Expression, production and excretion of Bla g 1, a major human allergen, in relation to food intake in the German cockroach, Blattella germanica

HcGr76 responds to fructose and chlorogenic acid and is involved in regulation of peptide expression in the midgut of Hyphantria cunea larvae

BACKGROUND

Sensing dietary components in the gut is important to ensure an appropriate hormonal response and metabolic regulation after food intake. The fall webworm, Hyphantria cunea, is a major invasive pest in China and has led to significant economic losses and ecosystem disruption. The larvae's broad host range and voracious appetite for leaves make H. cunea a primary cause of serious damage to both forests and crops. To date, however, the gustatory receptors (Grs) of H. cunea and their regulatory function remain largely unknown.

RESULTS

We identified the fall webworm gustatory receptor HcGr76 as a fructose and chlorogenic acid receptor using Ca2+ imaging and determination of intracellular Ca2+ concentration by a microplate reader. Moreover, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis revealed that HcGr76 is highly expressed in the anterior and middle midgut. Knockdown of HcGr76 caused a significant reduction in the expression of neuropeptide F 1 (NPF1) and CCHamide-2, and led to a decrease in carbohydrate and lipid levels in the hemolymph.

CONCLUSION

Our studies provide circumstantial evidence that HcGr76 expressed in the midgut is involved in sensing dietary components, and regulates the expression of relevant peptide hormones to alter metabolism in H. cunea larvae, thus providing a promising molecular target for the development of new insect-specific control products. © 2024 Society of Chemical Industry.

Evolution of a Cockroach Allergen into the Major Protein of Termite Royal Jelly

Termites live in colonies, and their members belong to different castes that each have their specific role within the termite society. In well-established colonies of higher termites, the only food the founding female, the queen, receives is saliva from workers; such queens can live for many years and produce up to 10,000 eggs per day. In higher termites, worker saliva must thus constitute a complete diet and therein resembles royal jelly produced by the hypopharyngeal glands of honeybee workers that serves as food for their queens; indeed, it might as well be called termite royal jelly. However, whereas the composition of honeybee royal jelly is well established, that of worker termite saliva in higher termites remains largely unknown. In lower termites, cellulose-digesting enzymes constitute the major proteins in worker saliva, but these enzymes are absent in higher termites. Others identified a partial protein sequence of the major saliva protein of a higher termite and identified it as a homolog of a cockroach allergen. Publicly available genome and transcriptome sequences from termites make it possible to study this protein in more detail. The gene coding the termite ortholog was duplicated, and the new paralog was preferentially expressed in the salivary gland. The amino acid sequence of the original allergen lacks the essential amino acids methionine, cysteine and tryptophan, but the salivary paralog incorporated these amino acids, thus allowing it to become more nutritionally balanced. The gene is found in both lower and higher termites, but it is in the latter that the salivary paralog gene got reamplified, facilitating an even higher expression of the allergen. This protein is not expressed in soldiers, and, like the major royal jelly proteins in honeybees, it is expressed in young but not old workers.

Dietary compounds activate an insect gustatory receptor on enteroendocrine cells to elicit myosuppressin secretion

Sensing of midgut internal contents is important for ensuring appropriate hormonal response and digestion following the ingestion of dietary components. Studies in mammals have demonstrated that taste receptors (TRs), a subgroup of G protein-coupled receptors (GPCRs), are expressed in gut enteroendocrine cells (EECs) to sense dietary compounds and regulate the production and/or secretion of peptide hormones. Although progress has been made in identifying expression patterns of gustatory receptors (GRs) in gut EECs, it is currently unknown whether these receptors, which act as ligand-gated ion channels, serve similar functions as mammalian GPCR TRs to elicit hormone production and/or secretion. A Bombyx mori Gr, BmGr6, has been demonstrated to express in cells by oral sensory organs, midgut and nervous system; and to sense isoquercitrin and chlorogenic acid, which are non-nutritional secondary metabolites of host mulberry. Here, we show that BmGr6 co-expresses with Bommo-myosuppressin (BMS) in midgut EECs, responds to dietary compounds and is involved in regulation of BMS secretion. The presence of dietary compounds in midgut lumen after food intake resulted in an increase of BMS secretions in hemolymph of both wild-type and BmGr9 knockout larvae, but BMS secretions in BmGr6 knockout larvae decreased relative to wild-type. In addition, loss of BmGr6 led to a significant decrease in weight gain, excrement, hemolymph carbohydrates levels and hemolymph lipid levels. Interestingly, although BMS is produced in both midgut EECs and brain neurosecretory cells (NSCs), BMS levels in tissue extracts suggested that the increase in hemolymph BMS during feeding conditions is primarily due to secretion from midgut EECs. Our studies indicate that BmGr6 expressed in midgut EECs responds to the presence of dietary compounds in the lumen by eliciting BMS secretion in B. mori larvae.

