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

Comparative transcriptome analysis reveals the different responding mechanisms of ovary and hepatopancreas following polyI:C challenge in Macrobrachium nipponense

The ovary in mammals has developed specialized mechanisms for protection against pathogen infections; however, the understanding of the innate immune system in the ovary of crustaceans is still limited. To elucidate the ovary's defense mechanisms in response to viral challenges, we subjected oriental river prawns (Macrobrachium nipponense) to poly I:C, a double-stranded RNA analog that emulates viral dsRNA, and analyzed the ovary's transcriptome profiles. Concurrently, RNA-seq analysis was performed on the hepatopancreas, a well-recognized immune-related tissue, following poly I:C challenge to investigate the distinct response mechanisms of the ovary and hepatopancreas and to gain a comprehensive understanding of the immune responses in both tissues. The results indicate that 1368 genes are differentially expressed in the ovary, with 903 genes upregulated and 465 genes downregulated. Subsequent analysis reveals that these differentially expressed genes (DEGs) include numerous genes associated with innate immunity, such as members of the C-type lectin, fibrinogen-related protein (Frep), Toll-like receptor, and NOD-like receptor (NLR) gene families, as well as acid phosphatase, scavenger receptor, crustin, Down syndrome cell adhesion molecule (Dscam), hemocyanin, and lipopolysaccharide and beta-1,3-glucan binding protein (LGBP). Furthermore, the DEGs include several genes related to ovary development, such as sox8, vitellogenin, progranulin, cyclin-dependent kinase, ecdysone receptor, frizzled, and members of the Fox gene family. In the hepatopancreas, a total of 729 DEGs were identified. Comparison of the DEGs in both tissues indicates that only 91 genes are common to both groups, highlighting significant tissue-specific responses to poly I:C stimulation. This study aims to enhance our understanding of the immune protective mechanisms employed by the ovary in response to pathogen exposure and establishes a foundation for investigating ovarian reproductive immunity in crustaceans.

Reference genes for qPCR expression in black tiger shrimp, Penaeus monodon

BACKGROUND

Gene expression profiling via qPCR is an essential tool for unraveling the intricate molecular mechanisms underlying growth and development. Identifying and validating the most appropriate reference genes is essential for qPCR experiments. Nevertheless, there exists a deficiency in a thorough assessment of reference genes concerning the expression of the genes in the research in the context of the growth and development of the Black Tiger Shrimp, P. monodon. This popular marine crustacean is extensively raised for human consumption. In this study, we assessed the expression stability of seven reference genes (ACTB, 18S, EF-1α, AK, PK, cox1, and CLTC) in adult tissues (hepatopancreas, gills, and stomach) of small and large polymorphs of P. monodon.

METHODS AND RESULTS

The stability of gene expressions was assessed utilizing NormFinder, BestKeeper, and geNorm, and a comprehensive ranking of these genes was conducted through the online tool RefFinder. In the overall ranking, 18S and CLTC emerged as the most stable genes in the hepatopancreas and stomach, while CLTC and AK exhibited significant statistical reliability in the gills of adult P. monodon. The validation of these identified stable genes was carried out using a growth-associated gene, insr-1.

CONCLUSION

The results indicated that 18S and CLTC stand out as the most versatile reference genes for conducting qPCR analysis focused on the growth of P. monodon. This study represents the first comprehensive exploration that identifies and assesses reference genes for qPCR analysis in P. monodon, providing valuable tools for research involving similar crustaceans.

Molecular and functional characterization of ribosome protein S24 in ovarian development of Macrobrachium nipponense

Ribosomal proteins (RPs) have mang extraribosomal functions including regulation of ovarian development in some organisms. In order to solve the problem of rapid ovarian maturation in Macrobrachium nipponense aquaculture, this study identified a RPS24 (MnRPS24) gene from M. nipponense, which encodes a protein of ββαβαααα folding structure type. MnRPS24 exhibited the greatest expressions in the female adult stage among the six growth stages, in the ovary among the nine tissues, and in the stage I ovary among the six ovarian development stages. The MnRPS24 protein located in the cytoplasm of oogonia, previtellogenic and early-vitellogenic oocytes, and the follicular cells surrounding the oocytes. The expression of the vitellogenin (MnVg), vitellogenin receptor (MnVgr), cell cycle protein B (MnCyclin B) and cell division cyclin 2 (MnCdc2) genes were increased by recombinant MnRPS24 protein incubation. Conversely, the expression of the Wee1 kinase (MnWee1) gene was decreased. MnRPS24 gene silencing downregulated the expression for MnVg, MnVgr, MnCyclin B and MnCdc2 and upregulated the expression for MnWee1. Furthermore, MnRPS24 gene silencing delayed the vitellogenesis of oocytes, halting the progression of ovarian development. The findings of this research demonstrate that MnRPS24 could potentially function as a stimulator in promoting the development of ovaries in M. nipponense.

