Vitellogenic blood protein synthesis by insect fat body

Sex-Biased Transcription Expression of Vitellogenins Reveals Fusion Gene and MicroRNA Regulation in the Sea Louse Caligus rogercresseyi

The caligid ectoparasite, Caligus rogercresseyi, is one of the main concerns in the Chilean salmon industry. The molecular mechanisms displayed by the parasite during the reproductive process represent an opportunity for developing novel control strategies. Vitellogenin is a multifunctional protein recognized as a critical player in several crustaceans' biological processes, including reproduction, embryonic development, and immune response. This study aimed to characterize the C. rogercresseyi vitellogenins, including discovering novel transcripts and regulatory mechanisms associated with microRNAs. Herein, vitellogenin genes were identified by homology analysis using the reference sea louse genome, transcriptome database, and arthropods vitellogenin-protein database. The validation of expression transcripts was conducted by RNA nanopore sequencing technology. Moreover, fusion gene profiling, miRNA target analysis, and functional validation were performed using luciferase assay. Six putative vitellogenin genes were identified in the C. rogercresseyi genome with high homology with other copepods vitellogenins. Furthermore, miR-996 showed a putative role in regulating the Cr_Vitellogenin1 gene, which is highly expressed in females. Moreover, vitellogenin-fusion genes were identified in adult stages and highly regulated in males, demonstrating sex-related expression patterns. In females, the identified fusion genes merged with several non-vitellogenin genes involved in biological processes of ribosome assembly, BMP signaling pathway, and biosynthetic processes. This study reports the genome array of vitellogenins in C. rogercresseyi for the first time, revealing the putative role of fusion genes and miRNA regulation in sea lice biology.

Effect of four chitinase genes on the female fecundity in Sogatella furcifera (Horváth)

BACKGROUND

The white-backed planthopper (WPH), Sogatella furcifera (Horváth), is a destructive rice pest with strong reproductive capacity. To gain insights into the roles of chitinases in the reproductive process of this insect species, this study represents the first-ever endeavor to conduct an in-depth exploration into the reproductive functions of four chitinase genes.

RESULTS

In this study, it was observed that four chitinase genes were expressed in female adults, with a relatively high expression level in the ovaries. SfCht2 and SfIDGF1 were highly expressed during later ovarian development. while SfENGase increased and then decreased with ovarian development. SfCht2, SfCht6-2 and SfENGase were highly expressed in fat body on the first and second days after eclosion, whereas SfIDGF1 highest on day 7. Compared with control group, Silencing four chitinase genes inhibited ovarian development and significantly shortened the oviposition period of S. furcifera, reducing egg-laying capacity but not affecting egg hatching. The detection demonstrated that the expression levels of SfVg, SfVgR and 70-90% juvenile hormone (JH) signaling pathway-related reproductive genes was significantly down-regulated. Moreover, SfCht6-2 and SfENGase significantly affected the expression levels of Target of Rapamycin (TOR) signaling pathway genes. SfENGase had the ability to impact nutrient signaling pathways and fatty acid metabolism, repressing vitellogenin synthesis and ultimately influencing ovarian development of S. furcifera.

CONCLUSIONS

Overall, this study provides insight into the function of chitinases in insect fecundity and is of great significance for enriching the cognition of insect chitinase function. They will become the suitable target genes for controlling the most destructive rice planthoppers. © 2023 Society of Chemical Industry.

New insight into molecular mechanisms underlying division of labor in honeybees

Honeybees are highly organized eusocial insects displaying a distinct division of labor. Juvenile hormone (JH) has long been hypothesized to be the major driver of behavioral transitions. However, more and more experiments in recent years have suggested that the role of this hormone is not as fundamental as hypothesized. Vitellogenin, a common egg yolk precursor protein, seems to be the major regulator of division of labor in honeybees, in connection with nutrition and the neurohormone and transmitter octopamine. Here, we review the role of vitellogenin in controlling honeybee division of labor and its modulation by JH, nutrition, and the catecholamine octopamine.

Effects of oral exposure to brake wear particulate matter on the springtail Orthonychiurus folsomi

Most of the heavy metals in urban environments derives from road traffic, particularly from tyres and brake wear (non-exhaust emission sources). These pollutants contaminate the soil, where several organisms have a primary ecosystem role (e.g., springtails, ants, earthworms). Springtails (Collembola) are soil-dwelling animals regulating soil fertility, flow of energy through above- and below-ground food webs, and they contribute to soil microbial community dispersion and biodiversity maintenance. In this study we investigated the ecotoxicological effects of oral exposure to particles emitted from brake pads and cast-iron brake discs in the euedaphic collembola species Orthonychiurus folsomi under laboratory conditions. Our results showed that chronic exposure to brake wear particles can have sub-lethal effects both at low and high concentrations and it can cause histological alterations. Here, SEM-EDX was applied to observe the particulate and we found its chemical markers in the gut and faeces of collembola, while histological analysis detected alterations of the digestive and reproductive systems and of the abdominal fat body at high concentrations.

Effect of temperature on the post-diapause developmental rate, survival, and body mass of the solitary wasp Isodontia elegans: Implications for rearing of trap-nesting Hymenoptera

We examined the relationship of post-diapause rearing temperature to developmental rate, survival, and adult body mass of the solitary wasp Isodontia elegans using prepupae from trap-nests. Isodontia elegans is a member of a genus often found in trap-nests in North America and Europe. Trap-nests are commonly used tools for studying cavity-nesting solitary wasps and bees. In temperate zones, progeny in nests usually overwinter as prepupae before pupating and emerging as adults. An important aspect of properly using trap-nests is determining temperatures that affect survival and health of developing offspring. After overwintering >600 cocoons containing prepupae after the summers of 2015 and 2016, we placed cocoons on a laboratory thermal gradient where offspring experienced one of 19 constant temperatures from 6 to 43 °C; emergence of adults was monitored for 100 days. Our conservative estimate for the critical thermal minimum for development is 14 °C, whereas that for the critical maximum is ∼33 °C. Prepupae transitioned to adults most rapidly at 29-33 °C, but developmental rate was lower for some progeny exposed to temperatures ≥30 °C. Offspring successfully reached the adult stage in <100 days at of temperatures of ∼19-33 °C. Adults from cocoons reared at lower temperatures weighed on average 6-10% more than expected based on their head widths, whereas those reared at higher temperatures weighed 4-10% less than expected. The difference may be due to greater rates of water loss and lipid metabolism during development at higher temperatures. Pre-overwintering cocoon mass was a significant predictor of relative adult body mass, indicating that adult health is partly related to their condition before overwintering. The trends we observed were similar to those for the bee Megachile rotundata, which we previously studied on the same gradient apparatus. However, data is needed on many other species of wasps and bees from a diversity of environments.

Physicochemical and bioinformatic characterization of Oreochromis niloticus vitellogenin as an endocrine disruption biomarker

Aquatic biota is increasingly being exposed to chemical pollutants due to human activities and the relationship between the level of environmental pollution and fish reproduction is a continuously ongoing issue. The vitellogenin (Vtg) protein synthesis can be induced in the liver of juvenile and male fish after stimulation of the estrogen receptor and therefore, Vtg has been used as a biomarker of xenoestrogen exposure in several fish species. The current study reported the first physicochemical characterization of Vtg from Oreochromis niloticus. Adult male fish were exposed to 17α-ethinylestradiol for Vtg induction. Purified vitellogenin from plasma showed low stability at 25 and 4 °C in saline conditions, and good stability in acidic (low pH) or in heated conditions. The 3D modeling provided useful information on the structure of O. niloticus Vtg showing conserved structural features. According to bioinformatics and experimental results, there are important structural differences between the two chemical forms of Vtg (VtgAb and VtgC) in a phylogenetic context. The present results add information about the development of ecotoxicological immunoassays to study the endocrine disruption in O. niloticus improving the Vtg performance as a biomarker of reproduction in fish.