Cockroach allergy: Understanding complex immune responses to develop novel therapies

Cockroach allergy is associated with the development of asthma. The identification of cockroach allergens, which began in the 1990 s, is an ongoing process that has led to the current listing of 20 official allergen groups in the WHO/IUIS Allergen Nomenclature database. The function and structure of some of these allergens has been determined and define their natural delivery into the environment and their allergenicity. Analysis of antigenic determinants by X-ray crystallography and rational design of site-directed mutagenesis led to the identification of IgE binding sites for the design of molecules with reduced IgE reactivity and T cell modulatory capacity. New developments in recent years include component analyses of B and T cell reactivity and a recent cockroach immunotherapy trial, CRITICAL, that will contribute to understand the immune response to cockroach and to define future directions for cockroach allergy diagnosis and immunotherapy.

Comparative Efficacy of a Fungal Entomopathogen with a Broad Host Range against Two Human-Associated Pests

The ability of a fungal entomopathogen to infect an insect depends on a variety of factors, including strain, host, and environmental conditions. Similarly, an insect’s ability to prevent fungal infection is dependent on its biology, environment, and evolutionary history. Synanthropic pests have adapted to thrive in the indoor environment, yet they arose from divergent evolutionary lineages and occupy different feeding guilds. The hematophagous bed bug (Cimex lectularius) and omnivorous German cockroach (Blattella germanica) are highly successful indoors, but have evolved different physiological and behavioral adaptations to cope with the human-built environment, some of which also reduce the efficacy of fungal biopesticides. In order to gain greater insight into the host barriers that prevent or constrain fungal infection in bed bugs and German cockroaches, we tested different doses of Beauveria bassiana GHA through surface contact, topical application, feeding, and injection. Bed bugs were generally more susceptible to infection by B. bassiana with the mode of delivery having a significant impact on infectivity. The German cockroach was highly resilient to infection, requiring high doses of fungal conidia (>8.8 × 104) delivered by injection into the hemocoel to cause mortality. Mortality occurred much faster in both insect species after exposure to surfaces dusted with dry conidia than surfaces treated with conidia suspended in water or oil. These findings highlight the importance of developing innovative delivery techniques to enhance fungal entomopathogens against bed bugs and cockroaches.

Reduced production of the major allergens Bla g 1 and Bla g 2 in Blattella germanica after antibiotic treatment

PURPOSE

Allergens present in the feces or frass of cockroaches can cause allergic sensitization in humans. The use of fecal and frass extracts for immunotherapy has been previously investigated but has not yet been fully standardized. Here, we treated cockroaches with ampicillin to produce extracts with reduced amounts of total bacteria.

METHODS

We performed targeted high-throughput sequencing of 16S rDNA to compare the microbiomes of ampicillin-treated and untreated (control) cockroaches. RNA-seq was performed to identify differentially expressed genes (DEGs) in ampicillin-treated cockroaches.

RESULTS

Analysis of the microbiome revealed that alpha diversity was lower in the ampicillin-treated group than in the control group. Beta diversity analysis indicated that ampicillin treatment altered bacterial composition in the microbiome of cockroaches. Quantitative polymerase chain reaction revealed that almost all bacteria were removed from ampicillin-treated cockroaches. RNA-seq analysis revealed 1,236 DEGs in ampicillin-treated cockroaches (compared to untreated cockroaches). Unlike bacterial composition, the DEGs varied between the two groups. Among major allergens, the expression of Bla g 2 decreased significantly in ampicillin-treated cockroaches (compared to untreated group).

CONCLUSIONS

In this study, the reduced level of allergens observed in cockroaches may be related to lower amounts of total bacteria caused by treatment with antibiotics. It is possible to make a protein extract with few bacteria for use in immunotherapy.

