Activation of plant toxins by herbivorous insects

草食性昆虫激活植物毒素

• 批准号: 422213951
• 负责人: Professorin Dr. Meret Huber, Ph.D.
• 金额: --
• 依托单位: Institut für Organismische und Molekulare Evolutionsbiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/422213951?language=en
• 关键词: Activation; plant; toxins; herbivorous; insects

Toxic secondary metabolites are of central importance to protect plants against herbivores. Many toxins are stored as precursors, so called protoxins, and are activated by compartmentalized enzymes upon tissue disruption. Curiously, protoxins are not always activated by plant-derived enzymes: in many cases, they seem to be cleaved by digestive enzymes from the herbivores. To date, the genetic basis of this phenomenon as well as its ecological implications are not well understood. During my previous work, I studied the interaction between the common dandelion (Taraxacum officinale agg.) and its major natural enemy, the larvae of the cockchafer (Melolontha melolontha). These experiments led to the identification of taraxinic acid β-D-glucopyranosyl ester (TA-G) as a major resistance factor of dandelion and showed that this compound is under positive selection by M. melolontha in nature. My recent unpublished work shows that TA-G is rapidly deglycosylated in the gut of M. melolontha by insect-derived ß-glucosidases. Through a transcriptome screen, I identified 19 M. melolontha gut ß-glucosidases whose expression pattern matches TA-G deglycosylation. Although preliminary evidence suggests that TA-G is a protoxin whose hydrolysis leads to the formation of the more toxic aglycone, the impact of TA-G deglycosylation on insect performance and behaviour remains unclear.Based on the state-of-the-art and our preliminary results, I propose a series of experiments to answer three major open questions regarding the role of herbivore digestive enzymes in plant protoxin activation: 1) Which enzymes deglycosylate TA-G in the gut of M. melolontha? 2) What is the impact of TA-G deglycosylation by digestive β-glucosidases on herbivore performance and behavior? 3) Do the TA-G activating ß-glucosidases have any primary digestive functions? To answer these questions, we will express all 19 M. melolontha ß-glucosidases in an insect expression system (High Five cells) and screen them for TA-G deglycosylation activity. In a second step, active TA-G ß-glucosidases will be silenced in M. melolontha using an efficient environmental RNA interference approach, and the impact of TA-G ß-glucosidase silencing on the behavior and performance of the herbivore on wild type and TA-G deficient dandelion plants will be assessed. Finally, we will investigate alternative substrates of the identified TA-G β-glucosidases in vitro and determine the potential benefits of digestive ß-glucosidases for the herbivore using the gene silencing platform in combination with artificial diet assays. Our project will be among the first to study the impact of protoxin activation by herbivore digestive enzymes on herbivore behavior and to elucidate both costs and benefits of producing the associated enzymes. Thereby, this project will shed light on an important, but understudied aspect of plant-herbivore interactions.

有毒次生代谢物对保护植物免受食草动物的侵害具有重要意义。许多毒素作为前体储存，所谓的原毒素，并在组织破坏时被区室化酶激活。奇怪的是，原毒素并不总是被植物来源的酶激活：在许多情况下，它们似乎被食草动物的消化酶裂解。迄今为止，这一现象的遗传基础及其生态影响尚未得到很好的理解。在以前的工作中，我研究了普通植物蒲公英（Taraxacum officinale agg.）及其主要天敌金龟子（Melolontha melolontha）幼虫。这些实验导致鉴定蒲公英酸β-D-吡喃葡萄糖酯（TA-G）作为主要的抗性因子，并表明该化合物处于M. Melolontha自然我最近未发表的工作表明，TA-G在M.通过昆虫衍生的β-葡糖苷酶对Melolontha进行的研究。通过转录组筛选，我鉴定了19个M。其表达模式与TA-G去糖基化匹配。尽管初步证据表明TA-G是一种原毒素，其水解导致形成毒性更大的糖苷配基，但TA-G去糖基化对昆虫性能和行为的影响仍不清楚。基于最新技术水平和我们的初步结果，我提出了一系列实验来回答关于草食动物消化酶在植物原毒素激活中的作用的三个主要开放性问题：（1）在M. melolontha？2)消化性β-葡萄糖苷酶对TA-G去糖基化对食草动物的性能和行为有何影响？3)TA-G激活的β-葡萄糖苷酶是否具有主要的消化功能？为了回答这些问题，我们将表达所有19 M。在昆虫表达系统（High Five细胞）中使用Melolontha β-葡糖苷酶，并筛选它们的TA-G去糖基化活性。在第二步中，活性TA-G β-葡糖苷酶将在M中沉默。将评估使用有效的环境RNA干扰方法对Melolontha进行基因沉默，以及TA-G β-葡糖苷酶沉默对食草动物在野生型和TA-G缺陷型植物上的行为和表现的影响。最后，我们将在体外研究所鉴定的TA-G β-葡萄糖苷酶的替代底物，并使用基因沉默平台结合人工饲料测定来确定消化性β-葡萄糖苷酶对草食动物的潜在益处。我们的项目将是第一个研究草食动物消化酶激活原毒素对草食动物行为的影响，并阐明生产相关酶的成本和效益。因此，这个项目将揭示一个重要的，但研究不足的方面植物-草食动物的相互作用。