Vitellogenin Receptor Research Articles

A mechanistic model for studying the initiation of anguillid vitellogenesis by comparing the European eel (Anguilla anguilla) and the shortfinned eel (A. australis)

An inverse relation exists between the maturation stage at the start of the oceanic reproductive migration and the migration distance to the spawning grounds for the various eel species. The European eel Anguilla anguilla migrates up to 5–6000 km and leaves in a previtellogenic state. The shortfinned eel A. australis migrates 2–4000 km and leaves in an early vitellogenic state. In this study, we compared the early pubertal events in European silver eels with those in silver shortfinned eels to gain insights into the initiation of vitellogenesis. Immediately after being caught, yellow and silver eels of both species were measured and sampled for blood and tissues. Eye index (EI), gonadosomatic index (GSI) and hepatosomatic index (HSI) were calculated. Plasma 11-ketotestosterone (11-KT) and 17β-estradiol (E2) levels were measured by radioimmunoassay. Pituitary, liver and ovaries were dissected for quantitative real-time PCR analyses (pituitary dopamine 2b receptor d2br, gonadotropin-releasing hormone receptors 1 and 2 gnrhr1 and gnrhr2, growth hormone gh and follicle-stimulating hormone-β fshb; liver estrogen receptor 1 esr1; gonad follicle-stimulating hormone receptor fshr, androgen receptors α and β ara and arb, vitellogenin receptor vtgr and P450 aromatase cyp19). Silver eels of both species showed a drop in pituitary gh expression, progressing gonadal development (GSI of ∼1.5 in European eels and ∼3.0 in shortfinned eels) and steroid level increases. In shortfinned eels, but not European eels, expression of fshb, gnrhr1 and gnrhr2, and d2br in the pituitary was up-regulated in the silver-stage as compared to yellow-stage females, as was expression of fshr, ara and arb in the ovaries. Expression of esr1 in European eels remained low while esr1 expression was up-regulated over 100-fold in silver shortfinned eels. The mechanistic model for anguillid vitellogenesis that we present suggests a first step that involves a drop in Gh and a second step that involves Fsh increase when switching in the life history trade-off from growth to reproduction. The drop in Gh is associated with gonadal development and plasma steroid increase but precedes brain-pituitary-gonad axis (BPG) activation. The Fsh increase marks BPG activation and increased sensitivity of the liver to estrogenic stimulation, but also an increase in D2br-mediated dopaminergic signaling to the pituitary.

Elucidation of molecular expression associated with abnormal development and sterility caused by electron beam irradiation in Spodoptera litura (F.) (Lepidoptera: Noctuidae)

Purpose: The objective of the present study was to elucidate the mode of indirect action of electron beam irradiation at the molecular level against a quarantine pest, Spodoptera litura (F.).Material and methods: Electron beam irradiation (50–200 Gy) was applied to S. litura eggs, larvae, pupae, and adults, after which the feeding area, body weight, deformity of pupae and adults, ovarian development, expression levels of vitellogenin (Vg) and vitellogenin receptor (VgR) genes, and protein levels were analyzed.Results: The amount of feeding by S. litura larvae and the synthesis level of 70 kDa storage protein significantly decreased as the electron beam dose increased. When larvae were treated with the electron beam, morphological deformities appeared in the pupae, and abnormal wing disc (AWD) expression significantly decreased. Ovarian development was completely inhibited in emerged adults that had undergone 200 Gy electron beam irradiation as pupae. Quantitative real-time PCR (qRT-PCR) assays showed significant downregulation of the Vg and VgR genes due to electron beam irradiation; whereas the synthesis level of Vg protein (190 kDa) did not decrease with time in eggs unlike in non-irradiated (control) S. litura eggs, exhibiting irradiation induced impairment of Vg functioning.Conclusions: These findings of radiation-induced abnormal development and sterility in S. litura together with the correlated changes at the molecular level may facilitate the development of a phytosanitary strategy against this quarantine pest using electron beam irradiation.

Adipokinetic Hormone Receptor Mediates Trehalose Homeostasis to Promote Vitellogenin Uptake by Oocytes in Nilaparvata lugens.

