Dataset Information

Chemosensillum immunolocalization and ligand specificity of chemosensory proteins in the alfalfa plant bug Adelphocoris lineolatus (Goeze).

ABSTRACT: Insect chemosensory proteins (CSPs) are a family of small soluble proteins. To date, their physiological functions in insect olfaction remain largely controversial in comparison to odorant binding proteins (OBPs). In present study, we reported the antenna specific expression of three CSPs (AlinCSP4-6) from Adelphocoris lineolatus, their distinct chemosensillum distribution as well as ligand binding capability thus providing the evidence for the possible roles that they could play in semiochemical detection of the plant bug A. lineolatus. The results of qRT-PCR and western blot assay clearly showed that all of these three CSPs are highly expressed in the adult antennae, the olfactory organ of insects. Further cellular investigation of their immunolocalization revealed their dynamic protein expression profiles among different types of antennal sensilla. In a fluorescence competitive binding assay, the selective ligand binding was observed for AlinCSP4-6. In ad`dition, a cooperative interaction was observed between two co-expressed CSPs resulting in an increase of the binding affinities by a mixture of AlinCSP5 and AlinCSP6 to terpenoids which do not bind to individual CSPs. These findings in combination with our previous data for AlinCSP1-3 indicate a possible functional differentiation of CSPs in the A. lineolatus olfactory system.

SUBMITTER: Sun L

PROVIDER: S-EPMC4308698 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Chemosensillum immunolocalization and ligand specificity of chemosensory proteins in the alfalfa plant bug Adelphocoris lineolatus (Goeze).

Sun Liang L Zhou Jing-Jiang JJ Gu Shao-Hua SH Xiao Hai-Jun HJ Guo Yu-Yuan YY Liu Ze-Wen ZW Zhang Yong-Jun YJ

Scientific reports 20150128

Insect chemosensory proteins (CSPs) are a family of small soluble proteins. To date, their physiological functions in insect olfaction remain largely controversial in comparison to odorant binding proteins (OBPs). In present study, we reported the antenna specific expression of three CSPs (AlinCSP4-6) from Adelphocoris lineolatus, their distinct chemosensillum distribution as well as ligand binding capability thus providing the evidence for the possible roles that they could play in semiochemica ...[more]

PMID: 25627422

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Project description:Insect chemosensory proteins (CSPs) have been proposed to capture and transport hydrophobic chemicals from air to olfactory receptors in the lymph of antennal chemosensilla. They may represent a new class of soluble carrier protein involved in insect chemoreception. However, their specific functional roles in insect chemoreception have not been fully elucidated. In this study, we report for the first time three novel CSP genes (AlinCSP1-3) of the alfalfa plant bug Adelphocoris lineolatus (Goeze) by screening the antennal cDNA library. The qRT-PCR examinations of the transcript levels revealed that all three genes (AlinCSP1-3) are mainly expressed in the antennae. Interestingly, these CSP genes AlinCSP1-3 are also highly expressed in the 5(th) instar nymphs, suggesting a proposed function of these CSP proteins (AlinCSP1-3) in the olfactory reception and in maintaining particular life activities into the adult stage. Using bacterial expression system, the three CSP proteins were expressed and purified. For the first time we characterized the types of sensilla in the antennae of the plant bug using scanning electron microscopy (SEM). Immunocytochemistry analysis indicated that the CSP proteins were expressed in the pheromone-sensitive sensilla trichodea and general odorant-sensitive sensilla basiconica, providing further evidence of their involvement in chemoreception. The antennal activity of 55 host-related semiochemicals and sex pheromone compounds in the host location and mate selection behavior of A. lineolatus was investigated using electroantennogram (EAG), and the binding affinities of these chemicals to the three CSPs (AlinCSP1-3) were measured using fluorescent binding assays. The results showed several host-related semiochemicals, (Z)-3-hexen-1-ol, (E)-2-hexen-1-al and valeraldehyde, have a high binding affinity with AlinCSP1-3 and can elicit significant high EAG responses of A. lineolatus antennae. Our studies indicate the three antennae-biased CSPs may mediate host recognition in the alfalfa plant bug A. lineolatus.

