Southern Insect Management Research Unit, Agricultural Research Service, United States Department of Agriculture, 141 Experiment Station Road, Stoneville, MS 38776, USA.
Biological Control of Pests Research Unit, Agricultural Research Service, United States Department of Agriculture, 59 Lee Road, Stoneville, MS 38776, USA.
Biomolecules. 2021 Oct 28;11(11):1595. doi: 10.3390/biom11111595.
Olfaction is crucial in mediating various behaviors of social insects such as red imported fire ants, Buren. Olfactory receptor (OR) complexes consist of odor-specific ORs and OR co-receptors (Orco). Orcos are highly conserved across insect taxa and are widely co-expressed with ORs. Odorant binding proteins (OBPs) can transport semiochemicals to ORs as protein carriers and thus constitute the first molecular recognition step in insect olfaction. In this study, three OBP genes highly expressed in antenna, OBP1, OBP5, OBP6, and Orco were partially silenced using RNA interference (RNAi). RNAi SiOBP5- and Orco-injected ants showed significantly lower EAG (electroantennography) responses to fire ant alarm pheromones and the alkaloid, 2,4,6-trimethylpyridine than water- or GFP-injected ants 72 h post injection. Subsequent qRT-PCR analysis demonstrated that the transcript level of the OBP1, OBP5, OBP6, and Orco significantly decreased 72 h after ants were injected with dsRNAs; however, there were no transcript level or EAG changes in ants fed dsRNAs. Our results suggest that Orco and SiOBP5 are crucial to fire ants for their responses to alarm pheromones. RNAi knocking down SiOBP5 can significantly disrupt alarm pheromone communication, suggesting that disrupting SiOBP5 and Orcos could be potentially useful in the management of red imported fire ants.
嗅觉在介导红火蚁等社会性昆虫的各种行为中至关重要。嗅觉受体（OR）复合物由特定气味的 OR 和 OR 共受体（Orco）组成。Orcos 在昆虫分类群中高度保守，广泛与 OR 共表达。气味结合蛋白（OBP）可以作为蛋白载体将信息素运输到 OR 上，因此构成了昆虫嗅觉的第一个分子识别步骤。在这项研究中，使用 RNA 干扰（RNAi）部分沉默了在触角中高度表达的三个 OBP 基因，OBP1、OBP5 和 OBP6 以及 Orco。RNAi SiOBP5 和 Orco 注射的蚂蚁对红火蚁报警信息素和生物碱 2,4,6-三甲基吡啶的 EAG（触角电图）反应明显低于水或 GFP 注射的蚂蚁 72 小时后。随后的 qRT-PCR 分析表明，蚂蚁注射 dsRNA 72 小时后，OBP1、OBP5、OBP6 和 Orco 的转录水平显著降低；然而，喂食 dsRNA 的蚂蚁的转录水平或 EAG 没有变化。我们的结果表明，Orco 和 SiOBP5 对红火蚁对报警信息素的反应至关重要。RNAi 敲低 SiOBP5 可显著破坏报警信息素通讯，表明干扰 SiOBP5 和 Orcos 可能对红火蚁的管理有用。
