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

蜘蛛的毒液是一种化学物质的混合物，进化上是为了固定猎物而设计的。在少数被研究的物种中，毒液成分的巨大差异使其余的39000种物种令人兴奋地发现了新的化学物质。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。这项职业补助金将资助一个以本科生为中心的研究项目的发展，该研究项目的重点是棕色隐士蜘蛛及其近亲（蜘蛛科）毒液中一种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）在被这些蜘蛛咬伤后会引起皮肤坏死。SMase D的进化特别有趣，因为这种酶是sicariid spider的毒液和致病菌所特有的，这些致病菌会导致农场动物患病。最近来自PI和合作者的证据表明，这种毒素的进化史包括蜘蛛和细菌之间的横向转移。此外，这种毒素是蜘蛛中一个基因家族的成员，该基因家族在不同成员之间经历周期性的同质化，基因复制和丢失，或者基因的开启和关闭，导致某些物种中SMase D活性的丧失。具体的研究目标是：(1)利用分子系统发育分析解决该谱系中全球代表性物种及其近亲之间的关系；(2)分析毒液表达的SMase D的起源和损失的动态，使用比较酶分析和毒液表达基因（cdna）的分析，从具有这种毒素的整个物种范围；(3)通过探索蜘蛛相关类群的相关基因来完善我们对起源来源的理解。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，并将提供与医学相关的信息。了解SMase D分子的分布和多样性将告诉我们被相关物种咬伤的风险，并将有助于开发有效对抗该蜘蛛家族任何成员咬伤的治疗方法。在这样做的过程中，它将促进人们认识到了解生物毒理学领域的基本系统学、生物多样性和进化的价值。教育目标：这项工作将让本科生参与跨生物和分子的跨学科合作研究。他们将学习用进化（历史）的观点来解决问题的价值。在课程方面，PI将：(1)扩展Lewis & Clark学院的系统发育生物学课程，包括生物信息学、树木拓扑重建和祖先特征状态，以及这些方法的应用；(2)开设一门非专业的机械学课程，强调生物进化方法和综合知识的价值；(3)建立连接到生命之树网站的基于Web的Loxosceles和Sicarius物种多样性交互式诊断键。

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.