Transcriptional Response of ABCH Transporter Genes to Host Allelochemicals in Dendroctonus armandi and Their Functional Analysis

Bark beetles depend on detoxifying enzymes to counteract the defensive terpenoids produced by host trees. Insect ABC transporters play a critical role in the detoxification of insecticides and plant secondary metabolites. However, the specific functions of <i>ABC</i> genes in the metabolism of host allelochemicals remain unclear in <i>D. armandi</i>. In this study, we observed that verapamil significantly enhanced the mortality of host allelochemicals in beetles, indicating that ABC transporter genes are involved in the metabolism of monoterpenes by <i>D. armandi</i>. We then sequenced and characterized the full-length cDNAs of three <i>ABCH</i> subfamily genes (<i>DaABCH1</i>-<i>DaABCH3</i>) from <i>D. armandi</i>. Spatiotemporal expression profiling revealed that all three genes were upregulated during developmental transitions (egg to larva and pupa to adult) and tissue-specific enrichment in detoxification-related organs (Malpighian tubules, fat body, and midgut). Additionally, <i>DaABCH3</i> expression was detected in the hindgut and brain. Furthermore, <i>DaABCH1</i> and <i>DaABCH2</i> were significantly induced by treatment with α-pinene and limonene, whereas <i>DaABCH3</i> was induced by β-pinene and limonene. Importantly, silencing <i>DaABCH1</i> significantly increased mortality in adults fumigated with α-pinene and limonene. These results strongly suggest that <i>DaABCH1</i> acts as a key regulator modulating <i>D. armandi</i>'s sensitivity to host plant allelochemicals. This finding provides a conceptual basis for developing novel control strategies against this economically significant forest pest.