Characterization and cloning of a Tenebrio molitor hemolymph protein with sequence similarity to insect odorant-binding proteins

Expression of foraging and Gp-9 are associated with social organization in the fire ant Solenopsis invicta

The aim of this study was to investigate levels of expression of two major genes, the odorant binding protein Gp-9 (general protein-9) and foraging, that have been shown to be associated with behavioural polymorphisms in ants. We analysed workers and young nonreproductive queens collected from nests of the monogyne (single reproductive queen per nest) and polygyne (multiple reproductive queens) social forms of Solenopsis invicta. In workers but not young queens, the level of foraging expression was significantly associated with social form and the task performed (ie localization in the nest or foraging area). The level of expression of Gp-9 was also associated with social form and worker localization. In addition there was a higher level of expression of the Gp-9(b) allele compared with the Gp-9(B) allele in the heterozygote workers and the young nonreproductive queens. Finally, in the polygyne colonies the level of expression of foraging was not significantly associated with the Gp-9 genotype for either workers or young nonreproductive queens, suggesting that both genes have independent non-epistatic effects on behaviour in S. invicta.

Construction and analysis of cDNA libraries from the antennae of Batocera horsfieldi and expression pattern of putative odorant binding proteins

A high-quality cDNA library was constructed from female and male antenna of the longhorned beetle, Batocera horsfieldi (Hope) (Coleoptera: Cerambycidae), a serious pest of Populus (Salicales: Salicaceae). The titer was approximately 2.37 × 106 pfu/mL, and this complies with the test requirement. From the libraries, 692 clones were selected randomly, sequenced, and further analyzed, and the recombinational efficiency reached 93.85%. By alignment and cluster analysis, we identified four odorant binding proteins, two pheromone-binding proteins (have the characteristic six conserved cysteine residues), four Minus-C odorant binding proteins (lost two conserved cysteines), and three chemosensory proteins. In this study, we describe the identification and characterization of four new cDNAs that encode Minus-C odorant binding proteins (Minus-C OBPs) from B. horsfieldi antennal cDNA libraries. Our investigation focused on the expression pattern of the Minus-C OBP genes in various tissues in both sexes at different developmental stages, using reverse transcription PCR (RT-PCR) and realtime PCR (qPCR) strategies. Minus-C OBP1, 2, and 3 were expressed in all tested tissues, with the exception of the head (without antenna, labial palps, and maxillary palps). Minus-C OBP4 was expressed in the antenna, legs, and abdomen, but not in the labial palps, maxillary palps, or head. The qPCR results revealed MinusC OBPs were expressed in the antenna throughout the adult life, and that the transcript levels of these genes depended on the sex, age, and mating status of adults.

Identification and tissue distribution of odorant binding protein genes in the beet armyworm, Spodoptera exigua

Odorant binding proteins (OBPs) contribute to the remarkable sensitivity of the insect's olfactory system and play an important role in insect chemical communication. In this study, we identified 11 putative cDNAs encoding OBPs (namely SexiOBP1-11) from the antennal full length cDNA library of the beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae) and examined their expression profiles in different adult body tissues (antennae, heads, thoraxes, abdomens, legs and wings) by real-time quantitative PCR (qPCR). All SexiOBPs had the characteristic typical features of the OBP family, with the exception of SexiOBP11, which lacked the predicted signal peptide sequence at the N-terminus. qPCR revealed that all of these genes were highly transcribed in the antennae. SexiOBP1-4 and SexiOBP10 were dominantly restricted to antennae. Within antennae, SexiOBP2-4 and SexiOBP10 exhibited female-biased expression patterns, while the expression of SexiOBP7 was male-biased, indicating that they might be involved in interacting with sex pheromones. In general, these OBPs were mainly expressed in chemosensory-specific tissues, although some displayed non-chemosensory or ubiquitous tissue expression. The data is helpful for further determining the potential physiological functions of S. exigua OBPs, and paves the way towards a better understanding of the chemosensory perception of this pest, which may help to uncover new targets for behavioral interference used as a control strategy.