Abundance and Stability as Common Properties of Allergens

There have been many attempts to identify common biophysical properties which differentiate allergens from their non-immunogenic counterparts. This review will focus on recent studies which examine two such factors: abundance and stability. Anecdotal accounts have speculated that the elevated abundance of potential allergens would increase the likelihood of human exposure and thus the probability of sensitization. Similarly, the stability of potential allergens dictates its ability to remain a viable immunogen during the transfer from the source to humans. This stability could also increase the resilience of potential allergens to both gastric and endosomal degradation, further skewing the immune system toward allergy. Statistical analyses confirm both abundance and stability as common properties of allergens, while epidemiological surveys show a correlation between exposure levels (abundance) and allergic disease. Additional studies show that changes in protein stability can predictably alter gastric/endosomal processing and immunogenicity, providing a mechanistic link between stability and allergenicity. However, notable exceptions exist to both hypotheses which highlight the multifaceted nature of immunological sensitization, and further inform our understanding of some of these other factors and their contribution to allergic disease.

Allergens and their associated small molecule ligands-their dual role in sensitization

Many allergens feature hydrophobic cavities that allow the binding of primarily hydrophobic small‐molecule ligands. Ligand‐binding specificities can be strict or promiscuous. Serum albumins from mammals and birds can assume multiple conformations that facilitate the binding of a broad spectrum of compounds. Pollen and plant food allergens of the family 10 of pathogenesis‐related proteins bind a variety of small molecules such as glycosylated flavonoid derivatives, flavonoids, cytokinins, and steroids in vitro. However, their natural ligand binding was reported to be highly specific. Insect and mammalian lipocalins transport odorants, pheromones, catecholamines, and fatty acids with a similar level of specificity, while the food allergen β‐lactoglobulin from cow's milk is notably more promiscuous. Non‐specific lipid transfer proteins from pollen and plant foods bind a wide variety of lipids, from phospholipids to fatty acids, as well as sterols and prostaglandin B2, aided by the high plasticity and flexibility displayed by their lipid‐binding cavities. Ligands increase the stability of allergens to thermal and/or proteolytic degradation. They can also act as immunomodulatory agents that favor a Th2 polarization. In summary, ligand‐binding allergens expose the immune system to a variety of biologically active compounds whose impact on the sensitization process has not been well studied thus far.

The allergenic activity and clinical impact of individual IgE-antibody binding molecules from indoor allergen sources

A large number of allergens have been discovered but we know little about their potential to induce inflammation (allergenic activity) and symptoms. Nowadays, the clinical importance of allergens is determined by the frequency and intensity of their IgE antibody binding (allergenicity). This is a rather limited parameter considering the development of experimental allergology in the last 20 years and the criteria that support personalized medicine. Now it is known that some allergens, in addition to their IgE antibody binding properties, can induce inflammation through non IgE mediated pathways, which can increase their allergenic activity. There are several ways to evaluate the allergenic activity, among them the provocation tests, the demonstration of non-IgE mediated pathways of inflammation, case control studies of IgE-binding frequencies, and animal models of respiratory allergy. In this review we have explored the current status of basic and clinical research on allergenic activity of indoor allergens and confirm that, for most of them, this important property has not been investigated. However, during recent years important advances have been made in the field, and we conclude that for at least the following, allergenic activity has been demonstrated: Der p 1, Der p 2, Der p 5 and Blo t 5 from HDMs; Per a 10 from P. americana; Asp f 1, Asp f 2, Asp f 3, Asp f 4 and Asp f 6 from A. fumigatus; Mala s 8 and Mala s 13 from M. sympodialis; Alt a 1 from A. alternata; Pen c 13 from P. chrysogenum; Fel d 1 from cats; Can f 1, Can f 2, Can f 3, Can f 4 and Can f 5 from dogs; Mus m 1 from mice and Bos d 2 from cows. Defining the allergenic activity of other indoor IgE antibody binding molecules is necessary for a precision-medicine-oriented management of allergic diseases.