Dual roles of CYP302A1 in regulating ovarian maturation and molting in Macrobrachium nipponense

CYP302A1 is a member of the Halloween genes in the cytochrome P450 supergene family, which play an important regulatory role in the synthesis of 20-hydroxyecdysone (20E) in crustaceans and insects. In this study, we found that the Mn-CYP302A1sequence included typical CYP450 conserved domains. Phylogenic showed that it is closely related to crustaceans and insects. q-PCR analysis indicated that Mn-CYP302A1 was highly expressed in the ovaries and peaked before ovarian maturation. Mn-CYP302A1 expression was higher at the post-larval stage of day 15 than at other stages of embryogenesis. In situ hybridization indicated that Mn-CYP302A1 was mainly distributed in the nucleus, yolk granules, cell membrane and cytoplasm To further establish the function of CYP302A1, a 21-day RNA interference experiment was conducted. On day 16, the Gonad Somatic Index of the control group and the experimental group showed significant differences, with GSI of 11.72% in the control group and 3.21% in the experimental group. The cumulative proportion of the second entry into stage O-Ⅲ was 100% in the control group, while it was 41.67% in the experimental group on day 21. The ecdysone content was 8.91nmol/L in the control group and 6.11nmol/L in the experimental group on day 9. A significant difference in the molting proportion between the control group and the experimental group was also observed (49% in the control group and 34% in the experimental group) on day 16. Statistical results showed that the average molting cycle of the control group was 14.5 days, while that of the experimental group was 16.5 days. However, the morphological structure of ovarian tissue did not abnormal change. Therefore, the results of this study suggest that Mn-CYP302A1 can promote ovarian maturation and molting in female M. nipponense.

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.

Sex Reversal Induced by Dietary Supplementation with 17α-Methyltestosterone during the Critical Period of Sex Differentiation in Oriental River Prawn (Macrobrachium nipponense)

The steroid 17α-methyltestosterone (MT) inhibits ovarian function and is often used to induce sex reversal artificially in vertebrates. In the present study, different concentrations of MT were added as dietary supplementation, and the effects on sex ratio, growth, and gonadal development were examined. After 40 days, the sex ratio (male:female) in each group increased at different degrees with 50 (1.36:1), 100 (1.57:1), and 200 (2.61:1) mg/kg MT, and neo-males with testis-ovary coexistence were observed in the 200 mg/kg MT group. Furthermore, 50 and 100 mg/kg MT could induce female reversion in neo-males. Histologically, the development of the testes in experimental groups was slower, but the ovaries of the experimental and control groups had similar developmental rates. The expression levels of DMRT11E, Foxl2, and SoxE1 in males at 200 mg/kg MT were 8.65-, 3.75-, and 3.45-fold greater than those of the control group. In crustaceans, sex reversal through vertebrate sex hormones can be observed. Neo-males (sex-reversed female prawns) were maintained by exogenous androgen, and over-reliance led to slow testis growth, small body size, and low growth rate, but sperm was still produced. In female prawns, MT inhibited ovary development and promoted growth.

Molecular Characterization Related to Ovary Early Development Mechanisms after Eyestalk Ablation in Exopalaemon carinicauda

Eyestalk ablation is an effective method to promote ovarian development in crustaceans. Herein, we performed transcriptome sequencing of ovary and hepatopancreas tissues after eyestalk ablation in Exopalaemon carinicauda to identify genes related to ovarian development. Our analyses led to the identification of 97,383 unigenes and 190,757 transcripts, with an average N50 length of 1757 bp. In the ovary, four pathways related to oogenesis and three related to oocyte rapid growth were enriched. In the hepatopancreas, two vitellogenesis-associated transcripts were identified. Furthermore, short time-series expression miner (STEM) and gene ontology (GO) enrichment analyses revealed five terms related to gamete generation. In addition, two-color fluorescent in situ hybridization results suggested that dmrt1 might play a vital role in oogenesis during the early stage of ovarian development. Overall, our insights should support future studies focusing on investigating oogenesis and ovarian development in E. carinicauda.

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.

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.

Effects of four chemosterilants on Bactrocera tau

Bactrocera tau (Walker) is a fly pest species mainly distributed in Southeast Asia and the South Pacific; it causes substantial ecological and economic issues because of its destructiveness and rapid reproduction. Chemical sterilization technology can reduce the use of insecticides and is widely applied for insect pest control. In this study, the sterilization efficacy of varying concentrations of four chemosterilants, namely, hexamethylphosphoramide (HMPA), CSII Aqua, 5-fluorouracil (5-FU), and colchicine, on adult pumpkin flies was investigated. The results indicated that a solution of 0.03% HMPA had the highest sterilization efficacy. When the number of sterile males was equal to or exceeded 20 times that of untreated males, the hatching rate of offspring eggs was less than 10%. Chemosterilant treatment significantly altered the levels of acid phosphatase (ACP), alkaline phosphatase (AKP), and B. tau vitellogenin (BtVg); these substances have an important impact on reproductive development. The treatment also decreased the size of the reproductive organs (i.e., testes and ovaries). Our results suggest that 0.03% HMPA has unique sterilization properties and may represent a new chemical agent for the control of B. tau populations in agricultural settings.

Hepatopancreas transcriptome analyses provide new insights into the molecular regulatory mechanism of fast ovary maturation in Macrobrachium nipponense

Background

Macrobrachium nipponense is an economically and ecologically important freshwater prawn that is widely farmed in China. In contrast to other species of marine shrimp, M. nipponense has a short sexual maturity period, resulting in not only high stocking densities, but also a reduced survival rate and increased risk of hypoxia. Therefore, there is an urgent need to study the molecular mechanisms underlying fast ovary maturation in this species.

