Function Research On Diaphorina Odor Binding Protein Based On RNAi

Huanglongbing(HLB)is a devastating disease in citrus,and Diaphorina citri is the only natural vector of HLB.The eradication of D.citri is an effective measure to control HLB,but in the past,the improper use of pesticides led to the resistance of D.citri to different insecticides.Therefore,it is necessary to develop a green pest control strategy.At present,odorant binding proteins(OBPs)and odorant receptors(ORs)are considered as molecular targets for novel odor compounds.Our previous research reveaed that D.citri OBP for host plant recognition have broad-spectrum and specific recognition patterns,but the evidence was only limited to fluorescence competitive binding test and molecular docking.In order to confirm the recognition pattern,we examined EAG responses to different odor compounds in sexually immature and mated individuals from both sexes.RNAi method was used to analyze the EAG responses and olfactory behavioral changes with single OBP gene and two OBPs interference.(1)This research the EAG data exhibited that D.citri in sexually mature response to β-Carnation,ethyl butyrate,1-hexanol,methyl salicylate,e-βOcimene,Basilene,laurene,Cymene,d-limonene,dimethyl disulfide,nonanal andγ-terpinene,which were significantly higher than that in sexually immature,but there was no significant difference in the EAG responses to acetic acid.(2)RNAi was used to interfere with the expression of OBP3,OBP6,OBP8 and OBP9,respectively.The EAG responses and olfactory behavioral response were compared.The results showed that there were significant male and female differences in EAG responses and olfactory behavioral response after OBP expression interference,and male D.citri not be affected β-Carnation was rarely attracted,while female D.citri were not attracted to γ-terpenes.The EAG response of basilene,laurene and cymene were decreased significantly.The recognition of laurene and Cymene may depend on both four OBPs.Each OBP will participate in the transport of laurene and Cymene.Silencing on only one OBP will reduce the EAG response to laurene and Cymene.(3)RNAi was used to interfere with broad-spectrum OBP3 plus specific OBPs(OBP6,OBP8 and OBP9).The EAG responses and olfactory behavioral response after RNAi treatment were compared.The results showed that the EAG response to some compounds during double OBP gene interference was significantly lower than that single OBP interference.These data indicated that there may be a combination recognition mode of D.citri OBPs,and the combination of OBP will lead to a significant decrease in olfactory sensitivity.Based on these data,we speculate that the D.citri OBPs may recognize and carry the host plant odors through combination,which may explain how oligovorous phytophagous insects use limited OBP proteins to carry and recognize different kinds of odor compounds.The results show that the intervention of a single OBP can significantly reduce the EAG response of D.citri to odor compounds,and the double OBP interference is significantly lower than the EAG response of single OBP interference.The OBP of D.citri may sense the odor molecules in the environment by co-transporting odorous compounds and superimposing potentials.Compared with other insects,the number of OBP of citrus psyllids is less,and there are only 4 olfactory receptors on a single antenna,which are shared by OBP.Recognition helps to improve the recognition of low-content odor molecules in the air.This mechanism can be used to design compounds with strong binding ability to a single OBP to interfere with the positioning of D.citri on host plants,or to study compounds that can bind to multiple OBPs to interfere with the olfactory sense of citrus psyllids.