Resolving the zinc binding capacity of honey bee vitellogenin and locating its putative binding sites

The protein vitellogenin (Vg) plays a central role in lipid transportation in most egg-laying animals. High Vg levels correlate with stress resistance and lifespan potential in honey bees (Apis mellifera). Vg is the primary circulating zinc-carrying protein in honey bees. Zinc is an essential metal ion in numerous biological processes, including the function and structure of many proteins. Measurements of Zn²⁺ suggest a variable number of ions per Vg molecule in different animal species, but the molecular implications of zinc-binding by this protein are not well-understood. We used inductively coupled plasma mass spectrometry to determine that, on average, each honey bee Vg molecule binds 3 Zn²⁺ -ions. Our full-length protein structure and sequence analysis revealed seven potential zinc-binding sites. These are located in the β-barrel and α-helical subdomains of the N-terminal domain, the lipid binding site, and the cysteine-rich C-terminal region of unknown function. Interestingly, two potential zinc-binding sites in the β-barrel can support a proposed role for this structure in DNA-binding. Overall, our findings suggest that honey bee Vg bind zinc at several functional regions, indicating that Zn²⁺ -ions are important for many of the activities of this protein. In addition to being potentially relevant for other egg-laying species, these insights provide a platform for studies of metal ions in bee health, which is of global interest due to recent declines in pollinator numbers.

Molecular Characterization of Vitellogenin and Its Receptor in Spodoptera frugiperda (J. E. Smith, 1797), and Their Function in Reproduction of Female

The fall armyworm Spodoptera frugiperda is a highly polyphagous invasive pest. The strong reproductive capacity is an important factor in the rapid colonization and expansion of S. frugiperda. Vitellogenin (Vg) and vitellogenin receptor (VgR) play important roles in insect reproduction. As the precursor of vitellin (Vn), Vg provides essential nutrition for embryonic development, and VgR mediates the uptake of Vg by oocytes. In this context, we cloned and characterized these two genes of S. frugiperda (SfVg and SfVgR) and evaluated their expression profiles in different developmental stages and tissues. The RNA interference experiment was used to investigate their function in vitellogenesis. The ORF values of SfVg and SfVgR were 5250 and 5445 bp, encoding 1749 and 1815 amino acid residues, respectively. The qRT-PCR results revealed that both SfVg and SfVgR were highly expressed in female adults; SfVg was specifically expressed in the fat body, whereas SfVgR was highly expressed in the ovary. In addition, the depletion of either SfVg or SfVgR hindered oocyte maturation and ovarian development, leading to a significant decrease in fecundity. The present study reveals the importance of SfVg and SfVgR in the vitellogenesis of S. frugiperda, laying a theoretical foundation for the development of pollution-free pest control strategies with SfVg and SfVgR as new targets.

How Honey Bee Vitellogenin Holds Lipid Cargo: A Role for the C-Terminal

Vitellogenin (Vg) is a phylogenetically broad glycolipophosphoprotein. A major function of this protein is holding lipid cargo for storage and transportation. Vg has been extensively studied in honey bees (Apis mellifera) due to additional functions in social traits. Using AlphaFold and EM contour mapping, we recently described the protein structure of honey bee Vg. The full-length protein structure reveals a large hydrophobic lipid binding site and a well-defined fold at the C-terminal region. Now, we outline a shielding mechanism that allows the C-terminal region of Vg to cover a large hydrophobic area exposed in the all-atom model. We propose that this C-terminal movement influences lipid molecules’ uptake, transport, and delivery. The mechanism requires elasticity in the Vg lipid core as described for homologous proteins in the large lipid transfer protein (LLTP) superfamily to which Vg belongs. Honey bee Vg has, additionally, several structural arrangements that we interpret as beneficial for the functional flexibility of the C-terminal region. The mechanism proposed here may be relevant for the Vg molecules of many species.

Breast Meat Fatty Acid Profiling and Proteomic Analysis of Beijing-You Chicken During the Laying Period

The disparity in fatty acids (FA) composition exhibits a significant impact on meat quality, however, the molecular regulatory mechanisms underlying this trait in chicken are far from clear. In this study, a total of 45 female Beijing-You chicken (BYC) hens, fed on the same diet, were collected at the slaughter age of 150, 300, or 450 days (D150, D300, and D450) from sexual maturation stage to culling stage (15 birds per age). Gas chromatography-mass spectrometry (GC-MS) and tandem mass tag labeling technology based on liquid chromatography mass spectrometry (TMT-LC-MS/MS) analysis strategies were applied to profile FA compositions and to compare differential expressed proteins (DEPs) between these different slaughter ages, respectively. The FA profiling showed that increasing hen ages resulted in increased contents of both saturated and unsaturated fatty acids. Proteomic analyses showed a total of 4,935 proteins in chicken breast muscle with the false discovery rate (FDR) < 1% and 664 of them were differentially expressed (fold change > 1.50 or < 0.67 and P < 0.01). There were 410 up- and 116 down-regulated proteins in D150 vs. D300 group, 32 up- and 20 down-regulated in D150 vs. D450 group, and 72 up- and 241 down-regulated in D300 vs. D450 group. A total of 57 DEPs related to FA/lipid-related metabolisms were obtained according to the enrichment analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). These DEPs were involved in 21 significantly enriched (P < 0.05) pathways, including well-known pathways for FA synthesis (metabolism, desaturation, and elongation) and the signaling pathways for lipid metabolism (PPAR, adipocytokine, calcium, VEGF, MAPK, and Wnt). In addition, there existed several representative DEPs (FABP, FABP3, apoA-I, apoA-IV, apoC-III, apoB, VTG1, and VTG2) involved in the regulation of FA/lipid transportation. The construction of the interaction networks indicated that HADH, ACAA2, HADHA, ACSL1, CD36, CPT1A, PPP3R1, and SPHK1 were the key core nodes. Finally, eight DEPs were quantified using parallel reaction monitoring (PRM) to validate the results from TMT analysis. These results expanded our understanding of how the laying age affects the FA compositions and metabolism in hen breast meat.

Inter-Alpha-Trypsin Inhibitor Heavy Chain 4 Plays an Important Role in the Development and Reproduction of Nilaparvata lugens

Simple Summary

The brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae), is a destructive insect pest of rice. It causes reductions in rice yield and great economic losses. In this study, we used RNAi to explore the function of the inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4) gene in the development and reproduction of the brown planthopper. Our results revealed that ITIH4 influences the survival, ovarian development, egg production, and egg hatching of this insect, indicating that ITIH4 plays important roles in development and reproduction. Considering the importance of ITIH4 in the brown planthopper, it may be a potential target for pest management.

Abstract

The brown planthopper, Nilaparvata lugens, is a difficult-to-control insect pest affecting rice yields in Asia. As a structural component of the inter-alpha-trypsin inhibitor (ITI), the inter-alpha-trypsin inhibitor heavy chain (ITIH) has been reported to be involved in various inflammatory or malignant disorders, ovarian development, and ovulation. To reveal the function of ITIH4 in N. lugens, the gene encoding N. lugens ITIH4 (NlITIH4) was cloned and characterized. NlITIH4 contains a signal peptide, a vault protein inter-alpha-trypsin domain, and a von Willebrand factor type A domain. qPCR analysis showed that NlITIH4 was expressed at all developmental stages and in all tissues (fat body, ovary, and gut), with the highest expression in the fat body. Double stranded NlITIH4 (dsNlITIH4) injection clearly led to an RNAi-mediated inhibition of the expression of NlITIH4 and resulted in reduced survival, delayed ovarian development, and reduced egg production and egg hatching. These results indicate that NlITIH4 plays an important role in the development and reproduction of N. lugens.