Results

Comparative transcriptome analysis was performed using hepatopancreatic tissue from female M. nipponense across five ovarian maturation stages to explore differentially expressed genes and pathways involved in ovarian maturation. In total, 118.01 Gb of data were generated from 15 transcriptomes. Approximately 90.46% of clean reads were mapped from the M. nipponense reference genome. A comprehensive comparative analysis between successive ovarian maturation stages generated 230–5814 differentially expressed genes. Gene Ontology (GO) enrichment was highly concentrated in the “biological process” category in all four comparison groups, and mainly focused on energy synthesis and accumulation, energy decomposition and transport. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment results showed that, among 20 significantly enriched KEGG pathways, nine were involved in the synthesis, degradation, and metabolism of carbohydrates, lipids, and other nutrient intermediates, suggesting that the hepatopancreas has an important role in energy supply during ovarian maturation. Furthermore, the “Insect hormone biosynthesis” pathway was found to have a dominant role in the development of the ovary from immaturity to maturity, supporting the hypothesis that ecdysteroid- and juvenile hormone-signaling pathways have an important role in hepatopancreas regulation of ovarian maturation.

Conclusion

Taken together, this study sheds light on the role of the hepatopancreas in the molecular regulation of ovary maturation in M. nipponense. The present study provided new insights for understanding the mechanisms of reproductive regulation in crustaceans.

Identification of ribosomal protein L24 (RPL24) from the oriental river prawn, Macrobrachium nipponense, and its roles in ovarian development

Ribosomal proteins exhibit various extraribosomal functions in addition to their roles in protein synthesis. In this study, complementary DNA (cDNA) of ribosomal protein L24 in Macrobrachium nipponense (MnRPL24) was isolated, and its role in ovarian development was investigated using quantitative real-time PCR (qPCR), immunohistochemistry (IHC), RNA interference (RNAi) and histological observations. The complete cDNA of MnRPL24 is 564 base pairs (bps) and contains a 486 bp open reading frame (ORF) encoding 162 amino acids (aas). The highest expression level of MnRPL24 among eight tissues was found in the ovary, specifically in the stage I ovary. The MnRPL24 protein existed in the cytoplasm and nucleus of developing oocytes, and also existed in the cytoplasm of follicle cells in developing ovaries. After MnRPL24 knockdown by RNAi, the expression levels of vitellogenin (Vg), vitellogenin receptor (Vgr), cyclin-dependent kinase 2 (Cdc2) and M-phase cyclin (Cyclin B) genes and the gonadsomatic index (GSI) did not show the typical trend of gradually elevation with ovarian development and finally decrease in the later stage of ovarian cycle. Moreover, the oviposition rate (OR) was downregulated, and oocyte development was delayed after MnRPL24 knockdown. After eyestalk ablation, the MnRPL24 expression level was considerably elevated in the initial stages and decreased in the late stage of the ovarian development cycle. This investigation illustrates a possible regulatory role of MnRPL24 in the ovarian development of M. nipponense, and MnRPL24 may act as a stimulator of early ovarian development.

Comparison of immune defense and antioxidant capacity between broodstock and hybrid offspring of juvenile shrimp (Macrobrachium nipponense): Response to acute ammonia stress

Ammonia is a major environmental pollutant in the aquatic system that poses a great threat to the health of shrimp. Macrobrachium nipponense, as one of the large-yield farmed shrimp, is facing germplasm degradation. Genetic improvement through hybridization is one of the effective methods to solve this problem. However, there are few studies on the effects of ammonia nitrogen on the germplasm resources of M. nipponense. In this study, the broodstock populations (Dianshan, DS) and hybrid offspring (DS ♀ × CD [Changjiang, CJ ♂ × Dongting, DT ♀], SCD) were exposed to 0, 5, or 20 mg/L of ammonia for 96 h. The survival rate of the SCD group was greater than the DS group, although there were no significant differences in weight gain rate and length gain rate (p > 0.05). The number of positive cells and apoptosis rates in the DS group were significantly greater than in the SCD group after ammonia exposure (p < 0.05). As the ammonia concentration increased, the antioxidant enzyme activities in the SCD group were significantly higher than DS group, while the hepatotoxicity enzyme activities in the SCD group were significantly lower than DS group (p < 0.05). The trends in the expression of antioxidant- and immune-related genes were generally consistent with the activities of antioxidant enzymes. Our study found that the hybrid population had stronger stress resistance than their parent populations at the same ammonia concentration. This study confirms our speculation that hybrid population has a greater advantage in antioxidant immunity, which also provides reference for the follow-up study of chronic ammonia toxicity.

Cloning, functional and regulation analysis of a novel male reproduction-related protein gene from the oriental river prawn Macrobrachium nipponense

Gonadogenesis processes in crustaceans are complex. There, however, has been a large amount of research focused on regulation of female gonad (ovary) development in crustaceans, however, there has been little focus on the male gonad (testis). In the current study, a novel male reproduction-related protein gene (Mn-MRP) was identified from Macrobrachium nipponense. The relative abundance of Mn-MRP mRNA transcript in tissues and at different developmental stages were investigated. The relative abundance of Mn-MRP mRNA transcript was larger in the testis than other tissues, and during the testis maturation stage than at other developmental stages, suggesting Mn-MRP may have important functions in reproduction processes. The RNA interference (RNAi) was used to further investigate the Mn-MRP biological function. Silencing of the Mn-MRP gene effectively decreased the abundance of the sperm gelatinase (Mn-SG) mRNA transcript, implying the protein encoded by this gene may have functions in sperm activity during the fertilization process. Further studies with RNAi and eyestalk ablation confirmed that gonad inhibiting hormone gene (Mn-GIH) is a negative regulator of Mn-MRP, and that the insulin-like androgenic gland hormone gene (Mn-IAG) is a positive regulator. There, therefore, was cloning of the Mn-MRP gene, and investigation of its potential biological function, as well as elucidation of the positive/negative regulators in current study. The results from this study provide for a greater understanding of regulatory mechanisms of male reproduction in crustaceans.

