A case study on the γ-octalactone induced expression of Obp83g-2 in Bactrocera dorsalis (Hendel) revealed the transcriptional regulation of insect odorant binding protein

As crucial components of the insect olfactory system, odorant binding proteins (OBPs) are involved in detecting environmental chemical cues. Expression alterations of OBPs induced by odorants are conserved in many species. It presents an intriguing initial screening tool when searching for novel OBP-odorant interaction. However, the transcriptional regulation mechanism that causes this expression alteration of OBPs still remains unclear. Here, we reported a case study on the transcriptional regulation of OBP in an invasive species, Bactrocera dorsalis, upon γ-octalactone (a host volatile that strongly attracts its females to lay eggs) induction. We identified OBP83g-2 as a key OBP was involved in γ-octalactone perception through in vitro and in vivo functional assay. In addition, we found transcription factor ADF-1-like positively regulated the expression of Obp83g-2 upon γ-octalactone induction through expression pattern analysis, dual-luciferase reporter system, electrophoretic mobility shift assay (EMSA) and RNAi. Based on this, we proposed a model for the transcriptional regulatory mechanism of OBP gene in B. dorsalis. Our data not only highlights the significant role of OBP83g-2 in γ-octalactone mediated oviposition behavior, but also provides a theoretical foundation for a deeper understanding of the transcriptional regulation of OBPs triggered by external odorants in insects.