Nuclear translocation of vitellogenin in the honey bee (Apis mellifera)

Vitellogenin (Vg) is a conserved protein used by nearly all oviparous animals to produce eggs. It is also pleiotropic and performs functions in oxidative stress resistance, immunity, and, in honey bees, behavioral development of the worker caste. It has remained enigmatic how Vg affects multiple traits. Here, we asked whether Vg enters the nucleus and acts via DNA-binding. We used cell fractionation, immunohistology, and cell culture to show that a structural subunit of honey bee Vg translocates into cell nuclei. We then demonstrated Vg-DNA binding theoretically and empirically with prediction software and chromatin immunoprecipitation with sequencing (ChIP-seq), finding binding sites at genes influencing immunity and behavior. Finally, we investigated the immunological and enzymatic conditions affecting Vg cleavage and nuclear translocation and constructed a 3D structural model. Our data are the first to show Vg in the nucleus and suggest a new fundamental regulatory role for this ubiquitous protein.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13592-022-00914-9.

Molecular Identification and Functional Characterization of Methoprene-Tolerant (Met) and Krüppel-Homolog 1 (Kr-h1) in Harmonia axyridis (Coleoptera: Coccinellidae)

Juvenile hormone (JH) plays a key role in regulating insect reproductive processes. Methoprene-tolerant (Met), as a putative JH receptor, transduces JH signals by activating the transcription factor krüppel homolog 1 (Kr-h1). To understand the effects of Met and Kr-h1 genes on female reproduction of natural enemy insects, the Met and Kr-h1 were identified and analyzed from Harmonia axyridis Pallas (HmMet and HmKr-h1). The HmMet protein belonged to the bHLH-PAS family with bHLH domain, PAS domains, and PAC domain. HmMet mRNA was detected in all developmental stages, and the highest expression was found in the ovaries of female adults. The HmKr-h1 protein had eight C2H2-type zinc finger domains. HmKr-h1 mRNA was highly expressed from day 7 to day 9 of female adults. The tissue expression showed that HmKr-h1 was highly expressed in its wing, leg, and fat body. Knockdown of HmMet and HmKr-h1 substantially reduced the transcription of HmVg1 and HmVg2, inhibited yolk protein deposition, and reduced fecundity using RNA interference. In addition, the preoviposition period was significantly prolonged after dsMet-injection, but there was no significant difference after dsKr-h1-silencing. However, the effect on hatchability results was the opposite. Therefore, we infer that both HmMet and HmKr-h1 are involved in female reproduction of H. axyridis, and their specific functions are different in certain physiological processes. In several continents, H. axyridis are not only beneficial insects, but also invasive pests. This report will provide basis for applying or controlling the H. axyridis.

Molecular underpinnings of division of labour among workers in a socially complex termite

Division of labour characterizes all major evolutionary transitions, such as the evolution of eukaryotic cells or multicellular organisms. Social insects are characterized by reproductive division of labour, with one or a few reproducing individuals (queens) and many non-reproducing nestmates (workers) forming a colony. Among the workers, further division of labour can occur with different individuals performing different tasks such as foraging, brood care or building. While mechanisms underlying task division are intensively studied in social Hymenoptera, less is known for termites, which independently evolved eusociality. We investigated molecular mechanisms underlying task division in termite workers to test for communality with social Hymenoptera. We compared similar-aged foraging workers with builders of the fungus-growing termite Macrotermes bellicosus using transcriptomes, endocrine measures and estimators of physiological condition. Based on results for social Hymenoptera and theory, we tested the hypotheses that (i) foragers are in worse physiological conditions than builders, (ii) builders are more similar in their gene expression profile to queens than foragers are, and (iii) builders invest more in anti-ageing mechanism than foragers. Our results support all three hypotheses. We found storage proteins to underlie task division of these similar-aged termite workers and these genes also characterize reproductive division of labour between queens and workers. This implies a co-option of nutrient-based pathways to regulate division of labour across lineages of termites and social Hymenoptera, which are separated by more than 133 million years.

Molecular evolution of bumble bee vitellogenin and vitellogenin-like genes

Vitellogenin (Vg), a storage protein, has been significantly studied for its egg yolk precursor role in oviparous animals. Recent studies found that vitellogenin and its Vg-like homologs were fundamentally involved in many other biological processes in social insects such as female caste differences and oxidative stress resilience. In this study, we conducted the first large-scale molecular evolutionary analyses of vitellogenin coding genes (Vg) and Vg-like genes of bumble bees, a primitively eusocial insect belonging to the genus Bombus. We obtained sequences for each of the four genes (Vg, Vg-like-A, Vg-like-B, and Vg-like-C) from 27 bumble bee genomes (nine were newly sequenced in this study), and sequences from the two closest clades of Bombus, including five Apis species and five Tetragonula species. Our molecular evolutionary analyses show that in bumble bee, the conventional Vg experienced strong positive selection, while the Vg-like genes showed overall relaxation of purifying selection. In Apis and Tetragonula; however, all four genes were found under purifying selection. Furthermore, the conventional Vg showed signs of strong positive selection in most subgenera in Bombus, apart from the obligate parasitic subgenus Psithyrus which has no caste differentiation. Together, these results indicate that the conventional Vg, a key pleiotropic gene in social insects, is the most rapidly evolving copy, potentially due to its multiple known social functions for both worker and queen castes. This study shows that concerted evolution and purifying selection shaped the evolution of the Vg gene family following their ancient gene duplication and may be the leading forces behind the evolution of new potential protein function enabling functional social pleiotropy.

Fat Body-Multifunctional Insect Tissue

Simple Summary

Efficient and proper functioning of processes within living organisms play key roles in times of climate change and strong human pressure. In insects, the most abundant group of organisms, many important changes occur within their tissues, including the fat body, which plays a key role in the development of insects. Fat body cells undergo numerous metabolic changes in basic energy compounds (i.e., lipids, carbohydrates, and proteins), enabling them to move and nourish themselves. In addition to metabolism, the fat body is involved in the development of insects by determining the time an individual becomes an adult, and creates humoral immunity via the synthesis of bactericidal proteins and polypeptides. As an important tissue that integrates all signals from the body, the processes taking place in the fat body have an impact on the functioning of the entire body.

Abstract

The biodiversity of useful organisms, e.g., insects, decreases due to many environmental factors and increasing anthropopressure. Multifunctional tissues, such as the fat body, are key elements in the proper functioning of invertebrate organisms and resistance factors. The fat body is the center of metabolism, integrating signals, controlling molting and metamorphosis, and synthesizing hormones that control the functioning of the whole body and the synthesis of immune system proteins. In fat body cells, lipids, carbohydrates and proteins are the substrates and products of many pathways that can be used for energy production, accumulate as reserves, and mobilize at the appropriate stage of life (diapause, metamorphosis, flight), determining the survival of an individual. The fat body is the main tissue responsible for innate and acquired humoral immunity. The tissue produces bactericidal proteins and polypeptides, i.e., lysozyme. The fat body is also important in the early stages of an insect’s life due to the production of vitellogenin, the yolk protein needed for the development of oocytes. Although a lot of information is available on its structure and biochemistry, the fat body is an interesting research topic on which much is still to be discovered.

Molecular cloning, characterisation and expression analysis of the vitellogenin genes vtgAo1 and vtgC during ovarian development in Chinese hook snout carp Opsariichthys bidens

Vitellogenesis is essential for oocyte maturation. Vitellogenin (Vtg), a yolk precursor protein, plays an important role in oogenesis and vitellogenesis. Chinese hook snout carp Opsariichthys bidens is an economically important freshwater fish in China whose reproductive and developmental biology are not well understood. In this study, we undertook histological analysis to examine ovary development and oogenesis in O. bidens. The ovaries were divided into Stages II-V and oocytes were divided into perinuclear oocytes, cortical alveoli oocytes, vitellogenic oocytes and mature oocytes. Full-length cDNA sequences were cloned of two vtg genes from the liver of O. bidens, namely Ob-vtgAo1 and Ob-vtgC. Ob-vtgAo1 and Ob-vtgC cDNA are made up of 4136 and 4392 bases respectively and encode proteins containing 1335 and 1250 amino acids respectively. Ob-vtgAo1 contains three yolk protein domains: lipovitellin heavy chain (LvH), phosvitin (Pv) and lipovitellin light chain (LvL), whereas Ob-VtgC contains LvH and LvL, which are incomplete Vtgs. Ob-vtgAo1 and Ob-vtgC mRNA expression was significantly higher in the liver of O. bidens than in all other tissues. In oocytes of Stage II-III ovaries, yolk granules are almost absent and ovarian and hepatic Ob-vtgAo1 and Ob-vtgC expression is low. At Stage IV, the oocyte is filled with yolk granules and ovarian and hepatic Ob-vtgAo1 and Ob-vtgC expression is significantly increased. Collectively, these findings help us better understand vitellogenesis in O. bidens.