Transcriptome analysis of five ovarian stages reveals gonad maturation in female Macrobrachium nipponense

Background

Macrobrachium nipponense is an economically important species of freshwater shrimp in China. Unlike other marine shrimps, the ovaries in adult female M. nipponense can mature rapidly and periodically during the reproductive period, but the resulting high stocking densities and environmental deterioration can negatively impact the harvest yield and economic benefits. To better understand ovary development in female M. nipponense, we performed systematic transcriptome sequencing of five different stages of ovarian maturation.

Results

We obtained 255,966 Gb of high quality transcriptome data from 15 samples. Of the 105,082 unigenes that were selected, 30,878 were successfully annotated. From these unigenes, we identified 17 differentially expressed genes and identified three distinct gene expression patterns related to different biological processes. We found that cathepins, legumains, and cystatin were enriched in the lysosome pathway, and they are related to vitellogenin hydrolysis. Additionally, we found that myosin heavy chain 67 participated in oocyte excretion.

Conclusions

We provide the first detailed transcriptome data relating to the ovarian maturation cycle in M. nipponense. Our results provide important reference information about the genomics, molecular biology, physiology, and population genetics of M. nipponense and other crustaceans. It is conducive to further solve the problem of M. nipponense rapid ovarian maturation from the aspects of energy supply and cell division.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07737-5.

Comparison of morphology and genetic diversity between broodstock and hybrid offspring of oriental river prawn, Macrobrachium nipponense based on morphological analysis and SNP markers

Hybridization is an effective method for the genetic improvement of farmed species. In this study, three broodstock populations (Changjiang, CJ, Dongting, DT, and Dianshan, DS) of oriental river prawn, Macrobrachium nipponense were used, and DS was used as the female broodstock. Through three-line hybridization, two hybrid populations were finally obtained. The F3 generation of the broodstock population and the F1 generation of the hybrid population were cultured indoors for 3 months. Through morphological analysis (cluster analysis, discriminant analysis and path analysis) it was found that the hybrid population and the broodstock had some differences, but not enough to reach the subspecies level, and the dominant traits exhibited differentiation and reorganization. This study identified SNP genetic markers, carried out systematic evolution analysis and genetic diversity analysis and found that the nucleotide diversity π and heterozygosity Het of the hybrid population were higher than those of the broodstock. Among broodstocks, the differentiation index (F_st ) of SCD and SDC was smallest (0.055). This research provides some valuable reference for genetic breeding.

Function analysis and molecular characterization of cyclin A in ovary development of oriental river prawn, Macrobrachium nipponense

Macrobrachium nipponense has the characteristics of fast ovarian development cycle, which leads to the coexistence of multiple generations, the reduction of commodity specifications and the low economic benefit. Therefore, the study on the mechanism of ovarian development is of great significance to the development of industry. Cyclin A (CycA)is a key gene regulating ovarian development in vertebrates, but little information was available for its function in crustaceans. In this study, the full-length cDNA of Mn-CycA was obtained from the ovary. The full-length cDNA (2033 bp) with an open reading frame of 1368 bp, encoded a 456-amino acid protein. qRT-PCR revealed tissue-specific expression pattern of Mn-CycA, with abundant expression in the ovary. Results in different developmental stages of ovary indicated that Mn-CycA expression is positively correlated with ovarian maturation. qRT-PCR In different developmental stages, the expression of Mn-CycA mRNA gradually increased during the embryonic stage and decreased significantly on the first day of the hatching stage. At the 25th day of the metamorphosis stage, the expression level of Mn-CycAmRNA in female shrimp was 3.5 times higher than that in male shrimp, which may be related to the proliferation of oogonia and the formation of oocytes. In situ hybridization (ISH) of ovary showed Mn-CycA was examined in all stages and was mainly located in oogonia and oocytes. Compared with the control group, the obvious change of gonad somatic index (GSI) proved that injection of Mn-CycA dsRNA could delay the ovarian development cycle, which provided strong evidence for the involvement of Mn-CycA in ovarian maturation and oogenesis, and expanded a new perspective for studying the fast ovarian development cycle in M. nipponense.

Comparison between cultured and wild Pacific white shrimp (Penaeus vannamei) vitellogenesis: next-generation sequencing and relative expression of genes directly and indirectly related to reproduction

Shrimp fisheries are among the most important fisheries worldwide, and shrimp culture has increased considerably in recent years. Most current studies on reproduction-related genes have been conducted on cultured shrimp. However, gene expression is intimately linked to physiological and environmental conditions, and therefore an organism’s growth environment has a great influence on reproduction. Thus, gene expression profiling, should be applied in fisheries studies. Here, we identified the expression patterns of 76 reproduction-related genes in P. vannamei via the analysis of pooled transcriptomes from a time-series experiment encompassing a full circadian cycle. The expression patterns of genes associated both directly (Vtg, ODP, and ProR) and indirectly (FAMet, CruA1, and CruC1) with reproduction were evaluated, as these genes could be used as molecular markers of previtellogenic and vitellogenic maturation stages. The evaluated genes were prominently upregulated during vitellogenic stages, with specific expression patterns depending on the organism’s environment, diet, and season. Vtg, ProR, ODP, and FaMet could serve as molecular markers for both wild and cultured organisms.

