Evolution of Secondary Herbivore Defense Metabolite Biosynthesis from Primary Metabolism in the non-model Crucifer Erysimum (wallflower)

本行动资助NSF国家植物基因组计划2018年度生物学博士后研究奖学金。该奖学金支持奖学金获得者在主办实验室的研究和培训计划，该奖学金获得者还提出了扩大生物学参与的计划。Cynthia Holland博士的研究和培训计划的标题是“非模式十字花科植物Erysimum（壁花）初级代谢的次生食草动物防御代谢物生物合成的进化”。该奖学金的主办机构是博伊斯·汤普森研究所，赞助科学家是博伊斯·汤普森博士。乔治·詹德和卢卡斯·穆勒。为了保护自己免受食草昆虫的侵害，植物进化出了各种各样的化学防御。有一类植物防御性代谢物，被称为心脏糖苷，至少在12个植物科中被发现，它的作用是减缓食肉动物心脏的收缩，增加心脏的泵力。尽管这些化合物用于治疗心律失常和充血性心力衰竭，但心脏糖苷生物合成的完整途径尚不清楚任何植物物种。本项目将利用产生心糖苷的虫籽壁花（Erysimum cheiranthoides）来鉴定这些化合物的生物合成途径基因。这些结果将有助于理解其他植物物种中防御化学物质的进化，包括玉米、大豆和小麦等重要作物。培训目标包括代谢组学、遗传学、基因表达技术和生物信息学。更广泛的影响包括通过美国国家科学基金会资助的REU项目，通过指导向代表性不足的学生介绍基因组学和化学生态学研究，向扬克斯（纽约州）一所城市高中的高中生推广，以及为纽约农村的初中和高中教师开发实验室工具包。作为一种生长迅速、自花授粉的一年生植物，cheiranthoides是一个很好的模型系统，可以用来研究一种新的代谢途径的进化，这种途径可以产生心心苷（一种参与食草动物防御的心心苷）。内源性植物类固醇（如油菜素内酯）普遍存在的生物合成途径的修饰，可能在进化过程中被反复选择以产生类似的抗食草动物毒素。本研究将确定在其他十字花科植物中通常参与初级代谢的cheiranthoides酶家族的扩展和新功能。将利用基因组组装和结构-功能序列分析鉴定其他物种已知的栀子内酯生物合成基因的Erysimum同源物。通过比较代谢组学、转录组学、基因组学和正向遗传筛选，将发现梨核内酯途径中缺失的基因。最后，生态“从草食中逃脱”的假设将通过检查心桂树在宿主-昆虫相互作用中的作用来验证。这项研究的结果将通过出版物、会议演讲和包含在www.erysimum.org中分享，www.erysimum.org是一个特定于墙花的网站，它将作为与该项目相关的所有数据的公开访问库。关键词：生物合成生物化学，植物生物胁迫，比较基因组学该奖项反映了美国国家科学基金会的法定使命，并通过基金会的知识价值和更广泛的影响审查标准进行评估，认为值得支持。

This action funds an NSF National Plant Genome Initiative Postdoctoral Research Fellowship in Biology for FY 2018. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Dr. Cynthia Holland is "Evolution of Secondary Herbivore Defense Metabolite Biosynthesis from Primary Metabolism in the non-model Crucifer Erysimum (wallflower)." The host institution for the fellowship is the Boyce Thompson Institute and the sponsoring scientists are Drs. Georg Jander and Lukas Mueller.To protect themselves against insect herbivores, plants have evolved a wide variety of chemical defenses. One class of plant defensive metabolites, known as cardiac glycosides, is found in at least twelve plant families and works by slowing the contractions and increasing the pumping force of the predator's heart. Despite the therapeutic use of these compounds in treating arrhythmias and congestive heart failure, a complete pathway for cardiac glycoside biosynthesis is not known for any plant species. This project will use the cardiac glycoside-producing wormseed wallflower (Erysimum cheiranthoides) to identify the biosynthetic pathway genes for these compounds. These results will contribute to the understanding of the evolution of defensive chemicals in other plant species, including important crops such as maize, soybean, and wheat. Training objectives include metabolomics, genetics, gene expression technologies and bioinformatics. Broader impacts include introducing underrepresented students to genomics and chemical ecology research via mentoring through an NSF-funded REU program, outreach to high school students at an urban high school in Yonkers (NY) and the development of laboratory kits for middle- and high-school teachers in rural New York.As a rapidly-growing, self-pollinating annual, E. cheiranthoides is an excellent model system for investigating the evolution of a new metabolic pathway for the production of cardenolides, a class of cardiac glycosides involved in herbivore defense. Modification of ubiquitous biosynthetic pathways of endogenous plant steroids, e.g. brassinosteroids, has likely been repeatedly selected for in the course of evolution to generate similar anti-herbivore toxins. This research will identify expansion and neofunctionalization of the enzyme families in E. cheiranthoides that normally contribute to primary metabolism in other crucifer species. Erysimum homologs of known cardenolide biosynthetic genes from other species will be identified using genome assemblies and characterized using structure-function-sequence analysis. Missing genes in the cardenolide pathway will be discovered through comparative metabolomics, transcriptomics, genomics, and forward genetic screens. Finally, the ecological "escape from herbivory" hypothesis will be tested by examining the role of cardenolides in host-insect interactions. Results from this research will be shared through publications, presentations at conferences, and inclusion in www.erysimum.org, a wallflower-specific website which will serve as a publicly accessible repository for all data related to this project.Keywords: biosynthesis biochemistry, plant biotic stress, comparative genomicsThis 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.