Vitellogenin gene expression and hemolymph vitellogenin during vitellogenesis, final maturation, and oviposition in female kuruma prawn, Marsupenaeus japonicus

Silencing of novel TtVtg6-like induced ovarian cell apoptosis in ancient chelicerate Tachypleus tridentatus

Vitellogenin (Vtg) serves as the precursor of yolk protein and exhibits widespread distribution in tissues, including in the ovary of both vertebrates and invertebrates. Vtg plays a critical role in facilitating oocyte maturation and embryonic development following oviposition. In this study, we have successfully elucidated the complete transcript sequence of TtVtg6-like from an ancient chelicerate Tachypleus tridentatus. The TtVtg6-like transcript encompassed a length of 4887 bp and encoded 1629 amino acids residues. Notably, TtVtg6-like was found to contain 25 exons. Furthermore, the molecular weight and isoelectric point of TtVtg6-like were determined to be 191.6 KDa and 6.73, respectively. Subsequent mRNA expression analysis demonstrated the specific expression of TtVtg6-like in ovary and yellow connective tissue. In addition, TtVtg6-like was located and distributed in both ovary and yellow connective tissue. Intriguingly, employing an siRNA approach to silence TtVtg6-like resulted in a decrease in TtVtg6-like transcription levels. Concomitantly, TtVtg6-like silencing led to increase production of ROS, ultimately resulting in DNA damage and cell apoptosis within the ovarian primary cell. The induction of apoptosis ovarian primary cells due to TtVtg6-like silencing was further corroborated through TUNEL assay and flow cytometry analysis. Overall, our findings underscore the significance of TtVtg6-like in ovarian cell development, revealing its potential association with ovarian cell apoptosis. Consequently, the insights gained from this study contribute to the future exploration of vitellogenesis and ovarian development in T. tridentatus.

Genome-wide identification, phylogeny, expression and eyestalk neuroendocrine regulation of vitellogenin gene family in the freshwater giant prawn Macrobrachium rosenbergii

Vitellogenin (Vg) is the precursor of vitellin, which is an important female-specific protein stored in oocytes as the major nutrient and energy sources for embryogenesis in oviparous animals. In this study, we performed comprehensive genome-wide analysis of Vg gene family in the prawn Macrobrachium rosenbergii, and eight Vg genes designated as MrVg1a, MrVg1b and MrVg2-7 were identified. MrVg1a clusters with the previously described MrVg1b near the end of chromosome 46 and MrVg2 is on the chromosome 42 while MrVg3-7 cluster on the chromosome 23. All the putative MrVg proteins are characterized by the presence of three conserved functional domains: LPD-N, DUF1943 and vWD. Phylogenetic analysis revealed that MrVg1a shares 93% identity with MrVg1b and groups together into a branch while MrVg2-7 group into another branch, suggesting that MrVg1a, 1b and MrVg2-7 might diversify from a common ancestral gene. All the corresponding MrVg transcripts especially for MrVg1 exhibit high expression in the female hepatopancreas at late vitellogensis stage but extremely low in the ovaries except MrVg5, indicating that hepatopancreas is the major site of MrVgs synthesis. In the male, interestingly, MrVg5 and MrVg6 are also highly expressed in the testis, suggesting their potential involvement in testicular development. Bilateral ablation of eyestalk significantly upregulate all the MrVgs mRNA in the female hepatopancreas and the MrVg1 in ovary, but have no effect on the expression of MrVg2-7 in the ovary, demonstrating that eyestalk hormones could promote the ovarian development mostly by inducing the synthesis of MrVgs in the hepatopancreas but rarely in the ovary. Our results provide new insights into the prawn MrVgs family and improve our understanding of the potential role for each member of the family in the gonadal development of M. rosenbergii.

Insight into crustacean cathepsins: Structure-evolutionary relationships and functional roles in physiological processes

Cathepsins belong to a group of proteins that are present in both prokaryotic and eukaryotic organisms and have an extremely high degree of evolutionary conservation. These proteins are functionally active in extracellular environments as soluble enzymatic proteins or attached to plasma membrane receptors. In addition, they occur in cellular secretory vesicles, mitochondria, the cytosol, and within the nuclei of eukaryotic cells. Cathepsins are classified into various groups based on their sequence variations, leading to their structural and functional diversification. The molecular understanding of the physiology of crustaceans has shown that proteases, including cathepsins, are expressed ubiquitously. They also contain one of the central regulatory systems for crustacean reproduction, growth, and immune responses. This review focuses on various aspects of the crustaceans cathepsins and emphasizes their biological roles in different physiological processes such as reproduction, growth, development, and immune responses. We also describe the bioactivity of crustaceans cathepsins. Because of the vital biological roles that cathepsins play as cellular proteases in physiological processes, they have been proposed as potential novel targets for the development of management strategies for the aquaculture industries.