Distinct vitellogenin domains differentially regulate immunological outcomes in invertebrates

The classical role of Vitellogenin (Vg) is providing energy reserves for developing embryos, but its roles appear to extend beyond this nutritional function, and its importance in host immune defense is garnering increasing research attention. However, Vg-regulated immunological functions are dependent on three different domains within different species and remain poorly understood. In the present study, we confirmed three conserved VG domains-LPD_N, DUF1943, and VWD-in the Chinese mitten crab (Eriocheir sinensis), highlighting functional similarities of Vg in vertebrates and invertebrates. Of these three domains, DUF1943 and VWD showed definitive bacterial binding activity via interaction with the signature components on microbial surfaces, but this activity was not exhibited by the LPD_N domain. Antibacterial assays indicated that only the VWD domain inhibits bacterial proliferation, and this function may be conserved between different species due to the conserved amino acid residues. To further explore the relationship between Vg and polymeric immunoglobulin receptor (pIgR), we expressed EspIgR and the three E. sinensis Vg (EsVg) domains in HEK293T cells, and coimmunoprecipitation assay demonstrated that only the DUF1943 domain interacts with EspIgR. Subsequent experiments demonstrated that EsVg regulates hemocyte phagocytosis by binding with EspIgR through the DUF1943 domain, thus promoting bacterial clearance and protecting the host from bacterial infection. To the best of our knowledge, our work is the first to report distinct domains in Vg inducing different immunological outcomes in invertebrates, providing new evidence that pIgR acts as a phagocytic receptor for Vg.

Effects of Sublethal Concentrations of Insecticides on the Fecundity of Sogatella furcifera (Hemiptera: Delphacidae) via the Regulation of Vitellogenin and Its Receptor

White-backed planthopper (Sogatella furcifera, Hemiptera: Delphacidae) is an important migratory pest of rice. It causes severe economic losses by reducing crop production. Vg and VgR are important proteins that help in the successful reproduction of insects and have been studied in many insects. To understand the molecular mechanisms underlying the effects of insecticides on white-backed planthopper reproduction, we studied the expression profiles of SfVg, SfVg-like, and SfVgR in white-backed planthopper exposed to insecticides. SfVg and SfVgR silencing inhibited the ovarian development, number of eggs laid by, and hatching rate of white-backed planthopper. Thiamethoxam LC10 significantly inhibited SfVg-like and SfVgR expression. In contrast, triazophos LC25 significantly promoted SfVg, SfVg-like, and SfVgR expression and increased vitellogenin content in white-backed planthopper. These results demonstrate that insecticides can regulate the reproduction of white-backed planthopper by altering the expression of SfVg and SfVgR, thereby affecting the population density of white-backed planthopper. These findings build a foundation for improving our understanding of the molecular mechanisms underlying the effects of insecticides on the reproduction and resurgence of pests.

Proteome analysis of male accessory gland secretions in Leucinodes orbonalis Guenee (Lepidoptera: Crambidae), a Solanum melongena L. pest

Male accessory gland (MAG) proteins are transferred along with the sperm to females at the time of mating and have diverse effects on female reproductive physiology in a wide range of insects. In this study, we sought to identify the MAG proteins in Leucinodes orbonalis Guenee, a Solanum melongena L. pest, by analyzing the MAG proteins of virgin and mated male moths by nano-LC-ESI-MS/MS techniques. A total of 142 and 131 proteins in virgin and mated males were identified, respectively, among which 17 (12.0%) and 10 (7.6%) proteins were found to show secretory signals in virgin and mated males, respectively. These secretory proteins were shown to be involved in several biological processes in insects, including egg development, sperm-related functions/capacitation, defense, metabolism, and protein chaperoning. To the best of our knowledge, this is the first study to perform a proteome analysis of the MAG proteins of L. orbonalis, and offers an opportunity for further investigation of the functions of these proteins. In insects, certain MAG proteins are known to inhibit mating whereas others accelerate egg-laying. Therefore, the identification of these proteins in L. orbonalis may be useful for pest control.

Levels of the endosymbiont Rickettsia in the whitefly Bemisia tabaci are influenced by the expression of vitellogenin

Bacterial endosymbionts play essential roles in the biology of their arthropod hosts by interacting with internal factors in the host. The whitefly Bemisia tabaci is a worldwide agricultural pest and a supervector for more than 100 plant viruses. Like many other arthropods, Be. tabaci harbours a primary endosymbiont, Porteira aleyrodidarum, and an array of secondary endosymbionts that coexist with Portiera inside bacteriocyte cells. Unlike all of the other secondary symbionts that infect Be. tabaci, Rickettsia has been shown to be an exception by infecting insect organs and not colocalizing with Portiera, and has been shown to significantly impact the insect biology and its interactions with the environment. Little is known about the molecular interactions that underlie insect-symbiont interactions in general, and particularly Be. tabaci-Rickettsia interactions. Here we performed transcriptomic analysis and identified vitellogenin as an important protein that influences the levels of Rickettsia in Be. tabaci. Vitellogenin expression levels were lower in whole insects, but higher in midguts of Rickettsia-infected insects. Immunocapture-PCR assay showed interaction between vitellogenin and Rickettsia, whereas silencing of vitellogenin resulted in nearly complete disappearance of Rickettsia from midguts. Altogether, these results suggest that vitellogenin plays an important role in influencing the levels of Rickettsia in Be. tabaci.

Crustacean Hemolymph Lipoproteins

Lipoproteins mediate the transport of apolar lipids in the hydrophilic environment of physiological fluids such as the vertebrate blood and the arthropod hemolymph. In this overview, we will focus on the hemolymph lipoproteins in Crustacea that have received most attention during the last years: the high density lipoprotein/β-glucan binding proteins (HDL-BGBPs), the vitellogenins (VGs), the clotting proteins (CPs) and the more recently discovered large discoidal lipoproteins (dLPs). VGs are female specific lipoproteins which supply both proteins and lipids as storage material for the oocyte for later use by the developing embryo. Unusual within the invertebrates, the crustacean yolk proteins-formerly designated VGs-are more related to the ApoB type lipoproteins of vertebrates and are now termed apolipocrustaceins. The CPs on the other hand, which are present in both sexes, are related to the (sex specific) VGs of insects and vertebrates. CPs serve in hemostasis and wound closure but also as storage proteins in the oocyte. The HDL-BGBPs are the main lipid transporters, but are also involved in immune defense. Most crustacean lipoproteins belong to the family of the large lipid transfer proteins (LLTPs) such as the intracellular microsomal triglyceride transfer protein, the VGs, CPs and the dLPs. In contrast, the HDL-BGBPs do not belong to the LLTPs and their relationship with other lipoproteins is unknown. However, they originate from a common precursor with the dLPs, whose functions are as yet unknown. The majority of lipoprotein studies have focused on decapod crustaceans, especially shrimps, due to their economic importance. However, we will present evidence that the HDL-BGBPs are restricted to the decapod crustaceans which raises the question as to the main lipid transporting proteins of the other crustacean groups. The diversity of crustaceans lipoproteins thus appears to be more complex than reflected by the present state of knowledge.