Characterization of prostanoid pathway and the control of its activity by the eyestalk optic ganglion in the female giant freshwater prawn, Macrobrachium rosenbergii

The giant freshwater prawn, Macrobrachium rosenbergii, is an economically valuable species that are distributed throughout the Asia-Pacific region. With the natural population declining due to overfishing, aquaculture of this species is deemed necessary. Hence, it is essential to understand the mechanisms regulating reproduction in order to increase their production. Prostaglandins (PGs) play an important role in reproduction in most vertebrates and several invertebrates. It has been proposed that crustaceans have PGs but the prostanoids pathway in the giant freshwater prawn is still unclear. In this study, we identified 25 prostanoid-related genes involved in the biosynthesis of active prostanoids in M. rosenbergii using in silico searches of transcriptome data. Comparative analysis of encoded proteins for the MroPGES2 gene with other species was performed to confirm their evolutionary conservation. Gene expression analysis revealed the correlation of MroPGES2 gene expression level with the progress of ovarian development. Eyestalk ablation increased the expression level of MroPGES2 gene compared to intact groups during the ovary maturation stages. Collectively, this study confirmed the existence of prostanoids in the giant freshwater prawn, as well as characterizing key gene MroPGES2 associated with the prostanoid pathway. We propose that MroPGES2 may play an important role in M. rosenbergii ovarian maturation and its expression is under the inhibitory control from the eyestalk optic ganglion hormones. Identification of genes in prostanoid pathway and their expressions enables future functional studies to be performed, which may lead to applications in the aquaculture of this species.

Regulatory Mechanisms of Vitellogenesis in Insects

Vitellogenesis is pre-requisite to insect egg production and embryonic development after oviposition. During insect vitellogenesis, the yolk protein precursor vitellogenin (Vg) is mainly synthesized in the fat body, transported by the hemolymph through the intercellular spaces (known as patency) in the follicular epithelium to reach the membrane of maturing oocytes, and sequestered into the maturing oocytes via receptor-mediated endocytosis. Insect vitellogenesis is governed by two critical hormones, the sesquiterpenoid juvenile hormone (JH) and the ecdysteriod 20-hydroxyecdysone (20E). JH acts as the principal gonadotropic hormone to stimulate vitellogenesis in basal hemimetabolous and most holometabolous insects. 20E is critical for vitellogenesis in some hymenopterans, lepidopterans and dipterans. Furthermore, microRNA (miRNA) and nutritional (amino acid/Target of Rapamycin and insulin) pathways interplay with JH and 20E signaling cascades to control insect vitellogenesis. Revealing the regulatory mechanisms underlying insect vitellogenesis is critical for understanding insect reproduction and helpful for developing new strategies of insect pest control. Here, we outline the recent research progress in the molecular action of gonadotropic JH and 20E along with the role of miRNA and nutritional sensor in regulating insect vitellogenesis. We highlight the advancements in the regulatory mechanisms of insect vitellogenesis by the coordination of hormone, miRNA and nutritional signaling pathways.

MnFtz-f1 Is Required for Molting and Ovulation of the Oriental River Prawn Macrobrachium nipponense

Molting and ovulation are the basic processes responsible for the growth and reproduction of Macrobrachium nipponense; however, the molecular mechanisms of molting and ovulation in M. nipponense are poorly understood. The present study aimed to use MnFtz-f1 as the starting point to study the molting and ovulation phenomena in M. nipponense at the molecular level. The full-length MnFtz-f1 cDNA sequence was 2,198 base pairs (bp) in length with an open reading frame of 1,899 bp encoding 632 amino acids. Quantitative real-time PCR analysis showed that MnFtz-f1 was highly expressed in the ovary at the cleavage stage and on the fifth day after hatching. In vivo administration of 20-hydroxyecdysone (20E) showed that 20E effectively inhibited the expression of the MnFtz-f1 gene, and the silencing of the MnFtz-f1 gene reduced the content of 20E in the ovary. In situ hybridization (ISH) analysis revealed the localization of MnFtz-f1 in the ovary. Silencing of MnFtz-f1 by RNA interference (RNAi) resulted in significant inhibition of the expression of the vitellogenin (Vg), Spook, and Phantom genes, thus confirming that MnFtz-f1 had a mutual regulatory relationship with Vg, Spook, and Phantom. After RNAi, the molting frequency and ovulation number of M. nipponense decreased significantly, which demonstrated that MnFtz-f1 played a pivotal role in the process of molting and ovulation.

Molecular Characterization of a Novel Cathepsin L in Macrobrachium nipponense and Its Function in Ovary Maturation

Cathepsin L genes, which belonged to cysteine proteases, were a series of multifunctional protease and played important roles in a lot of pathological and physiological processes. In this study, we analyzed the characteristics a cathepsin L (named Mn-CL2) in the female oriental river prawn, Macrobrachium nipponense which was involved in ovary maturation. The Mn-CL2 was1,582 bp in length, including a 978 bp open reading frame that encoded 326 amino acids. The Mn-CL2 was classified into the cathepsin L group by phylogenetic analysis. Real-time PCR (qPCR) analysis indicated that Mn-CL2 was highly expressed in the hepatopancreas and ovaries of female prawns. During the different ovarian stages, Mn-CL2 expression in the hepatopancreas and ovaries peaked before ovarian maturation. In situ hybridization studies revealed that Mn-CL2 was localized in the oocyte of the ovary. Injection of Mn-CL2 dsRNA significantly reduced the expression of vitellogenin. Changes in the gonad somatic index also confirmed the inhibitory effects of Mn-CL2 dsRNA on ovary maturation. These results suggest that Mn-CL2 has a key role in promoting ovary 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.