Adipokinetic hormones (AKHs) are well known to mobilize lipids and carbohydrates for energy-consuming activities in insects. These neuropeptides exert their functions by interacting with AKH receptors (AKHRs) located on the plasma membrane of fat body cells, which regulates energy mobilization by stimulating lipolysis of triacylglycerols (TAG) to diacylglycerols (DAG) and conversion of glycogen into trehalose. Here, we investigated the roles of AKH/AKHR signaling system in trehalose metabolism and vitellogenesis during female reproduction in the brown planthopper, Nilaparvata lugens. Knockdown of AKHR expression by RNA interference (RNAi) resulted in a decrease of the circulating trehalose in hemolymph and significantly increased levels of two trehalases in fat bodies, indicating that the modulation of hemolymph trehalose levels by AKHR may be mediated by regulating trehalose degradation. In addition, adult females that had been injected with double-stranded RNA (dsRNA) for AKHR exhibited delayed oocyte maturation, prolonged pre-oviposition period, as well as decline in egg number and reduction in fecundity. Considering that these phenotypes resulting from AKHR silencing are similar to those of vitellogenin receptor (VgR) RNAi, we further analyzed a possible connection between AKHR and vitellogenesis. Knockdown of AKHR showed no effects on the Vg synthesis in fat bodies, whereas it significantly reduced the levels of VgR in ovaries. With RNAi-females, we observed an increase of Vg accumulation in hemolymph and a decrease of Vg deposition in ovaries. Moreover, the decrease in VgR expression and Vg incorporation by developing oocytes could be partially rescued by injection of trehalose into AKHR RNAi females. The present study has implicated trehalose in the AKH/AKHR signaling-mediated control of reproduction and provided new insight into mechanisms of AKH/AKHR regulation of trehalose metabolism in insect vitellogenesis, oocyte maturation and fecundity.

Silencing expression of the Rhipicephalus microplus vitellogenin receptor gene blocks Babesia bovis transmission and interferes with oocyte maturation

BackgroundRhipicephalus microplus is an efficient biological vector of Babesia bovis, a causative agent of bovine babesiosis. Babesia bovis is passed transovarially to the next generation of ticks, which then transmit the parasite to naïve animals. Due to the importance of the R. microplus ovary for tick reproduction and transmission of B. bovis, we investigated the hypothesis that silencing vitellogenin receptor gene expression in the ovary during tick feeding on B. bovis-infected cattle would affect parasite transmission to the next generation of ticks.ResultsSilencing expression of the vitellogenin receptor in the ovary by RNA interference, resulted in reduced tick fertility. We observed reduced egg production (i.e. reduced weight of eggs), a lower rate of embryonic development, and a reduction in hatching. Analysis of individual larvae by PCR confirmed that RNAi mediated downregulation of the R. microplus vitellogenin receptor and also interfered with transovarial transmission of B. bovis. None of the larvae (0/58) from the RmVgR dsRNA-injected group were PCR-positive, whereas 12% (7/58) and 17% (10/58) of larvae from the non-injected and buffer-injected control groups, respectively, were infected with B. bovis.ConclusionsThe combined effects of reduced fecundity and reduced infection in surviving larvae resulting from silencing indicate that vitellogenin receptor is essential for tick reproduction and may play a vital role in B. bovis transmission.

The vitellogenin receptor has an essential role in vertical transmission of rice stripe virus during oogenesis in the small brown plant hopper.