CRISPR/Cas9 establishment-mediated targeted mutagenesis in Macrobrachium nipponense

Introduction: CRISPR/Cas9 is a gene-editing technology which could specifically cleave dsDNA and induce target gene mutation. CRISPR/Cas9 has been widely used in gene functional studies in many fields, such as medicine, biology, and agriculture due to its simple design, low cost, and high efficiency. Although it has been well developed in model fish and freshwater fish for gene function analysis, it is still novel in the studies dealing with economic crustacean species. Methods: In this study, we established a CRISPR/Cas9 system based on microinjection for M. nipponense, an important economic crustacean aquaculture species. The vitellogenin (Vg) gene and the eyeless (Ey) gene were selected as the targeted genes for mutation. Two sgRNAs were designed for Mn-Vg and Mn-Ey gene editing, respectively. Results and Discussion: For sg-Vg-1, the gastrula survival ratio was 8.69%, and the final hatching ratio was 4.83%. The blastula mutant ratio was 10%, and the hatching individual mutant ratio was 30%. For sg-Vg-2, the gastrula survival ratio was 5.85%, and the final hatching ratio was 3.89%. The blastula mutant ratio was 16.67%, and no mutant sequences were detected in hatching individuals. For sg-Ey-1, the gastrula survival ratio was 6.25%, and the final hatching ratio was 2.34%. The blastula mutant ratio was 10.00%, and the hatching individual mutant ratio was 66.67%. For sg-Ey-2, the gastrula survival ratio was 6.00%, and the final hatching ratio was 2.67%. No mutant sequence was detected in both blastula stage and hatching individuals. There were no significant morphological changes observed in the Mn-Vg group. Two deformed types were detected in sg-Ey-1-injected embryos. An evident developmental delay of the compound eye was detected in Ey-sg1-H1 in the zoea stage. The compound eyes of the Ey-sg1-H2 embryo could not form well-defined spheres, and the whole compound eye appeared to diffuse at the end of the late zoea stage. The establishment of a gene-editing platform based on CRISPR/Cas9 will not only provide an efficient and convenient method for gene function analysis but also provide a powerful tool for molecular-assisted breeding of Macrobrachium nipponense.

In vitro induction of catfish, Clarias batrachus, oocyte maturation by conspecific vitellogenin 1 (CFVg1)

Present study demonstrates that conspecific vitellogenin1 (CFVg1) induces oocyte maturation in the catfish, Clarias batrachus. CFVg1 is able to develop fertilizable eggs in the Clarias batrachus. Therefore, different in vitro oocyte culture experiments were designed to see whether CFVg1 has efficacy of oocyte maturation and its pathway. In in vitro oocyte culture experiment, CFVg1 showed a dose- and time-dependent response and 64% maturation was obtained at the dose level of 10 µg/ml or more. CFVg1 induction of oocyte maturation was confirmed by co-incubating CFVg1 with CFVg1-antiserum (a-CFVg1), which inhibited the CFVg1-induced oocyte maturation. To answer issues lead to the understanding of the mechanism of vitellogenin (Vg) on oocyte maturation, trypsin digested CFVg1 and Indian major carp Cirhinus mrigala Vg HAI (Hydroxy appetite peak I) also showed significant level of maturation. Actinomycin-D and cycloheximide blocked the effect of CFVg1, indicating that CFVg1 acts through transcription and translation. Theophylline, the phosphodiesterase inhibitor, and cAMP also inhibited the stimulatory effect of CFVg1 on oocyte maturation, indicating indirectly that CFVg1-induced oocyte maturation by decreasing the intracellular cAMP possibly by activating the phosphodiesterase enzyme. Trilostane, the 3β-HSD-blocker, did not inhibit the CFVg1-induced oocyte maturation but wortmannin and Ly294002 two mechanistically different specific inhibitors of PI3 kinase blocked the oocyte maturation. The results thus indicate that oocyte maturation in catfish by Vg may be regulated by two pathways: (1) through decreasing the intraoocyte cAMP level by activating the cAMP-PKA pathway and (2) by cAMP-dependent PI3K/Akt pathway. Therefore, there might be role of vitellogenin itself in initiation of oocyte maturation.

Vitellogenin receptor expression in ovaries controls innate immunity in the Chinese mitten crab (Eriocheir sinensis) by regulating vitellogenin accumulation in the hemolymph

The vitellogenin receptor (Vgr), which is specific for vitellogenin (Vtg), recognises and transports Vtg into the ovaries. Accumulating evidence suggests that Vtg also performs an immune defence function and plays critical roles in innate immunity in oviparous animals. However, whether Vgr is involved in innate immunity in the Chinese mitten crab (Eriocheir sinensis) is unknown. In this study, we obtained a 3009 nucleotide partial cDNA of the E. sinensis vitellogenin receptor gene (Es-vgr) encoding an open reading frame of 1003 amino acid residues. Bioinformatics analysis showed that the domains of Es-vgr were conserved during evolution. Quantitative real-time PCR and western blotting revealed that the highest Es-vgr expression levels occurred in the ovary, and expression was specific. Comparison of the expression levels of Es-vgr and the Vtg gene (Es-vtg1) at different ovary developmental stages suggested that there may be some regulatory relationship between them. Bacterial challenge induced high-level expression of antimicrobial peptide genes and reduced Es-vgr expression in ovaries, resulting in massive accumulation of Vtg in the hemolymph. The survival rate of crabs increased significantly after injection with recombinant Es-vtg1 protein following bacterial infection. Collectively, these results demonstrate that Es-vgr plays critical roles in antimicrobial function by regulating the accumulation of Vtg in the hemolymph.

