Department of Biological Sciences, Vanderbilt University, Nashville, TN, 37235, USA.
Eastern Virginia Medical School, Norfolk, VA, 23507, USA.
Insect Biochem Mol Biol. 2020 May;120:103360. doi: 10.1016/j.ibmb.2020.103360. Epub 2020 Feb 29.
Ammonia is one of the principal kairomones originating from human and other animal emanations and in that context, plays an essential role in the host-seeking behaviors of the malaria vector mosquito Anopheles gambiae. Nevertheless, despite its importance in directing host-seeking, the mechanisms underlying ammonia detection in the mosquito olfactory system remains largely unknown. In addition to ongoing efforts to identify and characterize the molecular receptors that underlie ammonia sensitivity, previous studies have revealed a prominent role for ammonium transporters (Amt) in modulating antennal and behavioral responses in Drosophila melanogaster and An. gambiae. In the former, localization of DmAmt in antennal sensilla to auxiliary cells surrounding the ammonia sensory neurons led to the hypothesis that its role was to clear excess ammonium ions in the sensillar lymph. In the latter, RT-PCR and heterologous expression have been used to examine the expression and functional characteristics of the An. gambiae ammonium transporter, AgAmt. We now employ advanced transgenic tools to comprehensively examine AgAmt spatial localization across the peripheral chemosensory appendages in larvae and adult female An. gambiae. In the larval antennae, AgAmt appears localized in both neuronal and auxiliary cells. In contrast to D. melanogaster, in the adult antennae, AgAmt-derived signals are observed in both non-neuronal auxiliary cells and in sensory neurons in ammonia-responsive basiconic and coeloconic sensilla. In the maxillary palps, labella, and tarsi, AgAmt appears restricted to sensory neurons. We have also characterized the responses to ammonia of adult antennal coeloconic sensilla and maxillary palp capitate pegs revealing a correlation between sensillar AgAmt expression and ammonia sensitivity. Taken together, these data suggest that AgAmt may play heterogeneous roles in the adult and larval chemosensory apparatus and potentially broad utility as a supra-receptor target in mosquito control.
氨是一种主要的信息素，来源于人类和其他动物的散发物，在疟蚊冈比亚按蚊的宿主寻找行为中起着至关重要的作用。然而，尽管它在指导宿主寻找方面很重要，但蚊子嗅觉系统中氨检测的机制在很大程度上仍然未知。除了正在努力识别和表征氨敏感性的分子受体外，先前的研究还揭示了铵转运体（Amt）在调节黑腹果蝇和冈比亚按蚊触角和行为反应中的重要作用。在前者中，DmAmt 在触角感觉细胞周围的辅助细胞中的定位导致了这样的假设，即其作用是清除感觉神经元中多余的铵离子。在后者中，已经使用 RT-PCR 和异源表达来检查冈比亚按蚊铵转运体 AgAmt 的表达和功能特征。我们现在使用先进的转基因工具来全面检查 AgAmt 在幼虫和成年雌性冈比亚按蚊的外周化学感觉附属物中的空间定位。在幼虫触角中，AgAmt 似乎定位于神经元和辅助细胞中。与黑腹果蝇不同，在成年触角中，AgAmt 衍生的信号在对氨有反应的锥形和腔锥形感觉细胞中的非神经元辅助细胞和感觉神经元中都观察到。在触角须、唇瓣和跗节中，AgAmt 似乎局限于感觉神经元。我们还对成年触角腔锥形感觉细胞和触角须帽状突起的氨反应进行了特征描述，揭示了感觉细胞 AgAmt 表达与氨敏感性之间的相关性。总之，这些数据表明，AgAmt 可能在成年和幼虫的化学感觉器官中发挥异构作用，并可能作为蚊子控制的超受体靶标具有广泛的用途。
