Characterization of the chemosensory protein EforCSP3 and its potential involvement in host location by Encarsia formosa

Chemosensory proteins(CSPs) perform several functions in insects.This study performed the gene expression,ligand-binding,and molecular docking assays on the EforCSP3 identified in the parasitoid wasp Encarsia formosa,to determine whether EforCSP3 functions in olfaction,especially in host location and host preference.The results showed that EforCSP3 was highly expressed in the female head,and its relative expression was much higher in adults than in other developmental stages.The fluorescence binding assays suggested that the EforCSP3 exhibited high binding affinities to a wide range of host-related volatiles,among which dibutyl phthalate,1-octene,β-elemene,and tridecane had the strongest binding affinity with EforCSP3,besides α-humulene and β-myrcene,and should be assessed as potential attractants.Protein structure modeling and molecular docking predicted the amino acid residues of EforCSP3possibly involved in volatile binding.α-Humulene and β-myrcene attracted E.formosa in a previous study and exhibited strong binding affinities with EforCSP3 in the current study.In conclusion,EforCSP3 may be involved in semiochemical reception by E.formosa.

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.

The role of chemosensory protein 10 in the detection of behaviorally active compounds in brown planthopper, Nilaparvata lugens

Chemosensory proteins(CSPs)play important roles in insects’chemoreception,although their specific functional roles have not been fully elucidated.In this study,we conducted the developmental expression patterns and competitive binding assay as well as knock‐down assay by RNA interference both in vitro and in vivo to reveal the function of NlugCSP10 from the brown planthopper(BPH),Nilaparvata lugens(Stål),a major pest in rice plants.The results showed that NlugCSP10 messenger RNA was significantly higher in males than in females and correlated to gender,development and wing forms.The fluorescence binding assays revealed that NlugCSP10 exhibited the highest binding affinity with cis‐3‐hexenyl acetate,eicosane,and(+)‐β‐pinene.Behavioral assay revealed that eicosane displayed attractant activity,while cis‐3‐hexenyl acetate,similar to(+)‐β‐pinene significantly repelled N.lugens adults.Silencing of NlugCSP10,which is responsible for cis‐3‐hexenyl acetate binding,significantly disrupted cis‐3‐hexenyl acetate communication.Overall,findings of the present study showed that NlugCSP10 could selectively interrelate with numerous volatiles emitted from host plants and these ligands could be designated to develop slow‐release mediators that attract/repel N.lugens and subsequently improve the exploration of plans to control this insect pest.

Bioinformatics-Based Identification of Chemosensory Proteins in African Malaria Mosquito, Anopheles gambiae

Chemosensory proteins (CSPs) are identifiable by four spatially conserved Cys-teine residues in their primary structure or by two disulfide bridges in their tertiary structure according to the previously identified olfactory specific-D related proteins. A genomics- and bioinformatics-based approach is taken in the present study to identify the putative CSPs in the malaria-carrying mosquito, Anopheles gambiae. The results show that five out of the nine annotated candidates are the most possible Anopheles CSPs of A. gambiae. This study lays the foundation for further functional identification of Anopheles CSPs, though all of these candidates need additional experimental verification.

Molecular cloning and comparative analysis of transcripts encoding chemosensory proteins from two plant bugs, Lygus lineolaris and Lygus hesperus

Chemosensory proteins(CSPs)are soluble carrier proteins typically characterized by a six‐helix bundle structure joined by two disulfide bridges and a conserved Cys spacing pattern(C1‐X6‐8‐C2‐X16‐21‐C3‐X2‐C4).CSPs are functionally diverse with reported roles in chemosensation,immunity,development,and resistance.To expand our molecular understanding of CSP function in plant bugs,we used recently developed transcriptomic resources for Lygus lineolaris and Lygus hesperus to identify 17 and 14 CSP‐like sequences,respectively.The Lygus CSPs are orthologous and share significant sequence identity with previously annotated CSPs.Three of the CSPs are predicted to deviate from the typical CSP structure with either five or seven helical segments rather than six.The seven helix CSP is further differentiated by an atypical C3‐X3‐C4 Cys spacing motif.Reverse transcriptase PCR‐based profiling of CSP transcript abundance in adult L.lineolaris tissues revealed broad expression for most of the CSPs with antenna specific expression limited to a subset of the CSPs.Comparative sequence analyses and homology modeling suggest that variations in the amino acids that comprise the Lygus CSP binding pockets affect the size and nature of the ligands accommodated.

Increased expression of CSP and CYP genes in adult silkworm females exposed to avermectins

We analyzed 20 chemosensory protein （CSP） genes of the silkworm Bombyx mori. We found a high number of retrotransposons inserted in introns. We then analyzed expression of the 20 BrnorCSP genes across tissues using quantitative real-time polymerase chain reaction （PCR）. Relatively low expression levels of BmorCSPs were found in the gut and fat body tissues. We thus tested the effects of endectocyte insecticide abamectin （B 1 a and Blb avermectins） on BmorCSP gene expression. Quantitative real-time PCR experi- ments showed that a single brief exposure to insecticide abamectin increased dramatically CSP expression not only in the antennae but in most tissues, including gut and fat body. Furthermore, our study showed coordinate expression of CSPs and metabolic cytochrome P450 enzymes in a tissue-dependent manner in response to the insecticide. The function of CSPs remains unknown. Based on our results, we suggest a role in detecting xenobiotics that are then detoxified by cytochrome P450 anti-xenobiotic enzymes.