Expression Pattern And Function Analysis Of BdorOBP50c In Bactrocera Dorsalis(Hendel)

Bactrocera dorsalis(Hendel)(Diptera: Tephritidae)is also known as the oriental fruit fly.It has the characteristics of wide host range,fast reproduction speed,strong adaptability and great harmfulness.At present,chemical agents is the mainstay control method.However,the abuse of chemical pesticides,not only seriously polluted the environment,but also increased the resistance of B.dorsalis.The difficulty of prevention is further enhanced.In recent years,the developing attractants has a good effect on the control of B.dorsalis.However,because its olfactory mechanism is still unclear,there are still many factors that limit its further promotion in actual production.Therefore,the molecular mechanism of the reaction of B.dorsalis to semiochemicals can provide new ideas and ways for the control of this insect.Odorant binding proteins(OBPs)play an important role in the recognition and transport of semiochemicals.The spatiotemporal expression pattern of the gene were explored based on the screening and identification the cDNA sequence of BdorOBP50 c.Aiming to provide new targets and new ideas for the control of B.dorsalis,RNAi,EAG and behavioral analysis techniques were used to explore the function of the gene in this dissertation.The main findings were as follows: 1 cDNA sequence cloning and phylogenetic analysis of BdorOBP50cThe cDNA sequence of BdorOBP50 c was obtained by PCR technology.The open reading frame(ORF)of BdorOBP50 c was 753 bp and encoded 251 amino acids.The signal peptide at the N-terminus contained 18 amino acids.The molecular weight of the mature peptide is 26.9 KD and the theoretical isoelectric point is 5.50.Sequence alignment revealed that the gene has eight conserved cysteine residues and belongs plusC OBP family,but lacking the ninth conserved cysteine.phylogenetie analysis revealed that all OBPs were clustered according to the number of conserved cysteine.Furthermore BdorOBP50 c and BminOBP50 c of Bactrocera minax have the highest homologous up to 70.38%,while the similarity with the DemlOBP50 e of Drosophila melanogaster sequence was only 5.41%.2 Spatiotemporal expression pattern of BdorOBP50cRT-qPCR was used to detect the expressions of BdorOBP50 c in different day-old and body parts or tissues of B.dorsalis.The data showed that BdorOBP50 c was stably expressed in females,but no significant difference among different ages.The highest expression was found in the males on the ninth day,which was significantly higher than other days.There are significant differences between male and female in age 5 and age 9,which may suggest that this gene present different functions.Different tissues expression indicated that BdorOBP50 c was expressed in the epidermis tissues of the head,thorax and abdomen as well as in the maxillary palps,antennae,legs and wings,but there was no significant difference between them.The expression level of BdorOBP50 c in fat body is significantly higher than that in other tissues.Therefore,We speculated that this gene is related to fat bodies physiological functions.3 Response to environmental stresses of BdorOBP50cLow temperature dose not induce the expression of this gene,but after high temperature treatment,the expression level was significantly lower than control,downregulated 22.29%,18.53% and 25.41%,respectively.After insecticide treatment,the expression level of BdorOBP50 c in the fat body was also significantly down-regulated.In starvation treatment,BdorOBP50 c decreased with the prolongation of starvation time,and the expression level of this gene returned to normal after restoring food.4 Preliminary study on the function of BdorOBP50cThe method of microinjecting dsBdorOBP50 c was used for interfering expression of BdorOBP50 c.The results showed that RNAi was effective against female and male adults,and the silence efficiency was stable,both of which were above 80%.There was no significant difference in the EAG response of the odorant compounds detected by the RNA i-treated females in comparison to the control GFP-treated females,but the RNA itreated males compared the control males to the EAG of the ethyl tigalate reaction was significantly reduced,and the reaction to benzothiazole also decreased.While the EAG for ?-octanolactone and(+),dipentene showed a tendency to increase.The behavioral analysis was further carried out using the trap.The results showed that the behavioral traits of the RNAi-treated test for ethyl tigalate were not significantly different from those of the control.Biological assay showed that the sensitivity to malathion did not change significantly after the interference.