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，允许许多猎物与捕食者共存，从而增加了群落的复杂性。特别是，化学防御通常为海洋海绵和藻类以及淡水环境中发现的植物和昆虫提供保护，使其免受捕食者的侵害。一个重要的谜团与捕食者用来检测化学防御和躲避有毒猎物的化学感受器的身份有关。在之前的工作中，McCarty&Amp；Kubanek发现了一种在不同鱼种头部表达的小蛋白质，这似乎解释了为什么海绵化学防御系统在这些鱼被放置在食物中时会被拒绝。这项工作的第一个目标是确定这种名为RL-TGR的蛋白质是如何发挥作用的。第二个目标是确定其他蛋白质，如RL-TGR，是否参与水环境中其他化学防御的化学传感。这些研究将使我们能够更好地理解捕食者和猎物在海洋环境中如何相互作用。该计划包括为多名本科生和研究生提供教育机会，以及与亚特兰大佐治亚州水族馆合作为高中生提供的探索计划。RL-TGR共受体与脊椎动物RAMP蛋白有关，因此该蛋白运输到细胞膜及其后续功能都需要G蛋白偶联受体(GPCR)的共同表达-然而，RL-TGR功能的决定因素尚未确定。该合作项目的目标包括：1)确定RL-TGR在化学感受中的作用机制。斑马鱼(一种模式生物)和蓝头鲸(一种海洋多面手捕食者)都会对食物中含有海绵衍生的威慑化合物做出反应。RL-TGR的解剖分布将通过基因和蛋白质表达方法在斑马鱼和蓝头鲸中定位。RL-TGR的哪些部分调节对化学防御的反应将通过突变、电生理检测和与GPCRs的共表达来确定。将鉴定与RL-TGR在物理和功能上偶联的内源GPCR(S)，以使FISH能够接受化学物质，包括通过质谱学蛋白质组学。2)探索RL-TGR信号转导途径的广泛性和基于萜苷的化学防御。将利用生物信息学方法探索动物体内RL-TGR样共受体的多样性和进化。我们将在使用模式鱼物种的RL-TGR同源基因的表达研究中，比较RL-TGR介导的对不同猎物的不同化学防御配体的结合和生理反应。这些研究将应用关于RL-TGR信号机制的新知识，使人们能够理解RL-TGR在化学防御化学接收中的功能广度。

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.