An odorant‐binding protein of Asian citrus psyllid, Diaphorina citri, participates in the response of host plant volatiles

BACKGROUND Odorant-binding proteins (OBPs) in insects contribute to the sensitivity of the olfactory system and function to connect external odorants to olfactory receptor neurons. Determination of the chemosensory functions in Diaphorina citri, a vector of the citrus Huanglongbing pathogen, may help in developing a potential target for pest management. RESULTS Diaphorina citri showed dose-dependent electroantennogram recording (EAG) responses to 12 host plant volatiles. A two-choice behavioral trap experiment revealed that four compounds (methyl salicylate, linalool, citral and R-(+)-limonene) that elicited high EAG responses also had significant attraction to adults. The expression profiles induced by these compounds were detected in nine OBP genes, such as DcitOBP1-9. DcitOBP3, DcitOBP6 and DcitOBP7 commonly showed significant upregulation or downregulation compared to the control. The recombinant protein DcitOBP7 had high in vitro binding activities (Kd < 10 μM) to methyl salicylate, linalool and R-(+)-limonene, and showed moderate binding affinity to citral with a Kd value of 15.95 μM using microscale thermophoresis. Furthermore, RNAi suppressed mRNA expression of DcitOBP7 resulted in significant reduction of EAG activity and the adult D. citri behavioral responses to tested volatiles and preferred host, Murraya paniculata. The hydrophilic residue Arg107 of DcitOBP7 may play a key role in binding odorants via formation of hydrogen bonds. CONCLUSION These results show evidence that DcitOBP7 plays an important role in olfactory response. This finding may provide new perception into the functions of OBP families in D. citri and may aid in the development of safe strategies for managing D. citri populations. This article is protected by copyright. All rights reserved.