Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany.
Cell. 2012 Dec 7;151(6):1345-57. doi: 10.1016/j.cell.2012.09.046.
Flies, like all animals, need to find suitable and safe food. Because the principal food source for Drosophila melanogaster is yeast growing on fermenting fruit, flies need to distinguish fruit with safe yeast from yeast covered with toxic microbes. We identify a functionally segregated olfactory circuit in flies that is activated exclusively by geosmin. This microbial odorant constitutes an ecologically relevant stimulus that alerts flies to the presence of harmful microbes. Geosmin activates only a single class of sensory neurons expressing the olfactory receptor Or56a. These neurons target the DA2 glomerulus and connect to projection neurons that respond exclusively to geosmin. Activation of DA2 is sufficient and necessary for aversion, overrides input from other olfactory pathways, and inhibits positive chemotaxis, oviposition, and feeding. The geosmin detection system is a conserved feature in the genus Drosophila that provides flies with a sensitive, specific means of identifying unsuitable feeding and breeding sites.
苍蝇和所有动物一样，需要找到合适和安全的食物。因为黑腹果蝇的主要食物来源是在发酵水果上生长的酵母，所以苍蝇需要从覆盖有毒微生物的酵母中区分出安全的酵母。我们在苍蝇中鉴定出一个功能上分离的嗅觉回路，该回路仅被地衣素激活。这种微生物气味构成了一个生态相关的刺激物，提醒苍蝇注意有害微生物的存在。地衣素仅激活表达嗅觉受体 Or56a 的单一类感觉神经元。这些神经元靶向 DA2 神经丛，并与仅对地衣素作出反应的投射神经元相连接。DA2 的激活足以引起厌恶感，它会忽略来自其他嗅觉途径的输入，并抑制正向趋化性、产卵和进食。地衣素检测系统是果蝇属中的一个保守特征，它为苍蝇提供了一种敏感、特异的识别不适宜的觅食和繁殖场所的方法。
