State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China.
CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, People's Republic of China.
BMC Biol. 2022 Sep 30;20(1):214. doi: 10.1186/s12915-022-01411-2.
Odorant receptors (ORs) as odorant-gated ion channels play a crucial role in insect olfaction. They are formed by a heteromultimeric complex of the odorant receptor co-receptor (Orco) and a ligand-selective Or. Other types of olfactory receptor proteins, such as ionotropic receptors (IRs) and some gustatory receptors (GRs), are also involved in the olfactory system of insects. Orco as an obligatory subunit of ORs is highly conserved, providing an opportunity to systematically evaluate OR-dependent olfactory responses.
Herein, we successfully established a homozygous mutant (Orco) of Helicoverpa armigera, a notorious crop pest, using the CRISPR/Cas9 gene editing technique. We then compared the olfactory response characteristics of wild type (WT) and Orco adults and larvae. Orco males were infertile, while Orco females were fertile. The lifespan of Orco females was longer than that of WT females. The expressions of most Ors, Irs, and other olfaction-related genes in adult antennae of Orco moths were not obviously affected, but some of them were up- or down-regulated. In addition, there was no change in the neuroanatomical phenotype of Orco moths at the level of the antennal lobe (including the macroglomerular complex region of the male). Using EAG and SSR techniques, we discovered that electrophysiological responses of Orco moths to sex pheromone components and many host plant odorants were absent. The upwind flight behaviors toward sex pheromones of Orco males were severely reduced in a wind tunnel experiment. The oviposition selectivity of Orco females to the host plant (green pepper) has completely disappeared, and the chemotaxis toward green pepper was also lost in Orco larvae.
Our study indicates that OR-mediated olfaction is essential for pheromone communication, oviposition selection, and larval chemotaxis of H. armigera, suggesting a strategy in which mate searching and host-seeking behaviors of moth pests could be disrupted by inhibiting or silencing Orco expression.
气味受体（ORs）作为气味门控离子通道，在昆虫嗅觉中起着至关重要的作用。它们由气味受体共受体（Orco）和配体选择性 Or 组成的异源多聚体复合物形成。其他类型的嗅觉受体蛋白，如离子型受体（IRs）和一些味觉受体（GRs），也参与昆虫的嗅觉系统。Orco 作为 ORs 的必需亚基高度保守，为系统评估 OR 依赖性嗅觉反应提供了机会。
本文利用 CRISPR/Cas9 基因编辑技术成功建立了一种鳞翅目害虫棉铃虫的纯合突变体（Orco）。然后，我们比较了野生型（WT）和 Orco 成虫和幼虫的嗅觉反应特征。Orco 雄虫不育，而 Orco 雌虫可育。Orco 雌虫的寿命长于 WT 雌虫。Orco 雄蛾触角中大多数 Ors、Irs 和其他嗅觉相关基因的表达没有明显受到影响，但有些基因表达上调或下调。此外，Orco 雄蛾触角的神经解剖表型在触角叶水平（包括雄蛾的大球型复合区）没有变化。利用 EAG 和 SSR 技术，我们发现 Orco 雄蛾对性信息素成分和许多寄主植物气味的电生理反应缺失。在风洞实验中，Orco 雄蛾对性信息素的上风向飞行行为严重减少。Orco 雌蛾对寄主植物（青椒）的产卵选择性完全丧失，Orco 幼虫对青椒的趋化性也丧失。
本研究表明，OR 介导的嗅觉对棉铃虫的性信息素通讯、产卵选择和幼虫趋化性至关重要，这表明通过抑制或沉默 Orco 的表达，可以破坏鳞翅目害虫的求偶和寻找寄主行为的策略。