Abundances of vitellogenin and heat shock protein 90 during ovarian and embryonic development of Exopalaemon carinicauda

To evaluate functions of vitellogenin (Vg) and heat shock protein 90 (Hsp90) during ovarian and embryonic development of Exopalaemon carinicauda, the cDNA of Vg (Ec-Vg) was cloned, and the abundances of Ec-Vg and heat shock protein 90 (Hsp90) (Ec-Hsp90) were determined during ovarian and embryonic development. During ovarian development, the concentration of Vg protein in hemolymph was markedly greater than in the ovary and hepatopancreas, and was greatest at sexual maturity. The relative abundance of Ec-Vg mRNA transcript was greatest in the hepatopancreas and almost undetectable in hemocytes. By combining mRNA transcript relative abundances with morphological results, a model was developed to explain the mRNA transcript relative abundance of Ec-Hsp90 and Ec-Vg during ovarian and embryonic development. The relative abundance of Ec-Vg mRNA transcript was greatest during the recovery period after reproduction had occurred (Stage V) and mature stage (Stage IV) in the ovary or hepatopancreas, respectively. There were marked associations of the patterns of Ec-Hsp90 and Ec-Vg mRNA transcript abundances both in hepatopancreas and ovary. During embryonic development, the relative abundance of the two mRNA transcripts were greatest at the metazoea and protozoea stages, respectively. These results indicate that Ec-Vg is produced primarily in the hepatopancreas, secreted into the hemolymph and transported into growing oocytes. It, therefore, is believed that Ec-Vg has an important function in the overall ovarian development and late embryonic development of E. carinicauda. In contrast, Ec-Hsp90 is a regulatory factor for Vg transcription and is important during early organogenesis in E. carinicauda.

Ovarian development pattern and vitellogenesis of ridgetail white prawn, Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda has the potential to be used as a model organism in crustacean research because it has a transparent body, available draft genome, and short life cycle. However, their ovarian development pattern remains unclear under laboratory culture conditions. This study investigated the changes of ovarian external feature, ovarian histology, gonadosomatic index (GSI), and hepatosomatic index (HSI), as well as the expression and localization of vitellogenin in the ovary and the hepatopancreas during the first ovarian development cycle of E. carinicauda under laboratory-reared condition. The results demonstrated that (1) the first ovarian development cycle of E. carinicauda could be divided into 5 different stages in which the ovary changes its color from white to yellow during the vitellogenesis process in parallel with increasing GSI. (2) After pubertal molt, most females reached ovarian stage II while the females reached stage V after premating molt. (3) During the ovarian development, GSI increased smoothly and HSI relatively stable during the period of stages I to IV, while GSI increased but HSI decreased significantly from stages IV to V. (4) In situ hybridization (ISH) revealed that EcVg was slightly expressed in the oocyte cytoplasm of previtellogenic oocytes. The positive signal was mainly detected in hepatopancreatic fibrillar cells, and a strong signal was found in the hepatopancreas at stage IV. Moreover, the expression level of EcVg-mRNA in the hepatopancreas is stage-specific, and the hepatopancreas contributes majority of vitellin precursor protein to support the ovarian development of E. carinicauda.

JNK signaling pathway regulates the development of ovaries and synthesis of vitellogenin (Vg) in the swimming crab Portunus trituberculatus

The development of Portunus trituberculatus egg cells is directly related to the nutritional status of the fertilized egg, which affects the key production stages of offspring hatching. Vitellogenin plays a key role in the nutrient supply required for the development of the egg cells. The c-Jun N-terminal kinase (JNK) is an important member of the mitogen-activated protein kinase (MAPK) superfamily and plays an important role in cell proliferation, transformation, differentiation, and apoptosis. At present, there are no reports on the involvement of the JNK signaling pathway in the reproductive regulation of P. trituberculatus. In this study, rapid amplification of complementary DNA ends amplification technology was used to clone the full length of JNK complementary DNA, which has a length of 2094 bp, including an open reading frame (ORF) of 1266 bp encoding a 421-amino acid protein. The protein includes the S_TKC conserved domain with a TPY phosphorylation site, which is a typical feature of the JNK gene family. Observing tissue sections found the oocytes in the inhibitor group developed slowly, while the oocytes in the activated group showed accelerated development. Meanwhile, Portunus trituberculatus JNK and vitellogenin (Vg) genes exhibited the same trend in the hepatopancreas and ovaries, and the expression of the SP600125 group was downregulated (P < 0.05), while the anisomycin group was upregulated (P < 0.05). In addition, JNK enzyme activity and vitellin (Vn) content in the ovarian tissue showed that the JNK activity of the SP600125 group decreased, while activity increased in the anisomycin group. The accumulation of Vn content in the SP600125 group decreased, and that in the anisomycin group increased. In summary, after injection with inhibitor or activator, the JNK signaling pathway of P. trituberculatus was inhibited or activated, the accumulation of Vn in the ovary was reduced or increased, and ovarian development was inhibited or accelerated, respectively. These results indicated that the JNK signaling pathway is involved in the regulation of Vg synthesis and ovarian development in P. trituberculatus. The results of this study further add to the knowledge of the breeding biology of P. trituberculatus and provide a theoretical reference for the optimization of breeding techniques in aquaculture production systems.

