Institute of Integrative Plant Biology, Jiangsu Key Laboratory of Phylogenomics & Comparative Genomics, School of Life Sciences, Jiangsu Normal University, Jiangsu, China.
Sweet Potato Laboratory, Maize Research Institute, Guangxi Academy of Agricultural Sciences, Guangxi, China.
Pest Manag Sci. 2021 Jan;77(1):300-312. doi: 10.1002/ps.6019. Epub 2020 Aug 16.
The sweet potato weevil, Cylas formicarius, is the most serious pest of sweet potato worldwide. The molecular mechanism of sex pheromone recognition in C. formicarius has not been reported. Odorant-binding proteins (OBPs) play a critical role in selectively binding and transporting pheromones or other odors to the surface of olfactory receptor neurons through the aqueous sensillar lymph, therefore the function of sweet potato OBPs is worth studying.
Herein, the CforOBP1-3 genes encoding three classical OBPs were cloned in C. formicarius by reverse transcription-polymerase chain reaction. Phylogenetic analysis showed that CforOBP1-3 were homologous genes, but the relationship between CforOBP2 and CforOBP3 was closest among the three genes. In addition, real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays demonstrated that the expression of CforOBP1 was higher in the antennae and legs of female and male insects, while CforOBP2 and CforOBP3 were mainly expressed in the antennae of male insects. The fluorescent competitive binding assay results indicated that CforOBP1-3 had strong binding affinities to sex pheromones and other tested ligands. Finally, the mRNA expression of CforOBP1-3 was successfully inhibited by RNA interference, and in vivo behavioral experiments showed that CforOBP1-3-deficient C. formicarius was partly anosmic and lost some of its ability to locate sex pheromones and host plant volatiles.
These results suggested that CforOBP1 was shown to be involved in the process of weevils feeding and finding sweet potato, and CforOBP2-3 were mainly involved in the mating behavior of adult male weevils.
甘薯小象甲，Cylas formicarius，是世界范围内甘薯最严重的害虫。C. formicarius 性信息素识别的分子机制尚未报道。气味结合蛋白（OBPs）在选择性结合和将信息素或其他气味通过水敏感器淋巴转运到嗅觉受体神经元表面方面起着关键作用，因此研究甘薯 OBPs 的功能是值得的。
本文通过反转录聚合酶链反应（RT-PCR）从甘薯小象甲中克隆了编码三个经典 OBPs 的 CforOBP1-3 基因。系统发育分析表明，CforOBP1-3 是同源基因，但在这三个基因中，CforOBP2 和 CforOBP3 之间的关系最为密切。此外，实时定量 RT-PCR（qRT-PCR）分析表明，CforOBP1 在雌性和雄性昆虫的触角和腿中表达水平较高，而 CforOBP2 和 CforOBP3 主要在雄性昆虫的触角中表达。荧光竞争结合试验结果表明，CforOBP1-3 对性信息素和其他测试配体具有较强的结合亲和力。最后，通过 RNA 干扰成功抑制了 CforOBP1-3 的 mRNA 表达，体内行为实验表明，C. formicarius 中的 CforOBP1-3 缺陷导致部分嗅觉丧失，并部分丧失了定位性信息素和寄主植物挥发物的能力。
这些结果表明 CforOBP1 参与了象甲的进食和寻找甘薯的过程，而 CforOBP2-3 主要参与了成年雄性象甲的交配行为。
