Functional Analysis of Adipokinetic Hormone and Its Receptor Genes in Regulating Energy Metabolism Under Stress Conditions in Dendroctonus armandi

<i>Dendroctonus armandi</i> is a major primary pest of Chinese white pine in the Qinling-Bashan forest region. By feeding on the phloem and vectoring symbiotic fungi that cause blue stain in the sapwood, it drives rapid decline and mortality of host trees. As a key wood-boring forest insect, its outbreaks are closely linked to adaptive strategies in energy metabolism. Adipokinetic hormone (AKH) is a highly conserved insect neuropeptide and plays a major role in regulating energy metabolism. This study aimed to determine how the <i>AKH</i> gene regulates energy use in <i>D. armandi</i> under different stress conditions. We cloned the <i>DaAKH</i> gene and its receptor gene, <i>DaAKHR</i>, from <i>D. armandi</i>. <i>DaAKH</i> and <i>DaAKHR</i> showed the highest expression in emerged adults and the lowest levels in pupae. In larvae and in adult males and females, <i>DaAKH</i> transcripts were predominantly expressed in the head, whereas <i>DaAKHR</i> was enriched in the fat body. Under starvation and cold stress, <i>DaAKH</i> and <i>DaAKHR</i> expression were significantly upregulated; under heat stress, expression first increased and then decreased. Across stress treatments, RNAi significantly downregulated <i>DaAKH</i> and <i>DaAKHR</i> expression in <i>D. armandi</i>. Under starvation, RNAi reduced mortality, lowered lipid metabolism, and led to lipid accumulation, thereby mitigating premature energy depletion and starvation-induced death. By contrast, under heat and cold stress, RNAi significantly increased mortality, significantly reduced triglyceride and glycogen consumption, and suppressed metabolism. These results indicate that <i>DaAKH</i> and <i>DaAKHR</i> regulate energy allocation under starvation stress and help maintain adaptive capacity under temperature stress in <i>D. armandi</i>. By tuning energy metabolism, <i>DaAKH</i> and <i>DaAKHR</i> help resist environmental stress and maintain reproduction and population size. This study advances understanding of the physiological responses and molecular mechanisms of <i>D. armandi</i> under stress conditions and provides a new avenue for metabolism-targeted control.