The small brown plant hopper (SBPH), Laodelphax striatellus Fallén, is one of the most destructive pests on rice. This pest transmits rice stripe virus (RSV) both horizontally and vertically, leading to major yield and economic losses in rice production. However, the way that RSV particles enter oocytes of SBPH remains largely unknown. Thus, identification of key factors involved in the interaction between SBPH and RSV in the ovary is crucial. Transcriptome of non-viruliferous (NV) or high viruliferous (HV) SBPH ovaries at 24 and 48 h of emergence was sequenced. Differentially expressed genes analysis showed that vitellogenin receptor was significantly highly expressed in the ovary of the HV SBPH strains compared to NV strains. Quantitative real-time polymer chain reaction showed that the vitellogenin receptor in L. striatellus (LsVgR) was highly expressed in the ovaries of female adults and maintained a high level of expression at the early stage of ovary development. By using RNA interference, the expression of LsVgR in the ovaries of the HV strain was significantly decreased by 98.1%. RSV titer was reduced by 60.9% as quantified by viral RNA3 intergenic region and the transcripts of nucleocapsid protein gene (CP) reduced by 46.3%. The numbers of offspring hatched were significantly reduced in dsRNA-treated groups. The transcripts of CP were not affected by silencing LsVgR, whereas the abundance of RNA-dependent RNA polymerase increased by 15-fold in the member of surviving progenies. Our results suggest that vitellogenin receptor participates in regulating RSV replication during oogenesis. © 2018 Society of Chemical Industry.

Molecular characterization and juvenile hormone-regulated transcription of the vitellogenin receptor in the cabbage beetle Colaphellus bowringi

The vitellogenin receptor (VgR) is highly expressed in the ovaries where it is responsible for vitellogenin (Vg) deposition during oogenesis in insects. Therefore, identifying the VgR of insect pests, and understanding the mechanism regulating its expression, could lead to the development of pest management strategies based on disrupting reproduction. We cloned and identified VgR in the cabbage beetle, Colaphellus bowringi, which is a serious pest of cruciferous vegetables in Asia. The regulation of VgR transcription by juvenile hormone (JH) was also investigated. The results show that C. bowringi VgR cDNA contains an open reading frame of 5310 bp encoding 1769 amino acid residues. Protein domain prediction indicates that C. bowringi VgR belongs to the LDLR gene superfamily, having the same group of structural domains that has been well characterized in other insects. VgR mRNA was highly expressed in the ovaries of reproductive female cabbage beetles. Knockdown of VgR reduced yolk deposition in the ovaries, increased the accumulation of Vg proteins in the hemolymph and decreased the transcription of Vg1 and Vg2 in the fat body. RNA interference and hormone challenge experiments showed that JH induced VgR transcription via the JH intracellular receptor methoprene-tolerant (Met) and the JH-responsive transcription factor Krüppel homolog 1 (Kr-h1). Our results suggest that there is a feedback loop between VgR transcription in the ovaries and Vg transcription in the fat body. JH acting through Met-Kr-h1 pathway induces the transcription of the VgR that is essential for Vg uptake and reproductive development. These findings not only reveal the potential JH signaling mechanism regulating VgR transcription, but may also contribute to the development of pest control strategies based on disrupting endocrine-regulated reproduction.

Heat Shock Protein 40 (HSP40) in Pacific White Shrimp (Litopenaeus vannamei): Molecular Cloning, Tissue Distribution and Ontogeny, Response to Temperature, Acidity/Alkalinity and Salinity Stresses, and Potential Role in Ovarian Development.

Heat shock proteins (HSPs), a family of conserved proteins that are produced by cells in response to stresses, are known as molecular chaperones with a range of housekeeping and cellular protective functions. The 40 kD heat shock protein (HSP40) is a co-chaperone for HSP70 in the regulation of ATP hydrolysis. Unlike its well-documented cofactor HSP70, little is currently known regarding the biological functions of HSP40 in crustacean species such as penaeid shrimp. In the present study, the cDNA encoding HSP40 (Lv-HSP40) was identified from the Pacific white shrimp Litopenaeus vannamei, a highly significant commercial culture species. The structural organization indicates that Lv-HSP40 belongs to the type-I HSP40s. The muscle, gill, and hepatopancreas are the main sites of Lv-HSP40 transcript expression. Within these tissues, Lv-HSP40 mRNA were predominantly exhibited in the myocytes, epithelial cells and hepatopancreatic cells, respectively. Under acute thermal stress in the culture environment, Lv-HSP40 transcript levels are significantly induced in these three tissues, while low pH stress only upregulates Lv-HSP40 mRNA in the hepatopancreas and gill. During ontogenesis, Lv-HSP40 transcript levels are high at early embryonic stages and drop sharply at late embryonic and early larval stages. The ovary is another major organ of Lv-HSP40 mRNA expression in female shrimp, and Lv-HSP40 transcripts were mainly presented in the follicle cells but only weekly detected in the oocytes. Ovarian Lv-HSP40 mRNA levels increase continuously during gonadal development. Silencing of the Lv-HSP40 gene by RNA interference may effectively delay ovarian maturation after unilateral eyestalk ablation. The roles of Lv-HSP40 in ovarian development are speculated to be independent of its cofactor HSP70, and the vitellogenesis factor vitellogenin (Vg) and vitellogenin receptor (VgR). Our study, as a whole, provides new insights into the roles of HSP40 in multiple physiological processes in L. vannamei: (1) HSP40 is a responding factor during stressful conditions; and (2) HSP40 participates in embryonic and ovarian development.

