Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, 07745 Jena, Germany; Research Group Olfactory Coding, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, 07745 Jena, Germany.
Curr Biol. 2023 Nov 20;33(22):4771-4785.e7. doi: 10.1016/j.cub.2023.09.039. Epub 2023 Oct 6.
Olfaction is a fundamental sense guiding animals to their food. How the olfactory system evolves and influences behavior is still poorly understood. Here, we selected five drosophilid species, including Drosophila melanogaster, inhabiting different ecological niches to compare their olfactory systems at multiple levels. We first identified ecologically relevant natural food odorants from every species and established species-specific odorant preferences. To compare odor coding in sensory neurons, we analyzed the antennal lobe (AL) structure, generated glomerular atlases, and developed GCaMP transgenic lines for all species. Although subsets of glomeruli showed distinct tuning profiles, odorants inducing species-specific preferences were coded generally similarly. Species distantly related or occupying different habitats showed more evident differences in odor coding, and further analysis revealed that changes in olfactory receptor (OR) sequences partially explain these differences. Our results demonstrate that genetic distance in phylogeny and ecological niche occupancy are key determinants in the evolution of ORs, AL structures, odor coding, and behavior. Interestingly, changes in odor coding among species could not be explained by evolutionary changes at a single olfactory processing level but rather are a complex phenomenon based on changes at multiple levels.
嗅觉是引导动物寻找食物的基本感觉。嗅觉系统如何进化以及影响行为仍然知之甚少。在这里，我们选择了五种果蝇物种，包括生活在不同生态位的黑腹果蝇，以在多个层面比较它们的嗅觉系统。我们首先从每个物种中鉴定出与生态相关的天然食物气味，并建立了物种特异性的气味偏好。为了比较感觉神经元中的气味编码，我们分析了触角叶（AL）的结构，生成了肾小球图谱，并为所有物种开发了 GCaMP 转基因系。尽管亚群的肾小球显示出不同的调谐谱，但诱导物种特异性偏好的气味通常编码方式相似。亲缘关系较远或占据不同栖息地的物种在气味编码方面表现出更明显的差异，进一步的分析表明，嗅觉受体（OR）序列的变化部分解释了这些差异。我们的研究结果表明，系统发育和生态位占据中的遗传距离是 OR、AL 结构、气味编码和行为进化的关键决定因素。有趣的是，物种间气味编码的变化不能用单一嗅觉处理水平的进化变化来解释，而是基于多个水平的变化的复杂现象。
