Hijacking plant immunity: winners and losers in dual pest and pathogen attacks on a shared host

当攻击者攻击植物时，植物不会逃走。无法逃离意味着他们承受着抵抗袭击者的压力……它们通过启动防御系统来做到这一点，比如生产抗生素植物化学物质。与此同时，攻击者已经适应了抑制植物防御反应，以殖民他们的宿主。一个有趣而重要的问题是，“当植物暴露在不止一个攻击者面前时会发生什么？”在这里，我们考虑小麦，一种对全球粮食安全具有全球重要性的作物，以及它的两个主要攻击者：蚜虫(绿蝇)和镰刀菌赤霉病(FHB)。赤霉病是由侵袭性真菌病原菌--禾谷镰刀菌引起的小麦主要病害。这种疾病还会在谷物中产生毒素(称为真菌毒素)、脱氧雪腐镰刀菌烯醇(DON)和雪腐镰刀菌烯醇(NIV)，这些毒素在食用时对人类和动物都有害。粮食作物生产受到病虫害的制约，降低了粮食的产量和质量。对农民来说，它们正变得越来越难以控制，因为由于杀虫剂抗药性的演变以及禁止使用杀虫剂的法律的变化，杀虫剂的可获得性正在下降，例如霓虹灯。以前对植物病虫害的大多数研究都是孤立地考虑它们，对它们之间的相互作用知之甚少。麦田中的蚜虫与赤霉病同时发生，并与病害和小麦寄主相互作用。我们的项目将发现小麦植物如何应对这些攻击者，不仅是它们自己，而且当受到双重攻击时也是如此。我们的早期发现表明，与干净的植物相比，有蚜虫的植物上的赤霉病感染率增加了一倍。在这里，我们将确定这种情况发生的方式和原因。我们将研究这种由蚜虫诱导的植物防御抑制的生化和分子基础。我们将对小麦寄主和蚜虫进行基因表达分析，并分析生化产物的差异。我们将在我们的生物学实验中定义和描述调制的宿主-防御网络，并确定它们的生物学意义。昆虫会受到植物释放的气味的影响：患病的植物与健康的植物气味不同，可能会变得令人厌恶。我们将收集植物气味，鉴定它们的化学结构，并将蚜虫暴露给它们，以测试它们的反应。我们将用昆虫的触角进行电子记录，以确定它们能闻到哪些化学物质，并进行行为测试，看看它们是被吸引还是被排斥。最后，该项目将进行实验，以确定蚜虫是否能够代谢FHB疾病产生的毒素。暴露在真菌毒素下的蚜虫基因表达和新陈代谢的变化结果将识别昆虫中与未来昆虫控制目标相关的新的解毒途径。我们的项目将使我们能够定义新的分子和代谢目标，使我们的作物对小麦上的蚜虫和引起赤霉病的病原体更具弹性。研究将促进对植物如何应对病虫害联合攻击的科学理解。这个项目将提供的信息是至关重要的，因为我们不知道蚜虫如何改变寄主来增加其对小麦赤霉病的敏感性。这是一种新的方法，因为以前的大多数研究都忽略了攻击者如何通过操纵宿主来影响彼此。我们的工作成果将创造未来的机会，以提高作物对这些攻击性生物的适应能力。

Plants cannot run away when an attacker comes to attack them. Being unable to flee means that they are under pressure to resist attackers... they do this by switching on defences such as the production of antibiotic plant chemicals. Meanwhile, the attackers have adapted to supress plant defence responses to colonise their host. An interesting and important question is, "what happens when plants are exposed to more than one attacker?" Here we consider the case of wheat, a globally important crop for global food security, and two of its key attackers: aphids (greenfly) and Fusarium head blight (FHB) disease. FHB is a major disease of wheat caused by Fusarium graminearium, an aggressive fungal pathogen. The disease also produces toxins (called mycotoxins), deoxynivalenol (DON) and nivalenol (NIV), in the grain, which are harmful to humans and animals when consumed. Cereal crop production is constrained by plant pests and diseases, which reduce the yield and quality of harvested grain. They are becoming more difficult for farmers to control because availability of pesticides is going down due to the evolution of pesticide resistance and changes in the law that ban pesticides, for example, neonics. Most previous studies of plant diseases and pests have considered them in isolation and little is known of the interactions between them. Aphids occur in cereal fields at the same time as FHB and interact with the disease and the wheat host plant. Our project will discover how wheat plants respond to these attackers, not only on their own but also when exposed to dual attack. Our early findings show that FHB disease infection is doubled on plants with aphids when compared to clean plants. Here we will determine how and why this happens. We will investigate the biochemical and molecular basis of this aphid-induced plant defence suppression. We will conduct gene expression analyses of the wheat host and the aphid and will analyse differences in biochemical production. We will define and characterise the modulated host-defence networks in our biological experiments and determine their biological significance. Insects are influenced by the odours that plants release: a diseased plant smells different from a healthy one and may become repellent. We will collect plant odours, identify their chemical structures and expose aphids to them to test how they respond. We will make electrical recordings from insect antennae to determine which chemicals they can smell and do behaviour tests to see if they are attracted or repelled. Finally, the project will carry out experiments to determine if the aphids are able to metabolise the toxins produced by the FHB disease. The results from changes in the gene expression and metabolism of the aphid exposed to the mycotoxins will identify new detoxification pathways in the insect relevant to future targets for insect control. Our project will allow us to define novel molecular and metabolomic targets for making our crops more resilient to the aphid pest and the pathogen causing FHB disease in wheat.The research will advance scientific understanding of how plants respond to combined attack from a pest and a disease. The information this project will provide is essential because we do not know how the aphids change the host to increase its susceptibility to FHB in wheat. This is a novel approach because most previous studies have overlooked how attackers sharing a host plant influence each other by manipulating the host. Outcomes of our work will create future opportunities to improve crop resilience to these attacking organisms.