CAREER: Venom Evolution in Sicariid Spiders: A System for Undergraduate Training in Integrative Biology

蜘蛛毒液是一种化学物质的混合物，经过进化设计，用于固定猎物。在为数不多的被研究物种中，毒液成分的巨大差异使其余39,000种物种成为发现新化学的令人兴奋的来源。此外，这种化学多样性为研究创造新毒素并随时间改变它们的进化机制提供了很好的背景。这项事业补助金将资助以本科生为中心的研究计划的发展，重点是棕色隐士蜘蛛及其亲属（Sicariidae）毒液中独特且具有医学重要性的毒素的进化起源和多样化。这种毒素，鞘磷脂酶D（SMase D）在这些蜘蛛叮咬后引起皮肤坏死性病变。SMase D的进化是特别有趣的，因为这种酶是蜘蛛毒液和导致农场动物疾病的病原菌所特有的。PI和合作者最近的证据表明，这种毒素的进化历史包括蜘蛛和细菌之间的横向转移。此外，该毒素是蜘蛛中一个基因家族的成员，在不同的成员之间经历周期性的同质化，基因的重复和丢失，或基因的开启和关闭，导致某些物种SMase D活性的丧失。（2）通过比较酶分析和来自具有该毒素的整个物种范围的毒液表达基因（cDNA）分析，分析毒液表达的SMase D的起源和损失的动态;（3）通过探测相关蜘蛛群体中的相关基因来完善我们对起源的理解。了解SMase D的起源和多样化机制将作为一种独特毒素分子进化的案例研究，并将提供医学相关信息。了解SMase D分子的分布和多样性将使我们了解相关物种叮咬的风险，并有助于开发有效对抗该蜘蛛家族任何成员叮咬的治疗方法。在这样做的时候，它将促进了解基本系统学，生物多样性和生物毒理学领域的进化的价值意识。教育目标：这项工作将涉及跨生物和分子的合作，跨学科的研究本科生。他们将学习以进化（历史）的视角处理问题的价值。在课程方面，PI将：（1）扩展刘易斯克拉克学院的系统发育生物学课程，包括生物信息学，树拓扑结构和祖先特征状态的重建，以及这些方法的应用;（2）创建一个非专业的蜘蛛学课程，强调进化方法的价值和有机体的综合知识;（3）创建一个基于网络的交互式诊断键，用于Loxosceles和Sicarius物种多样性，并连接到生命之树网站。

Spider venoms are cocktails of chemicals evolutionarily designed for prey immobilization. Large differences in venom composition among the few studied species make the rest of the 39,000 species exciting sources of discovery of novel chemistry. Moreover, this chemical diversity makes a great context for studying evolutionary mechanisms that create novel toxins and modify them over time. This CAREER grant will fund development of an undergraduate-centered research program focused on the evolutionary origin and diversification of a unique and medically important toxin in venoms of brown recluse spiders and their relatives (Sicariidae). This toxin, sphingomyelinase D (SMase D) causes dermonecrotic lesions after bites of these spiders. The evolution of SMase D is particularly interesting because this enzyme is unique to venoms of sicariid spiders and pathogenic bacteria that cause disease in farm animals. Recent evidence from the PI and collaborators indicates that the evolutionary history of this toxin includes lateral transfer between spiders and bacteria. Furthermore, this toxin is a member of a gene family in spiders that undergoes periodic homogenization among different members, and either gene duplication and loss, or turning on and off of genes, which has resulted in loss of SMase D activity in some species.The specific research goals are to: (1) resolve relationships among worldwide representatives of species in this lineage and their close relatives using molecular phylogenetic analyses; (2) analyze the dynamics of origin and loss of venom-expressed SMase D using comparative enzyme assays and analyses of venom-expressed genes (cDNAs) from across the complete range of species with this toxin; (3) refine our understanding of the source of origin by probing for related genes in related groups of spiders. Understanding the mechanisms of origin and diversification of SMase D will serve as a case study of the molecular evolution of a unique toxin, and will provide information of medical relevance. Understanding the distribution and diversity of the SMase D molecule will inform us about the risks of bites from related species, and will aid in the development of treatments that are effective against bites of any member of this spider family. In so doing, it will promote awareness of the value of understanding basic systematics, organismal diversity, and evolution for the field of biological toxicology.Educational goals: This work will involve undergraduates in collaborative, interdisciplinary research that spans organisms and molecules. They will learn the value of approaching questions with an evolutionary (historical) perspective. In coursework, the PI will: (1) expand a phylogenetic biology course at Lewis & Clark College that includes bioinformatics, reconstruction of tree topologies and ancestral character states, and applications of these methods; (2) create a non-majors arachnology course that emphasizes the value of evolutionary approaches and integrated knowledge of organisms; (3) create a Web-based interactive diagnostic key for Loxosceles and Sicarius species diversity that is connected to the Tree of Life Web site.