Camphor oil (EO) and its main component (i.e. d-camphor) form specific terpenoid defences in camphor trees, Cinnamomum camphora. However, an emerging insect pest, Pagiophloeus tsushimanus (Coleoptera: Curculionidae) has recently caused serious damage to this intractable plant species, which is largely elusive. To investigate the mechanism underlying the tolerance of this weevil to host-specific terpenoid defences, we carried out the bioassays, RNA-seq, and RT-qPCR analysis based on a simulated diet environment with EO or d-camphor exposure. First, a hormetic response (a highly generalized dose–response phenomenon in toxicology) in the larval overall performance was observed in terpenoid-feeding individuals. Then, genes encoding cytochrome P450 (CYP450) and cuticular protein (CP) were induced by both EO and d-camphor exposures using comparative transcriptome, suggesting that this weevil could deploy the dual mechanism (i.e. CYP450-mediated metabolic resistance and CP-mediated cuticular resistance) to counter host terpenoid defences. Furthermore, temporal expression of CYP450 and CP genes under a low dose of d-camphor exposure indicated that there was a trade-off relationship between the inductions of CYP450 and CP genes. We speculate that the dual mechanism of terpenoid tolerance in this specialist is an essential precondition for the hormetic response in larval growth and development, ultimately contributing to its successful colonization on camphor trees. Additionally, we found a few genes related to glucose transport, juvenile hormone, and odorant binding were fine-tuned under terpenoid exposures. Taken together, our study will open new avenues for understanding insect-plant coevolutionary adaptation and developing durable control strategies for this insect pest.

樟脑油 (EO) 及其主要成分 (即d-樟脑) 在樟树Cinnamomum camphora中形成特定的萜类化合物防御。然而，一种新出现的害虫Pagiophloeus tsushimanus (Coleoptera: Curculionidae) 最近对这种难以捉摸的难处理植物物种造成了严重损害。为了研究这种象鼻虫对宿主特异性萜类防御的耐受性的机制，我们在模拟饮食环境和 EO 或d的基础上进行了生物测定、RNA-seq 和 RT-qPCR 分析。-樟脑暴露。首先，在以萜类化合物为食的个体中观察到幼虫整体表现中的兴奋反应（毒理学中高度概括的剂量反应现象）。然后，使用比较转录组通过 EO 和d-樟脑暴露诱导编码细胞色素 P450 (CYP450) 和表皮蛋白 (CP) 的基因，这表明这种象鼻虫可以部署双重机制（即 CYP450 介导的代谢抗性和 CP 介导的表皮抗性）以对抗宿主萜类化合物的防御。此外，在低剂量d下 CYP450 和 CP 基因的时间表达-樟脑暴露表明CYP450和CP基因的诱导之间存在权衡关系。我们推测，该专家对萜类化合物耐受的双重机制是幼虫生长和发育过程中产生兴奋反应的必要先决条件，最终有助于其在樟树上成功定殖。此外，我们发现一些与葡萄糖转运、保幼激素和气味结合相关的基因在萜类化合物暴露下得到了微调。总之，我们的研究将为理解昆虫-植物共同进化适应和开发针对这种害虫的持久控制策略开辟新途径。