Molecular Characterization of Neoseiulus barkeri Vitellogenin Genes and Vitellogenin Receptor during Reproductive Diapause

The relationship between reproductive diapause and the genes related to vitellogenin (Vg) and its receptor (VgR) in insectoid ovarian development is still unclear. Accordingly, in the present study, we used hematoxylin and eosin staining to study the ovarian structure in the predatory mite Neoseiulus barkeri, a species that shows promise as a biological pest control agent. Staining revealed the presence of oocytes on ovary surfaces, and the oocytes were deposited as yolk granules through the intake of Vg and other nutrients with the development of the ovary. Development of the ovary stopped at the oocyte stage in diapausing adult mites, and this stage presented the same characteristics as the first day of adulthood in non-diapause female adults, where oocytes with nutrient cells, but no yolk granules are observed. In order to further explore the effects of the Vg gene and its receptor on reproduction, the sequences of the N. barkeri vitellogenin genes NbVg1, NbVg2, NbVg3, and NbVgR were analyzed using bioinformatics, and the expression levels of the NbVgs and the VgR at different developmental stages were determined by quantitative polymerase chain reaction (qPCR). The results showed that the NbVgs and NbVgR have complete domains and that the positions of many conservative regions and conservative motif are consistent. The expression levels of the NbVgs and NbVgR were highest in the ovipositional period, followed by those in the preovipositional period. The expression levels of the NbVgs and the VgR in non-diapause female adult mites were significantly higher than those in reproductive diapause female adult mites.

Regulation of vitellogenin gene expression under the negative modulator, gonad-inhibiting hormone in Penaeus monodon

Vitellogenesis is a principal process during ovarian maturation in crustaceans. This process is negatively regulated by gonad-inhibiting hormone (GIH), a neuronal peptide hormone from eyestalks. However, the detailed mechanism through which GIH regulates Vg expression is still ambiguous. In this study, suppression subtractive hybridization (SSH) under specific GIH-knockdown condition was utilized to determine the expression of genes in the ovary that may act downstream of GIH to control vitellogenin synthesis in Penaeus monodon. The total of 102 and 82 positive clones of up-regulated and down-regulated genes in GIH- knockdown shrimp were identified from the forward and reverse SSH libraries, respectively. Determination of the expression profiles of these reproduction-related genes during ovarian development revealed that the expression of calreticulin (CALR) was significantly reduced in vitellogenic ovary suggesting its role in vitellogenesis. Suppression of CALR by specific dsRNA showed elevated vitellogenin (Vg) transcript level in the ovary at day 7 post-dsRNA injection. Since CALR can bind to steroid hormone receptors and prevents the binding of the receptor to its responsive element to regulate gene expression, it is possible that CALR is an inhibitory mediator of vitellogenin synthesis via steroidal pathway. Our results posted a possible novel pathway of GIH signaling that might interfere the steroid signaling cascade to mediate Vg synthesis in the shrimp.

The protandric life history of the Northern spot shrimp Pandalus platyceros: molecular insights and implications for fishery management

The Northern spot shrimp, Pandalus platyceros, a protandric hermaphrodite of commercial importance in North America, is the primary target species for shrimp fisheries within Southeast Alaska. Fishery data obtained from the Alaska Department of Fish and Game indicate that spot shrimp populations have been declining significantly over the past 25 years. We collected spot shrimps in Southeast Alaska and measured reproductive-related morphological, gonadal and molecular changes during the entire life history. The appendix masculina, a major sexual morphological indicator, is indicative of the reproductive phase of the animal, lengthening during maturation from juvenile to the male phase and then gradually shortening throughout the transitional stages until its complete disappearance upon transformation to a female. This morphological change occurs in parallel with the degeneration of testicular tissue in the ovotestis and enhanced ovarian vitellogenesis. Moreover, we obtained the entire mRNA sequence of the yolk protein precursor, vitellogenin, and monitored its transcript levels throughout the entire shrimp life-cycle. Vitellogenin transcript levels in the hepatopancreas increased in the early transitional stage until reaching a peak prior to extruding eggs. Such transcriptomic analyses, coupled with a comprehensive description of the gonad, external sex characters and timing of the reproductive life history of spot shrimps contribute to a better understanding of the hermaphroditic reproduction process in the cold Southeast Alaskan waters. This knowledge can contribute to a revision of current conservation efforts to maintain wild populations sustainable for both commercial and ecological considerations.

