Ecophysiology of chemical defense evolution in poison frogs

毒蛙化学防御进化的生态生理学

• 批准号: 2337580
• 负责人: Lauren O'Connell
• 金额: $ 122.7万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-04-15 至 2028-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2337580&HistoricalAwards=false
• 关键词: Ecophysiology; chemical; defense; evolution; poison

Many organisms, including humans, are exposed to a variety of compounds in the diet that may result in toxicity. In nature, some animals have specialized physiology that allow them to ingest toxins without being harmed. Some Central and South American poison frogs can sequester neurotoxins in their diet and repurpose those toxins as a chemical defense from predation. These frogs move the alkaloids from the intestines, through the bloodstream and to the skin where toxins are stored in glands. This project investigates how these frogs cope with ingesting neurotoxins and the results may provide a more complete picture of oral drug distribution, metabolism, and new methods of toxin resistance, because many of the toxins are similar to pharmaceutical drugs used in humans. This research will provide learning experiences to all age groups in both the United States and Ecuador, where research and fieldwork on poison frogs is conducted. High school biology teachers will be involved in summer research and will incorporate their research findings into their science curriculum. This award will also provide research internships for local community college students, and a portion of this research will be conducted in an undergraduate laboratory course at Stanford University. In Ecuador, research will be communicated to the public through educational displays at the Centro Jambatu of Amphibian Research and Conservation in Quito. Poison frogs acquire alkaloid-based chemical defenses from dietary arthropods, although how these lipophilic alkaloids are moved across organs without self-toxicity is unclear. The goal of the proposed research is to understand the physiological mechanisms and convergent evolution of toxin sequestration and autoresistence in poison frogs through three aims: (1) Test the hypothesis that independent evolutionary origins of chemical defense is associated with expression changes of genes whose products are involved in small molecule transport and metabolism. Alkaloid profiles and gene expression in several tissues will be quantified across poison frog species that represent independent origins of chemical defense evolution. (2) Test the hypothesis that alkaloid sequestration evolved by co-opting transporter proteins for either sequestration or excretion. Gene expression profiling across organs in toxic and non-toxic lab-reared poison frogs will be used to identify membrane transporters enriched in tissues that sequester alkaloids. Candidate carriers will be functionally tested in cell-based assays. (3) A serpin protein in poison frogs that can bind a range of alkaloids was recently discovered by the research team. The binding profile of this toxin sponge for various alkaloids will be examined. Whether this toxin sponge is necessary for alkaloid sequestration will be tested through gene knockdown studies. Together, this work will test the hypothesis that chemical defense in poison frogs evolved via multiple mechanisms, each of which occur at a distinct level of organismal organization.This 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.

许多生物体，包括人类，暴露于饮食中可能导致毒性的各种化合物。在自然界中，一些动物具有特殊的生理机能，使它们能够在不受伤害的情况下摄入毒素。一些中美洲和南美洲的毒蛙可以在饮食中吸收神经毒素，并重新利用这些毒素作为免受捕食的化学防御。这些青蛙将生物碱从肠道通过血液转移到皮肤，毒素储存在腺体中。该项目研究了这些青蛙如何科普摄入性神经毒素，结果可能会提供口服药物分布，代谢和毒素抗性新方法的更完整的图片，因为许多毒素与人类使用的药物相似。这项研究将为美国和厄瓜多尔的所有年龄组提供学习经验，这两个国家对毒蛙进行了研究和实地考察。高中生物教师将参与暑期研究，并将他们的研究成果纳入他们的科学课程。该奖项还将为当地社区学院的学生提供研究实习机会，这项研究的一部分将在斯坦福大学的本科实验室课程中进行。在厄瓜多尔，将在基多的两栖动物研究和保护中心通过教育展览向公众宣传研究成果。毒蛙从食草节肢动物获得基于生物碱的化学防御，尽管这些亲脂性生物碱如何在器官间移动而不产生自毒尚不清楚。本研究的目的是通过以下三个方面来了解毒蛙毒素隔离和自身抗性的生理机制和趋同进化：（1）验证化学防御的独立进化起源与小分子转运和代谢产物基因表达变化相关的假说。生物碱配置文件和几个组织中的基因表达将在代表独立起源的化学防御进化的毒蛙物种之间进行量化。(2)检验生物碱螯合是通过选择转运蛋白进行螯合或排泄而进化的假设。在有毒和无毒的实验室饲养的毒蛙器官的基因表达谱将被用来确定在组织中富集的隔离生物碱的膜转运蛋白。候选载体将在基于细胞的试验中进行功能检测。(3)研究小组最近发现了毒蛙中的一种丝氨酸蛋白酶抑制剂蛋白，它可以结合一系列生物碱。将检查该毒素海绵对各种生物碱的结合概况。这种毒素海绵是否是生物碱螯合所必需的，将通过基因敲除研究进行测试。这项工作将共同检验这一假设，即毒蛙的化学防御是通过多种机制进化而来的，每种机制都发生在生物组织的不同层次上。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。