Two distinct vitellogenin genes are similar in function and expression in the bigfin reef squid Sepioteuthis lessoniana

Unlike vitellogenin, which is the sole major precursor of yolk protein in all oviparous vertebrates, a variety of major precursor of yolk proteins are found among oviparous invertebrates. Sea urchins have a transferrin-like yolk protein, while all other major precursors of yolk proteins in oviparous invertebrates belong to the superfamily of large lipid transfer proteins (LLTPs). However, a comprehensive understanding of vitellogenesis is absent in cephalopods. To understand control of vitellogenesis by the LLTPs gene, two vitellogenins (VTG1 and VTG2), two apolipophorins (APOLP2A and APOLP2B), and a cytosolic large subunit of microsomal triglyceride transfer protein (MTTP) found in the bigfin reef squid. Only the two VTGs showed high levels of expression in mature females compared to males. We further analyzed the expression profile and localization of both VTGs/VTGs during ovarian development. Our data showed that VTGs/VTGs expressions were correlated to the female reproductive cycle. Ovarian VTG1 and VTG2 were localized in the follicle cells but not in oocytes. In addition, VTG1 and VTG2 were represented in follicle cells and oocytes. Thus, our results showed that both VTGs were synthesized by follicle cells and are then delivered to oocytes. In addition, we demonstrated that VTGs were the major precursor of yolk protein in bigfin reef squid. We also found differential proteolytic cleavage processes of VTG1 and VTG2 during VTGs accumulation in oocytes. Therefore, our data shed light on the molecular mechanism of the yolk accumulation pathway in cephalopods.

Functions of Vitellogenin in Eggs

Our understanding of the functions of vitellogenin (Vtg) in reproduction has undergone an evolutionary transformation over the past decade. Primarily, Vtg was regarded as a female-specific reproductive protein, which is cleaved into yolk proteins including phosvitin (Pv) and lipovitellin (Lv), stored in eggs, providing the nutrients for early embryos. Recently, Vtg has been shown to be an immunocomponent factor capable of protecting the host against the attack by microbes including bacteria and viruses. Moreover, Pv and Lv that both are proteolytically cleaved products of maternal Vtg, as well as Pv-derived small peptides, all display an antibacterial role in developing embryos. In addition, both Vtg and yolk protein Pv possess antioxidant activity capable of protecting cells from damage by free radicals. Collectively, these data indicate that Vtg, in addition to being involved in yolk protein formation, also plays non-nutritional roles via functioning as immune-relevant molecules and antioxidant reagents.

Identification and Expression Patterns of Three Vitellogenin Genes and Their Roles in Reproduction of the Alligatorweed Flea Beetle Agasicles hygrophila (Coleoptera: Chrysomelidae)

The alligatorweed flea beetle Agasicles hygrophila is an insect used for biological control of the aquatic weed Alternanthera philoxeroides (alligatorweed). Because these insects are oviparous, synthesis, and transportation of yolk proteins is integral to reproduction. Vitellin, the chief protein constituent in egg yolk, is mainly synthesized in the fat body and its synthesis is regulated by the transcript levels of Vitellogenin (Vg). In our study, we first cloned and characterized three Vg genes from A. hygrophila and quantified the expression levels of these Vgs in different tissues and developmental stages by RT-qPCR. Analysis of the full-length cDNA sequences of the three A. hygrophila Vg genes revealed that the open reading frames of AhVg1, AhVg2, and AhVg3 were 5175, 5346, and 5385 bp, encoding 1724, 1781, and 1794 amino acids, respectively. RT-qPCR analysis revealed that these three AhVgs have similar expression patterns; expression in the fat body was significantly higher than that in other tissues, and the highest expression was observed in the adult developmental stage. RNA interference was used to explore the functions of the AhVgs. A. hygrophila female adults injected with dsRNA targeting the AhVg genes showed decreased AhVg gene expression. Down regulation of all three AhVgs significantly affected ovary development, reduced egg laying capacity, and reduced the egg hatch rate compared with the control groups. Our findings provide the basis for further study of the functions of Vg genes in other insect species.

The role of Vitellogenin in the transfer of immune elicitors from gut to hypopharyngeal glands in honey bees (Apis mellifera)

Female insects that survive a pathogen attack can produce more pathogen-resistant offspring in a process called trans-generational immune priming. In the honey bee (Apis mellifera), the egg-yolk precursor protein Vitellogenin transports fragments of pathogen cells into the egg, thereby setting the stage for a recruitment of immunological defenses prior to hatching. Honey bees live in complex societies where reproduction and communal tasks are divided between a queen and her sterile female workers. Worker bees metabolize Vitellogenin to synthesize royal jelly, a protein-rich glandular secretion fed to the queen and young larvae. We ask if workers can participate in trans-generational immune priming by transferring pathogen fragments to the queen or larvae via royal jelly. As a first step toward answering this question, we tested whether worker-ingested bacterial fragments can be transported to jelly-producing glands, and what role Vitellogenin plays in this transport. To do this, we fed fluorescently labelled Escherichia coli to workers with experimentally manipulated levels of Vitellogenin. We found that bacterial fragments were transported to the glands of control workers, while they were not detected at the glands of workers subjected to RNA interference-mediated Vitellogenin gene knockdown, suggesting that Vitellogenin plays a role in this transport. Our results provide initial evidence that trans-generational immune priming may operate at a colony-wide level in honey bees.

Vitellogenin regulates antimicrobial responses in Chinese mitten crab, Eriocheir sinensis

Vitellogenin (Vtg) is traditionally regarded as a key supplier of nutrients and energy during the early development of embryos and larvae, but accumulating evidence suggests that Vtg is also involved in innate immune defense. Whether Vtg is involved in innate immunity in Eriocheir sinensis, and its functions, remain largely unknown. In this study, a cDNA representing the vitellogenin1 gene from E. sinensis (Es-vtg1) was cloned. The full-length Es-vtg1 cDNA comprised 7939 nucleotides, encoding an open-reading frame of 2567 amino acid residues. Bioinformatic analysis showed that the domains of Es-Vtg1 have been conserved during evolution. Quantitative real-time PCR and western blotting showed that Es-vtg1 was highly expressed in ovary and hepatopancreas. Moreover, bacteria could induce the high-level expression of Es-Vtg1. Es-Vtg1 plays important roles in immunological defense, including binding to bacteria, inhibiting bacterial proliferation, and regulating the expression of antimicrobial peptides. Collectively, these results demonstrate that Es-Vtg1 plays critical roles in antimicrobial function.

Protein Corona Analysis of Silver Nanoparticles Exposed to Fish Plasma

Nanoparticles (NPs) in contact with biological fluids experience changes in surface chemistry that can impact their biodistribution and downstream physiological impact. One such change involves the formation of a protein corona (PC) on the surface of NPs. Here we present a foundational study on PC formation following the incubation of polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs, 50 nm) in the plasma of smallmouth bass (Micropterus dolomieu). PC formation increases with exposure time and is also affected by gender, with AgNPs incubated in male plasma having slightly thinner PCs and less negative zeta potentials than those incubated in female plasma. Proteomic analysis also revealed gender-specific differences in PC composition: in particular, egg-specific proteins (vitellogenin (VTG) and zona pellucida (ZP) were identified only in PCs derived from female plasma, raising the possibility of their roles in AgNP-related reproductive toxicity by promoting their accumulation in developing oocytes.

Identification of sea bass pIgR shows its interaction with vitellogenin inducing antibody-like activities in HEK 293T cells

Fish vitellogenin (Vg) has been shown to mediate the phagocytosis via interaction with a Fcγ-like phagocytic receptor on macrophages, but identification of such a receptor and its functional characterization remains lacking. In this study, we isolated a cDNA of polymeric immunoglobulin receptor (pIgR) from sea bass, which encoded a single-spanning transmembrane protein of 326 amino acids including a 21-amino acid signal peptide, an extracellular region, a transmembrane region and a 36-amino acid intracellular region included two Ig-like domains (ILDs), and was expressed in multiple lymphoid organs. We then showed that recombinant extracellular domain of sea bass pIgR was capable of binding to Vg as well as IgG and IgM. We also showed that Vg as well as IgG and IgM interacted with pIgR-expressing HEK 293T cells. Importantly, we demonstrated that Vg as well as IgG and IgM were all capable of enhancing phagocytosis by HEK 293T cells and inducing expression of tnf-α and il-1β, via interacting with pIgR. Collectively, these results suggest that fish Vg, analogous to IgG and IgM, can interact with pIgR and result in similar down-stream immune responses, providing an additional evidence that Vg plays an antibody-like role.