Function of myosuppressin in regulating digestive function in the two-spotted cricket, Gryllus bimaculatus

Myosuppressin is one of essential peptides controlling biological processes including feeding behavior. Here we identified and characterized the cDNAs that encode myosuppressin precursor and its receptor in the two-spotted cricket Gryllus bimaculatus. The presence of the mature peptide (Grybi-MS) was confirmed by direct measurement of adult brain. RT-PCR revealed the tissue distribution of these transcripts; myosuppressin is expressed predominantly in the brain and central nervous system, whereas its receptor is ubiquitously expressed in the cricket body. To address the function of Grybi-MS, we performed several bioassays to test concerning feeding behavior and digestive function upon exposure to Grybi-MS. Administration of synthetic Grybi-MS resulted in increased feeding motivation, accompanied by an increase in food intake. Meanwhile, the hemolymph lipid and carbohydrate titers were both elevated after Grybi-MS injection. As the intestinal contraction is significantly inhibited by the exposure to Grybi-MS, the upregulating feeding index might be complicated in the cricket body. The current data indicate that Grybi-MS modulates feeding behavior to control the physiological processes in the cricket.

Monomorium ant is a carrier for pathogenic and potentially pathogenic bacteria

Objectives

Household ants are regarded as a major household pest and their close association with microorganisms and people means that they may constitute a disease risk. Our study is the first to provide information on the pathogenicity of Monomorium spp. a common insect in Kuwait by quantifying and identifying the exoskeleton bacterial burden. Samples of Monomorium were collected in June from indoor and outdoor sites of 30 houses located in two residential districts.

Results

The study identified a total of 16 different species of Gram-negative bacteria of which the indoor isolates were 75% greater in species count than the outdoor samples. Indoor isolates identified from both districts were more frequent than the outdoors and similar trends were obtained for a single district. Outdoor ant samples on the other hand carried a high percentage of bacteria but with less diversity in both districts. There was a significant variability in bacterial species in relation to sample sources, indoor and outdoor, and discrete geographical location. The presence of a high percentage of pathogenic and potentially pathogenic bacteria indoor poses a great threat to domestic households, which would be further exacerbated in places with poor standards of hygiene.

Are Cockroaches an Important Source of Indoor Endotoxins?

Endotoxins are common indoor biocontaminants. Their levels have been shown to link to many sources and factors. One of them is cockroach infestation but the role of cockroaches and contamination mechanisms are unclear. We hypothesized that not only is cockroach infestation a sign of poor hygiene, but it also contributes to indoor endotoxins via fecal contamination. In this study, different cockroach species were caught in homes. The endotoxin and allergen levels and their ratios in cockroach feces were determined. To estimate the amount of indoor endotoxins that originated from cockroaches, a new approach of using these new cockroach endotoxin and allergen ratios to compare with environmental data was employed. We found that Supella (S.) longipalpa, Periplaneta (P.) australasiae, and Blattella (B.) germanica were dominant in homes. On average, P. australasiae feces had a higher level but greater variation of endotoxins. B. germanica feces had the highest levels of allergens measured. Depending on environmental bacterial load and the type of cockroaches present, cockroach endotoxins in the environment may vary greatly. Cockroaches directly contribute to indoor endotoxins rather than just being a sign of poor hygiene. The type and extent of cockroach infestation should be taken into consideration when assessing and remediating indoor endotoxin contamination.

Microarray-based annotation of the gut transcriptome of the migratory locust, Locusta migratoria

The migratory locust, Locusta migratoria, is a serious agricultural pest and important insect model in the study of insect digestion and feeding behaviour. The gut is one of the primary interfaces between the insect and its environment. Nevertheless, knowledge on the gut transcriptome of L. migratoria is still very limited. Here, 48 802 expressed sequence tags were extracted from publicly available databases and their expression in larval gut and/or brain tissue was determined using microarray hybridization. Our data show 2765 transcripts predominantly or exclusively expressed in the gut. Many transcripts had putative functions closely related to the physiological functions of the gut as a muscular digestive organ and as the first barrier against microorganisms and a wide range of toxins. By means of a ranking procedure based on the relative signal intensity, we estimated 15% of the transcripts to show high expression levels, the highest belonging to diverse digestive enzymes and muscle-related proteins. We also found evidence for very high expression of an allergen protein, which could have important implications, as locusts form a traditional food source in various parts of the world, and were also recently added to the list of insects fit for human consumption in Europe. Interestingly, many highly expressed sequences have as yet unknown functions. Taken together, the present data provide significant insight into locust larval gut physiology, and will be valuable for future studies on the insect gut.