Silencing of triazophos-induced Hexokinase-1-like reduces fecundity in Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

Hexokinase is a rate-limiting enzyme that plays pivotal roles in glucose homeostasis and energy metabolism via glucose (Glc) phosphorylation and Glc signaling mediation. Previous investigations have revealed the modulatory role of Hexokinase (Hex) genes involved in proper glucose regulation during insect diapause and embryo development, whereas whether it functions in insect fecundity remains largely unknown. We aimed to explore the relationship between Triazophos (TZP)-induced Hex-1 and fecundity of female Nilaparvata lugens. In this study, Hex-1 expression were characterized at different developmental stages and in various tissues of N. lugens, with the highest expression registered in brain tissues and 5th instar nymph. The present findings indicated that TZP + dsHex-1 silencing significantly reduced protein synthesis, including the fat body and ovarian protein content of female adults. Meanwhile, the glycometabolism with respect to the soluble sugar, trehalose and glucose content in female adults were strikingly influenced as a result of Hex-1 knockdown. The relative transcript level of Hex-1, vitellogenin (NlVg) and vitellogenin receptor (NlVgR) considerably decreased in TZP + dsHex-1 treated females compared to TZP and TZP + dsGFP-treated groups. More importantly, TZP + dsHex-1 silencing led to reduced number of eggs laid and vitellogenin (Vg) accumulation as well as retarded ovary development compared with TZP-treated and TZP + dsGFP-treated groups. Taken together, it is proposed that Hex-1 implicates in N. lugens fecundity by exerting profound effects on glycometabolism, protein sythesis and NlVg expression.

Methoprene-Tolerant (Met) Is Indispensable for Larval Metamorphosis and Female Reproduction in the Cotton Bollworm Helicoverpa armigera.

Juvenile hormone (JH) represses larval metamorphosis and induces adult reproduction in insects. Methoprene-tolerant (Met) is identified as an intranuclear receptor that mediates JH actions. In the present study, we characterized a Met from the severe agricultural pest, Helicoverpa armigera, namely HaMet. In the larval stage, HaMet is predominantly expressed in the epidermis and midgut, and is upregulated before each molting, whereas in adults HaMet is maximally expressed in the ovary, testis, and fat body. The immunofluorescence assay revealed that HaMet was distributed in the longitudinal and circular muscle layers of midgut in larvae, whereas in the ovary of female adults, HaMet was localized in the nucleus of the oolemma. Knockdown of HaMet in final-instar larvae shortened the time of pupation, induced abnormal pupation, and dampened pupation rate. In female adults, HaMet depletion severely suppressed the transcription of Vitellogenin (Vg) and Vitellogenin Receptor (VgR), disrupted the Vg accumulation in fat body and the yolk protein uptake in oocytes, and finally led to an impaired fecundity. Our findings therefore confirmed that HaMet acted as a nuclear receptor of JH and played an essential role in larval metamorphosis, vitellogenesis, and oocyte maturation.

Response Mechanism of Oviposition and Relevant Protein Expression of Bactrocera cucurbitae (Coquillet) to Short-Term High-Temperature Conditions.

Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) is an important pest of vegetables in Asia, the Middle East, Africa, and Hawaii. High temperature can significantly influence B. cucurbitae reproduction. The effect of short-term high-temperature exposure on proteins that affect oviposition was analyzed by proteomics. Among six key target genes for oviposition, the expression of Vitellogenin-1, Vitellogenin-2, and Vitellogenin receptor was similar in B. cucurbitae exposed to higher temperature compared to controls. However, levels of Vitellogenin-3 were reduced. Juvenile hormone (Jh)-inducible protein was downregulated and then upregulated, while the expression of Jh-epoxide hydrolase-2 showed the opposite Jh-inducible protein trend. Therefore, short-term high-temperature stress can cause differential expression of proteins related to oviposition in B. cucurbitae, which in turn further triggers the hormesis of oviposition. High-temperature conditions have become more frequent because of climate warming and are predicted to continue. The data indicate that climate effects on insect reproduction pose a significant threat to agriculture in a world of increasing population.

LC50 of lambda-cyhalothrin stimulates reproduction on the moth Mythimna separata (Walker)

Lambda-cyhalothrin has long been recommended as an effective insecticide to control the oriental armyworm, Mythimna separata (Walker), a notorious migratory pest of agricultural plants. Previous researches have suggested that survival, development, and reproduction of insects are influenced by sublethal concentrations of insecticides. However, the effects of sublethal concentrations of lambda-cyhalothrin on M. separata are less known. In this study, we determined the toxicity and effects of LC20 and LC50 concentration of lambda-cyhalothrin on development and reproduction of M. separata. Results indicate that LC20 of lambda-cyhalothrin tends to decrease the life traits of M. separate, with a shortening larvae period of offspring and oviposition period, whereas LC50 of lambda-cyhalothrin stimulates daily maximal fecundity and forwards the oviposition peak, suggesting a stimulation of reproduction by LC50 of lambda-cyhalothrin. The M. separata population was increased by an LC50 concentration of lambda-cyhalothrin, resulting in a net reproductive rate (R0) and intrinsic rate of increase (rm) significantly higher than that of the control. Transcripts of vitellogenin (MsVg) and vitellogenin receptor (MsVgR) genes were suppressed at day 1 after emergence of moth which developed from the larvae exposed to LC20 and LC50 of lambda-cyhalothrin, but were significant induced when the moth begin to lay eggs (day 4), with a more remarkable induction by LC50 of lambda-cyhalothrin than those of LC20 of lambda-cyhalothrin. Our results indicate that the observed stimulation of reproduction is therefore the results of up-regulation of MsVg and MsVgR by LC50 of lambda-cyhalothrin.

Characterization of Vitellogenin and Vitellogenin Receptor of Conopomorpha sinensis Bradley and Their Responses to Sublethal Concentrations of Insecticide.

Conopomorpha sinensis Bradley is the dominant borer pest of Litchi chinesis and Euphoria longan. Current management of C. sinensis relies upon insecticide application to adult moths. In addition to the direct mortality induced by insecticides, a sublethal dose of insecticides also affects growth, survival, and reproduction in the exposed insects. Vitellogenin (Vg) and vitellogenin receptor (VgR) are normally identified as essential reproduction-related proteins in insects. In this study, we characterized these two genes from C. sinensis, and investigated their differential responses to sublethal concentrations of insecticide. Cloned CsVg and CsVgR consist of 5391 and 5424-bp open reading frames, which encode proteins of 1796 and 1807 amino acid residues, respectively. The CsVg protein contains the typical vitellogenin, DUF1943 and VWFD domains as other reported lepidopteran Vgs. The CsVgR was characterized as a typical low density lipoprotein receptor with two highly conserved LBD and EGF precursor domains, one hydrophobic transmembrane domain, one cytoplasmic domain, and 13 putative N-glycosylation sites. We next assessed the sublethal effect of four major insecticides on egg-laying in C. sinensis. The toxicity against C. sinensis varied among the insecticides tested, with LC50 values ranging from 0.23 ppm for chlorpyrifos to 20.00 ppm for β-cypermethrin, among which emamectin benzoate (EB) showed a significant negative impact on egg-laying, survival rate, ovarian development, and mating rate of C. sinensis at LC30 doses. Further investigation showed that the transcriptional level of CsVg and CsVgR were impaired in different way at 24, 48, and 72 h after EB exposure, and this result was in agreement with the diminished egg-laying of C. sinensis in the sublethal concentration EB-treated group. A repressed transcription level of CsVgR was observed at 48 h after treatment, suggesting that EB elicits a delayed response in the abundance of CsVgR. These results established different roles of CsVg and CsVgR in response to the sublethal effect of insecticides. CsVg might be a better parameter than CsVgR for assessing the effect of sublethal insecticides on reproduction in C. sinensis.