Extraction and characterisation of protein fractions from five insect species

Tenebrio molitor, Zophobas morio, Alphitobius diaperinus, Acheta domesticus and Blaptica dubia were evaluated for their potential as a future protein source. Crude protein content ranged from 19% to 22% (Dumas analysis). Essential amino acid levels in all insect species were comparable with soybean proteins, but lower than for casein. After aqueous extraction, next to a fat fraction, a supernatant, pellet, and residue were obtained, containing 17-23%, 33-39%, 31-47% of total protein, respectively. At 3% (w/v), supernatant fractions did not form stable foams and gels at pH 3, 5, 7, and 10, except for gelation for A. domesticus at pH 7. At 30% w/v, gels at pH 7 and pH 10 were formed, but not at pH 3 and pH 5. In conclusion, the insect species studied have potential to be used in foods due to: (1) absolute protein levels; (2) protein quality; (3) ability to form gels.

Proteome response of Tribolium castaneum larvae to Bacillus thuringiensis toxin producing strains

Susceptibility of Tribolium castaneum (Tc) larvae was determined against spore-crystal mixtures of five coleopteran specific and one lepidopteran specific Bacillus thuringiensis Cry toxin producing strains and those containing the structurally unrelated Cry3Ba and Cry23Aa/Cry37Aa proteins were found toxic (LC(50) values 13.53 and 6.30 µg spore-crystal mixture/µL flour disc, respectively). Using iTRAQ combined with LC-MS/MS allowed the discovery of seven novel differentially expressed proteins in early response of Tc larvae to the two active spore-crystal mixtures. Proteins showing a statistically significant change in treated larvae compared to non-intoxicated larvae fell into two major categories; up-regulated proteins were involved in host defense (odorant binding protein C12, apolipophorin-III and chemosensory protein 18) and down-regulated proteins were linked to metabolic pathways affecting larval metabolism and development (pyruvate dehydrogenase Eα subunit, cuticular protein, ribosomal protein L13a and apolipoprotein LI-II). Among increased proteins, Odorant binding protein C12 showed the highest change, 4-fold increase in both toxin treatments. The protein displayed amino acid sequence and structural homology to Tenebrio molitor 12 kDa hemolymph protein b precursor, a non-olfactory odorant binding protein. Analysis of mRNA expression and mortality assays in Odorant binding protein C12 silenced larvae were consistent with a general immune defense function of non-olfactory odorant binding proteins. Regarding down-regulated proteins, at the transcriptional level, pyruvate dehydrogenase and cuticular genes were decreased in Tc larvae exposed to the Cry3Ba producing strain compared to the Cry23Aa/Cry37Aa producing strain, which may contribute to the developmental arrest that we observed with larvae fed the Cry3Ba producing strain. Results demonstrated a distinct host transcriptional regulation depending upon the Cry toxin treatment. Knowledge on how insects respond to Bt intoxication will allow designing more effective management strategies for pest control.

Lifestyle and host defense mechanisms of the dung beetle, Euoniticellus intermedius: the toll signaling pathway

The dung beetle, Euoniticellus intermedius (Reiche) (Coleoptera: Scarabaeidae) is an important ecological and agricultural agent. Their main activity, the burying of dung, improves quality of the soil and reduces pests that could cause illness in animals. E. intermedius are therefore important for agriculture and for good maintenance of the environment, and are regarded as effective biological control agents for parasites of the gastrointestinal tract in livestock. The ability of E. intermedius to co-exist comfortably with many microorganisms, some of which are important human pathogens, stimulated our interest in its host defense strategies. The aim of this study was to investigate the Toll signaling pathway, which is strongly activated by fungi. Gene expression associated with fungal infection was analyzed by using 2-D gel electrophoresis and mass spectroscopy. Furthermore, the partial adult transcriptome was investigated for the presence of known immune response genes by using high-throughput sequencing and bioinformatics. The results presented here suggest that E. intermedius responds to fungal challenge via the Toll signaling pathway.

