Department of Biological Sciences, Vanderbilt University, 465 21st Avenue South, Nashville, TN, 37235, USA.
Department of Biological Sciences, Vanderbilt University, 465 21st Avenue South, Nashville, TN, 37235, USA.
Insect Biochem Mol Biol. 2020 Dec;127:103497. doi: 10.1016/j.ibmb.2020.103497. Epub 2020 Nov 11.
Mosquitoes rely heavily on their olfactory systems for host seeking, selection of oviposition sites, and avoiding predators and other environmental dangers. Of these behaviors, the preferential selection of a human blood-meal host drives the vectorial capacity of anthropophilic female Anopheles coluzzii mosquitoes. Olfactory receptor neurons (ORNs) are dispersed across several appendages on the head and express an obligate odorant receptor co-receptor (Orco) coupled with a "tuning" odorant receptor (OR) to form heteromeric, odor-gated ion channels in the membrane of these neurons. To examine the mechanistic and functional contributions of Orco/OR complexes to the chemosensory processes of An. coluzzii, we utilized CRISPR/Cas9 gene editing to create a line of homozygous, Orco-knockout, mutant mosquitoes. As expected, orco ORNs across both adult and larval stages of An. coluzzii display significantly lower background activity and lack nearly all odor-evoked responses. In addition, blood-meal-seeking, adult female, orco mutant mosquitoes exhibit severely reduced attraction to human- and non-human-derived odors while gravid females are significantly less responsive to established oviposition attractants. These results reinforce observations in other insects that Orco is crucial in maintaining the activity of ORNs. In that light, it significantly influences a range of olfactory-driven behaviors central to the anthropophilic host preference that is critical to the vectorial capacity of An. coluzzii as a primary vector for human malaria.
蚊子在寻找宿主、选择产卵地点以及躲避捕食者和其他环境危险方面严重依赖嗅觉系统。在这些行为中，对人类血液宿主的优先选择驱动了嗜人按蚊雌性蚊子的媒介能力。嗅觉受体神经元（ORNs）分散在头部的几个附肢上，并表达必需的气味受体共受体（Orco）与“调谐”气味受体（OR）相结合，在这些神经元的膜中形成异源二聚体、气味门控离子通道。为了研究 Orco/OR 复合物对按蚊化学感觉过程的机械和功能贡献，我们利用 CRISPR/Cas9 基因编辑技术创建了一条纯合的 Orco 敲除突变蚊子系。正如预期的那样，按蚊的 Orco ORNs 在成虫和幼虫阶段的背景活性明显降低，几乎没有任何气味诱发的反应。此外，觅食血餐的雌性按蚊 Orco 突变体对人类和非人类来源的气味的吸引力严重降低，而怀孕的雌性对已建立的产卵引诱剂的反应性显著降低。这些结果强化了其他昆虫中观察到的 Orco 对维持 ORNs 活性至关重要的观点。从这个角度来看，它显著影响了一系列与嗅觉驱动行为相关的行为，这些行为是按蚊对人类的嗜人性偏好的核心，这对按蚊作为人类疟疾主要媒介的媒介能力至关重要。
