The olive fruit fly (Bactrocera oleae) is the most destructive pest of the olive cultivation worldwide causing significant production losses and olive fruit impoverishment, as its larvae feed exclusively on the olive fruit. Reproductive and sexual behavior, as well as host-plant recognition of the fly, are highly dependent on its chemosensory system. Therefore, exploring the role of genes that play a critical role in olfaction, could reveal potential molecular targets that determine species-specific features on chemical communication and could be used to impair sexual behavior. In this study we identified the gene that encodes the conserved olfactory co-receptor Orco (Odorant receptor co-receptor), which interacts with all divergent insect odorant receptors, and investigated how disruption of its expression affects chemoreception. We initially searched the expression profile of Bo-Orco in both sexes during sexual maturation, as well as pre- and post-mating communication by relative quantitative real time PCR (qRT-PCR) analysis suggesting that Bo-Orco was abundantly expressed in sexually mature adults. We further investigated the functional role of Bo-Orco in mating and oviposition behavior via transient gene silencing that was performed through in vivo dsRNA hemolymph injections in sexually mature flies 7 days after eclosion. Orco-knockdown phenotypes in both sexes showed reduced copulation rates in mating competitiveness tests, possibly through impaired olfactory-mediated detection of sex pheromone. In addition, oviposition was significantly inhibited in dsRNA-Orco injected females in a post-mating behavior test. Our results demonstrate that Orco plays a crucial role in the reproductive behavior of the olive fruit fly, since pre- and post-mating processes were affected. This is the first report in the olive fruit fly that links the chemosensory pathway with the mating behavior and the reproductive potential at a molecular basis, rendering this gene a potential target for the improvement of the olive fruit fly population control techniques.

中文翻译：

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厌食蝇：Orco沉默对橄榄果蝇的作用

橄榄果蝇（Bactrocera oleae）是全世界橄榄种植中最具破坏力的害虫，由于其幼虫仅以橄榄果为食，因此造成大量的生产损失和橄榄果的贫困。生殖和性行为以及对果蝇的寄主植物识别在很大程度上取决于其化学感应系统。因此，探索在嗅觉中起关键作用的基因的作用，可能揭示潜在的分子靶标，这些靶标决定了化学通讯中特定物种的特征，并可能被用于削弱性行为。在这项研究中，我们确定了编码保守的嗅觉共受体Orco（气味受体共受体）的基因，该基因与所有不同的昆虫气味受体相互作用，并研究了其表达的破坏如何影响化学感受。我们最初通过相对定量实时PCR（qRT-PCR）分析搜索了Bo-Orco在性成熟过程中男女双方的表达谱，以及交配前后的交流，这表明Bo-Orco在性成熟时大量表达大人。我们进一步研究了Bo-Orco通过瞬时基因沉默实现的交配和产卵行为中的功能性作用，该沉默是通过体内dsRNA血淋巴注射在性成熟后7天性成熟蝇体内进行的。在交配能力测试中，两性的Orco击倒表型显示交配率降低，这可能是由于嗅觉介导的性信息素检测受损所致。此外，在交配后行为测试中，dsRNA-Orco注射的雌性的产卵明显受到抑制。我们的结果表明，由于交配前和交配后的过程受到影响，Orco在橄榄果蝇的繁殖行为中起着至关重要的作用。这是橄榄果蝇中第一个将化学感应途径与交配行为和生殖潜能联系起来的报告，使该基因成为改善橄榄果蝇种群控制技术的潜在目标。