Aphidophagous syrphids (Diptera: Syrphidae) are important insects in agroecosystems for pollination and biological control. Insect chemoreception is essential for these processes and for insect survival and reproduction; however, molecular determinants is not well understood for these beneficial insects. Here, we used recent transcriptome data for the common hoverfly, Episyrphus balteatus, to characterize key molecular components of chemoreception: odorant-binding proteins (OBPs) and chemosensory proteins (CSPs). Six EbalCSPs and 44 EbalOBPs were cloned from this species, and sequence analysis showed that most share the characteristic hallmarks of their protein family, including a signal peptide and conserved cysteine signature. Some regular patterns and key conserved motifs of OBPs and CSPs in Diptera were identified using the online tool MEME. Motifs were also compared among the three OBP subgroups. Quantitative real-time PCR (qRT-PCR) showed that most of these chemosensory genes were expressed in chemosensory organs, suggesting these genes have chemoreceptive functions. An overall comparison of the Ka/Ks values of orthologous genes in E. balteatus and another predatory hoverfly species to analyze the evolution of these olfactory genes showed that OBPs and CSPs are under strong purifying selection. Overall, our results provide a molecular basis for further exploring the chemosensory mechanisms of E. balteatus, and consequently, may help us to understand the tritrophic interactions among plants, herbivorous insects, and natural enemies.

中文翻译：

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上皮淫羊（（Diptera：Syrphidae）中的气味结合蛋白和化学感应蛋白：分子克隆，表达谱分析和基因进化。

蚜虫蚜虫（双翅目：Syrphidae）是农业生态系统中用于授粉和生物防治的重要昆虫。昆虫化学感受对于这些过程以及昆虫的生存和繁殖至关重要。然而，对于这些有益的昆虫，分子决定因素还不是很了解。在这里，我们使用了最近的转录组数据来分析常见的蚜蝇（Episyrphus balteatus），以表征化学感受的关键分子成分：气味结合蛋白（OBP）和化学感应蛋白（CSP）。从该物种克隆了6个EbalCSP和44个EbalOBP，序列分析表明，大多数具有其蛋白家族的特征性标志，包括信号肽和保守的半胱氨酸特征。使用在线工具MEME鉴定了Diptera中OBP和CSP的一些规则模式和关键的保守基序。还对三个OBP子组的主题进行了比较。实时定量PCR（qRT-PCR）显示，大多数这些化学感应基因在化学感应器官中表达，表明这些基因具有化学感受功能。鲍氏大肠杆菌中直系同源基因Ka / Ks值的总体比较另一个捕食性的蚜蝇物种分析了这些嗅觉基因的进化，表明OBP和CSP处于强纯化选择之下。总体而言，我们的结果为进一步探索巴氏大肠杆菌的化学感应机制提供了分子基础，因此，可能有助于我们了解植物，草食性昆虫和天敌之间的三养相互作用。