Inhibitory Role of the Mud Crab Short Neuropeptide F in Vitellogenesis and Oocyte Maturation via Autocrine/Paracrine Signaling.

Neuropeptides, in addition to their classical role in the nervous system, act on intraovarian factors to regulate reproductive functions in vertebrates. However, this function of neuropeptides has not been characterized in crustaceans. Short neuropeptide F (sNPF), a highly conserved invertebrate neuropeptide, has been reported to be involved in feeding, metabolism, and in differentiation processes including reproduction. Although sNPF and its receptor (sNPFR) have been detected in the ovary in different species, ovarian colocalization of sNPF/sNPFR has not been investigated. In this study, we identified Scylla paramamosain (mud crab) sNPF (Sp-sNPF) as an endogenous ligand for the S. paramamosain orphan G protein-coupled receptor NPY2R in mammalian cell line HEK293T. We designated this receptor as Sp-sNPFR. RNA in situ hybridization in pre-vitellogenic ovary and reverse transcription-PCR on isolated denuded oocytes and follicle layers showed that Sp-sNPF was exclusively localized to the follicle cells, whereas Sp-sNPFR was detected in both follicle cells and oocytes. We also found that Sp-sNPF partly suppressed spontaneous maturation of denuded oocytes and caused intracellular cAMP accumulation and Ca2+ mobilization. Moreover, injection of synthetic Sp-sNPF peptides inhibited the expression of vitellogenin and vitellogenin receptor genes in vivo. These combined results suggest for the first time that Sp-sNPF may have inhibitory functions in vitellogenesis and oocyte maturation possibly via the autocrine/paracrine pathway.

Effects of dietary vitamin E on reproductive performance and antioxidant capacity of Macrobrachium nipponense female shrimp

We evaluated the effects of dietary vitamin E on the reproductive performance and antioxidant capacity of Macrobrachium nipponense female shrimp. Prawns were fed 0, 40, 80, 160, 320 or 640 mg vitamin E/kg diet for 60 days. The 80 mg/kg group had the highest weight gain and lowest feed conversion rates. And the highest spawning rates were observed in the 80 mg/kg group with no significant differences among the groups. The highest activities of lysozyme, acid phosphatase and alkaline phosphatase in hepatopancreas were obtained in the 160 mg/kg group. The activities of superoxide dismutase, catalase and glutathione peroxidase showed a decreasing trend in the hepatopancreas. The lowest content of malondialdehyde was obtained with 80 and 160 mg/kg vitamin E. Histological results showed that the number of restzellen cells in hepatopancreas and a number of follicular cells in ovaries increased with 160 mg/kg vitamin E. However, 640 mg/kg vitamin E resulted in damaged hepatopancreas tubules and oocytes. The highest vitellogenin and vitellogenin receptor gene expressions were observed with 160 mg/kg vitamin E. These results provide evidence that dietary vitamin E with 80 and 160 mg/kg plays a positive impact on reproductive performance and antioxidant capacity of female shrimp.

Optimal dietary lipid level promoted ovary development of Chinese sturgeon (Acipenser sinensis) broodstocks