Project description:The chemosensory system is essential for insects to detect exogenous compounds, and odorant binding proteins (OBPs) play crucial roles in odorant binding and transduction. In the alfalfa plant bug Adelphocoris lineolatus, an important pest of multiple crops, our understanding of the physiological roles of antenna-biased OBPs has increased dramatically, whereas OBPs related to gustation have remained mostly unexplored. In this study, we employed RNA sequencing and RACE PCR methods to identify putative OBPs from the adult forelegs of both sexes. Eight candidate OBPs were identified, and three OBPs (AlinOBP15, 16, and 17) were novel. Full-length sequence alignment and phylogenetic analyses suggested that these three candidate OBPs had characteristics typical of the insect OBP family. AlinOBP16 and 17 displayed six highly conserved cysteines, placing them in the classic OBP subfamily, whereas AlinOBP15 resembled AlinOBP14 and clustered with the Plus-C clade. Quantitative real-time PCR (qRT-PCR) revealed distinct and significant tissue- and sex-biased expression patterns. AlinOBP15 was highly expressed in female heads, and AlinOBP16 and 17 were strongly expressed in female antennae. In particular, AlinOBP11, the most abundant OBP gene in our foreleg transcriptome dataset, was predominately expressed in adult legs. Furthermore, four types of sensilla hairs were observed on the forelegs of adult A. lineolatus, including sensilla trichodea, setae, and two types of sensilla chaetica (Sch1 and Sch2). Anti-AlinOBP11 antiserum strongly labeled the outer sensillum lymph of Sch2, implying that it has important gustatory functions in A. lineolatus. Our current findings provide evidence that OBPs can be functionally expressed in the tarsal gustatory sensilla of hemipteran mirid species, broadening our understanding of OBP chemosensory function in insects and facilitating the discovery of new functional targets for the regulation of insect host-searching behaviors.

Project description:The three-dimensional structures of two odorant binding proteins (OBPs) and one chemosensory protein (CSP) from a polyphagous ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) were resolved bioinformatically. The results show that both SguaOBP1 and OBP2 are classic OBPs, whereas SguaCSP1 belongs to non-classic CSPs which are considered as the "Plus-C" CSP in this report. The structural differences between the two OBPs and between OBP and CSP are thoroughly described, and the structural and functional significance of the divergent C-terminal regions (e.g., the prolonged C-terminal region in SguaOBP2 and the additional pair of cysteines in SguaCSP1) are discussed. The immunoblot analyses with antisera raised against recombinant SguaOBP1, OBP2, and CSP1, respectively, indicate that two SguaOBPs are specific to antennae, whereas SguaCSP1, which are more abundant than OBPs and detected in both male and female wasps, expresses ubiquitously across different tissues.We also describe the ultrastructure of the antennal sensilla types in S. guani and compare them to 19 species of parasitic Hymenoptera. There are 11 types of sensilla in the flagellum and pedicel segments of antennae in both male and female wasps. Seven of them, including sensilla placodea (SP), long sensilla basiconica (LSB), sensilla coeloconica (SC), two types of double-walled wall pore sensilla (DWPS-I and DWPS-II), and two types of sensilla trichodea (ST-I and ST-II), are multiporous chemosensilla. The ultralsturctures of these sensilla are morphologically characterized. In comparison to monophagous specialists, the highly polyphagous generalist ectoparasitoids such as S. guani possess more diverse sensilla types which are likely related to their broad host ranges and complex life styles. Our immunocytochemistry study demonstrated that each of the seven sensilla immunoreacts with at least one antiserum against SguaOBP1, OBP2, and CSP1, respectively. Anti-OBP2 is specifically labeled in DWPS-II, whereas the anti-OBP1 shows a broad spectrum of immunoactivity toward four different sensilla (LSB, SP, ST-I and ST-II). On the other hand, anti-CSP1 is immunoactive toward SP, DWPS-I and SC. Interestingly, a cross co-localization pattern between SguaOBP1 and CSP1 is documented for the first time. Given that the numbers of OBPs and CSPs in many insect species greatly outnumber their antennal sensilla types, it is germane to suggest such phenomenon could be the rule rather than the exception.

Dataset Information

Chemosensillum immunolocalization and ligand specificity of chemosensory proteins in the alfalfa plant bug Adelphocoris lineolatus (Goeze).

Publications

Chemosensillum immunolocalization and ligand specificity of chemosensory proteins in the alfalfa plant bug Adelphocoris lineolatus (Goeze).

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