Allergenic characterization of a novel allergen, homologous to chymotrypsin, from german cockroach

Purpose

Cockroach feces are known to be rich in IgE-reactive components. Various protease allergens were identified by proteomic analysis of German cockroach fecal extract in a previous study. In this study, we characterized a novel allergen, a chymotrypsin-like serine protease.

Methods

A cDNA sequence homologous to chymotrypsin was obtained by analysis of German cockroach expressed sequence tag (EST) clones. The recombinant chymotrypsins from the German cockroach and house dust mite (Der f 6) were expressed in Escherichia coli using the pEXP5NT/TOPO vector system, and their allergenicity was investigated by ELISA.

Results

The deduced amino acid sequence of German cockroach chymotrypsin showed 32.7 to 43.1% identity with mite group 3 (trypsin) and group 6 (chymotrypsin) allergens. Sera from 8 of 28 German cockroach allergy subjects (28.6%) showed IgE binding to the recombinant protein. IgE binding to the recombinant cockroach chymotrypsin was inhibited by house dust mite chymotrypsin Der f 6, while it minimally inhibited the German cockroach whole body extract.

Conclusions

A novel allergen homologous to chymotrypsin was identified from the German cockroach and was cross-reactive with Der f 6.

Genomic, RNAseq, and molecular modeling evidence suggests that the major allergen domain in insects evolved from a homodimeric origin

The major allergen domain (MA) is widely distributed in insects. The crystal structure of a single Bla g 1 MA revealed a novel protein fold in which the fundamental structure was a duplex of two subsequences (monomers), which had diverged over time. This suggested that the evolutionary origin of the MA structure may have been a homodimer of this smaller subsequence. Using publicly available genomic data, the distribution of the basic unit of this class of proteins was determined to better understand its evolutionary history. The duplication and divergence is examined at three distinct levels of resolution: 1) within the orders Diptera and Hymenoptera, 2) within one genus Drosophila, and 3) within one species Aedes aegypti. Within the family Culicidae, we have found two separate occurrences of monomers as independent genes. The organization of the gene family in A. aegypti shows a common evolutionary origin for its monomer and several closely related MAs. Molecular modeling of the A. aegypti monomer with the unique Bla g 1 fold confirms the distant evolutionary relationship and supports the feasibility of homodimer formation from a single monomer. RNAseq data for A. aegypti confirms that the monomer is expressed in the mosquito similar to other A. aegypti MAs after a blood meal. Together, these data support the contention that the detected monomer shares similar functional characteristics to related MAs in other insects. An extensive search for this domain outside of Insecta confirms that the MAs are restricted to insects.

Recombinant allergens for diagnosis of cockroach allergy

Molecular cloning of cockroach allergens and their expression as recombinant proteins have allowed a better understanding of the mechanisms of cockroach allergic disease. Recombinant cockroach allergens have been used for skin testing or in vitro methods to measure IgE antibody levels in serum. Early studies evaluating selected U.S. patients revealed that a cocktail of four cockroach allergens, Bla g 1, Bla g 2, Bla g 4, and Bla g 5, would identify 95 % of cockroach allergic patients. More recent studies pointed to an important role of sensitization to tropomyosin among certain populations, and suggested that a cocktail of five allergens Bla g 1 and/or Per a 1, Bla g 2, Bla g 4, Bla g 5, and Bla g 7, and/or Per a 7, would be expected to diagnose 50- 64 % of cockroach-allergic patients worldwide. Variation in IgE reactivity profiles could be in part due to IgE responses to cross-reactive homologous allergens from different origins. The availability of purified natural or recombinant cockroach allergens provides the capacity to improve diagnosis of cockroach allergy and to develop novel forms of immunotherapy for cockroach-allergic patients.

Current status of standardization of inhalant allergen extracts in Korea

Allergy diagnosis and immunotherapy in Korea rely mostly on imported allergen extracts. However, some allergens that are not important in Western countries are not commercially available, and even the same species of allergen source often displays differences in allergenicity due to amino acid sequence polymorphisms. Therefore, it is essential to prepare allergen extracts that reflect regional characteristics. Allergen standardization has been performed since 2009 with the support of the Korea Center for Disease Control and Prevention. Here, we summarize the current status of allergen standardization, focusing on the house dust mite and cockroach. Pollen allergens that are under investigation are also briefly described.