Identification of genes encoding atypical odorant-binding proteins in Aedes albopictus (Diptera: Culicidae)

Insect odorant-binding proteins (OBPs) are a diverse gene family that encode proteins thought to function as molecular chaperones by binding semiochemicals and transporting them through the aqueous lymph of insect sensilla. Between 66 and 68 genes have been classified as OBPs in both Anopheles gambiae (Giles) and Aedes aegypti L. based on bioninformatics criteria. We have cloned and sequenced from a subtracted cDNA library three OBPs in Aedes albopcitus (Skuse). BLASTP and phylogenetic analysis of deduced amino acid sequences identified a unique putative ortholog in Ae. aegypti for each Ae. albopictus OBP. Comparison of these putative Ae. aegypti orthologs with the results of previous bioinformatics analyses of OBP genes in Ae. aegypti highlight the potential variability of bioinformatics analyses and suggest that the OBP gene family of Culicids is even more diverse than previously described. Alignment of deduced amino acid sequences and phylogenetic analysis identified the N-terminal region of Culicid OBPs that is associated with aedine-specific diversification. Analysis of tissue-specific expression indicates that two of the Ae. albopictus OBPs are expressed both in preadult stages and in the hemolymph of adults, suggesting that the proteins encoded by these genes may be involved in the transport of hydrophobic ligands in the hemolymph. The other Ae. albopictus OBP is expressed exclusively in antennae and leg, suggesting a chemosensory function. These results are discussed within the context of the evolution and functional diversification of OBPs in mosquitoes.

Cloning and expression of Tenebrio molitor antifreeze protein in Escherichia coli

A novel antifreeze protein cDNA was cloned by RT-PCR from the larva of the yellow mealworm Tenebrio molitor. The coding fragment of 339 bp encodes a protein of 112 amino acid residues and was fused to the expression vectors pET32a and pTWIN1. The resulted expression plasmids were transformed into Escherischia coli strains BL21 (DE3), ER2566, and Origami B (DE3), respectively. Several strategies were used for expression of the highly disulfide-bonded beta-helix-contained protein with the activity of antifreeze in different expression systems. A protocol for production of refolded and active T. molitor antifreeze protein in bacteria was obtained.

Genetic regulation of colony social organization in fire ants: an integrative overview

Expression of colony social organization in fire ants appears to be under the control of a single Mendelian factor of large effect. Variation in colony queen number in Solenopsis invicta and its relatives is associated with allelic variation at the gene Gp-9, but not with variation at other unlinked genes; workers regulate queen identity and number on the basis of Gp-9 genotypic compatibility. Nongenetic factors, such as prior social experience, queen reproductive status, and local environment, have negligible effects on queen numbers which illustrates the nearly complete penetrance of Gp-9. As predicted, queen number can be manipulated experimentally by altering worker Gp-9 genotype frequencies. The Gp-9 allele lineage associated with polygyny in South American fire ants has been retained across multiple speciation events, which may signal the action of balancing selection to maintain social polymorphism in these species. Moreover, positive selection is implicated in driving the molecular evolution of Gp-9 in association with the origin of polygyny. The identity of the product of Gp-9 as an odorant-binding protein suggests plausible scenarios for its direct involvement in the regulation of queen number via a role in chemical communication. While these and other lines of evidence show that Gp-9 represents a legitimate candidate gene of major effect, studies aimed at determining (i) the biochemical pathways in which GP-9 functions; (ii) the phenotypic effects of molecular variation at Gp-9 and other pathway genes; and (iii) the potential involvement of genes in linkage disequilibrium with Gp-9 are needed to elucidate the genetic architecture underlying social organization in fire ants. Information that reveals the links between molecular variation, individual phenotype, and colony-level behaviors, combined with behavioral models that incorporate details of the chemical communication involved in regulating queen number, will yield a novel integrated view of the evolutionary changes underlying a key social adaptation.

A machine learning approach for the identification of odorant binding proteins from sequence-derived properties

Background

Odorant binding proteins (OBPs) are believed to shuttle odorants from the environment to the underlying odorant receptors, for which they could potentially serve as odorant presenters. Although several sequence based search methods have been exploited for protein family prediction, less effort has been devoted to the prediction of OBPs from sequence data and this area is more challenging due to poor sequence identity between these proteins.

Results

In this paper, we propose a new algorithm that uses Regularized Least Squares Classifier (RLSC) in conjunction with multiple physicochemical properties of amino acids to predict odorant-binding proteins. The algorithm was applied to the dataset derived from Pfam and GenDiS database and we obtained overall prediction accuracy of 97.7% (94.5% and 98.4% for positive and negative classes respectively).

