Molecular genetics of contact chemosensation

描述(申请人提供)：拟议研究的长期目标是阐明果蝇通过接触性化学传感检测和识别化学物质的分子机制。接触式化学感受器使苍蝇能够区分甜味和苦味分子，以及非挥发性信息素。昆虫的味觉器官表达多种候选分子探测器。这些受体包括味觉受体(GRs)、Trp通道、离子受体(IR)和气味结合蛋白(OBP)，后者通过受体蛋白促进对化学物质的检测。然而，这些候选味觉受体和结合蛋白中的大多数功能尚不清楚，或者知之甚少。我们建议进行实验，使用包括电生理学、行为学、遗传学和细胞生物学方法在内的多学科方法来剖析苍蝇接触性化学感觉的潜在机制。在过去的几年里，GRs被广泛用于感测糖类和苦味化合物的概念已经得到证实。然而，GRs的生化功能尚不清楚。目的1是验证GRs是味觉激活的阳离子通道的假设。目标2解决了味觉中一个长期存在的问题--酸味感受器的性质。这些受体被认为是阳离子通道，已经提出了许多候选方案。我们建议进行实验，分析是否对大多数酸味的反应需要IR，哪些细胞需要IR，并研究另外两个主要在味觉感受器神经元中表达的IR的作用。目标3致力于描述气味结合蛋白(OBP)在接触性化学感觉中的作用。众所周知，OBP主要是为了促进某些嗅觉刺激的检测。我们发现，一些OBP在味觉器官中高度浓缩，是其他组织的800倍。实验是为了验证味觉OBP促进由非挥发性信息素介导的行为的假设。最后，我们的最终目标是剖析选择性味觉可塑性的分子、细胞和生物学基础。我们提供的初步数据表明，暴露在樟脑中的苍蝇减少了对樟脑而不是其他苦味剂的排斥，这种味道可塑性是色氨酸通道水平降低的结果。目标4是区分这种味觉可塑性背后的不同可能的模型，并解决适应某些(但不是所有)不吸引人的味觉的生物学基础。这项研究的另一个长期目标是将研究结果应用于控制传播疾病的害虫。

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to clarify the molecular mechanisms underlying the detection and discrimination of chemicals through contact chemosensation in the fruit fly, Drosophila melanogaster. Contact chemosensation allows flies to distinguish sweet from bitter molecules, as well as nonvolatile pheromones. Insect gustatory organs express a diversity of candidate molecular detectors. These include gustatory receptors (GRs), TRP channels, ionotropic receptors (IRs) and odorant binding proteins (OBPs), the latter of which promote the detection of chemicals by receptor proteins. However, the functions of most of these candidate gustatory receptors and binding proteins are unknown, or are understood poorly. We propose experiments to dissect the mechanisms underlying contact chemosensation in flies using a multidisciplinary approach that includes electrophysiology, behavior, genetics, and cell biological approaches. During the last few years, the concept that GRs are required broadly for sensing sugars and bitter-tasting compounds has been confirmed. However, the biochemical functions of GRs are unclear. Aim 1 is to test the hypothesis that GRs are tastant-activated cation channels. Aim 2 addresses one of the longstanding questions in taste sensation- the nature of sour receptors. These receptors are thought to be cation channels, and many candidates have been suggested. We propose experiments to dissect whether an IR is required for the responses to most sour tastants, which cells require the IR, and investigate the contributions of two other IRs that are expressed primarily in gustatory receptor neurons. Aim 3 is devoted to characterizing the roles for odorant binding proteins (OBPs) in contact chemosensation. OBPs are known primarily for promoting the detection of certain olfactory stimuli. We found that some OBPs are highly enriched in taste organs up to 800- fold over other tissues. Experiments are proposed to test the hypothesis that gustatory OBPs promote behaviors mediated by nonvolatile pheromones. Finally, the goal of our last aim is to dissect the molecular, cellular and biological basis for selective taste plasticity. We present preliminary data indicating that flies exposed to camphor reduce their repulsion specifically to camphor and not other bitter tastants, and this taste plasticity results from a reduction in the level of a TRP channel. Aim 4 is to distinguish between different possible models underlying this taste plasticity, and to address the biological basis for adaptation to some, but not all, unappealing tastants. An additional long-term goal of this research is to apply the findings to the control of insect pests that spread disease.