Zhang Liwei, Li Hongwei, Zhang Long
Department of Entomology, China Agricultural University, Beijing 100193, PR China.
Int J Biol Sci. 2017 May 27;13(6):759-771. doi: 10.7150/ijbs.19820. eCollection 2017.
Sensing chemical cues is crucial for insects through their olfactory systems to adapt the environments. The receptors employed in insect olfactory system belong to the Odorant Receptor (ORs) and Ionotropic Receptor (IRs) families. In general, ORs and IRs are present in distinct olfactory sensory neurons and function independently. Here, we present evidence that in locust, the abundant host plant odor Hexanal is detected by both IR- and OR-expressing neurons. Use of the palp opening response (POR) as a simple behavioral paradigm in conjunction with RNA interference (RNAi) revealed that these two pathways are both needed for the detection of Hexanal. Two-color fluorescence hybridization showed that OR2 and odorant-binding protein 1 (obp1) were co-localized in palps sensilla basiconica. Obp2a and IR8a were co-localized as well, but associated with sensilla chaetica on the palps. Furthermore, both OR2- and obp1-knockdowns showed reduced POR responses to Hexanal and E-2-Hexenal, and the same was true for Hexanal with IR8a- and obp2a-knockdowns. Detection to E-2-Hexenal was independent of IR8a-mediated gene silencing. Besides, Hexanal and E-2-Hexenal evoked dose-dependent responses in palp basiconica via extracellular recordings. Our results indicate that both OR and IR pathways are involved in the detection of one aldehyde.
通过嗅觉系统感知化学信号对于昆虫适应环境至关重要。昆虫嗅觉系统中使用的受体属于气味受体（ORs）和离子型受体（IRs）家族。一般来说，ORs和IRs存在于不同的嗅觉感觉神经元中并独立发挥作用。在此，我们提供证据表明，在蝗虫中，表达IR和OR的神经元均可检测到丰富的寄主植物气味己醛。将触须开口反应（POR）作为一种简单的行为范式与RNA干扰（RNAi）结合使用，结果表明这两条途径对于己醛的检测均是必需的。双色荧光杂交显示，OR2和气味结合蛋白1（obp1）共定位于触须锥形感器中。Obp2a和IR8a也共定位，但与触须上的毛形感器相关。此外，OR2和obp1基因敲低均显示对己醛和反-2-己烯醛的POR反应降低，IR8a和obp2a基因敲低对己醛的反应也是如此。对反-2-己烯醛的检测独立于IR8a介导的基因沉默。此外，通过细胞外记录，己醛和反-2-己烯醛在触须锥形感器中引发剂量依赖性反应。我们的结果表明，OR和IR途径均参与一种醛类的检测。