Molecular cloning, characterization and functional analysis of two neuropeptide F genes from the oriental river prawn (Macrobrachium nipponense)

In invertebrates, neuropeptide F (NPF) has many regulatory functions, similar to NPY, its homologous peptide. In this study, two neuropeptide F genes were identified in Macrobrachium nipponense: Mn-NPF1 and Mn-NPF2. Mn-NPF2 shared the same amino acid sequence with Mn-NPF1, except for a 37 amino acid insert in the middle of the NPF region. The quantitative-PCR (qPCR) results indicated that Mn-NPF1 expression was positively correlated with ovarian maturation, whereas Mn-NPF2 had opposing expression patterns. Both Mn-NPFs were poorly expressed at early embryonic stages, but enhanced expression levels were observed up to day 10 after hatching, when the gonads began to differentiate. Ovary in situ hybridization (ISH) analyses showed that both Mn-NPFs were present at all stages, but were differentially localized to distinct compartments. Temperature gradient studies showed that both Mn-NPFs were implicated in the seasonal regulation of reproduction. A double-stranded (ds) RNA-Mn-NPF2 injection led to a significant 38.5% increase in the vitellogenin (VG) transcript (P < 0.05). These results demonstrated that Mn-NPF2 plays an important role in inhibiting ovarian maturation.

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.

Expression dynamics of solute carrier family 15 member 4 (SLC15A4) and its potential regulatory role in ovarian development of the Indian white shrimp, Penaeus indicus

Solute carrier proteins (SLC) are essential membrane transport proteins responsible for transporting lipids, amino acids, sugars, neurotransmitters, and drugs across the biological membranes. Dysfunction of these carrier proteins may lead to an imbalance of biological mechanisms and also in the failure of the transporting pathways of several signaling neurotransmitters. In the present study, a 646 bp of a solute carrier protein (SLC15A4) was cloned and sequenced from the Indian white shrimp, Penaeus indicus. Multiple sequence alignment using ClustalW and phylogenetic analysis of putative SLC15A4 fragment from P. indicus (PiSLC15A4) was performed using Mega X tool. Tissue distribution analysis was carried out using real-time PCR. The differential expressions of PiSLC15A4 were also analyzed in the ovaries and brain tissues of wild-caught female shrimps at different maturation stages and in the brain tissues of captive females subjected to induce maturation by eyestalk ablation. Significant diversity in SLC15A4 sequence obtained from P. indicus was observed when compared to the other species. Tissue distribution analysis confirmed the ubiquitous expression of PiSLC15A4 in all the tissues examined. The differential expressions of PiSLC15A4 indicated higher expression of the gene in brain tissue of females at the vitellogenic stage, while the expressions in ovaries were significantly higher in the immature stage. The differential expressions of PiSLC15A4 in the brain tissues were substantially higher in eyestalk ablated shrimps compared to the eyestalk intact females. The study suggests a role for SLC15A4 in the endocrine signaling pathways stimulating ovarian maturation in P. indicus.

Analysis of testis metabolome and transcriptome from the oriental river prawn (Macrobrachium nipponense) in response to different temperatures and illumination times

A better understanding of the mechanisms underlying the male sexual differentiation of Macrobrachium nipponense is urgently needed in order to maintain sustainable development of the M. nipponense industry. Environmental factors, especially temperature and illumination, have dramatic effects on gonadal development. The aim of the present study was to identify key genes and metabolites involved in the male sexual differentiation and development of M. nipponense through integrated metabolomics and transcriptome analyses of the testis in response to different temperatures and illumination times. A total of 268 differentially abundant metabolites and 11,832 differentially expressed genes (DEGs) were identified. According to integrated metabolomics and transcriptome analyses, glycerophospholipid and sphingolipid metabolism was predicted to have dramatic effects on the male sexual differentiation and development of M. nipponense. According to the KEGG enrichment analysis of DEGs, oxidative phosphorylation, glycolysis/gluconeogenesis, the HIF-1 signaling pathway, the citrate cycle, steroid hormone synthesis, and the spliceosome complex were predicted to promote male differentiation and development by providing adenosine triphosphate, promoting the synthesis of steroid hormones, and providing correct gene products. Quantitative polymerase chain reaction analysis and in situ hybridization showed that the SDHB, PDE1, HSDL1, CYP81F2, SRSF, and SNRNP40 genes were differentially expressed, suggesting roles in the male sexual differentiation and development of M. nipponense. Strong candidate sex-related metabolic pathways and genes in M. nipponense were identified by integrated metabolomics and transcriptome analyses of the testis in response to different temperatures and illumination times, as confirmed by PCR analysis and in situ hybridization.

Comparative metabolomics analysis of ovarian developmental stages in Macrobrachium nipponense

Rapid sexual maturity of female Macrobrachium nipponense is a severe problem for the aquaculture industry. To date, there have been only transcriptome studies investigating ovarian development, and studies using other tools, such as metabolomics are lacking. Metabolomics reveals changes in the level of metabolites in tissues in relation to current physiological characteristics, and can yield valuable insight into the growth and development of organisms. In this study, we systematically analyzed 15 samples from five different ovarian developmental stages in M. nipponense to learn more about how metabolites change over reproduction. Gas chromatography/time-of-flight mass spectroscopy revealed an array of different compounds and 83-162 pathways depending on the stage. Furthermore, 89 metabolites and 14 pathways were significantly different across stages. It is hypothesized that N-acetyl-N-formyl-5-methoxykynurenamine, ascorbate, fructose-2,6-bisphosphate, cortexolone and other metabolites that significantly differed by stage are regulated by hormones and are closely related to ovarian development. However, for other metabolites that changed with development, such as cytidine and xanthine, an association with ovarian development has yet to be revealed. Quantitative polymerase chain reaction was used to correlate gene changes to metabolites in the pathway for biosynthesis of plant secondary metabolites. We found that the TCA cycle rate may be the cause of female miniaturization during the reproductive period, and that the control of fatty acid content via aquaculture nutrition may be an exogenous tool for regulatory control of maturation. This study provides a systematic and comprehensive metabolomics analysis of ovarian development in M. nipponense and lays a foundation for addressing the problem of rapid sexual maturity.