Transcriptomic Analysis of the Kuruma Prawn Marsupenaeus japonicus Reveals Possible Peripheral Regulation of the Ovary

Crustacean reproduction has been hypothesized to be under complex endocrinological regulation by peptide hormones. To further improve our understanding of the mechanisms underlying this complex regulation, knowledge is needed regarding the hormones not only of the central nervous system (CNS) such as the X-organ/sinus gland (XOSG), brain, and thoracic ganglia, but also the peripheral gonadal tissues. For example, in vertebrates, some gonadal peptide hormones including activin, inhibin, follistatin, and relaxin are known to be involved in the reproductive physiology. Therefore, it is highly likely that some peptide factors from the ovary are serving as the signals among peripheral tissues and central nervous tissues in crustaceans. In this work, we sought to find gonadal peptide hormones and peptide hormone receptors by analyzing the transcriptome of the ovary of the kuruma prawn Marsupenaeus japonicus. The generated ovarian transcriptome data led to the identification of five possible peptide hormones, including bursicon-α and -β, the crustacean hyperglycemic hormone (CHH)-like peptide, insulin-like peptide (ILP), and neuroparsin-like peptide (NPLP). Dominant gene expressions for the bursicons were observed in the thoracic ganglia and the ovary, in the CNS for the CHH-like peptide, in the heart for NPLP, and in the ovary for ILP. Since the gene expressions of CHH-like peptide and NPLP were affected by a CHH (Penaeus japonicus sinus gland peptide-I) from XOSG, we produced recombinant peptides for CHH-like peptide and NPLP using Escherichia coli expression system to examine their possible peripheral regulation. As a result, we found that the recombinant NPLP increased vitellogenin gene expression in incubated ovarian tissue fragments. Moreover, contigs encoding putative receptors for insulin-like androgenic gland factor, insulin, neuroparsin, and neuropeptide Y/F, as well as several contigs encoding orphan G-protein coupled receptors and receptor-type guanylyl cyclases were also identified in the ovarian transcriptome. These results suggest that reproductive physiology in crustaceans is regulated by various gonadal peptide hormones, akin to vertebrates.

Investigation of Gene Sequence Divergence, Expression Dynamics, and Endocrine Regulation of the Vitellogenin Gene Family in the Whiteleg Shrimp Litopenaeus vannamei

In this report, we studied the vitellogenin gene family in the whiteleg shrimp Litopenaeus vannamei by transcriptomics, bioinformatics, and molecular biology methods. At least three moderately homologous vitellogenin (Vg) genes (i.e. LvVg1, LvVg2, and LvVg3) were identified in the genome. The deduced LvVg proteins consisted of a vitellogenin_N domain, a DUF1943 domain, and a VWD domain typical of most vitellogenins from oviparous animals. LvVg1 was the most abundant Vg expressed in the hepatopancreas and ovary of maturing females. Furthermore, multiple isoforms of LvVg1 were evolved presumably due to the need for rapid Vg production during the rapid phase of vitellogenesis. LvVg transcripts were detected in different larval stages, juveniles, and subadults. During the non-reproductive cycle, LvVg expression in the hepatopancreas peaked at the intermolt stages. During the female vitellogenesis cycle, a two-phase expression pattern of LvVg1 gene was observed in the hepatopancreas and ovary. Moreover, the eyestalk optic nerve, brain, and thoracic ganglion consisted of factors that differentially regulated the expression of the three Vg genes. In addition to their reproduction-related roles, Vg may also be involved in growth and molt-related processes. Phylogenetic analysis revealed the early expansion and separation of these Vg genes, and it is most likely correlated with the expansion of Vg's function. In conclusion, the evolution of multiple LvVg1 isoforms and the acquisition of different Vg genes (i.e. LvVg2 and LvVg3) may occur universally in most decapods. Full information on the total number of Vg genes and precise knowledge on the expression pattern and endocrine regulation of each Vg during all life cycle stages are crucial for us to understand the roles of this emerging gene family in the control of shrimp reproduction and other non-reproductive processes.

Environmental Pollutants Impair Transcriptional Regulation of the Vitellogenin Gene in the Burrowing Mud Crab (Macrophthalmus Japonicus)

Vitellogenesis is a pivotal reproductive process of the yolk formation in crustaceans. Vitellogenin (VTG) is the precursor of main yolk proteins and synthesized by endogenous estrogens. The intertidal mud crab (Macrophthalmus japonicus) inhabits sediment and is a good indicator for assessing polluted benthic environments. The purpose of this study was to identify potential responses of M. japonicus VTG under environmental stresses caused by chemical pollutants, such as 1, 10, and 30 µg L−1 concentrations in di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA) and irgarol. We characterized the M. japonicus VTG gene and analyzed the transcriptional expression of VTG mRNA in M. japonicus exposed to various chemicals and exposure periods. A phylogenetic analysis revealed that the M. japonicus VTG clustered closely with Eriocheir sinensis (Chinese mitten crab) VTG, in contrast with another clade that included the VTG ortholog of other crabs. The basal level of VTG expression was the highest in the hepatopancreas and ovaries, and tissues. VTG expression significantly increased in the ovaries and hepatopancreas after 24 h exposure to DEHP. Increased responses of VTG transcripts were found in M. japonicus exposed to DEHP and BPA for 96 h; however, VTG expression decreased in both tissues after irgarol exposure. After an exposure of 7 d, VTG expression significantly increased in the ovaries and hepatopancreas for all concentrations of all chemicals. These results suggest that the crustacean embryogenesis and endocrine processes are impaired by the environmental chemical pollutants DEHP, BPA, and irgarol.

