Abstract
Insect attractants are important prevention tools for managing populations of the Oriental fruit fly, Bactrocera dorsalis (Hendel), which is a highly destructive agricultural pest with health implications in tropical and subtropical countries. Methyl eugenol (ME) is still considered the gold standard of B. dorsalis attractants. Mature male flies use their olfactory system to detect ME, but the molecular mechanism underlying their olfactory detection of ME largely remains unclear. Here, we showed that ME activates the odorant receptors OR63a-1 and OR88a in mature B. dorsalis males antennae by RNA-Seq and qRT-PCR analysis. Interestingly, ME only elicited robust responses in the BdorOR88a/BdorOrco-expressing Xenopus oocytes, thus suggesting that BdorOR88a is necessary for ME reception and tropism in B. dorsalis. Next, our indoor behavioral assays demonstrated that BdorOR63a-1 knockdown had no significant effects on ME detection and tropism. By contrast, reducing the BdorOR88a transcript levels led to a significant decrease in the males’ responsiveness to ME. Taken together, our results gave novel insight in the understanding of the olfactory background to the Oriental fruit fly’s attraction toward ME.
Highlights
Insects rely primarily on sophisticated olfactory reception systems to detect and discriminate many exogenous chemical signals, and odorant receptors (ORs) are at the core of odorant detection (Hallem and Carlson, 2006; Missbach et al, 2014; Zhang et al, 2016; Fleischer et al, 2017; Wang et al, 2017)
Based on the results presented here, we infer that BdorOR88a likely plays an essential role in the molecular mechanism underlying B. dorsalis olfactory detection of Methyl eugenol (ME)
Based on the literature and our Gene Ontology (GO)/KEGG enrichment analyses, we identified putative Differentially Expressed Genes (DEGs) encoding proteins involved in insect olfactory transport, viz: three DEGs for odorant binding proteins (BdorOBP57c, BdorOBP5, and BdorOBP2), two for ORs (BdorOR88a and BdorOR63a-1), one encoding an ionotropic receptor (BdorIR92a), and one encoding a sensory neuron membrane protein (BdorSNMP1-1) (Figure 2)
Summary
Insects rely primarily on sophisticated olfactory reception systems to detect and discriminate many exogenous chemical signals, and odorant receptors (ORs) are at the core of odorant detection (Hallem and Carlson, 2006; Missbach et al, 2014; Zhang et al, 2016; Fleischer et al, 2017; Wang et al, 2017). Knockdown of AjapOR35 in Anastatus japonicus reduced its antennal response to two oviposition attractants, β-caryophyllene and (E)-α-farnesene (Wang et al, 2017). In this respect, using a “computational reverse chemical ecology” strategy will likely generate new insights for the rapid screening of potentially effective semiochemicals that modify the behavioral patterns of insects (Siderhurst and Jang, 2006; Wu et al, 2015)
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