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.

Integrative Proteomic and MicroRNA Analysis: Insights Into Mechanisms of Eyestalk Ablation-Induced Ovarian Maturation in the Swimming Crab Portunus trituberculatus

Eyestalk ablation is the most common method to induce ovarian maturation in decapod crustacean aquaculture, but it jeopardizes broodstock survival and larvae production. It is important to understand the molecular basis underlying the maturation triggered by ablation and thereby develop an alternative measure for maturation manipulation. In this study, we investigate alterations of ovarian proteome and miRNA profile after ablation in a commercially important marine crab Portunus trituberculatus. Quantitative proteomic analysis using iTRAQ reveals that 163 proteins are differentially expressed following ablation, and modulation of methyl farnesoate metabolism and activation of calcium signaling may play important roles in the ovarian maturation induced by ablation. miRNA expression profiling identifies 31 miRNAs that show statistically significant changes. Integration of miRNA and proteome expression data with miRNA target prediction algorithms generates a potential regulatory network consisting of 26 miRNAs and 30 proteins linked by 71 possible functional associations. The miRNA-protein network analysis suggests that miRNAs are involved in promoting ovarian maturation by controlling expression of proteins related to methyl farnesoate synthesis, calcium signals, and energy metabolism. Experimental validation and temporal expression analysis indicate multiple miRNAs can act synergistically to regulate expression of Farnesoic acid O-methyltransferase and Calmodulin. Our findings provide new insights for elucidating the mechanisms underlying eyestalk ablation-induced ovarian maturation and could be useful for devising an alternative technique for manipulating reproduction in P. trituberculatus and other decapods.

Identification and Characterization of the DMRT11E Gene in the Oriental River Prawn Macrobrachium nipponense

The doublesex and mab-3 related transcription factor (DMRT) gene family involvement in sex development is widely conserved from invertebrates to humans. In this study, we identified a DM (Doublesex/Mab-3)-domain gene in Macrobrachium nipponense, which we named MniDMRT11E because it has many similarities to and phylogenetically close relationships with the arthropod DMRT11E. Amino acid alignments and structural prediction uncovered conservation and putative active sites of the DM domain. Real-time PCR analysis showed that the MniDMRT11E was highly expressed in the ovary and testis in both males and females. Cellular localization analysis showed that DMRT11E was mainly located in the oocytes of the ovary and the spermatocyte of the testis. During embryogenesis, the expression level of MniDMRT11E was higher at the cleavage stage than at other stages. During the different stages of ovarian development, MniDMRT11E expression gradually increased from OI to OIII and decreased to the lowest level at the end of OIV. The results indicated that MniDMRT11E probably played important roles in embryonic development and sex maturity in M. nipponense. MniDMRT11E dsRNA injection also significantly reduced vitellogenin (VG) expression and significantly increased insulin-like androgenic gland factor (IAG) expression, indicating a close relationship in gonad development.

Comparative transcriptional analysis and RNA interference reveal immunoregulatory pathways involved in growth of the oriental river prawn Macrobrachium nipponense

A source of premium animal protein, crustaceans are widely distributed and cultivated around the world. Short-term or long-term starvation events occur frequently owing to natural environment changes or manual management strategies in the life cycle of crustaceans. The result induced by starvation is that somatic growth of crustaceans will be retarded, while the immune mechanism is activated in this process. The aim of this study was to investigate whether the immune regulatory pathways are involved in the growth of crustaceans. Twelve muscle tissue transcriptomes of the oriental river prawn Macrobrachium nipponense were sequenced across four fasting stages lasting 0, 7, 14 and 21 d. The results showed that three immune-related pathways were involved in the growth of M. nipponense by regulating actin expression inducing the chemokine signaling pathway, the leukocyte transendothelial migration pathway and the FcR-mediated phagocytosis pathway. Furthermore, we employed RNA interference (RNAi) to further verify the effects that genes involved in the pathways had on regulating growth of M. nipponense. Comparative transcriptional analysis and RNA interference reveal that VASP and WAVE positively regulated the expression of actin; however, WASP negatively regulated the expression of actin. This is the first report that the immune regulatory pathways play key roles in the growth of crustaceans. Our results will not only provide an entirely new understanding of the immune mechanism of crustaceans from a unique angle but also further enrich and develop the theory of growth and developmental biology in crustaceans.

