From health to sickness; the metabolomics transition associated with plant disease and defense.

由于植物牢牢扎根于地面，它们很容易受到昆虫、真菌、细菌和病毒等各种讨厌生物的攻击。令人着迷的是，尽管不断侵犯隐私，但疾病是一个例外，因为它部署了一个非常复杂和高效的协同防御策略网络-统称为基础防御或非宿主抵抗。许多防御性屏障是一种或多种代谢物--小化学物质--作用的组合。代谢物由植物合成，并以多种方式发挥作用--作为信号、镇静剂甚至毒素--以单独或协同防止病原体进入。当病原体，如细菌，确实成功入侵植物时，它们自己采用各种策略来进一步抑制或逃避寄主防御，并操纵寄主新陈代谢，为它们的繁殖提供营养。总而言之，他们把细胞间的环境变成了一个舒适的公寓，网上有食物和营养。它们通过一种被称为III型分泌系统的注射器状结构，积极地将蛋白质注入植物细胞中，从而实现了这一“成功”。这些“效应器”蛋白质操纵宿主转录(作为蛋白质合成模板的基因的表达)和蛋白质表达，以协调一个复杂的信号事件网络。有时，这些效应蛋白中的一个或多个被识别并触发警报信号，局部和系统地诱导免疫，导致对植物的消毒。我们的研究支持这一建议，使用了一种被称为转录图谱的技术来观察各种病原体挑战是如何改变所有植物基因的表达的。对非常复杂的表达模式的分析揭示了特定涉及基础防御和疾病的基因家族。特别是，我们发现成功的病原体诱导的基因表达模式与不成功的感染尝试中看到的相比有所改变。这些数据代表了我们理解植物防御的一个重要里程碑，因为这些基因中的许多编码蛋白质，这些蛋白质本身产生或修改可能增强或干扰植物免疫的代谢物。通过现代技术的结合，我们现在希望发现协调防御的化学物质。我们将尝试研究所有的小分子/一种称为代谢组学或代谢物图谱的程序/并确定哪些小分子在特定治疗后数量发生变化。分析可以是有针对性的(以识别已知化合物)，也可以是非有针对性的，以衡量变化的模式。新技术使我们能够进行大规模的新陈代谢分析，以确定不同处理方式或经历不同反应的植物组织之间的差异。通过这种方式，我们可以识别不同的代谢物，即使我们实际上可能无法从初步筛选中识别代谢物。通过将这项技术与无法完全激活特定防御途径的突变体结合使用，我们将获得重要化合物如何保护或破坏抗性的线索，甚至可能识别启动整个防御过程的信号分子。简而言之，我们的目标是确定与防御的各个方面具体相关的代谢物‘特征’。这项工作的长期成果将是更好地了解小分子(I)被招募用于植物防御和(Ii)那些与成功感染相关的代谢物。这些结果将为未来旨在操纵植物反应以发展对病原体的广谱免疫的战略提供参考。

As plants are firmly rooted to the ground, they are open to attack by a wide variety of nasties such as insects, fungi, bacteria and viruses. Fascinatingly, despite this constant invasion of privacy, disease is an exception due to the deployment of an extraordinary complex and highly effective network of synergistic defensive strategies -collectively known as basal defense or non-host resistance. Many of these defensive barriers are the combination of actions of one or more metabolites - small chemicals. Metabolites are synthesised by the plant and act in a multitude of ways - as signals, as sedatives or even as toxins - to individually or cooperatively prevent pathogen ingress. When pathogens, such as bacteria, do successfully invade a plant, they themselves employ a variety of strategies to further suppress or evade host defenses and manipulate host metabolism to provide nutrients for their multiplication. In sum, they turn their intercellular environment into a cosy apartment with food and nutrients online. They achieve this 'success' by actively injecting proteins into the plant cell via what is basically a syringe-like structure known as a type III secretion system. These 'effector' proteins manipulate host transcription (expression of genes which are the template for protein synthesis) and by definition protein expression, to orchestrate a complex network of signalling events. Occasionally, one or more of these effector proteins is recognised and triggers an alarm signal that both locally and systemically induces immunity, leading to disinfection of the plant. Our studies underpinning this proposal have used a technique known as transcriptional profiling to look at how the expression of all plant genes is modified by various pathogen challenges. Analysis of the very complex expression patterns revealed families of genes specifically involved in basal defense and disease. In particular, we found the successful pathogens induced gene expression patterns modified from those seen in unsuccessful attempts to infect. These data represent a significant milestone in our understanding of plant defense as many of these genes encode proteins which themselves produce or modify metabolites that might enhance or interfere with plant immunity. Through a combination of modern technologies we now wish to discover the chemicals that coordinate defense. We will attempt to look at all the small molecules / a procedure known as metabolomics or metabolite profiling / and identify which ones change in quantity following specific treatments. Profiling can be targeted (to identify known compounds) or non-targeted, measuring the pattern of changes. New technologies allow us to undertake large scale metabolic profiling to identify differences between plant tissues treated in different ways or undergoing different reactions. This way we can identify metabolites that differ, even though we may not actually be able to identify the metabolite from the preliminary screen. By using this technology in combination with mutants which cannot fully activate specific defense pathways, we will obtain clues to how the important compounds protect or destablise resistance and maybe even identity the signal molecules that start the whole process of defense. In short, we aim to identify metabolite 'signatures' specifically associated with various aspects of defense. The long-term outcome of this work will be better understanding of the small molecules (i) recruited for plant defense and (ii) those metabolites associated with successful infections. These results will inform future strategies aimed toward manipulating plant responses to develop broad spectrum immunity to pathogens.