Environmental assessment and exposure reduction of cockroaches: a practice parameter

This parameter was developed by the Joint Task Force on Practice Parameters, representing the American Academy of Allergy, Asthma & Immunology (AAAAI); the American College of Allergy, Asthma & Immunology (ACAAI); and the Joint Council of Allergy, Asthma & Immunology. The AAAAI and the ACAAI have jointly accepted responsibility for establishing "Environmental assessment and remediation: a practice parameter." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single person, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion. The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention (CDC).

Investigating cockroach allergens: aiming to improve diagnosis and treatment of cockroach allergic patients

Cockroach allergy is an important health problem associated with the development of asthma, as a consequence of chronic exposure to low levels of allergens in susceptible individuals. In the last 20 years, progress in understanding the disease has been possible, thanks to the identification and molecular cloning of cockroach allergens and their expression as recombinant proteins. Assays for assessment of environmental allergen exposure have been developed and used to measure Bla g 1 and Bla g 2, as markers of cockroach exposure. IgE antibodies to cockroach extracts and to specific purified allergens have been measured to assess sensitization and analyze association with exposure and disease. With the development of the field of structural biology and the expression of recombinant cockroach allergens, insights into allergen structure, function, epitope mapping and allergen-antibody interactions have provided further understanding of mechanisms of cockroach allergic disease at the molecular level. This information will contribute to develop new approaches to allergen avoidance and to improve diagnosis and therapy of cockroach allergy.

The novel structure of the cockroach allergen Bla g 1 has implications for allergenicity and exposure assessment

BACKGROUND

Sensitization to cockroach allergens is a major risk factor for asthma. The cockroach allergen Bla g 1 has multiple repeats of approximately 100 amino acids, but the fold of the protein and its biological function are unknown.

OBJECTIVE

We sought to determine the structure of Bla g 1, investigate the implications for allergic disease, and standardize cockroach exposure assays.

METHODS

nBla g 1 and recombinant constructs were compared by using ELISA with specific murine IgG and human IgE. The structure of Bla g 1 was determined by x-ray crystallography. Mass spectrometry and nuclear magnetic resonance spectroscopy were used to examine the ligand-binding properties of the allergen.

RESULTS

The structure of an rBla g 1 construct with comparable IgE and IgG reactivity to the natural allergen was solved by x-ray crystallography. The Bla g 1 repeat forms a novel fold with 6 helices. Two repeats encapsulate a large and nearly spherical hydrophobic cavity, defining the basic structural unit. Lipids in the cavity varied depending on the allergen origin. Palmitic, oleic, and stearic acids were associated with nBla g 1 from cockroach frass. One unit of Bla g 1 was equivalent to 104 ng of allergen.

CONCLUSIONS

Bla g 1 has a novel fold with a capacity to bind various lipids, which suggests a digestive function associated with nonspecific transport of lipid molecules in cockroaches. Defining the basic structural unit of Bla g 1 facilitates the standardization of assays in absolute units for the assessment of environmental allergen exposure.

Knockdown of the adipokinetic hormone receptor increases feeding frequency in the two-spotted cricket Gryllus bimaculatus

Adipokinetic hormone (AKH) is a peptide hormone that regulates the nutritional state in insects by supporting the mobilization of lipids. In the present study, we manipulated AKH signaling to evaluate how metabolic state regulates feeding in an orthopteran insect, the two-spotted cricket, Gryllus bimaculatus. This was accomplished by RNA interference (RNAi) targeting the receptor gene for AKH [G. bimaculatus AKHR (GrybiAKHR)]. We found that the knockdown of GrybiAKHR by AKHR-double-stranded RNA treatment decreased the levels of 1,2-diacylglycerol and trehalose in the hemolymph, whereas it increased the level of triacylglycerol in the fat body. In addition, the knockdown of GrybiAKHR enhanced starvation resistance and increased food intake. Furthermore, direct observation of GrybiAKHR(RNAi) crickets revealed that the knockdown of GrybiAKHR increased feeding frequency but did not alter meal duration, whereas locomotor activity decreased. The increased frequency of feeding by GrybiAKHR(RNAi) crickets eventually resulted in an increase of food intake. These data demonstrate that the regulation of the metabolic state by AKH signaling affects feeding frequency, probably through nutritional control.