Two vitellogenins in the loliginid squid Uroteuthis edulis: Identification and specific expression in ovarian follicles

Vitellogenenesis is a physiological process common in oviparous animals. The molecular profile, modifications, and utilization of vitellogenin (VTG), a precursor of yolk protein, have been characterized in various taxa to understand oogenesis within different modes of reproduction. Hormonal regulation of VTGs has been investigated in invertebrates, such as insects and crustaceans; conversely, little is known for cephalopods. In this study, we isolated two VTG genes (ue-VTG1 and ue-VTG2) from the loliginid swordtip squid, Uroteuthis edulis, via a comprehensive survey of a transcriptome database and subsequent cDNA cloning. Structural analysis of the two ue-VTGs revealed their unique features, namely the absence of two domains usually found in VTGs from other organisms: the von Willebrand factor D domain (vWD) and the domain of unknown function 1943 (DUF1943). Levels of ue-VTG1 and ue-VTG2 transcripts in the ovary, specifically in follicular cells, increased during the late-vitellogenic phase, suggesting that yolk accumulation progresses via paracrine interactions involving follicular cells and oocytes. N-terminal amino acid sequencing of biochemically purified yolk protein revealed its origins from these two VTGs, indicating that both are functional precursors of yolk protein. These results provide information that is essential to understanding the physiological pathway of yolk synthesis, accumulation, and storage in loliginid squids.

Functional characterization of Vitellogenin_N domain, domain of unknown function 1943, and von Willebrand factor type D domain in vitellogenin of the non-bilaterian coral Euphyllia ancora: Implications for emergence of immune activity of vitellogenin in basal metazoan

Our understanding of the function of vitellogenin (Vg) in reproduction has undergone a transformation over the past decade in parallel with new insights into the role of Vg in immunity. However, the time when Vg was endowed with immunological activities during animal evolution remains elusive. Here we demonstrate for the first time that the recombinant proteins rVitellogenin_N, rDUF1943, and rVWD from Vg of the basal metazoan coral Euphyllia ancora not only interact with Gram-positive and negative bacteria as well as their conserved surface components LTA and LPS but also enhance phagocytosis of bacteria by macrophages. Moreover, challenge with LPS results in a marked up-regulation of vg in the coral E. ancora. These data suggest that E. ancora Vg, like that described in the bilaterian oviparous animals fish and amphioxus, is a molecule related to antibacterial defense, indicating that the timing of the emergence of immune role of Vg predates the divergence of the cnidarian (non-bilaterian) and bilaterian lineages.

Vitellogenin2: spermatozoon specificity and immunoprotection in mud crabs

As the precursor of vitellin (Vn), vitellogenin (Vg) has initially been considered as a female-specific protein involved in vitellogenesis, while it was also present in males induced by hormones or organs manipulation. Distinct from vtg1 we previously found in female mud crab Scylla paramamosain, vtg2 was intriguingly detected in male testis under normal physiological conditions in this study. Sequence analysis showed that vtg2 and vtg1 were actually two isoforms of Vg caused by different types of alternative splicing. PCR and in situ hybridization analysis revealed that vtg2 was localized only in the testicular spermatozoa, while Vn was detected in both the spermatozoa of the testis and seminal vesicle. Therefore, we speculated that Vn was initially translated in testicular spermatozoa, then migrated with spermatozoa, and finally stored in the seminal vesicle, where spermatozoa gradually accomplished maturation. We presumed that vtg2/Vn might act as an immune-relevant molecule in the male reproduction system. In the subsequent experiment, the expression of vtg2/Vn in testis was significantly induced in response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) injection at both transcriptional and translational levels. In the light of the results presented above, we deemed that vtg2/Vn is a novel candidate of immune-relevant molecules involved in immunoprotection during the spermatozoon maturation, and this research helps to open a new avenue for further exploring the role of Vg.

Protein content of the Hylesia metabus egg nest setae (Cramer [1775]) (Lepidoptera: Saturniidae) and its association with the parental investment for the reproductive success and lepidopterism

Hylesia metabus is a neotropical moth possessing toxic setae, which once in contact with the skin cause a severe dermatitis to humans known as lepidopterism. The only known function of the setae in the life cycle is to provide protection during the mating and egg-hatching stages. Approximately 65% of the protein content of the setae is a cluster of five proteases (28-45kDa) showing sequence homology to other S1A serine proteases. The N-glycans of a 40kDa protease are a mixture of neutral and sulfated G0F structures. The sulfated N-glycans have an important role in triggering the inflammatory response typical of lepidopterism while the proteolytic activity may promote the erosion of blood vessels and tissues causing focal hemorrhages. The presence of Chitinase and a 30kDa lipoprotein is probably related to the antifungal defense. In addition, chitin digestion of the setae may potentiate the inflammatory reaction caused by the toxins due to the formation of chitin adjuvants fragments. The combined effect of proteases and a chitinase may dissuade predating arthropods, by damaging their exoskeletons. Vitellogenin, a bacteriostatic protein, is able to recognize pathogen-associated patterns, which suggests its possible role in protecting the embryonated eggs from pathogenic microorganisms.

SIGNIFICANCE

The present study is the first report describing the different protein species present in the urticating egg nest setae of the neotropical moth Hylesia metabus - the most harmful of the Hylesia moths - causing a severe urticating dermatitis in humans known as lepidopterism. A distinctive feature of the venom is the presence of five different S1A serine proteases probably used to guarantee a more efficient degradation of a wider number of protein substrates. This work confirms that the presence of sulfated N-glycans is not an isolated finding since its presence has been demonstrated in two different proteases affirming that this PTM is of importance for the activation of the inflammatory response typical of lepidopterism. Additionally, this study gives useful information on the defense mechanisms used for protection of its progeny vs. vertebrate predators, fungus, bacteria or other arthropods such as ants. The proteins detected in the egg nest should be seen as an extended parental effort made by the females in order to achieve an optimal reproductive success, thus compensating for the considerable loss of progeny during the larval stages that seriously limits the number of sexually mature adults reaching the reproductive phase.

Reference gene selection and RNA preservation protocol in the cat flea, Ctenocephalides felis, for gene expression studies

The cat flea, Ctenocephalides felis, is a major pest species on companion animals thus of significant importance to the animal health industry. The aim of this study was to develop sampling and storage protocols and identify stable reference genes for gene expression studies to fully utilize the growing body of molecular knowledge of C. felis. RNA integrity was assessed in adult and larvae samples, which were either pierced or not pierced and stored in RNAlater at ambient temperature. RNA quality was maintained best in pierced samples, with negligible degradation evident after 10 days. RNA quality from non-pierced samples was poor within 3 days. Ten candidate reference genes were evaluated for their stability across four group comparisons (developmental stages, genders, feeding statuses and insecticide-treatment statuses). Glyceraldehyde 3 phosphate dehydrogenase (GAPDH), 60S ribosomal protein L19 (RPL19) and elongation factor-1α (Ef) were ranked highly in all stability comparisons, thus are recommended as reference genes under similar conditions. Employing just two of these three stable reference genes was sufficient for accurate normalization. Our results make a significant contribution to the future of gene expression studies in C. felis, describing validated sample preparation procedures and reference genes for use in this common pest.

Genetics of Lipid-Storage Management in Caenorhabditis elegans Embryos

Lipids play a pivotal role in embryogenesis as structural components of cellular membranes, as a source of energy, and as signaling molecules. On the basis of a collection of temperature-sensitive embryonic lethal mutants, a systematic database search, and a subsequent microscopic analysis of >300 interference RNA (RNAi)-treated/mutant worms, we identified a couple of evolutionary conserved genes associated with lipid storage in Caenorhabditis elegans embryos. The genes include cpl-1 (cathepsin L-like cysteine protease), ccz-1 (guanine nucleotide exchange factor subunit), and asm-3 (acid sphingomyelinase), which is closely related to the human Niemann-Pick disease-causing gene SMPD1. The respective mutant embryos accumulate enlarged droplets of neutral lipids (cpl-1) and yolk-containing lipid droplets (ccz-1) or have larger genuine lipid droplets (asm-3). The asm-3 mutant embryos additionally showed an enhanced resistance against C band ultraviolet (UV-C) light. Herein we propose that cpl-1, ccz-1, and asm-3 are genes required for the processing of lipid-containing droplets in C. elegans embryos. Owing to the high levels of conservation, the identified genes are also useful in studies of embryonic lipid storage in other organisms.

