Collaborative Research: Insect herbivore feeding guilds and compartmentalized plant defense

植物是几乎所有食物链的基本能源，并负责养活世界。然而，千百年来，昆虫对植物的巨大压力导致了防御被吃掉的各种策略的演变。植物用毒素、刺和粘性汁液防御。尽管展示了植物特性如何减少食草性，但在大多数野生植物系统中，科学家们缺乏对植物防御反应机制的了解。植物是否会产生针对根部取食者而不是取叶者的特定毒素，同时又不会毒害授粉者等有益的访客？破译植物防御机制不仅促进了对生态学和进化论的科学认识，而且可能具有重要的社会效益。由于野生植物与害虫进行了长期的进化斗争，研究其防御机制可能会加强作物病虫害的防治。这个项目的重点是乳草，它们是衰落的帝王蝴蝶的唯一宿主。将获得关于君主和马利筋之间相互作用的基本知识，这可能有助于维持君主受到威胁的迁徙。该项目融合了基因组操作、毒理学和化学的最新进展，将培训科学家将自然历史和重要的生态问题融合在一起。调查人员将通过学校、演讲和博客扩大他们与公众的交流。人们对植物防御如何针对不同的攻击者、是否存在与多个军备竞赛相关的权衡以及组织特异性表型可塑性是否是管理与几种害虫相互作用的手段知之甚少。这项工作使用乳草作为自然系统的模型，具有良好的防御化学特性，以测试与各种昆虫攻击者相互作用的特异性和相互依赖性，这些昆虫包括食叶的帝王蝶、食根的甲虫和食籽的昆虫。从工厂的角度来看，将评估多种防御措施及其对授粉熊蜂的非目标影响之间的权衡，作为与构成防御或诱导防御相关的成本。从食草动物的角度来看，植物毒素表达的分析将与对昆虫靶点酶功能、行为和整个生物体性能的影响相结合。除了行会特定的植物防御和权衡假设外，还将测试对植物防御多样性的经典解释：非排他性假设，即(I)自然产生的毒素混合物在植物部分有不同的表达，(Ii)混合物比同等剂量的单一化合物更有效。这种关于专业化和相互作用的观点解决了攻防特征的动态匹配，这些特征可能通过从根到果的不同军备竞赛在植物和昆虫中产生多样性。喂养试验将被用于研究单一的香豆内酯和天然混合物如何影响生理功能、昆虫行为、隔离和健康。通过从不同昆虫中提取Na/K-ATPase(Cardenolide的靶标)，毒素的具体作用也将在体外进行评估。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Plants are the basic energy source in nearly all food chains and are responsible for feeding the world. Yet over the eons, tremendous insect pressure on plants has led to the evolution of a remarkable diversity of tactics to defend against being consumed. Plants defend with toxins, spines, and sticky sap. Despite demonstrations of how plant traits can reduce herbivory, in most wild plant systems scientists lack an understanding of the mechanisms of plant defensive responses. Do plants make specific toxins targeted at root feeders versus leaf feeders, all the while not poisoning beneficial visitors such as pollinators? Deciphering the mechanisms of plant defense not only advances scientific knowledge of ecology and evolution but may have important societal benefits. Because wild plants have been engaged in a long-term evolutionary battle with insect pests, studying the mechanisms of defense may enhance crop pest management. This project focuses on milkweeds, which are the only host for the declining monarch butterfly. Basic knowledge of the interaction between monarchs and milkweed will be gained, which could help sustain the monarch's threatened migration. This project blends the latest advances in genomic manipulation, toxicology and chemistry in a way that will train scientists to meld natural history and important ecological problems. The investigators will expand their communication to the public through schools, presentations, and a blog.Little is known about how plant defenses are aimed at different attackers, whether there are trade-offs associated with multiple arms races, and whether tissue-specific phenotypic plasticity is a means to manage interactions with several pests. This work uses milkweeds as a model natural system with well-characterized defense chemistry to test the specificity and interdependence of interactions with diverse insect attackers that include leaf-feeding monarch butterflies, root-feeding beetles, and seed-feeding bugs. From the plant's perspective, trade-offs will be evaluated between multiple defenses and their non-target impacts on pollinating bumblebees as costs associated with constitutive or induced defenses. From the herbivores' perspective, assays of plant toxin expression will be coupled to impacts on insect target site enzymatic function, behavior, and whole-organism performance. Beyond guild-specific plant defense and trade-off hypotheses, classic explanations for diversity in plant defense will also be tested: the non-exclusive hypotheses that (i) naturally occurring toxin mixtures are differentially expressed in plant parts and (ii) mixtures are more effective than equal doses of single compounds. This view on specialization and interaction addresses the dynamic match in offense-defense traits that may generate diversity within plants and insects through distinct arms races occurring from roots to fruits. Feeding trials will be used to address how single cardenolides and natural mixtures impact physiological function, insect behavior, sequestration, and fitness. By extracting the Na/K-ATPase (the target of cardenolides) from the different insects, the specific action of toxins will also be assessed in vitro.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.