关键词: 烟粉虱, 气味结合蛋白, 植物挥发物, 行为反应, RNA干扰

Abstract:

【Background】The whitefly, Bemisia tabaci, is a highly polyphagous agricultural pest of global significance, exhibiting a distinct preference for specific host plants. Odorant-binding proteins (OBPs), which specifically bind to environmental odor molecules, play a pivotal role in insect behaviors such as host location, oviposition site selection, and predator avoidance. 【Objective】The purpose of this study is to deeply elucidate the molecular mechanism of OBP in the chemosensory and behavioral regulation of B. tabaci, reveal the physiological basis of its host adaptability, and to provide a theoretical basis for the development of new green prevention and control technologies based on olfactory interference. 【Method】Quantitative real-time PCR (qRT-PCR) was used to detect the expression profile of BtabOBP4 in different developmental stages (egg, 1st-4th instar nymphs, adult) and different adult tissues (head, thorax, abdomen) of B. tabaci. The full-length BtabOBP4 was cloned, and the recombinant BtabOBP4 protein was induced for heterologous expression and purified. Fluorescence competitive binding assays were conducted to screen the binding capacity of BtabOBP4 to plant volatiles and secondary metabolites. Y-tube olfactometer was used to determine the behavioral tropism of B. tabaci to candidate ligands. Feeding-mediated RNA interference (RNAi) technology was employed to silence the BtabOBP4 to verify its regulatory effect on chemosensory behavior in B. tabaci. 【Result】BtabOBP4 showed the highest expression level at the 3rd instar nymph stage of B. tabaci, and exhibited sexual dimorphism in the adult stage (male was approximately 4 times that of female), and was specifically enriched in the head. BtabOBP4 could specifically bind to myrcene, β-ionone, and α-pinene (the K_i values were 25.68, 43.95, and 33.65 μmol·L^-1, respectively). Notably, 100 mg·L^-1 myrcene, 100 mg·L^-1 β-ionone, and 1 000 mg·L^-1 α-pinene repelled B. tabaci by 33%, 43%, and 44%, respectively. After 24 h of dsRNA feeding, the silencing efficiency of BtabOBP4 reached 55% in females and 51% in males. The repellent responses of B. tabaci to myrcene and α-pinene were completely abolished, while the repellency toward β-ionone was significantly attenuated. 【Conclusion】BtabOBP4 is highly expressed in the 3rd instar nymphs and male adults of B. tabaci, with specific enrichment in the head tissue, suggesting its pivotal role in chemical communication. The BtabOBP4 protein exhibits specific binding affinity to myrcene, β-ionone, and α-pinene. Notably, silencing of BtabOBP4 via RNA interference significantly abolished or attenuated the repellent behavior of B. tabaci toward these compounds. These findings indicate that BtabOBP4 functions as a key olfactory receptor mediating host plant recognition and selection in B. tabaci, regulating repellent responses by perceiving specific plant volatiles.

Key words: Bemisia tabaci, odorant-binding protein (OBP), plant volatile, behavioral response, RNA interference (RNAi)