Immunolocalization and changes of 17beta-estradiol during ovarian development of Chinese mitten crab Eriocheir sinensis' [corrected]

17beta-estradiol (E₂) is important for crustacean ovarian development. This study aims to investigate the distribution and change pattern of E₂ in the ovary, hepatopancreas, thoracic ganglion and brain ganglion as well as Vg-mRNA expression level during ovarian development of Chinese mitten crab Eriocheir sinensis. Results showed that strongly positive signals of E₂ were mainly distributed in follicle cells of ovaries for all developmental stages as well as oocyte cytoplasm of stages III to V ovaries. In hepatopancreas, the E₂-positive signal was mainly detected in the cytoplasm and nucleus of fibrillar cells and the nucleus of resorptive cells, while the maximum fluorescence intensity was observed in stage III hepatopancreas. On the contrary, the E₂ immunoreactivities in nervous tissues were relatively stable during ovarian development. Moreover, the changing pattern of E₂ concentration was similar within hemolymph, ovary and hepatopancreas during the ovarian development. From stages I to III, the E₂ content in three tissues increased significantly, then decreased gradually until stage V. As for the Vg-mRNA expression level in hepatopancreas and ovaries, an increasing trend was found in ovaries but no significant difference was detected during the period of ovarian stages III to V. Hepatopancreatic Vg-mRNA expression level increased significantly during stages I to IV and dramatically decreased at stage V. In conclusion, our study suggests that ovary, hepatopancreas, hemolymph and nervous tissues are the target organs of E₂ in E. sinensis and E₂ concentrations in different tissues are closely related to vitellogenesis in ovary and hepatopancreas during ovarian development.

Mechanisms for type-II vitellogenesis-inhibiting hormone suppression of vitellogenin transcription in shrimp hepatopancreas: Crosstalk of GC/cGMP pathway with different MAPK-dependent cascades

Vitellogenesis is the process of yolk formation via accumulating vitellin (Vn) with nutrients in the oocytes. Expression of vitellogenin (Vg), the precursor of Vn, is one of the indicators for the start of vitellogenesis. In Pacific white shrimp (Litopenaeus vannamei), the type-II vitellogenesis-inhibiting hormone (VIH-2) effectively suppresses hepatopancreatic Vg mRNA expression. In this study, we demonstrate the increasing transcript levels of hepatopancreatic Vg during L. vannamei ovarian development, suggesting that the hepatopancreas-derived Vg/Vn may also contribute to vitellogenesis in this species. Using a combination of in vivo injections and in vitro primary cell cultures, we provide evidences that the inhibition of VIH-2 on hepatopancreatic Vg gene expression is mediated through a functional coupling of the GC/cGMP pathway with different MAPK-dependent cascades in female shrimp. In VIH-2 signaling, the NO-independent GC/cGMP/PKG cascades were upstream of the MAPKs. Activations of the MAPK signal by VIH-2 include the phosphorylation of JNK and the mRNA/protein expression of P³⁸MAPK. Additionally, the cAMP/PKA pathway is another positive intracellular signal for hepatopancreatic Vg mRNA expression but is independent of its VIH-2 regulation. Our findings establish a model for the signal transduction mechanism of Vg regulation by VIH and shed light on the biological functions and signaling of the CHH family in crustaceans.

Characterization of distinct ovarian isoform of crustacean female sex hormone in the kuruma prawn Marsupenaeus japonicus

The eyestalk hormone, crustacean female sex hormone (CFSH), regulates the development of female secondary sexual characteristics in the blue crab Callinectes sapidus. After its discovery, several CFSH gene orthologs have been identified in some species of the suborder Pleocyemata as well. Similarly, in species of another suborder (Dendrobranchiata), an ortholog (Maj-CFSH) has been characterized as an eyestalk factor expressed in both females and males of the kuruma prawn, Marsupenaeus japonicus. In this study, another novel CFSH isoform was identified in the same species using cDNA cloning, expression analysis, and recombinant protein production. The isoform has "CFSH-family" structural characteristics but is dominantly expressed in the ovary, and was therefore designated as Maj-CFSH-ov. Its mRNA and protein levels in vitellogenic ovaries are higher than those in non-vitellogenic ovaries. In the vitellogenic ovary, both mRNA and protein expression of Maj-CFSH-ov are localized to oogonia and previtellogenic oocytes that occupy a small portion of vitellogenic ovaries, but not to the major developing oocytes. A vitellogenesis-inhibiting peptide of M. japonicus (Pej-SGP-I) reduced the expression of vitellogenin in incubated ovarian fragments, but not that of Maj-CFSH-ov. These results indicate that M. japonicus possesses two CFSH isoforms that are derived from distinct tissues, the central X-organ/sinus gland complex and peripheral ovaries. The expression profile of Maj-CFSH-ov suggests its involvement in some reproductive process other than vitellogenesis.

