Vitellogenin of Blattella germanica (L.) (Dictyoptera, blattellidae): nucleotide sequence of the cDNA and analysis of the protein primary structure

IgE and T Cell Reactivity to a Comprehensive Panel of Cockroach Allergens in Relation to Disease

IgE sensitization to cockroach allergens is associated with development of allergic diseases, such as asthma. To understand the relevance of different cockroach allergens for diagnosis and immunotherapy, a comprehensive analysis of IgE antibody levels and T cell reactivity to an expanded set of cockroach allergens and their relationship to disease was performed in a cohort of USA cockroach sensitized patients. IgE antibody levels to recombinant chitinase and hemocyanin were measured for 23 subjects by custom-made ImmunoCAPs and compared with IgE levels to eight cockroach allergens we previously reported for the same cohort. Ex vivo T cell activation (Ox40/PDL-1 expression) of PBMCs stimulated with peptide pools derived from 11 German cockroach proteins, including nine official cockroach allergens, plus chitinase and vitellogenin, was determined by flow cytometry. IgE prevalences to chitinase (17%) and hemocyanin (44%) were comparable to values for the other eight allergens that we previously reported (21-57%). Hemocyanin (Bla g 3), was a major allergen (one to which more than 50% of patients with an allergy to its source react) for a sub-group of 15 highly cockroach-sensitized subjects (IgE > 3.5 kU_A/L: 53%). Chitinase was officially named as new allergen Bla g 12. Cockroach-specific IgE levels in plasma showed excellent correlation with the sum of 10 allergen-specific IgE (r = 0.94, p < 0.001). T cell reactivity to 11 proteins was highly variable among subjects, the highest being for vitellogenin, followed by Bla g 3. The main finding was that cockroach allergen-specific IgE and T cell reactivity patterns were unique per subject, and lacked immunodominant allergens and correlation with clinical phenotype/disease severity in the studied cohort. Knowing the subject-specific B/T cell reactivity profiles to a comprehensive panel of cockroach allergens will contribute to diagnosis of cockroach allergy and will be important for planning and assessing allergen immunotherapy outcomes, according to the allergen content in therapeutic cockroach extracts.

Chrysopa septempunctata (Neuroptera: Chrysopidae) Vitellogenin Functions Through Effects on Egg Production and Hatching

Vitellogenin (Vg) is a precursor of major egg storage protein, vitellin (Vt), and plays primary roles in reproduction of oviparous vertebrates and invertebrates. Chrysopa septempunctata Wesmael is an important and common predator of various insect pests. Here, we first cloned C. septempunctata Vg gene, CsVg. The complete CsVg cDNA was 5664 bp, which encodes an 1810-residues protein with a predicted molecular mass of 206.23 kDa. Expression profile revealed that CsVg mRNA first appeared on day 4 after emergence, maximally accumulated on day 10, and then declined gradually. RNAi mediated by injection of dsRNA depleted CsVg transcripts, significantly reduced egg-laying amount, and decreased egg hatching rate, suggesting that CsVg functions through effects on egg production and hatching in C. septempunctata.

Temporal variation of vitellogenin synthesis in Ectatomma tuberculatum (Formicidae: Ectatomminae) workers

Workers of the ant species Ectatomma tuberculatum (Ectatomminae) have active ovaries and lay eggs that are eaten by the queen and larvae (trophic eggs). Vitellogenins are the main proteins found in the eggs of insects and are a source of nutrients. The aim of this study was to characterize the period of vitellogenin production in workers of E. tuberculatum. The vitellogenin was identified from queen and worker eggs by SDS-PAGE. Anti-vitellogenin antibodies were obtained and used to detect this protein in the fat body and haemolymph of workers at different ages. Vitellogenin from E. tuberculatum consists of two polypeptides of 31 and 156 kDa. In the eggs of queens, the 156 kDa polypeptide is cleaved into two subunits of 36 and 123 kDa. The analysis of the haemolymph of workers showed that the secretion of vitellogenin varies with age. The secretion is initiated around the fifth day after emergence, with peak production from days 20 to 60, and stops around day 100. The variation in production is related to the different activities performed by the workers within the colony, suggesting that vitellogenin may have an important role in maintaining age polyethism.

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.

