Characterisation of cue-dependent behaviour in plant parasitic nematodes (PPNs); the neurobiology of host plant invasion

线虫是一种圆形的蠕虫，生活在从最高的山脉到最深的海洋的许多栖息地。有许多不同的线虫已经进化出不同的生活方式。它们包括非寄生和寄生蠕虫。后者包括寄生线虫，它们以农业上重要的作物和动物为宿主，经常影响它们的活力和/或生存能力。这些寄生虫导致的疾病过程花费了数十亿英镑，并降低了粮食自给自足和安全的能力。在英国和世界各地，我们面临着一个日益严重的问题，即感染动物的线虫，以及影响作物的植物寄生线虫。对后者来说，由于人们日益认识到目前的治疗方法由于环境和人类健康影响以及停止使用而变得越来越不可接受，这使情况更加恶化。这使得农业处于非常脆弱的地位。植物寄生线虫（PPNs）直接造成危害，也是疾病的二次载体。在英国，它们对马铃薯作物造成了严重的负担。ppn的生命周期包括蠕虫在寄主根部的成熟，在那里它将植物营养转移到自己的发育和繁殖中。随后，从资源耗尽的受感染的根中释放出一种自由的生命形式，它会重新侵入另一个根。这些线虫中的一些对一种植物表现出选择性的味道，而另一些则可以针对一系列宿主。在这两种情况下，寄生虫经常感染集约化种植和经济上重要的作物并降低产量。成功完成PPN生命周期的一个重要方面是从释放点开始通过土壤运动，找到并重新侵入新的寄主根。这是通过一个简单的三步过程实现的。首先，自由的活蠕虫检测来自根部的信号。其次，它用它的感应器官来探测这些暴露的宿主线索。第三，它使用这些线索追踪到新的词根。关于这种蠕虫的传感器是什么以及它们如何引导其运动到合适的宿主的细节，人们知之甚少，但显然对维持这种寄生虫的生命周期非常重要。这与我们对另一种线虫，即所谓的“模式”生物秀丽隐杆线虫的详细了解完全相反。自20世纪60年代以来，生物学家对这种非寄生性蠕虫进行了广泛的研究，它作为生物学模型的成功体现在它是第一个进行基因组测序的动物（1998年）。事实上，它在三个诺贝尔奖的颁发中发挥了重要作用。神经生物学家已经精确地定义了这种蠕虫感知食物并向其移动的分子、细胞和行为机制的细节。此外，对寄生线虫起作用的化学物质也对秀丽隐杆线虫有影响，这与后者为理解ppn的信号传导和行为提供了一个很好的模型的观点一致。我们将使用秀丽隐杆线虫的技术，专业知识和理解，并将这些转化为ppn中宿主位置行为的详细分析。我们将使用基于实验室的研究，其中来自寄主植物的根提取物可以改变PPN的行为，并研究可能对PPN起作用的化学物质，以阻止它们定位和/或向寄主植物移动的能力。正在进行的ppn基因组测序将有助于这一点，这将揭示杀线虫化学物质作用的新靶点的分子特性。这样做的目的是为了确定杀线虫剂的新化学靶点。这些努力将由合作的工业同事提供的化学物质促进，这些化学物质有可能提供PPN选择性杀线虫剂，这种杀线虫剂通过削弱寄生虫寻找寄主植物的能力来起作用。通过这种方式，该项目将解决缺乏有效的、环境安全的杀线虫剂对农业造成的威胁。

Nematodes are rounds worms that live in many habitats ranging from the highest mountains to the deepest seas. There are a number of different nematodes that have evolved for distinct life-styles. They encompass both non-parasitic and parasitic worms. Amongst the latter are parasitic nematodes that use agriculturally important crops and animals as hosts often affecting their vitality and/or viability. Such parasites lead to disease processes that cost billions of pounds and reduce the capability for food self-sufficiency and security. In the UK and across the world we face an increasing problem from nematodes that infect animals and also plant parasitic nematodes that infest crops. For the latter, this is worsened by the growing realization that current treatments are becoming increasingly unacceptable due to environmental and human health implications and their withdrawal from use. This places farming in a very vulnerable position. The plant parasitic nematodes (PPNs) directly cause damage and also act as secondary carriers for diseases. In the UK they place a severe burden on potato crops. The life cycle of the PPNs involves the maturation of the worm in the host's root where it diverts plant nutrients to its own development and reproduction. This is followed by release of a free living form, from resource exhausted infected roots, that goes onto re-invade a different root. Some of these nematodes show a selective taste for one kind of plant while others can target a range of hosts. In either case the parasites often infect and reduce yields from intensively farmed and economically important crops. An essential aspect of the successful completion of the PPN life cycle is movement through the soil from the point of release to locate and reinvade new host roots. This is achieved through a simple three step process. Firstly, the free living worm detects signals from the root. Secondly it uses its sensor organs to detect these tell-tale host cues. Thirdly it uses these cues to track towards the new root. The details of what the worm's sensors are and how they guide its movement to an appropriate host are poorly understood but clearly very important for maintaining the parasite's life cycle. This is in complete contrast to the detailed understanding we have for another species of nematode, the so-called 'model' organism, C. elegans. This non-parasitic worm has been extensively studied by biologists since the 1960s and its success as a biological model is manifest by the fact that it was the first animal to have its genome sequenced (1998). Indeed, it has been instrumental in the award of three Nobel prizes. Neurobiologists have defined in precise detail the molecular, cellular and behavioural mechanisms through which this worm senses food and moves towards it. Furthermore, chemicals that act against parasitic nematodes also have effects on C. elegans consistent with the view that the latter provide a good model for understanding signalling and behaviour in PPNs. We will use the techniques, expertise and understanding of C. elegans and translate these to a detailed analysis of host location behaviour in PPNs. We will use laboratory based investigations in which root extracts from host plants modify PPN behaviour and investigate chemicals that could act against PPNs to prevent their ability to locate and/or move towards the host plant. This will be facilitated by ongoing genome sequencing for PPNs which will reveal the molecular identity of new targets through which nematicidal chemicals act. This will be done with a view to identifying new chemical targets for nematicides. These efforts will be facilitated by a supply of chemicals from collaborating industrial colleagues that have the potential to provide PPN selective nematicides that act by impairing the parasite's ability to find its host plant. In this way the project will address the threat to farming posed by the lack of effective, environmentally safe nematicides.