Transcriptomic information from Pacific white shrimp (Litopenaeus vannamei) ovary and eyestalk, and expression patterns for genes putatively involved in the reproductive process

The increased use of massive sequencing technologies has enabled the identification of several genes known to be involved in different mechanisms associated with reproduction that so far have only been studied in vertebrates and other model invertebrate species. In order to further investigate the genes involved in Litopenaeus vannamei reproduction, cDNA and SSH libraries derived from female eyestalk and gonad were produced, allowing the identification of expressed sequences tags (ESTs) that potentially have a role in the regulation of gonadal maturation. In the present study, different transcripts involved in reproduction were identified and a number of them were characterized as full-length. These transcripts were evaluated in males and females in order to establish their tissue expression profiles during developmental stages (juvenile, subadult and adult), and in the case of females, their possible association with gonad maturation was assessed through expression analysis of vitellogenin. The results indicated that the expression of vitellogenin receptor (vtgr) and minichromosome maintenance (mcm) family members in the female gonad suggest an important role during previtellogenesis. Additionally, the expression profiles of genes such as famet, igfbp and gpcr in brain tissues suggest an interaction between the insulin/insulin-like growth factor signaling pathway (IIS) and methyl farnesoate (MF) biosynthesis for control of reproduction. Furthermore, the specific expression pattern of farnesoic acid O-methyltransferase suggests that final synthesis of MF is carried out in different target tissues, where it is regulated by esterase enzymes under a tissue-specific hormonal control. Finally, the presence of a vertebrate type steroid receptor in hepatopancreas and intestine besides being highly expressed in female gonads, suggest a role of that receptor during sexual maturation.

Tissue distribution and functional analysis of vitellogenin-6 of Toxocara canis

Toxocara canis is an common intestinal nematode of canids and the principal causative agent of human toxocariasis. Vitellogenin (Vg), a source of amino acids and lipids in the eggs, are considered to play an important role in embryo development of a wide range of organisms. In the present study, the transcriptional levels of Tc-vit-6 gene in male and female adult T. canis were determined by quantitative real-time PCR, which indicated high transcription of Tc-vit-6 in the intestine, reproductive tract and body wall of male and female adult T. canis. The fragment of Tc-vit-6 encoding a vWD domain, was cloned and expressed to produce a rabbit anti-TcvWD polyclonal antibody. Tissue distribution of TcVg6 was detected by immunohistochemical assays, which showed predominant distribution of TcVg6 in the tissues of intestine, as well as reproductive tract (including some of the germ cells) and musculature of male and female adult worms. Collectively, these results indicated multiple biological roles of TcVg6 apart from that in the reproduction of T. canis.

Transcriptional changes during Daphnia pulex development indicate that the maturation decision resembles a rate more than a threshold

Maturation is a critical developmental process, and the age and size at which it occurs have important fitness consequences. Although maturation is remarkably variable, certain mechanisms, including a minimum size or state threshold, are proposed to underlie the process across a broad diversity of taxa. Recent evidence suggests that thresholds may themselves be developmentally plastic, and in the crustacean Daphnia pulex it is unclear whether maturation follows a threshold or is a gradual process more akin to a rate. Changes in gene expression across four instars before and during maturation were compared in a cDNA microarray experiment. Developmental stage was treated statistically both as a discontinuous and as a continuous variable, to determine whether genes showed gradual or discrete changes in expression. The continuous analysis identified a greater number of genes with significant differential expression (45) than the discontinuous analysis (11). The majority of genes, including those coding for histones, factors relating to transcription and cell cycle processes, and a putative developmental hormone showed continuous increases or decreases in expression from the first to the fourth instars that were studied, suggestive of a prolonged and gradual maturation process. Three genes coding for a fused vitellogenin/superoxide dismutase showed increases in expression following the second instar and coincided with the posited maturation threshold, but even their expression increased in a continuous fashion.

Molecular characterization and developmental expression of vitellogenin in the oriental river prawn Macrobrachium nipponense and the effects of RNA interference and eyestalk ablation on ovarian maturation

Vitellogenin (Vg) is the precursor of yolk protein, which functions as a nutritive resource that is important for embryonic growth and gonad development. In this study, the cDNA encoding the Vg gene from the oriental river prawn Macrobrachium nipponense was cloned using expressed sequence tag (EST) analysis and the rapid amplification of cDNA ends (RACE) approach. The transcript encoded 2536 amino acids with an estimated molecular mass of 286.810 kDa. Quantitative real-time PCR indicated high expression of Mn-Vg in the female ovary, hemocytes, and hepatopancreas. As ovaries developed, the expression level of Mn-Vg increased in both the hepatopancreas and ovary. In the hepatopancreas, the expression level rose more slowly at the early stage of vitellogenesis and reached the peak more rapidly compared to the expression pattern in ovary. The observed changes in Mn-Vg expression level at different development stages suggest the role of nutrient source in embryonic and larval development. Eyestalk ablation caused the Mn-Vg expression level to increase significantly compared to eyestalk-intact groups during the ovary development stages. Ablation accelerated ovary maturation by removing hormone inhibition of Mn-Vg in the hepatopancreas and ovary. In adult females, Mn-Vg dsRNA injection resulted in decreased expression of Mn-Vg in both the hepatopancreas and ovary, and two injection treatment dramatically delayed ovary maturation. Vg RNA interference down-regulated the vitellogenin receptor (VgR) expression level in the ovary, which illustrates the close relationship between Vg and VgR in the process of vitellogenesis.

