Immunity in an Ecological Context: The Intersection of Host Physiology, Medicinal Food Plants and Microbiomes in a Natural Butterfly-parasite System

几乎所有的有机体都受到寄生虫的攻击。最近的研究表明，从蝴蝶到黑猩猩，许多动物都可以通过自我用药(使用抗寄生虫物质或饮食)来保护自己免受寄生虫的侵袭。然而，药物行为减少寄生虫感染和疾病的机制仍然知之甚少。这个项目的重点是帝王蝶和它们的原生动物寄生虫。帝王毛虫是专门以马利筋植物为食的动物，而马利筋的浓度和毒性不同，其化学物质称为卡登内酯。当以有毒的乳草为食时，帝王蝶的病情会减轻，受感染的雌性蝴蝶会优先在有毒的乳草上产卵，以减少后代的疾病。该项目将确定有毒的乳草是通过直接杀死寄生虫、通过增加帝王的免疫反应，还是通过为帝王提供防止寄生虫感染的肠道菌群来减少疾病。除了帝王蝶，这个项目还与其他动物有广泛的相关性，其中许多动物使用药用植物。本文研究的寄生虫与在农业动物和人类中引起疾病的寄生虫有关，从而阐明了乳草化学物质的抗寄生虫活性可能在未来的疾病治疗中应用。该项目还将通过培训研究生和本科生，包括那些来自科学领域代表性不足的群体的学生，将研究与教育相结合。研究人员还将与总部位于亚特兰大的非营利组织怀尔德中心(Wylde Center)共同开发课程模块，通过社区花园户外项目传授环境意识。作为这一项目的一部分，该项目将直接为数千名K-12学生的科学教育做出贡献。宿主进化出了一系列针对寄生虫的防御系统，包括行为和微生物防御系统。这种防御可能会对生理免疫的进化产生重要影响，但关于生理免疫、行为免疫和微生物保护之间的相互作用的研究仍然很少。这个项目将研究帝王蝶、它们的乳草寄主植物和它们的原生动物寄生虫之间的相互作用，以解决三个假设：(1)药用乳草的行为使用直接减少寄生虫感染，使生理免疫多余，并减少对这种免疫机制的投资；(2)药用黄花不会降低帝王蝴蝶的免疫力，相反，它通过增强生理免疫反应发挥保护作用；以及(3)药用乳草调节帝王中肠微生物群，使其能够抵抗寄生虫感染。这些假说将通过阐明抵抗和敏感种群的蝴蝶感染时不同的免疫反应，比较以药用和非药用乳草为食的帝王的抗寄生虫免疫反应，并通过分析乳草次级和营养化学物质对帝王免疫和抵抗力的影响来解决这些假说。此外，用药用和非药用乳草饲养的帝王的中肠微生物区系的比较将与操纵肠道微生物群的实验相结合，以测试药用乳草微生物群落对帝王抵抗感染的影响。研究人员将结合实地工作、对照实验和下一代测序技术，包括使用RNAseq来量化差异免疫反应，使用MiSeq来量化细菌和真菌毛虫肠道群落。

Almost all organisms are attacked by parasites. Recent studies have shown that many animals, from butterflies to chimpanzees, can protect themselves against parasites through self-medication (the use of anti-parasitic substances or diets). However, the mechanisms by which medication behaviors reduce parasite infection and disease remain poorly understood. This project focuses on monarch butterflies and their protozoan parasites. Monarch caterpillars are specialist feeders on milkweed plants, and milkweeds vary in their concentrations and toxicity of chemicals called cardenolides. When feeding on toxic milkweed, monarchs become less sick, and infected female butterflies preferentially lay their eggs on toxic milkweed to reduce disease in their offspring. This project will determine whether toxic milkweeds reduce disease by directly killing parasites, by increasing the immune response of monarchs, or by providing monarchs with a gut flora that prevents parasite infection. Beyond monarch butterflies, this project has broad relevance to other animals, many of which use medicinal plants. The parasites studied here are related to parasites causing disease in agricultural animals and humans, thus elucidating the anti-parasitic activity of milkweed chemicals could have future applications for treating disease. The project will also integrate research with education, by training graduate and undergraduate students, including those from underrepresented groups in science. The researchers will also develop lesson modules with the Wylde Center, an Atlanta-based non-profit organization that teaches environmental awareness through community-garden based outdoor programs. As part of this, the project will directly contribute to the science education of thousands of K-12 students. Hosts have evolved a range of defenses against their parasites, including behavioral and microbial defenses. Such defenses may have important consequences for the evolution of physiological immunity, but research on the interplay between physiological immunity, behavioral immunity and microbial protection remains scarce. This project will study the interaction between monarch butterflies, their milkweed host plants and their protozoan parasites to address three hypotheses: (1) behavioral use of medicinal milkweeds directly decreases parasite infection, rendering physiological immunity superfluous and reducing investment in such immune mechanisms; (2) medicinal milkweeds do not reduce monarch immunity but instead exert their protective effects by enhancing physiological immune responses; and (3) medicinal milkweeds modulate monarch midgut microbiota to a state that confers resistance to parasite infection. These hypotheses will be addressed by elucidating immune responses differentially mounted upon infection of butterflies from resistant and susceptible populations, comparing anti-parasite immune responses in monarchs fed on medicinal and non-medicinal milkweed plants, and by analyzing the effects of milkweed secondary and nutritional chemicals on monarch immunity and resistance. In addition, comparison of the midgut microbiota of monarchs reared on medicinal and non-medicinal milkweeds will be coupled with experiments manipulating gut microbiota to test for the effect of medicinal milkweed microbial communities on monarch resistance to infection. The researchers will use a combination of fieldwork, controlled experiments and next generation sequencing technology, including the use of RNASeq to quantify differential immune responses and MiSeq to quantify bacterial and fungal caterpillar gut communities.