Immune-Relevant and Antioxidant Activities of Vitellogenin and Yolk Proteins in Fish

Vitellogenin (Vtg), the major egg yolk precursor protein, is traditionally thought to provide protein- and lipid-rich nutrients for developing embryos and larvae. However, the roles of Vtg as well as its derived yolk proteins lipovitellin (Lv) and phosvitin (Pv) extend beyond nutritional functions. Accumulating data have demonstrated that Vtg, Lv and Pv participate in host innate immune defense with multifaceted functions. They can all act as multivalent pattern recognition receptors capable of identifying invading microbes. Vtg and Pv can also act as immune effectors capable of killing bacteria and virus. Moreover, Vtg and Lv are shown to possess phagocytosis-promoting activity as opsonins. In addition to these immune-relevant functions, Vtg and Pv are found to have antioxidant activity, which is able to protect the host from oxidant stress. These non-nutritional functions clearly deepen our understanding of the physiological roles of the molecules, and at the same time, provide a sound basis for potential application of the molecules in human health.

Immune-Relevant and Antioxidant Activities of Vitellogenin and Yolk Proteins in Fish

Vitellogenin (Vtg), the major egg yolk precursor protein, is traditionally thought to provide protein- and lipid-rich nutrients for developing embryos and larvae. However, the roles of Vtg as well as its derived yolk proteins lipovitellin (Lv) and phosvitin (Pv) extend beyond nutritional functions. Accumulating data have demonstrated that Vtg, Lv and Pv participate in host innate immune defense with multifaceted functions. They can all act as multivalent pattern recognition receptors capable of identifying invading microbes. Vtg and Pv can also act as immune effectors capable of killing bacteria and virus. Moreover, Vtg and Lv are shown to possess phagocytosis-promoting activity as opsonins. In addition to these immune-relevant functions, Vtg and Pv are found to have antioxidant activity, which is able to protect the host from oxidant stress. These non-nutritional functions clearly deepen our understanding of the physiological roles of the molecules, and at the same time, provide a sound basis for potential application of the molecules in human health.

Vitellogenin is an immunocompetent molecule for mother and offspring in fish

Our understanding of the function of vitellogenin (Vg) in reproduction has undergone a transformation over the past decade in parallel with new insights into the role of Vg in immunity. Initially, Vg was regarded as a female-specific reproductive protein, which is cleaved into yolk proteins such as phosvitin (Pv) and lipovitellin (Lv), stored in egg, providing the nutrients for developing embryos. Recently, Vg is shown to be an immune-relevant molecule involved in the defense of the host against the microbes including bacterium and virus. Furthermore, Pv and Lv, that both are proteolytically cleaved products of Vg, play a defense role in developing embryos. Importantly, yolk protein-derived small peptides also display antimicrobial activity. These data together indicate that Vg, in addition to being involved in yolk protein formation, plays a non-reproductive role via functioning as an immune-relevant molecule in both parent fishes and their offspring. It also shows that yolk proteins and their degraded peptides are novel players in maternal immunity, opening a new avenue to study the functions of reproductive proteins.

Cloning, constitutive activity and expression profiling of two receptors related to relaxin receptors in Drosophila melanogaster

Leucine-rich repeat containing G protein-coupled receptors (LGRs) comprise a cluster of transmembrane proteins, characterized by the presence of a large N-terminal extracellular domain. This receptor group can be classified into three subtypes. Belonging to the subtype C LGRs are the mammalian relaxin receptors LGR7 (RXFP1) and LGR8 (RXFP2), which mediate important reproductive and other processes. We identified two related receptors in the genome of the fruit fly and cloned their open reading frames into an expression vector. Interestingly, dLGR3 demonstrated constitutive activity at very low doses of transfected plasmid, whereas dLGR4 did not show any basal activity. Both receptors exhibited a similar expression pattern during development, with relatively high transcript levels during the first larval stage. In addition, both receptors displayed higher expression in male adult flies as compared to female flies. Analysis of the tissue distribution of both receptor transcripts revealed a high expression of dLGR3 in the female fat body, while the expression of dLGR4 peaked in the midgut of both the wandering and adult stage.

Seasonal trends in the condition of nesting females of a solitary bee: wing wear, lipid content, and oocyte size

During the nesting season, adult females of the solitary bee Megachile rotundata (F.) face considerable physical and energy demands that could include increasing wear and tear on their bodies and decreasing lipid reserves. Consequently, their reproductive performance may be affected not only by extrinsic factors (e.g., weather and floral resource availability), but intrinsic changes in their own bodies. Because of the potential fitness effects of seasonal changes in body condition, our objectives were to determine how wing wear, lipid reserves, and oocyte sizes vary during nesting seasons, beginning when females emerge as adults. As nesting progressed, females in two populations experienced a steady increase in wing wear, which is known to reduce foraging efficiency and increase risk of mortality in other bees. Soon after emergence, females exhibited sharp declines in lipid content which remained low for the remainder of the season. Newly-emerged females ingested pollen, an activity known to be correlated with the initiation of egg maturation in this species. Additionally, the early summer drop in lipid stores was correlated with an increase in the size of the oocytes carried. However, by ∼6 weeks after emergence, oocytes began to decrease in length and volume, perhaps due to nutrient deficiencies related to loss of stored lipids. Our results suggest management of M. rotundata should include rearing bees at temperatures that maximize stored lipid reserves in adults and timing bee release so that significant pollen resources are available for both adults and offspring.

A fat body-derived apical extracellular matrix enzyme is transported to the tracheal lumen and is required for tube morphogenesis in Drosophila

The apical extracellular matrix plays a central role in epithelial tube morphogenesis. In the Drosophila tracheal system, Serpentine (Serp), a secreted chitin deacetylase expressed by the tracheal cells plays a key role in regulating tube length. Here, we show that the fly fat body, which is functionally equivalent to the mammalian liver, also contributes to tracheal morphogenesis. Serp was expressed by the fat body, and the secreted Serp was taken up by the tracheal cells and translocated to the lumen to functionally support normal tracheal development. This process was defective in rab9 and shrub/vps32 mutants and in wild-type embryos treated with a secretory pathway inhibitor, leading to an abundant accumulation of Serp in the fat body. We demonstrated that fat body-derived Serp reached the tracheal lumen after establishment of epithelial barrier function and was retained in the lumen in a chitin synthase-dependent manner. Our results thus reveal that the fat body, a mesodermal organ, actively contributes to tracheal development.

Not only for egg yolk--functional and evolutionary insights from expression, selection, and structural analyses of Formica ant vitellogenins

Vitellogenin (Vg), a storage protein, has been extensively studied for its egg-yolk precursor role, and it has been suggested to be fundamentally involved in caste differences in social insects. More than one Vg copy has been reported in several oviparous species, including ants. However, the number and function of different Vgs, their phylogenetic relatedness, and their role in reproductive queens and nonreproductive workers have been studied in few species only. We studied caste-biased expression of Vgs in seven Formica ant species. Only one copy of conventional Vg was identified in Formica species, and three Vg homologs, derived from ancient duplications, which represent yet undiscovered Vg-like genes. We show that each of these Vg-like genes is present in all studied Hymenoptera and some of them in other insects as well. We show that after each major duplication event, at least one of the Vg-like genes has experienced a period of positive selection. This, combined with the observation that the Vg-like genes have acquired or lost specific protein domains suggests sub- or neofunctionalization between Vg and the duplicated genes. In contrast to earlier studies, Vg was not consistently queen biased in its expression, and the caste bias of the three Vg-like genes was highly variable among species. Furthermore, a truncated and Hymenoptera-specific Vg-like gene, Vg-like-C, was consistently worker biased. Multispecies comparisons are essential for Vg expression studies, and for gene expression studies in general, as we show that expression and also, putative functions cannot be generalized even among closely related species.

