Differential processing of host plant toxins by insect herbivores as a driver of multi-trophic interactions

昆虫食草动物对宿主植物毒素的差异加工作为多营养相互作用的驱动力

• 批准号: 325915028
• 负责人: Professor Dr. Georg Petschenka
• 金额: --
• 依托单位: Fachgebiet Angewandte Entomologie (360c)
• 依托单位国家: 德国
• 项目类别: Independent Junior Research Groups
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/325915028?language=en
• 关键词: Differential; processing; host; plant; toxins

Plant toxins play a major role for insect-plant coevolution as they represent a barrier that herbivorous insects must overcome through adaptations. It is generally assumed that insects develop resistance to certain plant toxins for exploiting plants as a dietary resource. In addition, however, many insects store plant toxins for protection against predators and parasitoids (sequestration). Notably, certain resistance mechanisms are directly related to the sequestration of plant toxins, i.e. predators and parasitoids can also select for resistance mechanisms. We showed that in the milkweed bugs (Heteroptera: Lygaeinae) pre-existing resistance mechanisms and the ability to sequester favored evolutionarily novel associations with certain plants that produce the same plant toxins as the ancestral host family of this group. Accordingly, the acquisition of defense substances and not just the colonization of novel dietary resources can mediate specialized plant-insect interactions. The milkweed bug Spilostethus saxatilis sequesters large amounts of the toxic tubulin inhibitor colchicine from autumn crocus (Colchicum autumnale). This is of special interest since it is already able to sequester cardiac glycosides and has a cardiac glycoside-resistant Na+/K+-ATPase like all milkweed bugs. In addition, S. saxatilis possesses a resistance mechanism to colchicine, which is missing in the closely related S. pandurus. Here, we will examine the basis of colchicine resistance in S. saxatilis and address the evolution of colchicine sequestration and colchicine resistance. We will test hypotheses a) at the molecular level, b) at the functional level, and c) in a phylogenetic and organismic context. Using existing transcriptome and genome data, we will investigate whether S. saxatilis has evolved target site insensitivity to colchicine. For this purpose, we will anaylze the α- and β-tubulin encoding genes of S. saxatilis for amino acid exchanges in the colchicine binding site as well as for gene duplications and compare them with other milkweed bug species. Furthermore, we will study S. saxatilis tubulin in vitro to test if it shows reduced affinity to colchicine. At the same time, we will carry out injection experiments with competitive colchicine antagonists to test if S. saxatilis shows cross-resistance to these substances. Finally, we will conduct comparative studies in a phylogenetic context to understand the evolution of colchicine sequestration, resistance to orally ingested (as observed in S. pandurus) and sequestered colchicine. Our investigations will allow the mechanistic basis and the evolution of a novel sequestration syndrome to be understood comprehensively.

植物毒素在昆虫-植物协同进化中起着重要作用，因为它们代表了植食性昆虫必须通过适应来克服的障碍。一般认为，昆虫对某些植物毒素产生抗性是为了利用植物作为食物资源。然而，此外，许多昆虫还储存植物毒素，以保护免受捕食者和拟寄生虫的侵害（隔离）。值得注意的是，某些抗性机制与植物毒素的螯合直接相关，即捕食者和寄生虫也可以选择抗性机制。我们发现，在马利筋错误（异翅目：Lygaeinae）预先存在的阻力机制和能力，以螯合有利于进化的新协会与某些植物，产生相同的植物毒素作为这组的祖先宿主家庭。因此，获得防御物质，而不仅仅是新的饮食资源的殖民化可以介导专门的植物-昆虫相互作用。乳草属昆虫岩生穗ostethus saxatilis从秋番红花（秋水仙）中分离出大量有毒的微管蛋白抑制剂秋水仙碱。这是特别令人感兴趣的，因为它已经能够螯合强心苷，并且像所有乳草虫一样具有抗强心苷的Na+/K+-ATP酶。此外，S. saxatilis对秋水仙素具有抗性机制，而在近缘的S.潘杜鲁斯。在这里，我们将研究秋水仙素抗性的基础在S。saxatilis和解决秋水仙素螯合和秋水仙素抗性的进化。我们将测试假设a）在分子水平上，B）在功能水平上，和c）在系统发育和器官背景下。利用现有的转录组和基因组数据，我们将调查是否S。岩藻已进化出对秋水仙碱不敏感的靶位点。为此，我们将分析S. saxatilis的秋水仙碱结合位点的氨基酸交换以及基因复制，并与其他马利筋虫种进行比较。此外，我们将研究S。saxatilistubulin体外培养以测试其是否显示对秋水仙碱的亲和力降低。同时，我们还将进行竞争性秋水仙素拮抗剂的注射实验，以检测S。saxatilis对这些物质显示交叉抗性。最后，我们将在系统发育的背景下进行比较研究，以了解秋水仙素螯合的进化，对口服摄入的抗性（如在S。pandurus）和螯合的秋水仙碱。我们的研究将使一种新的隔离综合征的机制基础和演变得到全面的理解。