The Molecular Recognition Function Of Odorant Binding Protein In Aygus Lucorum

Olfaction plays a crucial role in many kinds of insect behaviors,including host selection and mating behavior. Insect odorant-bindingprotein (OBP) is one kind of soluble secreted protein existing in thelymph of the olfactory receptor which is associated with olfaction.This protein can transport, as vector, the odour molecule to thereceptors on the surface of nerve cell. OBP is thought to be the firststep in molecular recognition and the transportation of semi-chemical.And it has become a hot spot of research in recent years. In many ofthese studies, OBPs were the target genes, recognition mechanism ofinsect smell sense was applied，interference with insect’s matingand host positioning behaviors that has much theoretical andpractical application are the focus for these researches.Aygus lucorum, one species of major phytophagous agriculturalinsect pests that not only cause huge losses in crops like cotton,alfalfa, sunflower etc., but also to a variety of fruit trees (like Chinesedate) and vegetables (like artemisia). In this study, Aygus lucorumPlus-C OBP was expressed in a prokaryotic expression system, in turn its function was verified using fluorescence probe technique. Mainresults of this study are listed as the following:1. A suitable expression strain was selected for Plus-C OBP study.To avoid the rare anticodon influencing the protein expression, aseries of rare anticodon analysis were conducted; and in the end,Rosetta (DE3) was selected as the expression strain of LlucOBP1.2. A novel Plus-C OBP (AlucOBP1) in the Aygus lucorum wasexpressed and determined. A novel Plus-C OBP (AlucOBP1) in theAygus lucorum, after being cloned, expressed and purified, and then itwas verified to be AlucOBP1 by mass spectrometry appraisal andWestern blot, that determined its molecular weight about 37 KD byHisTag. After purification with HisTrap Affinity Chromatography, itwas found that both 200mM and 300mM were its optimal elutionconcentrations. Its molecular weight would become about 25 KD aftercutting down HisTag. Its protein concentration was 1.462 mg/mlmeasured by Bradford method.3. The binding efficiency of AlucOBP1 with 50 odorants of differentchemical classes was measured using a fluorescence probe 1-NPN ina fluorescence competitive binding study. Results showed that manyodorants can bind with AlucOBP1, among which, heptadecanol,1-Heptanol, ethyl butyrate, n-butyl butyrate, farnesene, ocimene,2-octanone could significantly bind with LlucOBP1. These resultssuggested that AlucOBP1 might play a key role in perception of sexpheromones and host selection for this insect species.