The melon fly, Zeugodacus cucurbitae (Coquillett), is a globally significant agricultural pest causing substantial economic losses. Odorant-binding proteins (OBPs) are critical of the insect olfactory system, yet their specific physiological functions in Z. cucurbitae remain largely uncharacterized. In this study, we functionally characterized ZcucOBP14 and investigated its putative involvement in host chemoreception and insecticide tolerance. Sequence alignment and phylogenetic analysis indicated that ZcucOBP14 belongs to the Minus-C OBP subfamily, and quantitative reverse transcription PCR (RT-qPCR) showed that it was predominantly expressed in both the head and abdomen. Fluorescence binding assays revealed that ZcucOBP14 exhibited broad binding affinity to 11 host plant volatiles, three sex pheromones, and two insecticides. Subsequent electroantennography (EAG) and behavioral bioassays identified isopulegol, 1-hexanol, linalool, and α-pinene as key ligands regulating the behavioral responses of Z. cucurbitae. RNA interference (RNAi)-mediated knockdown of ZcucOBP14 significantly reduced EAG responses to key ligands, eliminated behavioral preference, and increased insecticide-induced mortality by 20%. Molecular docking further identified that Tyr71, Ile67, Trp50, Val107, Phe116 and Leu70 were critical residues involved in ligand interactions. Collectively, these findings highlight the indispensable role of ZcucOBP14 in olfactory perception and its contribution to insecticide tolerance, laying a solid theoretical foundation for the development of novel behavior-modifying agents, attractants, and optimized integrated pest management (IPM) strategies against this pest.

Antibiotic exposure can perturb the gut microbiota of honey bees, but its associations with host physiological responses remain incompletely understood. Here, we investigated the effects of tetracycline exposure on survival, locomotor activity, gut bacterial communities, and immune- and antioxidant-related gene expression in Apis mellifera workers maintained under controlled laboratory cage conditions. Tetracycline exposure at 100, 300, and 450 μg/mL reduced worker survival in a concentration-dependent manner, while 100 μg/mL increased daytime locomotor activity without affecting sucrose consumption. Tetracycline also altered gut bacterial community structure, with marked reductions in several core taxa, particularly Snodgrassella and Bartonella, whereas Commensalibacter, Lactobacillus Firm4 and Firm5 increased, especially at the highest concentration. Changes in immune- and antioxidant-related gene expression were more pronounced in the gut than in the head. Moreover, Snodgrassella abundance was positively correlated with Relish expression in the head and with Apidaecin and CAT expression in the gut. These findings demonstrate that tetracycline exposure reduces honey bee survival and is associated with coordinated alterations in gut bacterial communities and host physiological responses.

External environment shapes the cold adaptation of Ophraella communa, a specialist natural enemy of the invasive common ragweed, and further affects its biological control efficacy. Our study aims to clarify the cold tolerance correlation between ragweed and leaf beetle and explore whether host cold acclimation can enhance the beetle’s low-temperature adaptability. We measured cold-resistant substances, supercooling point (SCP), and chill-coma recovery time (CCRT) of four geographic populations, and conducted indoor low-temperature acclimation of ragweed at 13 °C, 17 °C, 21 °C for 3–9 d, then fed leaf beetle with treated leaves. Results showed that cold-resistant substances in both species varied with latitude and were highly heritable. Cold acclimation can elevate sugars, trehalose, glycerol, and proline in ragweed; the cold tolerance of beetles feeding on these plants was significantly improved. We conclude that cold-resistant substances in ragweed can be trophically transferred to leaf beetle to enhance its cold hardiness, providing a new strategy to improve biocontrol in high-latitude regions.