Conclusion

Our study suggests that RLSC is potentially useful for predicting the odorant binding proteins from sequence-derived properties irrespective of sequence similarity. Our method predicts 92.8% of 56 odorant binding proteins non-homologous to any protein in the swissprot database and 97.1% of the 414 independent dataset proteins, suggesting the usefulness of RLSC method for facilitating the prediction of odorant binding proteins from sequence information.

Antibodies from dogs with canine visceral leishmaniasis recognise two proteins from the saliva of Lutzomyia longipalpis

The saliva of the sand fly Lutzomyia longipalpis, a major vector of Leishmania, exhibits pharmacological and immunomodulatory activities that may facilitate entry and establishment of parasites into the vertebrate host. Salivary gland components of the sand fly are, therefore, potential candidates in the development of a vaccine against human leishmaniasis. With the objective of identifying sand fly saliva proteins that could be used to immunise animals against canine visceral leishmaniasis, we have evaluated anti-saliva antibody reactivity using serum samples collected from dogs naturally infected with Leishmania chagasi. Two proteins with molecular weights of 28.6 and 47.3 kDa were recognised by dog antibodies in Western blot assays. Protein bands were excised from an SDS-PAGE gel and the sequences determined by mass spectrometry. The proteins were identified as LuLo-D7 and Lulo YELLOW, respectively. The significance of these findings in the context of the development of multi-component vaccination experiments is discussed.

Disulfide connectivity and reduction in pheromone-binding proteins of the gypsy moth, Lymantria dispar

Males of the gypsy moth, Lymantria dispar, are attracted by a pheromone released by females. Pheromones are detected by olfactory neurons housed in specialized sensory hairs located on the antennae of the male moth. Once pheromone molecules enter the sensilla lymph, a highly abundant pheromone-binding protein (PBP) transports the molecule to the sensory neuron. The PBPs are members of the insect odorant-binding protein family, with six conserved cysteine residues. In this study, the disulfide bond connectivities of the pheromone-binding proteins PBP1 and PBP2 from the gypsy moth were found to be cysteines 19-54, 50-109, and 97-118 for PBP1, and cysteines 19-54, 50-110, and 97-119 for PBP2, as determined by cyanylation reactions and cyanogen bromide chemical cleavage. We have discovered that the second disulfide linkage is the most easily reduced of the three, and this same linkage is missing among four cysteine-containing insect odorant-binding proteins (OBPs). We are the first to identify the unique steric and electronic properties of this second disulfide linkage.

Antennal expressed genes of the yellow fever mosquito (Aedes aegypti L.); characterization of odorant-binding protein 10 and takeout

A small cDNA library was constructed from antennae of 100 adult male Aedes aegypti yellow fever mosquitoes. Sequencing of 80 clones identified 49 unique gene products, including a member of the Odorant Binding Protein family (Aaeg-OBP10), a homologue of Takeout (Aaeg-TO), and transposable elements of the LINE, SINE and MITE classes. Aaeg-OBP10 encodes a 140 amino acid protein including a predicted 25 amino acid signal peptide. Aaeg-OBP10 expression was adult male enriched, increased with adult age, and greatest in antennae and wings but also present in maxillary palps, proboscis and leg. Aaeg-OBP10 is a likely orthologue of Agam-OBP10 of the malaria mosquito Anopheles gambiae and shares significant similarity with members of the OBP56 gene cluster of Drosophila melanogaster. These OBP genes may represent a unified class of OBPs with unique roles in chemodetection; the expression pattern of Aaeg-OBP10 suggests it may play a role in adult male chemosensory behavior. Aaeg-TO encodes a 248 amino acid protein including a predicted 22 amino acid signal peptide. Aaeg-TO is homologous with the circadian/feeding regulated D. melanogaster Takeout protein (Dmel-TO) and a subclass of Juvenile Hormone Binding Proteins (JHBP) characterized by Moling from Manduca sexta; both Dmel-TO and Moling are sensitive to feeding, suggesting Aaeg-TO might regulate the antennal response to food, host or pheromonal odors in a JH sensitive manner. Aaeg-TO was used to identify 25 D. melanogaster and 13 A. gambiae homologues by Blast analysis suggesting these may comprise a relatively large class of protein involved in the hormonal regulation of behavior.