The vitellogenin of the bumblebee, Bombus hypocrita: studies on structural analysis of the cDNA and expression of the mRNA

In this present study, the cDNA of Bombus hypocrita vitellogenin (Vg) was cloned and sequenced. It is composed of 5,478 bp and contains an ORF of 1,772 amino acids within a putative signal peptide of 16 residues. The deduced amino acid sequence shows significant similarity with Bombus ignitus (95%) and Apis mellifera (52%) and a high number of conserved motifs. Close to the C terminus there is a GL/ICG motif followed by nine cysteines, and a DGXR motif is located 18 residues upstream from the GL/ICG motif. Moreover, we predicted the 3D structure of B. hypocrita Vg. Furthermore, the Vg mRNA of B. hypocrita was spatio-temporally analyzed in different castes (such as queen, worker and drone) from pupae to adult. The Vg mRNA was found in the white-eyed pupal (Pw) stage in queens, and the expression increased during the entire pupal development and attained its peak in the dark brown pupal stage. It also had a high expression in the adult fat body. In workers, the Vg expression was detected in the Pw stage, and its levels increased with age with the highest in 15 days. Afterward, it decreased progressively. Vg mRNA was also observed in drones, with a higher level of expression shown in only freshly molted adult drones.

Molecular characterization and expression pattern of Spodoptera litura (Lepidoptera: Noctuidae) vitellogenin, and its response to lead stress

Vitellogenin (Vg) cDNA from Spodoptera litura Fabricius was cloned and sequenced. The open reading frame (ORF) of Vg cDNA was 5247 nucleotides in length (GenBank Accession no. EU095334), which encoded for a protein of 1748 amino acids. S. litura Vg comprised three conserved regions (Vitellogenin-N domain, DUF1943 and von Willebrand factor type D domain (VWD)), a 17 amino-acid signal peptide and a RXXR cleavage signal (RTIR). The highly conserved GL/ICG motif, the DGXR motif and cysteine residues were found in the C-terminus of the Vg. Vg mRNA was found specifically in the female fat body. Vg expression was first transcribed in 6th day female pupae and levels increased with insect development. The maximum level of Vg mRNA appeared in 24-h-old adults. When S. litura larvae were exposed to lead (Pb) (25-200 mg Pb/kg), there was a significant inhibition in Vg of female adults. The start of Vg expression was advanced ahead by Pb, from 6th day pupae to 3rd day or 4th day pupae. Low levels of Vg in male adults were also induced by low concentrations of Pb (12.5 and 25 mg Pb/kg). These data show that Pb stress elicits an important Vg response in S. litura.

Molecular characteristics of insect vitellogenins

Vitellogenins (Vgs) are precursors of the major egg storage protein, vitellin (Vn), in many oviparous animals. Insects Vgs are large molecules ( approximately 200-kD) synthesized in the fat body in a process that involves substantial structural modifications (e.g., glycosylation, lipidation, phosphorylation, and proteolytic cleavage, etc.) of the nascent protein prior to its secretion and transport to the ovaries. However, the extent to which Vgs are processed in the fat body varies greatly among different insect groups. We provide evidence by cloning and peptide mapping of four Vg molecules from two cockroach species (Periplaneta americana and Leucophaea maderae) that, in hemimetabolous insects, the pro-Vg is cleaved into several polypeptides (ranging from 50-to 180-kD), unlike the holometabolans where the Vg precursor is cleaved into two polypeptides (one large and one small). An exception is the Vg of Apocrita (higher Hymenoptera) where the Vg gene product remains uncleaved. The yolk proteins (YPs) of higher Diptera (such as Drosophila) form a different family of proteins and are also not cleaved. So far, Vgs have been sequenced from 25 insect species; 9 of them belong to Hemimetabola and 16 to Holometabola. Alignment of the coding sequences revealed that some features, like the GL/ICG motif, cysteine residues, and a DGXR motif upstream of the GLI/CG motif, were highly conserved near the carboxy terminal of all insect Vgs. Moreover, a consensus RXXR cleavage sequence motif exists at the N-terminus of all sequences outside the Apocrita except for Lymantria dispar where it exists at the C-terminus. Phylogenetic analysis using 31 Vg sequences from 25 insect species reflects, in general, the current phylogenies of insects, suggesting that Vgs are still phylogenetically bound, although a divergence exists among them.

