Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Curr Biol. 2010 Sep 28;20(18):1672-8. doi: 10.1016/j.cub.2010.08.016.
Plants produce insect repellents, such as citronellal, which is the main component of citronellal oil. However, the molecular pathways through which insects sense botanical repellents are unknown. Here, we show that Drosophila use two pathways for direct avoidance of citronellal. The olfactory coreceptor OR83b contributes to citronellal repulsion and is essential for citronellal-evoked action potentials. Mutations affecting the Ca(2+)-permeable cation channel TRPA1 result in a comparable defect in avoiding citronellal vapor. The TRPA1-dependent aversion to citronellal relies on a G protein (Gq)/phospholipase C (PLC) signaling cascade rather than direct detection of citronellal by TRPA1. Loss of TRPA1, Gq, or PLC causes an increase in the frequency of citronellal-evoked action potentials in olfactory receptor neurons. Absence of the Ca(2+)-activated K(+) channel (BK channel) Slowpoke results in a similar impairment in citronellal avoidance and an increase in the frequency of action potentials. These results suggest that TRPA1 is required for activation of a BK channel to modulate citronellal-evoked action potentials and for aversion to citronellal. In contrast to Drosophila TRPA1, Anopheles gambiae TRPA1 is directly and potently activated by citronellal, thereby raising the possibility that mosquito TRPA1 may be a target for developing improved repellents to reduce insect-borne diseases such as malaria.
植物会产生驱虫剂，例如香茅醛，它是香茅油的主要成分。然而，昆虫感知植物驱虫剂的分子途径尚不清楚。在这里，我们表明果蝇使用两种途径来直接避免香茅醛。嗅觉核心受体 OR83b 有助于香茅醛的排斥，并且对于香茅醛引发的动作电位是必需的。影响钙通透阳离子通道 TRPA1 的突变导致对香茅醛蒸气的回避出现类似缺陷。TRPA1 依赖性对香茅醛的厌恶依赖于 G 蛋白（Gq）/磷脂酶 C（PLC）信号级联，而不是 TRPA1 对香茅醛的直接检测。TRPA1、Gq 或 PLC 的缺失导致嗅觉受体神经元中香茅醛引发的动作电位频率增加。钙激活的钾通道（BK 通道）Slowpoke 的缺失导致香茅醛回避的类似损伤和动作电位频率增加。这些结果表明，TRPA1 被要求激活 BK 通道以调节香茅醛引发的动作电位，并对香茅醛产生厌恶。与果蝇 TRPA1 不同，冈比亚按蚊 TRPA1 被香茅醛直接且强效激活，从而提高了蚊子 TRPA1 可能成为开发改进的驱虫剂以减少疟疾等虫媒疾病的目标的可能性。