A one-year feeding trial was conducted to determine the effects of dietary lipid level on gonad development and steroidogenesis-related gene expressions of Chinese sturgeon (Acipenser sinensis). Three isonitrogenous experimental diets (L10, L14 and L18) were compounded with different lipid levels. Results of the feeding trial showed that 2 female Chinese sturgeons in L18 group had developed the ovary to stage III. Chi-square independence test indicated that ovary development was significantly affected by dietary lipid level (P < .05). Po and d values of ovary also increased with dietary lipid level. Serum estradiol (E2) and testosterone (T) of L14 group was significantly higher than those in the other two groups (P < .05). Blood urea nitrogen (BUN) content decreased as dietary lipid level increased, while triglyceride (TG) and glucose (GLU) contents increased with dietary lipid level (P < .05). Vitellogenin receptor (vtgr) mRNA expression increased with dietary lipid level (P < .05); Gene expressions of androgen receptor (ar), cytochrome p450 17A1 (cyp17a1), steroidogenic acute regulatory protein (star), follicle stimulating hormone receptor (fshr), luteinizing hormone receptor (lhr) and cytochrome p450 aromatase (cyp19a1) were significantly higher in L14 group than in other groups (P < .05), whereas mRNA expression of leptin receptor (lepr) and DNA-binding protein inhibitor ID-1 (dbi) in L14 group were significantly lower (P < .05). Based on the gonad development, higher dietary lipid level (16.31%) would promote ovary development of Chinese sturgeon broodstocks through the elevation of vtgr expression to increase the assimilation of vitellogenin in ovary.

Vitellogenin transcytosis in follicular cells of the honeybee Apis mellifera and the wasp Polistes simillimus.

Vitellogenin receptor (VgR) is a low-density lipoprotein receptor responsible for the mediated endocytosis of vitellogenin (Vg) during egg formation in insects. The maturing oocyte is enveloped by a follicular epithelium, which has large intercellular spaces during Vg accumulation (patency). However, Vg has been reported in the cytoplasm of follicular cells, indicating that there may be a transcellular route for its transport. This study verified the presence of VgR in the follicular cells of the ovaries of the honeybee Apis mellifera and the wasp Polistes simillimus in order to evaluate if Vg is transported via transcytosis in these insects. Antibodies specific for vitellogenin receptor (anti-VgR), vitellogenin (anti-Vg), and clathrin (anti-Clt) were used for immunolocalization. The results showed the presence of VgR on the apical and basal plasma membranes of follicular cells of the vitellogenic follicles in both species, indicating that VgR may have been transported from the basal to the apical cell domain, followed by its release into the perivitelline space, evidenced by the presence of apical plasma membrane projections containing VgR. Co-localization proved that Vg bind to VgR and that the transport of this protein is mediated by clathrin. These data suggest that, in these social insects, Vg is transported via clathrin-mediated VgR transcytosis in follicular cells.

Molecular Characterization and Expression of Vitellogenin and Vitellogenin Receptor of Thitarodes pui (Lepidoptera: Hepialidae), an Insect on the Tibetan Plateau.

Vitellogenin (Vg) and vitellogenin receptor (VgR) play important roles in the vitellogenesis of insects. In this study, we cloned and characterized the two corresponding genes (TpVg and TpVgR) in an economically important insect, Thitarodes pui (Lepidoptera: Hepialidae), from the Tibetan plateau. The full length of TpVg is 5566 bp with a 5373 bp open reading frame (ORF) encoding 1,790 amino acids. Sequence alignment revealed that TpVg has three conserved domains: a Vitellogenin_N domain, a DUF1943 domain, and a von Willebrand factor type D domain (VWD). The full length of TpVgR is 5732 bp, with a 5397 bp ORF encoding 1798 amino acids. BLASTP showed that TpVgR belongs to the low-density lipoprotein receptor (LDLR) gene superfamily. Structural analysis revealed that TpVgR has a group of four structural domains: a ligand-binding domain (LBD), an epidermal growth factor (EGF)–precursor homology domain, a transmembrane (TM) domain, and a cytoplasmic domain. In addition, TpVgR has four cysteine-rich LDL repeats in the first ligand-binding site and seven in the second. Quantitative real-time polymerase chain reaction analysis revealed that the expression levels of TpVg and TpVgR are much higher in later pupa than in either the larval or adult stage, implying that the synthesis and uptake of Vg in T. pui occurs in the later pupal stage. These results will help us to understand the molecular mechanism of the reproductive capacity and will provide new insight into the mass rearing and utilization of T. pui.