Induction of ovarian maturation in Penaeus monodon by molecular signal interventional approach

Vitellogenin (VTG) synthesis in the hepatopancreas and ovary is negatively regulated by vitellogenesis-inhibiting hormone (VIH) produced in the neurosecretory cell of X-organ/sinus gland complex of the eyestalks of penaeid shrimp. Eyestalk ablation is used commercially to induce ovarian maturation in shrimps which leads to an eventual loss of the spawner. The aim of the present study was to understand the molecular mechanism of VIH regulation in ovarian development and its inhibition of VTG gene expression by using a MEK-specific inhibitor (U0126). The real-time quantitative PCR results showed VTG mRNA level was progressively increased in the ovary and hepatopancreas of unilateral eyestalk-ablated and inhibitor-treated shrimps. Western blot analysis also showed that phosphoMEK was detected only in the unilateral eyestalk-ablated and control shrimp, whereas phospho-MEK was not detected in inhibitor-treated shrimp. DAX-1, SF-1, and StAR expression correlated with changes in VIH mRNA and altered phospho-ERK levels. This is consistent with the hypothesis that suppression of DAX-1 results in SF-1-mediated StAR protein upregulation of estradiol that is implicated in vitellogenesis. This is the first report that demonstrates the molecular mechanism of VIH suppression via MEK pathway to induce ovarian maturation in female Penaeus monodon by molecular signal intervention, a less-invasive method than traditional eyestalk ablation.

Vitellogenin-like gene expression in freshwater amphipod Gammarus fossarum (Koch, 1835): functional characterization in females and potential for use as an endocrine disruption biomarker in males

The induction of vitellogenin (Vtg) synthesis is widely accepted as a biomarker of estrogenic exposure in male and juvenile fish. Vtg synthesis has emerged as an interesting endpoint to assess endocrine disruptor (ED) effects in crustaceans. However, studies reporting induction of Vtg in male crustaceans are lacking. This study investigated the expression of the Vtg gene in a freshwater amphipod, Gammarus fossarum, using calibrated real-time reverse transcription polymerase chain reaction (real-time RT PCR). First, we described the basal pattern of expression in healthy male and female organisms at different reproductive moult stages, in order to validate the function of this gene. Females expressed from 200 to 700 times more Vtg transcripts than males, depending on the female reproductive stage. Females displayed significant elevation of Vtg mRNA levels at the end of the inter-moult phase and at the beginning of the pre-moult phase. Second, male gammarids were exposed to the estrogenic compound nonylphenol (NP) (0.05, 0.5, 5 and 50 μg L(-1)) and to the anti-androgen cyproterone (1, 10, 100 and 1000 μg L(-1)) for 2, 4, 8 and 16 days. Both chemicals altered the pattern of interindividual variability of Vtg gene expression in males with strong induction in some individuals. Finally, the impact of urban wastewater treatment plants (WWTP) on male Vtg gene expression was assessed in organisms transplanted in the field during in situ bioassay campaigns in three different watersheds. Induction of the Vtg mRNA level was observed in males transplanted downstream from WWTP effluent discharge in two of the three study sites.

Seasonal variations in the biochemical composition and reproductive cycle of the ghost crab Ocypode quadrata (Fabricius, 1787) in Southern Brazil

The ghost crab, Ocypode quadrata, is found on sandy beaches from the United States to Southern Brazil. Because there is still little information about the metabolism and reproduction of O. quadrata on the southern coast of Brazil, the objectives of this study were to (i) evaluate the effect of seasonal variations on the carbohydrate, lipid, and protein metabolism of O. quadrata at Rondinha Beach, a beach with high anthropogenic activity, and to compare it with data from Siriú Beach, which has less human activity; and (ii) describe the effect of seasonal variations on the histological characteristics of male and female gonads, in order to assess the reproductive capacity of the crabs. The gonads of male crabs showed no significant variations in the gonadosomatic index (GSI) and glycogen levels; however, histological analysis of the testes revealed that they are mature in the summer. In females, the GSI and glycogen values are higher in summer, concomitantly with the presence of mature oocytes. These results suggest that the reproductive peak of O. quadrata occurs in summer. The seasonal analysis of the biochemical parameters, as well as comparison with Siriú Beach, demonstrated that the ghost crabs of Rondinha Beach have a different pattern of metabolism than those of Siriú. This difference may be a consequence of differences in the environmental conditions as well as in the anthropogenic pressures, such as vehicle traffic and the increase in human population at the beach in summer.