The biogenic amine octopamine plays a critical role in the regulation of many physiological processes in insects. Octopamine transmits its action through a set of specific G-protein coupled receptors (GPCRs), namely octopamine receptors. Here, we report on a β-adrenergic-like octopamine receptor gene (BdOctβR1) from the oriental fruit fly, Bactrocera dorsalis (Hendel), a destructive agricultural pest that occurs in North America and the Asia-Pacific region. As indicated by RT-qPCR, BdOctβR1 was highly expressed in the central nervous system (CNS) and Malpighian tubules (MT) in the adult flies, suggesting it may undertake important roles in neural signaling in the CNS as well as physiological functions in the MT of this fly. Furthermore, its ligand specificities were tested in a heterologous expression system where BdOctβR1 was expressed in HEK-293 cells. Based on cyclic AMP response assays, we found that BdOctβR1 could be activated by octopamine in a concentration-dependent manner, confirming that this receptor was functional, while tyramine and dopamine had much less potency than octopamine. Naphazoline possessed the highest agonistic activity among the tested agonists. In antagonistic assays, mianserin had the strongest activity and was followed by phentolamine and chlorpromazine. Furthermore, when the flies were kept under starvation, there was a corresponding increase in the transcript level of BdOctβR1, while high or low temperature stress could not induce significant expression changes. The above results suggest that BdOctβR1 may be involved in the regulation of feeding processes in Bactrocera dorsalis and may provide new potential insecticide leads targeting octopamine receptors.

The fall armyworm, Spodoptera frugiperda, is one of the most notorious pest insects, causing damage to more than 350 plant species, and is feared worldwide as an invasive pest species since it exhibits high adaptivity against environmental stress. Here, we therefore investigated its transcriptome responses to four different types of stresses, namely cold, heat, no water and no food. We used brain samples as our interest was in the neuroendocrine responses, while previous studies used whole bodies of larvae or moths. In general, the responses were complex and encompassed a vast array of neuropeptides (NPs) and biogenic amines (BAs). The NPs were mainly involved in ion homeostasis regulation (ITP and ITPL) and metabolic pathways (AKH, ILP), and this was accompanied by changes in BA (DA, OA) biosynthesis. Cold and no-water stress changed the NP gene expression with the same patterns of expression but clearly separated from each other, and the most divergent pattern of expression was shown after no-food stress. In conclusion, our data provide a foundation in an important model and pest insect with candidate NPs and BAs and other marker candidate genes in response to environmental stress, and also potential new targets to manage pest insects.

Background: Plant resistance inducers based on nanomaterials (NMs) are a cutting-edge and promising field of interdisciplinary research, focused on developing environmentally and ecologically friendly alternatives for protecting crops. Studies have shown that NMs composed of silicon (SiO₂) and carbon quantum dots (CDs) can help plants better withstand various environmental and pest-related stresses. Results: We synthesized and characterized SiO₂-coated CDs (SiO₂@CDs) NMs that were found to be absorbed by tobacco leaves. Our research demonstrated that spraying tobacco leaves with a solution containing 100 mg/L SiO₂@CDs was more effective in promoting plant growth and controlling pest populations, specifically adult aphids compared to using either CDs or SiO₂ alone at the same concentration. The group treated with SiO₂@CDs achieved a significant 71% mortality of adult aphids after just 7 days, which was significantly different from the control group. Mechanistically, SiO₂@CDs enhanced both the plant’s physical resistance by utilizing Si, and stimulated the production of chemical defense compounds (such as salicylic acid), thereby improving aphid resistance. Additionally, the application of SiO₂@CDs significantly reduced oxidative stress in the leaves caused by aphid infestation, bolstered the activity of antioxidant enzymes like superoxide dismutase and peroxidase, and reduced malondialdehyde accumulation. Our biosafety experiments indicated that the SiO₂@CDs were less toxic and safer for non-target organisms in the environment, as well as for human cells. Conclusion: This study demonstrates that SiO₂@CDs exhibit excellent performance as a multifunctional insecticide in managing aphid-induced plant pest infestations, highlighting their promising and environmentally friendly potential in pest control and agroecosystem optimization.