RNAi studies reveal a conserved role for RXR in molting in the cockroach Blattella germanica

Ecdysteroids play a major role during developmental growth in insects. The more active form of these hormones, 20-hydroxyecdysone (20E), acts upon binding to its heterodimeric receptor, formed by the two nuclear receptors, EcR and RXR/USP. Functional characterization of USP has been exclusively conducted on the holometabolous insect Drosophila melanogaster. However, it has been impossible to extend such analysis to primitive-hemimetabolous insects since species of this group are not amenable to genetic analysis. The development of methodologies based on gene silencing using RNA interference (RNAi) after treatment with double-stranded RNA (dsRNA) in vivo has resolved such limitations. In this paper, we show that injection of dsRNA into the haemocoel of nymphs and adults of the cockroach Blattella germanica can be used to silence gene function in vivo. In our initial attempt to test RNAi techniques, we halted the expression of the adult-specific vitellogenin gene. We then used the same technique to silence the expression of the B. germanica RXR/USP (BgRXR) gene in vivo during the last nymphal instar. BgRXR knockdown nymphs progressed through the instar correctly but they arrested development at the end of the stage and were unable to molt into adults. The results described herein suggest that RXR/USP function, in relation to molting, is conserved across the insect Class.

Vitellogenin of the parasitoid wasp, Encarsia formosa (Hymenoptera: Aphelinidae): gene organization and differential use by members of the genus

The vitellogenin (Vg) gene of the parasitoid wasp, Encarsia formosa (Hymenoptera: Aphelinidae), has been cloned and sequenced. The gene codes for a protein consisting of 1814 amino acids in seven exons. The position of the six introns in the E. formosa gene align with those inferred for the Vg gene of the honeybee, Apis mellifera. The position of two introns in the hymenopteran sequences are shared with every full-length insect Vg gene characterized to date. The deduced amino acid sequence of the E. formosa Vg gene most closely resembles that of the ichneumonid parasitoid, Pimpla nipponica (38% identity). The gene product, less the putative signal peptide, contains large quantities of serine (11.3% of total residues) but lacks the extensive polyserine tracts found in the Vgs of insects outside the apocritan Hymenoptera. The gene also codes for the highest level of lysine (9.5%), and lowest levels of phenylalanine (2.6%) and tyrosine (2.3%), observed in any insect Vg characterized to date. The mature gene product retains 12 cysteine residues in positions conserved in other insect Vgs. Ovary homogenates suggest that processed Vg is stored in the egg as an uncleaved molecule of approximately 200 kDa. Vg expression was examined in three additional Encarsia species. The protein was found in female E. sophia and E. luteola, but not in male E. luteola or female E. pergandiella. Despite extensive screening of a phage library prepared from E. pergandiella genomic DNA, a Vg gene was not detected in this species.

Quantity does matter. Juvenile hormone and the onset of vitellogenesis in the German cockroach

We aimed to elucidate why cockroaches do not produce vitellogenin in immature stages, by studying the appearance of vitellogenin mRNA in larvae of Blattella germanica. Treatment of female larvae in any of the last three instars with 1 microg of juvenile hormone (JH) III induces vitellogenin gene transcription, which indicates that the fat body is competent to transcribe vitellogenin at least from the antepenultimate instar larvae. In untreated females, vitellogenin production starts on day 1 after the imaginal molt, when corpora allata begin to synthesize JH III at rates doubling the maximal of larval stages. This coincidence suggests that the female reaches the threshold of JH production necessary to induce vitellogenin synthesis on day 1 of adult life. These data lead to postulate that larvae do not synthesize vitellogenin simply because they do not produce enough JH, not because their fat body is incompetent.

The role of 20-hydroxyecdysone on the control of spider vitellogenesis

We investigated the role of 20-hydroxyecdysone (20E) on the ovarian maturation and protein levels and pattern in adult females of the spider Tegenaria atrica. In unmated females, the ovaries did not initiate vitellogenesis and levels of proteins in the hemolymph and ovaries were low. Unmated females treated with 20E showed an increase in the total amount of proteins in their hemolymph and ovaries, comparable with that in untreated mated females. Vitellogenesis was observable histologically in 20E treated unmated females as in untreated mated ones. The electrophoretic analysis of total proteins revealed a 47 kDa band expressed in the vitellogenic ovaries and hemolymph of 20E treated unmated females and untreated mated ones as in newly laid eggs. We hypothesize that this 47 kDa protein could belong to the vitellogenin-vitellin complex. We describe in this paper, for the first time in a spider, the partial characterization of putative yolk protein.

