Functional Characteristics of a Novel Chemosensory Protein in the Cotton Bollworm Helicoverpa armigera (Hübner)

A chemosensory protein named HarmCSP5 in cotton bollworm Helicoverpa armigera （Hvbner） was obtained from antennal eDNA libraries and expressed in Escherichia coll. The real time quantitative PCR （RT-qPCR） results indicated that HarmCSP5 gene was mainly expressed in male and female antennae but also expressed in female legs and wings. Competitive binding assays were performed to test the binding affinity of recombinant HarmCSP5 to 60 odor molecules including some cotton volatiles. The resules showed that HarmCSP5 showed strong binding abilities to 4-ehtylbenzaldehyde and 3,4-dimethlbenz aldehyde, whereas methyl phenylacetate, 2-decanone, 1-pentanol, carvenol, isobomeol, nerolidol, 2- nonanone and ethyl heptanoate have relatively weak binding affinity. Moreover, the predicted 3D model of HarmCSP5 consists of six α-helices located among residues 33-38 （αl）, 40-48 （α2）, 62-72 （α3）, 80-96 （α4）, 98-108 （α5）, and 116-119 （α6）, two pairs of disulfide bridges Cys49-Cys55, Cys75-Cys78. The two amino acid residues, Ile94 and Trpl01, may play crucial roles in HarmCSP5 binding with ligands and need further study for confirmation.

Molecular and in vitro biochemical assessment of chemosensory protein 10 from brown planthopper Nilaparvata lugens at acidic pH

Chemosensory proteins(CSPs)are important molecular components of the insect olfactory system,which are involved in capturing,binding,and transporting hydrophobic odour molecules across the sensillum in sensillar lymph in regulating insect behavior.This protein family(CSPs)is also involved in many other systems that are not linked to olfactory receptors in olfactory sensilla.The brown planthopper(BPH)is a monophagous pest of rice that causes damage by sucking phloem sap and transmitting a number of diseases caused by viruses.In this study,fluorescence competitive binding assay and fluorescence quenching assay at acidic p H were performed as well as homology modelling to describe the binding affinity of Nlug CSP10.Fluorescence competitive binding assay(FCBA)demonstrated that Nlug CSP10 bound strongly to nonadecane,farnesene,and 2-tridecanone at acidic p H.The results of FCBA indicated that Nlug CSP10 bound different ligands at the physiological p H(5.0)of the bulk sensillum lymph.Fluorescence quenching assay demonstrated that Nlug CSP10 generated a stable complex with 2-tridecanone,while two ligands nonadecane and farnesene collided due to molecular collisions.The interaction of selected ligands with the modelled structure of Nlug CSP10 was also analyzed,which found the key amino acids(Gln23,Gln24,Gln25,Asn27,Met33,Ser34,Ile35,Tyr36,Asn42,Met43,Val45,Asn46,Asn93,Arg96,Ala97,Lys99,and Ala100)in Nlug CSP10 that were involved in binding of volatile compounds.The present study contributes to the binding profile of Nlug CSP10 that promotes the development of behaviorally active ligands based on BPH olfactory system.