Molecular basis for the detection of nutrients and toxins by the honeybee

蜜蜂检测营养物质和毒素的分子基础

基本信息

批准号：
BB/M00709X/1
负责人：
Geraldine Wright
金额：
$ 64.07万
依托单位：
Newcastle University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FM00709X%2F1
关键词：
Molecular basis detection nutrients toxins

项目摘要

Our sense of taste is our primary means of detecting nutrients and toxins in food, and its function is important for our health and well-being. The principles of gustation are shared in mammals and insects making it possible to use insects as model organisms to understand how chemical information is detected and encoded by the gustatory system. When animals ingest food, nutrients like sugars are detected by cells in taste buds on the tongue, and in insects by neurons in chemosensory sensilla. In general, the gustatory system is organized such that a subset of gustatory cells or neurons is excited by sugars, whereas others are excited by toxic (bitter) compounds, by amino acids, by salts, or by water. In insects, gustatory receptors (Grs) on the membranes of taste neurons selectively bind to classes of chemical compounds (e.g. sugars) and their activation indicates which compounds are present in food. Animals may have as many as a few hundred Grs, but millions of potential ligands exist. We do not know how Gr diversity affords the detection and classification of chemical compounds. Decoding gustation, therefore, first requires the identification of the nutrients or toxins that activate specific Grs in one animal species. This could then be related to the response properties of its Gr neurons and to its taste perception and acuity. The research proposed here will develop the honeybee as a model system for understanding the logic of the gustatory code. The honeybee has only 10 Gr genes - the least reported from insects with sequenced genomes. Based on sequence homology with Drosophila and what we know about the structure of the bee's Gr genes, we predict it has less than 20 functional Grs. For this reason, it would be possible to identify the chemical ligands for the Grs produced by these genes with the aim of using the bee as a model to understand the principles of gustatory coding. Having few Gr genes makes the bee a tractable model system in contrast to Drosophila with its 60 genes. Ligands have been determined for only 13 Drosophila Grs.This proposal describes a project that will use two approaches to identify the ligands for the receptors associated with the honeybee's Gr genes. Using a 'gain-of-function' approach, we will employ a newly-developed transgenic fruit fly line in which all of the putative genes for sugar receptors have been knocked out. Each of the bee's Gr genes will be expressed in this line. Flies from each bee Gr line will be assayed using calcium imaging of their tarsal gustatory neurons. By stimulating with a series of ligands, we will be able to identify whether functional receptors are produced by the expression of single Gr genes and to identify their Grs' ligands. Based on what we know about fruit fly sugar receptors and their bee homologues, we will also test whether expression of multiple Gr genes that encode sugar receptors is necessary to form functional Grs. We do not know if several Gr genes must be expressed to form functional receptors for the detection of compounds other than sugars. For this reason, we must also use a 'loss-of-function' approach in which we knock down expression of each Gr gene in vivo in the bee using small-interfering RNA (siRNA). Using this method, we will knock down expression of each Gr gene and assay the bee's taste neurons using electrophysiology and behaviour. We will test a suite of nutrients and toxic compounds that includes common pesticides encountered by bees in flowering crops. In spite of the fact that bees have only 10 Gr genes, they are still able to detect some toxins and to regulate their intake of nutrients like sugars and amino acids that are detected by Grs. The experiments proposed here will reveal how the bee's few Gr genes translates into the spectrum of what it can taste and will lead to future work that identifies how populations of Gr neurons encode information about the chemical nature and complexity of food.

我们的味觉是检测食物中营养成分和毒素的主要手段，其功能对于我们的健康和福祉非常重要。哺乳动物和昆虫具有相同的味觉原理，因此可以使用昆虫作为模式生物来了解味觉系统如何检测和编码化学信息。当动物摄入食物时，舌头上的味蕾细胞会检测到糖等营养物质，而昆虫则通过化学感应器中的神经元检测到。一般来说，味觉系统的组织方式使得一部分味觉细胞或神经元被糖兴奋，而其他味觉细胞或神经元则被有毒（苦味）化合物、氨基酸、盐或水兴奋。在昆虫中，味觉神经元膜上的味觉受体（Grs）选择性地与一类化合物（例如糖）结合，它们的激活表明食物中存在哪些化合物。动物可能有多达几百 Grs，但存在数百万个潜在配体。我们不知道 Gr 多样性如何提供化合物的检测和分类。因此，解码味觉首先需要识别激活某一动物物种中特定 Grs 的营养物质或毒素。这可能与其 Gr 神经元的反应特性及其味觉和敏锐度有关。这里提出的研究将把蜜蜂开发为理解味觉代码逻辑的模型系统。蜜蜂只有 10 个 Gr 基因，这是基因组测序昆虫中报道最少的基因。根据与果蝇的序列同源性以及我们对蜜蜂 Gr 基因结构的了解，我们预测它有不到 20 个功能性 Gr。因此，有可能鉴定这些基因产生的 Grs 的化学配体，目的是使用蜜蜂作为模型来理解味觉编码的原理。与拥有 60 个基因的果蝇相比，Gr 基因很少，使得蜜蜂成为易于处理的模型系统。仅确定了 13 种果蝇 Grs 的配体。该提案描述了一个项目，该项目将使用两种方法来识别与蜜蜂 Gr 基因相关的受体的配体。通过“功能获得”方法，我们将采用新开发的转基因果蝇品系，其中所有假定的糖受体基因都已被敲除。蜜蜂的每个 Gr 基因都将在该品系中表达。来自每只蜜蜂 Gr 系的苍蝇将使用其跗骨味觉神经元的钙成像进行分析。通过一系列配体的刺激，我们将能够鉴定功能性受体是否是由单个Gr基因的表达产生的，并鉴定其Grs的配体。根据我们对果蝇糖受体及其蜜蜂同源物的了解，我们还将测试编码糖受体的多个 Gr 基因的表达是否是形成功能性 Grs 所必需的。我们不知道是否必须表达几个 Gr 基因才能形成检测糖以外的化合物的功能受体。因此，我们还必须使用“功能丧失”方法，即使用小干扰 RNA (siRNA) 敲低蜜蜂体内每个 Gr 基因的表达。使用这种方法，我们将敲低每个 Gr 基因的表达，并利用电生理学和行为分析蜜蜂的味觉神经元。我们将测试一系列营养物质和有毒化合物，其中包括蜜蜂在开花作物中遇到的常见农药。尽管蜜蜂只有 10 个 Gr 基因，但它们仍然能够检测到一些毒素并调节 Grs 检测到的糖和氨基酸等营养物质的摄入量。这里提出的实验将揭示蜜蜂的少数 Gr 基因如何转化为它能尝到的味道的范围，并将导致未来的工作确定 Gr 神经元群体如何编码有关食物的化学性质和复杂性的信息。