The major salivary gland antigens of Culex quinquefasciatus are D7-related proteins

The sera of persons with strong allergic responses to the bites of the mosquito, Culex quinquefasciatus, contained IgE antibodies reactive with two major salivary gland proteins with molecular weights of 35 and 28 kDa. These antigens were purified, their amino termini sequenced, and the sequences were used to search for similar sequences in public databases. Two cDNAs, CuQu-D7Clu1 and CuQu-D7Clu12, which encode D7-related proteins, were identified as containing predicted amino acid sequences identical to the 35 and 28 kDa antigens, respectively. These proteins are expressed specifically in adult female salivary glands and, their predicted tertiary structures are consistent with a role as carriers of hydrophobic molecules in mosquito saliva.

The major acid soluble proteins of adult female Anopheles darlingi salivary glands include a member of the D7-related family of proteins

The salivary gland proteins of adult female Anopheles darlingi were fractionated by reverse-phase HPLC and the five major peaks were submitted for amino-terminal sequencing using automated Edman degradation. The amino acid sequence of one of the purified salivary gland proteins showed similarity with the D7r3 protein of An. gambiae. Cloning and sequencing of two cDNAs allowed the prediction of the complete sequence of the An. darlingi D7 protein. The D7r3 protein is present specifically in adult female salivary glands of An. darlingi and despite being one of the major salivary gland proteins its function is not known. Predictions of secondary and tertiary structures revealed the similarity of the An. darlingi D7 protein to insect odorant binding proteins. This suggests that D7 proteins may act as carriers of hydrophobic molecules in mosquito saliva.

Toward a description of the sialome of the adult female mosquito Aedes aegypti

To describe the set of mRNA and protein expressed in the salivary glands (sialome) of Aedes aegypti mosquitoes, we randomly sequenced a full-length cDNA library of this insect and performed Edman degradation of PVDF-transferred protein bands from salivary homogenates. We found 238 cDNA clusters which contained those coding for 10 of the 11 proteins found by aminoterminal degradation. All six previously described salivary proteins were found in this library. Full-length sequences of 32 novel cDNA sequences are reported, one of which is the product of a transposable element. Among the 31 novel protein sequences are 4 additional members of the D7 protein family; 4 novel members of the antigen 5 family (a protein family not reported in Aedes); a novel serpin; a novel member of the 30-kDa allergen of Ae. Aegypti; a secreted calreticulin; 2 proteins similar to mammalian angiopoietins; adenosine deaminase; purine hydrolase; lysozyme; a C-type lectin; 3 serine proteases, including one with high similarity to Bombyx prophenoloxidase activating enzyme; 2 proteins related to invertebrate immunity; and several sequences that have no significant matches to known proteins. The possible role of these proteins in blood and sugar feeding by the mosquito is discussed.

Genome-wide analysis of the odorant-binding protein gene family in Drosophila melanogaster

Olfaction is of considerable importance to many insects in behaviors critical for survival and reproduction, including location of food sources, selection of mates, recognition of colony con-specifics, and determination of oviposition sites. An ubiquitous, but poorly understood, component of the insect's olfactory system is a group of odorant-binding proteins (OBPs) that are present at high concentrations in the aqueous lymph surrounding the dendrites of olfactory receptor neurons. OBPs are believed to shuttle odorants from the environment to the underlying odorant receptors, for which they could potentially serve as odorant presenters. Here we show that the Drosophila genome carries 51 potential OBP genes, a number comparable to that of its odorant-receptor genes. We find that the majority (73%) of these OBP-like genes occur in clusters of as many as nine genes, in contrast to what has been observed for the Drosophila odorant-receptor genes. Two of the presumptive OBP gene clusters each carries an odorant-receptor gene. We also report an intriguing subfamily of 12 putative OBPs that share a unique C-terminal structure with three conserved cysteines and a conserved proline. Members of this subfamily have not previously been described for any insect. We have performed phylogenetic analyses of the OBP-related proteins in Drosophila as well as other insects, and we discuss the duplication and divergence of the genes for this large family. [The sequence data from this study have been submitted to FlyBase. Annotations for these sequences are available as supplementary material at http://www.genome.org.]

