Detection, Prevention and Immune Mechanisms for Pathogens with Diverse Lifestyles (Patho-Lifestyle)

我们这个时代最大的挑战之一是养活不断增长的全球人口。由于气候变化和城市发展，世界可耕地实际上已达到其最大容量，并将在未来几年减少。因此，必须提高我们粮食系统的生产力，以应对世界饥饿和加强粮食安全。实现这一目标的一个特殊战略是减少虫害造成的损失。大麦是世界第四大作物，在英国排名第二。大麦的最大威胁是病害，包括由褐锈病和天鹅锈菌引起的病害，造成高达40%的产量损失。根据病原真菌的生活方式和与寄主的相互作用，病原真菌可分为生物营养型和坏死型。生养真菌和坏死型真菌的关键区别在于，生态型真菌从活的植物细胞中获取营养，维持它们的生命，而坏死型真菌杀死植物组织，然后从植物组织中获取营养。然而，许多病原真菌使用顺序的生物营养和坏死营养感染阶段。在生物营养阶段，它们入侵并以最小的损害广泛地在植物上定居，然后切换到通常是致命的死亡营养阶段。重要的是，在感染的早期生物营养阶段使用杀菌剂在减少疾病方面最有效，但由于这一阶段无法肉眼识别，在病原体已经确立的情况下使用往往为时已晚。作为对病原体攻击的反应，植物发起足以抵御大多数病原体的免疫反应。然而，适应病原菌分泌的效应蛋白能够抑制宿主的免疫反应，促进成功的感染，造成严重的作物损害。这些效应器在不断进化，从而避免了现有的寄主抗性或当前的植物保护策略。因此，需要其他方法来提高作物的抗性。使用免疫激发子或保护性生物刺激剂是一种非常有希望的可持续诱导长期抗病的方法，但这些化学物质的作用模式和植物细胞靶标仍不清楚。植物使用保守的蛋白质泛素来调节免疫反应。泛素化是一种快速和可逆的蛋白质修饰，调节免疫反应的幅度和强度。使用我们实验室开发的蛋白质组管道，我们发现蛋白质泛素化是一种比目前可用的基因组和转录标记更好的早期生物营养性病原体感染的生物标记物。我们在大麦品种上进行的田间试验结果表明，所有受感染的大麦品种都普遍存在泛素介导的免疫激活，这意味着泛素对免疫系统的调节是品种间的一种保守机制。因此，在这个项目中，我们将研究大麦对激发子/生物刺激剂和生活方式变化的经济相关病原体的泛素依赖反应。这些将与响应生物营养和死亡营养阶段的植物免疫激素的泛素蛋白质组进行比较，揭示激发子/生物刺激剂的作用模式，准确地识别病原体改变其生活方式的时间，识别新的生物标记物，以早期发现‘看不见的’生物营养疾病阶段。综上所述，该项目将解决一个关键的知识差距，并揭示在生物营养和死亡真菌感染期间植物免疫的激活和调节的新的基本见解，以及将用于增强作物抗性的激发子和生物刺激剂的真实作用模式。这些新颖、可持续的方法将对全球粮食安全产生重大影响，并推动农业食品部门的创新。

One of the biggest challenges of our time is to feed the growing global population. World arable land is practically at its maximum capacity, and will decrease in coming years due to climate change and urban development. Therefore, the productivity of our food system must be increased to tackle world hunger and increase food security. One exceptional strategy to achieve this goal is to reduce losses by pests. Barley (Hordeum vulgare) is the fourth most important crop worldwide and second in the UK. Diseases, including those caused by the brown rust Puccinia hordei and Ramulaira collo-cygni, represent the largest threat to barley, causing yield losses of up to 40%. Based on their lifestyle and interaction with the host, pathogenic fungi can be classified as either biotrophic or necrotrophic. The key difference between biotrophic and necrotrophic fungi is that biotrophic fungi derive nutrients from living plant cells, maintaining them alive, while necrotrophic fungi kill the plant tissues and then obtain nutrients from them. However, many pathogenic fungi use sequential biotrophic and necrotrophic infection phases. During the biotrophic phase they invade and extensively colonise the plant with minimum damage, before switching to the often fatalnecrotrophic phase. Importantly, fungicides are most effective at reducing disease when applied during the early biotrophic stages of infection, but since this phase cannot be visually identified, they are often applied too late when the pathogen is already well established. In response to pathogen attack, plants initiate immune responses that are sufficient to fend off most pathogens. However, adapted pathogens secret effector proteins that are capable of suppressing the host immune response and promote successful infection, causing severe crop damage. These effectors are constantly evolving, thereby avoiding existing host resistance or current plant protection strategies. Consequently, alternative methods to enhance crop resistance are required. The use of immune elicitors or protective biostimulants is a highly promising sustainable method for inducing long-lasting disease resistance, but the modes of action and plant cell targets of these chemicals remain unknown. Plants use the conserved protein ubiquitin to regulate immune responses. Ubiquitination is a fast and reversible protein modification that regulates the amplitude and intensity of the immune response. Using a proteomic pipeline developed in our laboratories, we discovered that protein ubiquitination is a far better biomarker for early biotrophic pathogen infection than currently available genomic and transcriptomic markers. Our results in barley cultivars on a field trial with P. hordei showed a general ubiquitin-mediated immune activation of all infected barley cultivars, implying that ubiquitin regulation of the immune system is a conserved mechanism across cultivars. Therefore, in this project we will investigate the ubiquitin-dependent response of barley to elicitors/biostimulants and economically relevant pathogens with changing lifestyles. These will be compared to the ubiquitin proteomes of plant immune hormones responsive to biotrophic and necrotrophic stages, revealing the modes of action of elicitors/biostimulants and precisely identifying when pathogens change their lifestyle, identifying new biomarkers for early detection of the 'invisible' biotrophic disease phase.In summary, this project will address a crucial gap in knowledge and uncover new fundamental insights into the activation and modulation of plant immunity during biotrophic and necrotophic fungal infections, and real the mode of action of elicitors and biostimulants, which will be used to enhance crop resistance. These novel, sustainable approaches will have a significant impact on global food security and drive innovation in the agrifood sector.