Collaborative research: Chemoreception of prey chemical defenses

化学防御是生物体与环境相互作用的主要机制，通过允许许多猎物与捕食者共存来增加群落的复杂性。特别是，化学防御通常为海洋海绵和藻类以及淡水环境中的植物和昆虫提供保护，使其免受捕食者的侵害。一个重要的谜团是关于捕食者用来探测化学防御和躲避有毒猎物的化学感受器的身份。在之前的工作中，McCarty & Kubanek发现了一种在各种鱼类头部中表达的小蛋白质，这似乎解释了为什么海绵化学防御被这些鱼类放在食物中时会被它们拒绝。这项工作的第一个目标是确定这种名为RL-TGR的蛋白质是如何起作用的。第二个目标是确定其他蛋白质，如RL-TGR，是否参与水生环境中其他化学防御的化学感知。这些研究将使人们对捕食者和猎物在海洋环境中如何相互作用有一个新的认识。该项目包括为本科生和研究生提供的教育机会，以及为与亚特兰大乔治亚水族馆有关的高中生提供的探索项目。“RL-TGR”共受体与脊椎动物RAMP蛋白相关，因此该蛋白转运到细胞膜及其随后的功能都需要g蛋白偶联受体（GPCR）的共表达。然而，RL-TGR功能的决定因素尚未确定。合作项目的目标包括：1)确定RL-TGR在化学接受中的作用机制。斑马鱼（一种模式生物）和蓝头濑鱼（一种海洋多面手捕食者）都对食物中含有海绵体衍生的威慑化合物做出反应。RL-TGR在斑马鱼和蓝头濑鱼中的解剖分布将采用基因和蛋白表达的方法进行定位。RL-TGR的哪些部分调节对化学防御的反应将通过诱变、电生理测定和与gpcr共表达来确定。内源性GPCR(s)与RL-TGR在物理和功能上偶联，使鱼类能够接受化学反应，将被鉴定，包括通过质谱蛋白质组学。2)探索RL-TGR信号和萜烯苷化学防御的广度。动物rl - tgr样共受体的多样性和进化将利用生物信息学方法进行探讨。我们将比较RL-TGR介导的结合和对来自不同猎物的各种化学防御配体的生理反应，并使用来自模式鱼类的RL-TGR同源物进行表达研究。这些研究将应用有关RL-TGR信号传导机制的新知识，以了解RL-TGR在化学防御化学接受中的功能广度。

Chemical defenses are a major mechanism by which organisms interact with their environment, increasing community complexity by allowing many prey to co-occur with predators. In particular, chemical defenses commonly provide protection from predators for marine sponges and algae, as well as plants and insects found in freshwater environments. An important mystery regards the identity of chemoreceptors used by predators to detect chemical defenses and avoid noxious prey. In previous work, McCarty & Kubanek discovered a small protein expressed in the heads of various fish species that appears to explain why sponge chemical defenses are rejected by these fish when placed in their food. The first goal of this work is to determine how this protein, named RL-TGR, functions. The second goal is to determine whether other proteins, like RL-TGR, are involved in chemical sensing of other chemical defenses in aquatic environments. These studies will enable a new level of understanding of how predators and prey interact in the marine environment. This program includes educational opportunities for multiple undergraduates and graduate students, as well as an exploration program for high school students in association with the Georgia Aquarium in Atlanta.The "RL-TGR" co-receptor is related to vertebrate RAMP proteins and thereby both the trafficking of this protein to cell membranes and its subsequent function require co-expression of a G-protein coupled receptor (GPCR) - however, the determinants of RL-TGR function have yet to be identified. Objectives of the collaborative project include the following: 1) Determine the mechanism of action of RL-TGR in chemoreception. Both zebrafish (a model organism) and bluehead wrasse (a marine generalist predator) respond to the presence of sponge-derived deterrent compounds laced into their food. The anatomical distribution of RL-TGR will be mapped in zebrafish and bluehead wrasse using both gene and protein expression approaches. Which portions of RL-TGR modulate responses to chemical defenses will be determined using mutagenesis, electrophysiological assays, and co-expression with GPCRs. The endogenous GPCR(s) that physically and functionally couple with RL-TGR to enable chemoreception by fish will be identified, including via mass spectrometric proteomics. 2) Explore the breadth of RL-TGR signaling and terpene glycoside-based chemical defense. The diversity and evolution of RL-TGR-like co-receptors in animals will be explored using bioinformatic approaches. We will compare RL-TGR-mediated binding and physiological responses to various chemical defense ligands from diverse prey in expression studies using RL-TGR orthologs from model fish species. These studies will apply new knowledge about the mechanism of RL-TGR signaling to enable an understanding of the breadth of RL-TGR function in chemical defense chemoreception.