How do interactions between herbivores and mycorrhizal fungi regulate production of plant signalling compounds and parasitoid behaviour?

食草动物和菌根真菌之间的相互作用如何调节植物信号化合物的产生和寄生行为？

• 批准号: NE/G012008/1
• 金额: $ 8.4万
• 依托单位: University of Aberdeen
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG012008%2F1
• 关键词: How; do; interactions; between; herbivores

One of the most fascinating adaptive responses by plants when they are subjected to attack by leaf herbivores is the release of semiochemicals into the atmosphere. These volatile signalling compounds can travel significant distances and are detected by parasitoid wasps that use them to locate and parasitise leaf herbivores. In many cases, it has been shown that certain parasitoids respond only to particular semiochemicals and that they are produced systemically by the plant. This mechanism of semiochemicals release has potential to be an effective strategy by plants for control of aphid populations. The three-way interaction among plant shoots, aphids and parasitoids is relatively well understood. However, there has been very little research on an intriguing additional dimension to the story - that of below ground pathways of semiochemicals transfer and the relationship between leaf herbivores, plant roots and beneficial microorganisms in the rhizosphere. There is evidence from highly simplified hydroponic systems that plants have the potential to release semiochemicals into the rhizosphere, which are available for uptake by neighbours. In natural soils, there is the possibility of a direct transfer process of semiochemicals between plants via mycorrhizal fungi. These fungi heavily colonise the roots of virtually all land plants and produce vast lengths of mycelium that interlink individual plants into a common network. It has been suggested that they may be able to act as conduits for transfer of semiochemicals into bulk soil and to neighbouring plants uninfected by aphids, a hypothesis that remains untested. While many of the experiments undertaken to date have identified the importance of particular ecological components, it is clear that a more holistic approach needs to be undertaken to determine the relative importance of top-down and bottom-up controls of plant signalling, and indirect and direct pathways of semiochemical transfers (Bruce & Pickett, 2007). This PhD studentship therefore will, firstly, seek to determine the impact of leaf herbivores on the key functional traits (nutrient fluxes) and diversity of mycorrhizal fungi, and secondly, identify the below ground pathways by which semiochemicals are transferred between plants. These aims will be achieved by testing the following hypotheses: 1. Aphid infestation of plants affects the functional diversity of mycorrhizal fungi; 2. Aphid infestation of plants modifies semiochemical release into the rhizosphere and mycorrhizosphere; 3. Indirect transfer of semiochemicals in the rhizosphere and mycorrhizosphere occurs between different plant species; 4. Common mycorrhizal mycelial networks enable direct plant-to-plant transfer of semiochemicals; 5. The outcome of interactions between arbuscular mycorrhizal fungi and aphids is dependent on the degree of colonisation of each organism, and the species composition of the fungi. The work will use a combination of microcosm based systems of increasing biological complexity. This approach means that we can identify key mechanisms while controlling potentially confounding factors, manage project risk and build up to more ecologically relevant systems. The work will in the first instance use broad bean (Vicia faba L.) as a test species. This plant readily forms arbuscular mycorrhizas and produces semiochemicals when infested with aphids. Pot experiments will be developed to enable the plants to become integrated into common mycelial networks, and selected individuals will be infested with aphids and the response of parasitoids to this treatment measured. These measurements will be made at the CASE partner's laboratory using olfactometer and video camera techniques. The impacts of aphids on mycorrhizal fungi will be determined using 13CO2 and 33P pulse chase experiments, molecular community profile analysis (TRFLP).

当植物受到食草动物攻击时，植物最吸引人的适应性反应之一是将半化学物质释放到大气中。这些挥发性的信号传导化合物可以传播很大的距离，并通过使用它们来定位和寄生的叶片食草动物来检测到寄生虫。在许多情况下，已经表明某些寄生虫仅对特定的半化学物质反应，并且它们是由植物系统地生产的。 Semiophemicals释放的这种机制有可能成为植物控制蚜虫种群的有效策略。植物芽，蚜虫和寄生虫之间的三向相互作用相对众所周知。但是，关于故事的额外维度的研究很少 - 半化学物质转移的地下途径以及根茎中叶片食草动物，植物根和有益的微生物之间的关系。高度简化的水培系统有证据表明，植物有可能将半化学物质释放到根际，可用于邻居的吸收。在天然土壤中，有可能通过菌根真菌在植物之间直接转移半化学物质。这些真菌大量地殖民了几乎所有陆地植物的根源，并产生大量的菌丝体，使单个植物将单个植物互为共同的网络。有人提出，他们可能能够充当将半化学物质转移到散装土壤和未感染蚜虫的邻近植物的导管，这一假设尚未经过测试。尽管迄今为止进行的许多实验都确定了特定的生态成分的重要性，但很明显，需要采取更全面的方法来确定植物信号的自上而下和自下而上控制的相对重要性，以及半化学转换的间接和直接途径（Bruce＆Pickett，2007年）。因此，首先，该博士学位学生将寻求确定食草动物对菌根真菌的关键功能性状（营养通量）和多样性的影响，其次，确定植物之间将半化学物质转移的下面的地面途径。这些目标将通过检验以下假设来实现：1。植物的蚜虫侵扰会影响菌根真菌的功能多样性； 2。植物的蚜虫侵染会将半化学释放改变为根际和菌根圈； 3。在根际和菌根圈中的半化学物质的间接转移发生在不同的植物物种之间。 4。常见的菌根菌丝网网络可以直接的植物到植物转移。 5。羊膜菌根真菌与蚜虫之间相互作用的结果取决于每个生物的定殖程度以及真菌的物种组成。这项工作将结合基于微观的生物学复杂性系统。这种方法意味着我们可以在控制潜在的混淆因素，管理项目风险并建立更加生态相关的系统的同时确定关键机制。这项工作首先将使用Broad Bean（Vicia Faba L.）作为测试物种。该植物很容易形成羊膜菌根，并在蚜虫出没时会产生半化学物质。将开发盆栽实验，以使植物能够整合到常见的菌丝网网络中，并且选定的个体将被蚜虫感染，以及寄生虫对这种治疗方法的反应。这些测量将在情况伙伴的实验室使用嗅觉计和摄像机技术进行。蚜虫对菌根真菌的影响将使用13CO2和33P脉冲追逐实验，分子社区概况分析（TRFLP）确定。