Inhibitional effects of metal Zn²⁺ on the reproduction of Aphis medicaginis and its predation by Harmonia axyridis

BACKGROUND

Contamination, including metals, can disturb the reproductive processes of many organisms, including both prey and predatory insects. However, there is virtually no information on the effects of high level Zinc (Zn) pollution on aphids and ladybirds. The high concentrations of Zn²⁺ or Zn pollution inhibit reproduction in the phytophagous aphid, Aphis medicaginis, and the predatory ladybird Harmonia axyridis could provide important information.

RESULTS

It was observed in this study that Zn concentrations in Vicia faba (broad bean) seeds and seedlings in all Zn²⁺ treatments were significantly higher than that in the control group, and increased with increasing Zn²⁺ concentrations in the solution. The rate of reproduction in A. medicaginis declined significantly (p<0.05) over time in the five groups fed on broad bean seedlings treated with different concentrations of Zn²⁺ solution compared with the control group. These results showed that higher concentrations of Zn²⁺ significantly inhibited the reproductive capacity of A. medicaginis. We also cloned and identified a gene encoding vitellogenin (Vg) from A. medicaginis, which has an important role in vitellogenesis, and therefore, reproduction was affected by exposure to Zn²⁺. Expression of AmVg was reduced with increasing exposure to Zn²⁺ and also in the F1-F3 generations of aphids exposed to different Zn²⁺ concentrations. Predation by H. axyridis was also reduced in aphids exposed to high-levels of Zn²⁺. Similarly, ovipositioning by H. axyridis was also reduced.

CONCLUSIONS

Our results suggest that Zn²⁺ can significantly affect the reproductive capacity of both A. medicaginis and its predator H. axyridis, the former through effects on the expression of AmVg and the latter through avoidance of aphids containing high levels of Zn²⁺.

Vitellogenin from the silkworm, Bombyx mori: an effective anti-bacterial agent

Silkworm, Bombyx mori, vitellogenin (Vg) was isolated from perivisceral fat body of day 3 of pupa. Both Vg subunits were co-purified as verified by mass spectrometry and immunoblot. Purified Vg responded to specific tests for major posttranslational modifications on native gels indicating its nature as lipo-glyco-phosphoprotein. The Vg fraction had strong antibacterial activity against Gram negative bacterium Escherichia coli and Gram positive bacterium Bacillus subtilis. Microscopic images showed binding of Vg to bacterial cells and their destruction. When infected silkworm larvae were treated with purified Vg they survived the full life cycle in contrast to untreated animals. This result showed that Vg has the ability to inhibit the proliferation of bacteria in the silkworm fluid system without disturbing the regular metabolism of the host.

Identification and characterization of the vitellogenin receptor in Macrobrachium rosenbergii and its expression during vitellogenesis

In oviparous organisms, oocyte maturation depends on massive production of the egg yolk-precursor protein, vitellogenin (Vg). Vg is taken up by the developing oocytes through receptor-mediated endocytosis (RME), a process essential to successful reproduction. The aims of this study were to identify and characterize the yet-unknown vitellogenin receptor (VgR) from the pleocyamate crustacean Macrobrachium rosenbergii, and to investigate its expression levels during vitellogenesis and its interaction with Vg. The VgR gene was cloned, and its translated protein was specifically located at the oocyte membrane. Moreover, for the first time, a VgR protein was identified and sequenced by mass spectrometry. The putative MrVgR displayed high sequence similarity to VgRs from crustaceans, insects, and vertebrates, and its structure includes typical elements, such as an extracellular, lipoprotein-binding domain (LBD), EGF-like, and O-glycosylation domains, a transmembrane domain, and a short, C-terminal, cytosolic tail. In this article, we identify the first crustacean VgR protein, and present data demonstrating its high affinity for a Vg column followed by elution with suramin and EDTA. Additionally we demonstrate that VgR expression in the oocyte is elevated during vitellogenesis. Our results contribute to the fundamental understanding of oocyte maturation in crustaceans, and particularly elucidate Vg uptake through RME via the VgR.

The molecular and structural characterization of two vitellogenins from the free-living nematode Oscheius tipulae

This paper describes the purification of yolk proteins, which are important for the reproduction of egg-laying animals, and the structural characterization of two vitellogenins, VT1 and OTI-VIT-6, of the nematode Oscheius tipulae. O. tipulae is an alternative model organism to its relative, the widely used Caenorhabditis elegans, and is a good model to understand reproduction in insect parasitic nematodes of the genus Heterorhabditis. The native purified O. tipulae vitellogenin is composed of three polypeptides (VT1, VT2 and VT3), whereas in C. elegans, vitellogenin is composed of four polypeptides. The gene (Oti-vit-1) encoding yolk polypeptide VT1 has been recently identified in the genome of O. tipulae. Immunoblotting and N-terminal sequencing confirmed that VT1 is indeed coded by Oti-vit-1. Utilizing the same experimental approaches, we showed that the polypeptides VT2 and VT3 are derived from the proteolytic processing of the C- and N-terminal portions of the precursor OTI-VIT-6, respectively. We also showed that the recombinant polypeptide (P40), corresponding to the N-terminal sequence of OTI-VIT-6, preferentially interacts with a 100-kDa polypeptide found in adult worm extracts, as we have previously shown for the native vitellins of O. tipulae. Using the putative nematode vitellogenin amino acid sequences available in the UniProtKB database, we constructed a phylogenetic tree and showed that the O. tipulae vitellogenins characterized in this study are orthologous to those of the Caenorhabditis spp. Together, these results represent the first structural and functional comparative study of nematode yolk proteins outside the Caenorhabditis genus and provide insight into the evolution of these lipoproteins within the Nematode Phylum.

Vitellogenesis in the fruit fly, Drosophila melanogaster: antagonists demonstrate that the PLC, IP3/DAG, PK-C pathway is triggered by calmodulin

In Drosophila melanogaster M. (Diptera: Drosophilidae), a phospholipase-C to proteininase-C signal cascade leads to the endocytic uptake of yolk precursor molecules. The data suggest that D. melanogaster has a phospholipase-C/proteinkinase-C signaling pathway similar to that previously shown to be required for vitellogenesis in the milkweed bug, Oncopeltus fasciatus Dallas (Hemiptera: Lygaeidae). Calmodulin, derived from epithelial cells and transported to the oocytes via gap junctions, may trigger this pathway. To investigate this, a series of known antagonists to various elements of the pathway were used. W-7 (which prevents calmodulin binding to phospholipase-C), U-73122 (which prevents activation of phospholipase-C), verapamil (which blocks Ca(2+) release by IP3), HAG (which blocks diacylglycerol), and staurosporine (which inactivates proteinkinase-C) were each shown to inhibit endocytosis, thereby blocking formation of nascent yolk spheres.

Maternal immunity in fish

Both innate and adaptive immune-relevant factors are transferred from mother to offspring in fishes. These maternally-transferred factors include IgM, lysozymes, lectin, cathelicidin and complement components. Recently, yolk proteins, phosvitin and lipovitellin, have been shown to be maternally-transferred factors, functioning in the defense of teleost larvae against pathogens. Among these factors, the mode of action of complement components and yolk proteins has been explored, whereas that of all the other factors remains elusive. At present, the transfer mechanisms of maternally-derived immune factors are largely unknown although those of IgM and yolk protein transmission from mother to offspring have been reported in some fishes. Maternal transfer of immunity is affected by many elements, including biological factors, such as age and maturation, and environmental conditions experienced by brood fish, such as pathogens and nutritional supply. Practically, the manipulation of maternal immunity transfer can be used to enhance the survival rate of fish larvae.