Molecular and functional characterization of nucleoside diphosphate kinase (nm23 ) gene in oriental river prawn Macrobrachium nipponense during ovarian development

nm23 belongs to nucleoside diphosphate kinase superfamily―a group of multifunctional regulatory proteins. In this study, Macrobrachium nipponense nm23 (Mnnm23) complementary DNA (cDNA) was isolated and characterized. Full-length cDNA of Mnnm23 measured 829 bp, with a 531 bp open reading frame encoding for 177 amino acids (aa). Specific functional sites of Mnnm23 aa sequence were highly conserved with those in other decapod crustaceans. Mnnm23 transcripts were ubiquitously distributed in various tissues. Expression level of Mnnm23 was highest in stage I ovaries and gradually decreased as ovaries developed. After Mnnm23 knockdown by RNA interference, expression levels of Cyclin B and cyclin-dependent kinase 2 in ovaries increased in comparison with that of vehicle control (VC); vitellogenin and vitellogenin receptor transcripts in ovaries and gonadosomatic indexes of prawn reached peak values in advance during ovarian cycle in comparison with VC. In histological observation, more advanced oocyte and ovarian development were observed in prawns after Mnnm23 knockdown in comparison with that of VC. These results suggest that Mnnm23 is involved in ovarian development in M. nipponense and possibly functions in hindering rapid oocyte and ovarian maturation of this prawn species.

Vitellogenin and vitellogenin receptor gene expression profiles in Spodoptera exigua are related to host plant suitability.

The beet armyworm Spodoptera exigua, a worldwide phytophagous pest, causes considerable economic agricultural losses. Understanding the relationship between its fecundity and the host plant is a basic and important component of early forecasting of beet armyworm outbreaks. However, little is known about the molecular mechanism by which distinct hosts affect S. exigua fecundity. In this study, key life-history parameters of S. exigua reared on distinct hosts were investigated; the host plants could be ranked as lettuce > shallot > tomato > celery in their order of suitability. Full-length S. exigua vitellogenin receptor (SeVgR) cDNA was cloned, and sex-, stage- and tissue-specific expression characteristics were assessed. Spodoptera exigua vitellogenin (SeVg) and SeVgR expression levels were markedly modulated by host nutrients (P < 0.05). SeVg and SeVgR expression levels were significantly higher in S. exigua reared on lettuce, the most preferred and most nutritive host, than in those reared on tomato and celery. Interestingly, significant linear regression correlations were found between SeVg and SeVgR expression levels and key S. exigua life-history parameters, especially life span, pupa weight, and female fecundity (P < 0.01). Host plant type and suitability could affect the expression pattern of SeVg and SeVgR, which influenced S. exigua fecundity. Vg and VgR have the potential to be used as molecular markers of S. exigua fecundity and for forecasting outbreaks of S. exigua on different hosts. © 2017 Society of Chemical Industry.

Biofunctional analysis of Vitellogenin and Vitellogenin receptor in citrus red mites, Panonychus citri by RNA interference

Panonychus citri is one of the most damaging pests of horticultural crops. Conventional control of this pest population through pesticides has led to the enhanced pest resistance. Management of P. citri population through RNAi, is still largely unknown. In oviparous organisms, fabrication and development of yolk protein play a vital role in the reproduction. Vitellin (Vn) is the source of eggs storage that helps in proper functioning of Vitellogenin (Vg) and Vitellogenin receptor (VgR). VgR is very compulsory protein for the development of Vg into oocytes. In the current study, Vg (PcVg) and VgR (PcVgR) genes were studied and their expressions at different developmental stages were quantified by RT-qPCR. Females treated with dsRNA of PcVg and PcVgR genes exhibited reduction in gene expression. Down regulation of target genes significantly effected oviposition and reduced the egg laying capacity up to 48% as compared to control (ds-egfp). Synergistic effect of target gene’s dsRNA was also accessed that reduced the egg laying up to 60.42%. Furthermore, combination of target dsRNA on deutonymph and protonymph also resulted in 67% and 70% reduction in eggs, respectively. Synergistic effect of dsRNA at 1000 ng/ul resulted in longer life span as compared to control treatments. This study suggests to develop a new strategy of P. citri population control by reducing its reproduction.