The vitellogenin of the honey bee, Apis mellifera: structural analysis of the cDNA and expression studies

The cDNA of Apis mellifera vitellogenin was cloned and sequenced. It is 5440 bp long and contains an ORF of 1770 amino acids (including a putative signal peptide of 16 residues). The deduced amino acid sequence shows significant similarity with other hymenopteran vitellogenins (58% with Pimpla nipponica and 54% with Athalia rosae). The alignment with 19 insect vitellogenins shows a high number of conserved motifs; for example, close to the C-terminus there is a GL/ICG motif followed by nine cysteines, as occurs in all hymenopteran species, and, as in other insect vitellogenins, a DGXR motif is located 18 residues upstream the GL/ICG motif. Phylogenetic analysis of vitellogenin sequences available in insects gave a tree that is congruent with the currently accepted insect phylogenetic schemes. Using two fragments of the vitellogenin cDNA as probes, we analyzed by Northern blot the sex- and caste-specific patterns of vitellogenin expression in pupae and adults of A. mellifera. In queens, vitellogenin mRNA was first detected in mid-late pupal stage, whereas in workers it was first detected in late pupal stage. Vitellogenin mRNA was also observed in drones, although it was first detected not in pupae but in freshly molted adults.

Drosophila yolk protein produced in E. coli is accumulated by mosquito ovaries

Despite similar functions, the yolk proteins of the higher dipteran flies and the vitellogenins found in other insects are unrelated at the sequence level and have evolved from different genes. Both are selectively endocytosed into the ovary via receptors belonging to the LDLR receptor subfamily. We cloned the Drosophila yp1 gene into an E. coli expression vector and showed that the yolk protein produced by E. coli is taken up into ovaries of both Drosophila melanogaster and the malaria mosquito Anopheles gambiae, which normally uses vitellogenin.

Induction of vitellogenin gene transcription in vitro by juvenile hormone in Blattella germanica

In the cockroach Blattella germanica, the synthesis of vitellogenin is juvenile hormone III (JH III)-dependent. We have studied the effect of JH III upon vitellogenin gene expression in periovaric fat bodies incubated in vitro. Periovaric fat bodies were obtained from cardioallatectomized females. The response to JH III was measured in terms of vitellogenin and vitellogenin mRNA after 7 h of incubation. A hormonal concentration as low as 1 nM was enough to induce vitellogenin production and its release to the medium, whereas the concentration of 10 nM produced the maximal effects. Although the response of the vitellogenin gene to JH III is fast and efficient, it seems that the action is mediated by protein factors, given that cycloheximide treatment impairs the hormonal effect. The presence in the medium of brain extract (0.5 equivalents), corpora cardiaca (one pair) or hypertrehalosemic hormone (10(-7) or 10(-8) M), partially inhibited the response to JH III.

Cloning of vitellogenin cDNA of the American cockroach, Periplaneta americana (Dictyoptera), and its structural and expression analyses

A cDNA expression library constructed from poly (A)(+) RNA prepared from vitellogenic female fat body cells of the American cockroach, Periplaneta americana (Dictyoptera) was screened using a polyclonal antiserum against the 100-kD polypeptide(s) from the egg extract. A partial Vg cDNA clone was obtained and sequenced. The 5' end portion of the cDNA was then obtained by the RACE method, cloned, and sequenced. The combined complete Vg cDNA was 5,854 bp long and contained a single ORF encoding 1,896 amino acids. The entire deduced amino acid sequence was aligned confidently with those of the known insect Vgs. A GL/ICG motif, a number of cysteines at conserved locations following this motif, and a DGXR motif upstream of the GL/ICG motif were present near the C-terminal. The chemically determined N-terminal amino acid sequence of the 170-kD polypeptide from the egg extract completely matched the deduced sequence starting from just after one of the consensus (RXXR) cleavage sites, indicating the occurrence of post-translational cleavage in the fat body cells. The Vg gene begins to be expressed in the 2-day-old adult female fat body cells but is never expressed in ovaries or in male fat body cells. Hemolymph Vg was first detected by immunoblotting in 4-day-old adult females, 2 days after the beginning of gene expression. Western blot analysis of major yolk polypeptides in nine cockroach species belonging to the two superfamilies, Blattoidea and Blaberoidea, using the antisera against P. americana major yolk polypeptides showed that the similarities in Vn antigenicity are basically limited to within a superfamily.