The odorant-binding proteins of Drosophila melanogaster: annotation and characterization of a divergent gene family

Insect odorant-binding proteins (OBPs) are thought to facilitate the delivery of hydrophobic odorants, such as sex pheromones or food odors, to receptors on sensory neurons. Increasingly, OBP family members are also being found in non-sensory tissues where they might carry other types of small hydrophobic molecules. They are identifiable by four or six conserved Cys residues and contain six alpha-helices which enclose a hydrophobic ligand-binding pocket. Through exhaustive BLAST searches we have increased the total number of OBPs identified in Drosophila melanogaster to 38, and have amplified the DNA complementary to RNA corresponding to 21 of these by reverse transcriptase polymerase chain reaction. Isoforms frequently share less than 30% amino acid identity and appear to have radically changed since the separation of the major insect orders. However, their sequences are consistent with known OBP structures. Most are located in clusters of between four and 14 genes and several were unusual in that they contained additions, deletions, or fusions. These hexa-helical insect OBPs are structurally unrelated to the functionally analogous lipocalin-like beta-barrel OBPs of vertebrates. As only two lipocalin-like proteins have been found in D. melanogaster, these helical proteins appear to be the dominant carrier of small hydrophobic molecules in insects.

The D7 family of salivary proteins in blood sucking diptera

The D7 subfamily of salivary proteins is widespread in blood sucking Diptera and belongs to the superfamily of pheromone/odourant binding proteins. Although D7 proteins are among the most abundant salivary proteins in adult female mosquitoes and sand flies, their role in blood feeding remains elusive. In the present work we report the sequence of seventeen novel D7 proteins, and propose an evolutionary scenario for the appearance of the several forms of this protein, based on a total of twenty-one sequences from Culex quinquefasciatus, Aedes aegypti, Anopheles gambiae, An. arabiensis, An. stephensi, An. darlingi mosquitoes and Lutzomyia longipalpis and Phlebotomus papatasi sand flies.

Isolation of cDNA clones encoding putative odourant binding proteins from the antennae of the malaria-transmitting mosquito, Anopheles gambiae

One way of controlling disease transmission by blood-feeding mosquitoes is to reduce the frequency of insect-host interaction, thus reducing the probability of parasite transmission and re-infection. A better understanding of the olfactory processes responsible for allowing mosquitoes to identify human hosts is required in order to develop methods that will interfere with host seeking. We have therefore initiated a molecular approach to isolate and characterize the genes and their products that are involved in the olfactory recognition pathway of the mosquito Anopheles gambiae, which is the main malaria vector in sub-Saharan Africa. We report here the isolation and preliminary characterization of several cDNAs from male and female A. gambiae antennal libraries that encode putative odourant binding proteins. Their conceptual translation products show extensive sequence similarity to known insect odourant binding proteins (OBPs)/pheromone binding proteins (PBPs), especially to those of D. melanogaster. The A. gambiae OBPs described here are expressed in the antennae of both genders, and some of the A. gambiae OBP genes are well conserved in other disease-transmitting mosquito species, such as Aedes aegypti and Culex quinquefasciatus.

A cluster of four D7-related genes is expressed in the salivary glands of the African malaria vector Anopheles gambiae

Four genes expressed in the Anopheles gambiae adult female salivary glands and similar in sequence to the Aedes aegypti D7 gene were identified. The genes, called D7-related (D7r), are included in a single cluster encompassing approximately six kilobases on chromosome arm 3R. The deduced proteins contain secretory signals and they are probably injected by the mosquito into the host with the saliva during blood feeding. The region of similarity to D7 encompasses the carboxy-terminal part of the Ae. aegypti protein and the different An. gambiae D7r show a degree of similarity to each other, varying from 53% to 73%. The weak but significant similarity to members of a wide family of insect proteins, including odourant- and pheromone-binding proteins, raises the possibility that the D7r-encoded proteins may bind and/or carry small hydrophobic ligands.