是否正确。SnRK1与其他植物防御机制有关，包括对食草动物、病毒和细菌以及其他真菌的防御机制。此外，小麦谷物中天冬酰胺的含量对食品安全也有影响，因为天冬酰胺在烘焙过程中会转化为一种叫做丙烯酰胺的致癌污染物。这意味着该项目虽然侧重于基础科学，但将对农业食品部门的一系列利益相关者产生潜在影响。

This project arises from discoveries that an amino acid called asparagine accumulates in wheat grain in response to disease and that the plant's response to floral infection by a disease-causing fungus called Fusarium graminearum (Fg) involves a protein called SnRK1. SnRK1 is a master regulator of plant metabolism and it controls the activity of genes encoding an enzyme called asparagine synthetase that is responsible for making asparagine. The project will involve a multidisciplinary team from Rothamsted Research, with collaboration from a team from University College Dublin (not eligible for BBSRC funding but fully involved in the project through the sharing of resources, expertise and data analyses). It will define what we are calling a signalling hub (a control point within a network) involving SnRK1 and partner proteins that links pathogen infection with asparagine synthesis and accumulation in wheat grain. We believe that the increase in asparagine concentration induced through the activation of this hub upon Fg infection is an important part of how plants defend themselves when under attack from disease-causing organisms. Fg causes Fusarium head blight disease, which reduces yield and grain quality, and contaminates grain with toxic compounds called mycotoxins, of which the most common is called deoxynivalenol (DON). SnRK1 is involved in the regulation of defence mechanisms when wheat is infected by Fg and a protein that partners with SnRK1, called TaFROG, has also been shown to contribute to Fg and DON resistance. Recent work has shown that Fg infection and DON treatment both affect SnRK1 but in different ways, with Fg infection causing the SnRK1 protein to be divided into smaller proteins in a way not seen with DON on its own. Subsequently, a protein that is secreted by the fungus, called OSP24, has been shown to partner with SnRK1 and to cause SnRK1 to be broken down. TaFROG, on the other hand, competes with OSP24 for partnering with SnRK1 and protects SnRK1 from degradation. These fascinating discoveries mean that this project can focus directly on the signalling hub and its relationships to other proteins in SnRK1's wider network. That network likely includes several proteins called bZIP transcription factors. These proteins control the activity of some target genes, possibly including asparagine synthetase genes involved in asparagine synthesis, and have characteristics suggesting that they could be controlled by SnRK1. We aim to identify all the components of this signalling hub linking Fg infection with asparagine accumulation in wheat grain. We will dissect the hub in different types of wheat using different strains of Fg, such as strains that do not make DON and/or the OSP24 protein. We will use a technique called RNA-seq that will enable us to identify all of the genes affected by infection by Fg or treatment with DON, looking in particular for those that could be involved in making or breaking down asparagine. We will use protein-based studies to identify additional hub components, and find out if the bZIP transcription factors we are interested in do control the activity of asparagine synthetase genes. Finally, we will see if the ability of different Fg strains to cause disease is linked to their effect on the signalling hub and asparagine. These experiments will enable us to model the signalling hub and perform further experiments to target the genes involved in the hub so that we can test whether our model is correct. SnRK1 has been implicated in other plant defence mechanisms, including those against herbivores, viruses and bacteria, as well as other fungi. In addition, the amount of asparagine in wheat grain has implications for food safety because asparagine can be converted into a cancer-causing contaminant called acrylamide during baking. This means that the project, while focussed on basic science, will have potential impact for a range of stakeholders in the agrifood sector.