Complete mitochondrial genomes of two cockroaches, Blattella germanica and Periplaneta americana, and the phylogenetic position of termites

The mitochondrial genomes are one of the most information-rich markers in phylogenetics. The relationships within superorder Dictyoptera have been debated in the literature. However, the closely related termites (Isoptera) are retained as unranked taxon within the order Blattaria (cockroaches). In this work, we sequenced the complete mitogenomes of two cockroaches, reconstructed the molecular phylogeny and attempted to infer the phylogenetic position of termites in Blattaria more reliably. The complete mtDNA nucleotide sequences of the peridomestic American cockroach (Periplaneta americana L.) and the domestic German cockroach (Blattella germanica L.) are 15,025 and 15,584 bp in size, respectively. The genome shares the gene order and orientation with previously known Blattaria mitogenomes. Most tRNAs could be folded into the typical cloverleaf secondary structure, but the tRNA-Ser (AGN) of P. americana appears to be missing the dihydrouridine arm. Using nucleotide and amino acid sequences as phylogenetic markers, we proposed that termites should be treated as a superfamily (Termitoidea) of cockroaches. We suggested that Polyphagoidea was the sister group of Termitoidea in Blattaria and supported that the suborder Caelifera is more closely related to the Phasmatodea than to the suborder Ensifera of Orthoptera.

Proteome mining for novel IgE-binding proteins from the German cockroach (Blattella germanica) and allergen profiling of patients

Although cockroaches are known to produce allergens that can cause IgE-mediated hypersensitivity reactions, including perennial rhinitis and asthma, the various cockroach allergens have not yet been fully studied. Many proteins from the German cockroach show high IgE reactivity, but have never been comprehensively characterized. To identify these potential allergens, proteins were separated by 2-DE and IgE-binding proteins were analyzed by nanoLC-MS/MS or N-terminal sequencing analysis. Using a combination of proteomic techniques and bioinformatic allergen database analysis, we identified a total of ten new B. germanica IgE-binding proteins. Of these, aldolase, arginine kinase, enolase, Hsp70, triosephosphate isomerase, and vitellogenin have been reported as allergens in species other than B. germanica. Analysis of the Food Allergy Research and Resource Program allergen database indicated that arginine kinase, enolase, and triosephosphate isomerase showed significant potential cross-reactivity with other related allergens. This study revealed that vitellogenin is an important novel B. germanica allergen. Personalized profiling and reactivity of IgE Abs against the panel of IgE-binding proteins varied between cockroach-allergic individuals. These findings make it possible to monitor the individual IgE reactivity profile of each patient and facilitate personalized immunotherapies for German cockroach allergy disorders.

RNA interference-mediated knock-down of Bla g 1 in the German cockroach, Blattella germanica L., implicates this allergen-encoding gene in digestion and nutrient absorption

We used RNA interference (RNAi) to silence the expression of a gene encoding Bla g 1, a human allergen produced by the German cockroach, Blattella germanica L., to study its function in cockroach physiology. Females injected with 1 microg of double-stranded RNA contained 64% less Bla g 1 protein and Bla g 1 mRNA abundance was reduced by 91.4% compared to sham-injected females. Bla g 1 knockdown slowed the pace of weight gain, midgut growth, and colleterial gland and basal oocyte maturation, resulting in delayed egg case formation and lower fecundity. Exogenous juvenile hormone treatments rescued reproduction in RNAi-treated females, suggesting that Bla g 1 silencing lowered endogenous juvenile hormone, probably by reducing food intake and nutrient absorption.

