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Collaborative Research: Macroevolution of a group of plant secondary defense compounds (pyrrolizidine alkaloids) in the dogbane and milkweed flowering plant family (Apocynaceae)

合作研究：罗布麻和马利筋开花植物家族（夹竹桃科）中一组植物二级防御化合物（吡咯里西啶生物碱）的宏观进化

基本信息

批准号：
1655223
负责人：
Shannon Straub
金额：
$ 13.09万
依托单位：
Hobart and William Smith Colleges
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-06-01 至 2023-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1655223&HistoricalAwards=false
关键词：
Collaborative Research Macroevolution group plant

项目摘要

Plants are known to synthesize about 200,000 distinct secondary metabolites, chemical compounds that are not essential for their cellular metabolism. These plant secondary chemicals are important sources of medicines (e.g. aspirin), pesticides (e.g. pyrethrin), industrial compounds (e.g. latex), flavors (e.g. mint), and poisons (e.g. strychnine). To plants, these chemicals are essential defenses against herbivores, particularly insects. The efficacy of these defenses is not static over time, however, as herbivores adapt to their host plants defenses, evolving mechanisms to detoxify them or even co-opt them for their own defense against their predators. Thus a chemical that was once a valuable defense may become a liability, and its production lost. This project will investigate the evolution of a group of plant defense secondary compounds (pyrrolizidine alkaloids) in the dogbane and milkweed family (Apocynaceae). Plant secondary compounds in the Apocynaceae are diverse, with many having medicinal properties. Pyrrolizidine alkaloids in members of the Apocynaceae are highly toxic to non-adapted herbivores, but have little effect on specialist insects that store them within their tissues for defense against predators. Researchers will sample broadly across the Apocynaceae and reconstruct evolutionary relationships within the family using DNA sequence data. The resulting evolutionary tree will then be used as a framework to reconstruct the evolution of pyrrolizidine alkaloids within the group and better understand the relationship between these chemicals, the plants that produce them, and their herbivores. Undergraduate students will be trained in diverse molecular, evolutionary and biochemistry methods. Results from this project will also be integrated into undergraduate classes at three institutions, including two primarily undergraduate institutions. The research will provide new insights into evolutionary relationships within the medically important Apocynaceae plant family that can be used as a framework for broader questions within the family. An exhibit at the Academy of Natural Sciences in Philadelphia will broadly disseminate results from this research, and information on the broader topics of plant and insect defense, chemistry, and co-evolution, to the public. The overarching hypothesis to be tested in this research project proposes that the diversity of pyrrolizidine alkaloids will be lower in plant lineages that are highly exploited by insects immune to the effects of these compounds. To test this hypothesis researchers will use a combination of targeted enrichment and genome skimming (Hyb-Seq) to sequence ca. 850 low-copy nuclear loci, whole chloroplast genomes, and nuclear ribosomal genes, from 2 species of each of the 287 genera of the APSA clade (the lineage within Apocynaceae that includes most known milkweed butterfly host plants) to generate the required well-resolved and supported phylogeny and chronogram of the family. Researchers will then conduct a systematic survey of pyrrolizidine alkaloids occurrence in leaves across the APSA clade and reconstruct the evolution of both the pyrrolizidine alkaloids phenotype and of the underlying biosynthetic pathway, as well as expression and functional analyses in a subset of species. The origin of pyrrolizidine alkaloid biosynthesis in Apocynaceae will then be compared to the age of pyrrolizidine alkaloid co-option by Danainae, and test if the loss of pyrrolizidine alkaloids is correlated with host plant status.

众所周知，植物合成了大约20万种不同的次生代谢物，这些化合物对植物的细胞新陈代谢不是必需的。这些植物次生化学物质是药物(如阿司匹林)、杀虫剂(如除虫菊酯)、工业化合物(如乳胶)、香料(如薄荷)和毒药(如士的宁)的重要来源。对于植物来说，这些化学物质是抵御食草动物，特别是昆虫的基本防御。然而，随着食草动物适应寄主植物的防御，这些防御的效果并不是随着时间的推移而静止的，它们会进化出机制来为它们解毒，甚至利用它们来防御捕食者。因此，一种曾经是一种有价值的防御措施的化学品可能会成为一种负担，其生产可能会损失。本项目将研究罗布麻科(罗布麻科)中一组植物防御次生化合物(吡咯里西丁生物碱)的进化。罗布麻科植物次生化合物种类繁多，许多具有药用价值。夹竹桃科成员中的吡咯里西丁生物碱对非适应的食草动物具有高度毒性，但对专业昆虫几乎没有影响，这些昆虫将它们储存在组织中以防御捕食者。研究人员将在罗布麻科中广泛取样，并使用DNA序列数据重建该家族内的进化关系。由此产生的进化树将被用作一个框架，以重建该组内吡咯里西丁生物碱的进化，并更好地了解这些化学物质、产生它们的植物和它们的食草动物之间的关系。本科生将接受不同的分子、进化和生物化学方法的培训。该项目的成果还将被整合到三个机构的本科班级中，其中包括两个以本科为主的机构。这项研究将为医学上重要的罗布麻科植物家族内的进化关系提供新的见解，可用作该家族内更广泛问题的框架。费城自然科学学院的一个展览将向公众广泛传播这项研究的结果，以及有关植物和昆虫防御、化学和共同进化等更广泛主题的信息。这项研究项目中将要检验的最重要的假设是，在高度被昆虫利用的植物谱系中，吡咯里西丁生物碱的多样性将较低，这些植物对这些化合物的影响免疫。为了验证这一假设，研究人员将使用定向浓缩和基因组略读(Hyb-Seq)相结合的方法对APSA分支(夹竹桃科内包括最已知的马利筋蝴蝶寄主植物的谱系)中的287个属中的每一个物种的约850个低拷贝核基因、完整的叶绿体基因组和核核糖体基因进行测序，以生成所需的、解析良好和支持的系统发育和该家族的年表。然后，研究人员将对整个APSA分支的叶片中吡咯里西丁生物碱的存在进行系统调查，并重建吡咯里西丁生物碱表型和潜在生物合成途径的进化，以及在一组物种中的表达和功能分析。然后，将罗布麻科植物中吡咯里西丁生物碱生物合成的起源与达奈亚科植物对吡咯里西丁生物碱的选择年龄进行比较，并检验吡咯里西丁生物碱的损失是否与寄主植物的状况有关。