Identification and functional characterization of two antenna-specifc odorant-binding proteins in Plutella xylostella response to 2,3-dimethyl-6-(1-hydroxy)-pyrazine

Plutella xylostella is an important cruciferous crop pest with a serious resistance to multiple insecticides, a novel natural compound, 2,3-dimethyl-6-(1-hydroxy)-pyrazine were isolated, that showed significant repellent activity against P. xylostella with olfactory system as a potential target. Eight odorant-binding proteins (OBPs) were determined as candidate target genes using RT-qPCR (Quantitative reverse transcription PCR), most of them were clustered with OBPs from Spodoptera frugiperda. Fluorescence competitive binding assays showed that PxylPBP2 (Pheromone binding protein) and PxylOBP3 had Ki values of 7.13 +/- 0.41 mu M and 9.56 +/- 0.35 mu M, indicating a high binding affinity to the pyrazine. Moreover, the binding style between these two OBPs and the pyrazine was determined as a hydrophobic interaction by using molecular docking. The binding between PxylPBP2 and the pyrazine was found to be more stable, and the carbon atoms of C-2 and C-3 in this pyrazine showed potential optimization characteristics. Both PxylPBP2 and PxylOBP3 were highly expressed in the antennae of both sexes. These results can be used to design and develop novel green pesticides with the pyrazine as the active or lead compound to reduce the utilization of chemical pesticides and postpone development of resistance.