Effects of heat shock on ovary development and hsp83 expression in Tribolium castaneum (Coleoptera: Tenebrionidae)

Heat shock affects reproductive performance in insects including Tribolium castaneum. In this study, the effects of heat shock on ovary development and hsp83 expression in T. castaneum were investigated. Two lines of T. castaneum, H line and C line, from the same base population were established and maintained for five successive generations. In each generation, the newly hatched beetles (within 3 h after eclosion) in the H line were treated with a heat shock at 40 degrees C for 1 h, and those in the C line were raised at normal temperature (30 degrees C) as control treatment. Four traits related to ovary development were measured for the beetles of the fifth generation: days from eclosion to laying the first eggs (T(o)), days from eclosion to laying the first hatchable eggs (T(h)), ovariole size on the third day after eclosion, and pupal mass of their offspring. The results showed that the beetles of the H line had a significantly longer pre-oviposition period (0.6 more days) and smaller ovariole size than those of the C line. No significant difference in pupal mass was observed. Applying heat shock to the offspring of the fifth generation of both lines led to significantly higher hsp83 expression in offspring of the C line than in offspring of the H line. Within each line, the hsp83 expression level in offspring with heat shock was significantly higher than that of offspring without heat shock, but the difference in the C line was much larger than that in the H line. We infer from these results that a tradeoff between heat resistance, registered as hsp83 expression, and ovarian development operates under heat stress in T. castaneum.

Evolutionary origins of a novel host plant detoxification gene in butterflies

Chemical interactions between plants and their insect herbivores provide an excellent opportunity to study the evolution of species interactions on a molecular level. Here, we investigate the molecular evolutionary events that gave rise to a novel detoxifying enzyme (nitrile-specifier protein [NSP]) in the butterfly family Pieridae, previously identified as a coevolutionary key innovation. By generating and sequencing expressed sequence tags, genomic libraries, and screening databases we found NSP to be a member of an insect-specific gene family, which we characterized and named the NSP-like gene family. Members consist of variable tandem repeats, are gut expressed, and are found across Insecta evolving in a dynamic, ongoing birth-death process. In the Lepidoptera, multiple copies of single-domain major allergen genes are present and originate via tandem duplications. Multiple domain genes are found solely within the brassicaceous-feeding Pieridae butterflies, one of them being NSP and another called major allergen (MA). Analyses suggest that NSP and its paralog MA have a unique single-domain evolutionary origin, being formed by intragenic domain duplication followed by tandem whole-gene duplication. Duplicates subsequently experienced a period of relaxed constraint followed by an increase in constraint, perhaps after neofunctionalization. NSP and its ortholog MA are still experiencing high rates of change, reflecting a dynamic evolution consistent with the known role of NSP in plant-insect interactions. Our results provide direct evidence to the hypothesis that gene duplication is one of the driving forces for speciation and adaptation, showing that both within- and whole-gene tandem duplications are a powerful force underlying evolutionary adaptation.

Cockroach allergen biology and mitigation in the indoor environment

For nearly a half century, cockroaches have been recognized as a major cause of asthma morbidity in the urban, inner-city environment. Several cockroach-produced allergens have been identified and characterized, and a few have been produced as recombinant proteins. Recent research has moved beyond clinical, patient-based investigations to a more entomological perspective that addresses the production, physiological regulation, and developmental expression of cockroach allergens, thus providing insight into their functional biology and their relationship to current cockroach control strategies. Although successful removal of cockroach allergens from the infested environment has been difficult to accomplish with remedial sanitation, large-scale reductions in cockroach allergens below clinically relevant thresholds have recently been realized through suppression of cockroach populations. Here we review the current understanding of cockroach allergen biology and the demographics associated with human exposure and sensitization. We also critically evaluate allergen mitigation studies from an entomological perspective, highlighting disparities between successful and failed attempts to lessen the cockroach allergen burden in homes.

Cloning and expression of trypsin-encoding cDNA from Blattella germanica and its possibility as an allergen

In this study, the trypsin gene (bgtryp-1) from the German cockroach, Blattella germanica, was cloned via the immunoscreening of patients with allergies to cockroaches. Nucleotide sequence analysis predicted an 863 bp open reading frame which encodes for 257 amino acids. The deduced amino acid sequence exhibited 42-57% homology with the serine protease from dust mites, and consisted of a conserved catalytic domain (GDSGGPLV). bgtryp-1 was determined by both Northern and Southern analysis to be a 0.9 kb, single-copy gene. SDS-PAGE and Western blotting analyses of the recombinant protein (Bgtryp-1) over-expressed in Escherichia coli revealed that the molecular mass of the expressed protein was 35 kDa, and the expressed protein was capable of reacting with the sera of cockroach allergy patients. We also discussed the possibility that trypsin excreted by the digestive system of the German cockroach not only functions as an allergen, but also may perform a vital role in the activation of PAR-2.