Validation and Evaluation of Reference Genes for Quantitative Real-Time PCR in Macrobrachium Nipponense

Quantitative real-time PCR (qPCR) is widely used in molecular biology, although the accuracy of the quantitative results is determined by the stability of the reference genes used. Recent studies have investigated suitable reference genes for some crustaceans under various conditions, but studies in Macrobrachium nipponense are currently lacking. In this study, we selected the following seven genes from among 35 commonly used housekeeping genes as candidate qPCR reference genes for temporal and spatial expression: EIF (eukaryotic translation initiation factor 5A), 18S (18S ribosomal RNA), EF-1α (elongation factor-1α), GAPDH (glyceraldehyde-3-phosphate dehydrogenase), TUB (α-tubulin), β-act (β-actin), and RPL18 (Ribosomal protein L18). The stability of each reference gene was evaluated by GeNorm, NormFinder, BestKeeper, and comparative ∆C _t methods, and was comprehensively ranked using RefFinder. RPL18 was shown to be the most suitable reference gene for adult M. nipponense tissues, while EIF was the most stable in different ovarian and embryo stages and in white spot syndrome virus infection, and β-act was the most stable reference gene under hypoxia stress. The reliability of the rankings was confirmed by RNA interference experiments. To the best of our knowledge, this represents the first systematic analysis of reference genes for qPCR experiments in M. nipponense, and the results will provide invaluable information for future research in closely related crustaceans.

Genomic structure, expression, and functional characterization of checkpoint kinase 1 from Penaeus monodon

Chk1 is a cell-cycle regulator. Chk1 has been identified in organisms ranging from yeast to humans, but few researchers have studied Chk1 in shrimps. We cloned Chk1 from the black tiger shrimp (Penaeus monodon). The full-length cDNA sequence of PmChk1 had 3,334 base pairs (bp), with an open reading frame of 1,455 bp. The complete genomic sequence of PmChk1 (11,081 bp) contained 10 exons separated by nine introns. qRT-PCR showed that PmChk1 was highly expressed in the ovaries and gills of P. monodon. The lowest PmChk1 expression was noted in stage III of ovarian development in P. monodon. PmChk1 expression decreased significantly after injection of 5-hydroxytryptamine and eyestalk ablation in P. monodon ovaries. RNA interference experiments were undertaken to examine the expression of PmChk1, PmCDC2, and PmCyclin B. PmChk1 knockdown in the ovaries and hepatopancreas by dsRNA-Chk1 was successful. The localization and level of PmChk1 expression in the hepatopancreas was studied using in situ hybridization, which showed that data were in accordance with those of qRT-PCR. The Gonadosomatic Index of P. monodon after dsRNA-Chk1 injection was significantly higher than that after injection of dsRNA-GFP or phosphate-buffered saline. These data suggest that PmChk1 may have important roles in the ovarian maturation of P. monodon.

Identification and characterization of opsin gene and its role in ovarian maturation in the oriental river prawn Macrobrachium nipponense

Opsins are photoreceptors with important roles in reproductive regulation in birds and fishes. In the present study, we identified an opsin gene from the eyes of the oriental river prawn Macrobrachium nipponense using expressed sequence tag analysis and rapid amplification of cDNA ends. The full-length transcript contained 1382 base pairs, encoding 375 amino acids. It was classified into the long-wavelength opsin group by phylogenetic analysis, and designated Mn-LW. Mn-LW expression demonstrated significant seasonal variation in somatic tissues from both male and female prawns, with the highest expression in the eyes, and expression also shown in the ovary. The expression profiles of Mn-LW in eyes and ovary were positively related to ovarian development. In situ hybridization showed that Mn-LW was present in retinular cells in the eye and oocytes in the ovary. Injection of Mn-LW dsRNA in vivo effectively down-regulated Mn-LW expression levels compared with control levels. Mn-LW dsRNA injection also significantly reduced vitellogenin (Vg) expression, indicating a close relationship between Mn-LW and Vg in ovarian development. These results suggest that Mn-LW may play an important role in Vg synthesis and accumulation during ovarian maturation in M. nipponense.

Molecular insights into reproduction regulation of female Oriental River prawns Macrobrachium nipponense through comparative transcriptomic analysis

The oriental river prawn, Macrobrachium nipponense, is an important commercial aquaculture resource in China. During breeding season, short ovary maturation cycles of female prawns cause multi-generation reunions in ponds and affect the growth of females representing individual miniaturization (known as autumn -propagation). These reproductive characteristics pose problems for in large - scale farming. To date, the molecular mechanisms of reproduction regulation of M. nipponense remain unclear. To address this issue, we performed transcriptome sequencing and gene expression analyses of eyestalk and cerebral ganglia of female M. nipponense during breeding and non-breeding seasons. Differentially expressed gene enrichment analysis results revealed several important reproduction related terms and signaling pathways, such as "photoreceptor activity", "structural constituent of cuticle" and "G-protein coupled receptor activity". The following six key genes from the transcriptome were predicted to mediate environmental factors regulating reproduction of M. nipponense: neuroparsin, neuropeptide F II, orcokinin II, crustacean cardioactive peptide, pigment-dispersing hormone 3 and tachykinin. These results will contribute to a better understanding of the molecular mechanisms of reproduction of oriental river prawns. Further detailed functional analyses of the candidate reproduction regulation related neuropeptides are needed to shed light on the mechanisms of reproduction of crustacean.

Genomic structure, expression pattern, and functional characterization of transcription factor E2F-2 from black tiger shrimp (Penaeus monodon)

Transcription factor E2F-2 is a regulator of cell cycle. Researchers identified E2F-2 genes from yeasts to humans, but few reports investigated E2F-2 gene from black tiger shrimp. In the present study, we cloned E2F-2 gene from black tiger shrimp (Penaeus monodon). Full-length PmE2F-2 complementary DNA sequence measures 3,189 bp with an open reading frame of 1,371 bp. Complete PmE2F-2 genomic sequence (17,305 bp) of P. monodon contains nine exons, which are separated by eight introns. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that PmE2F-2 is highly expressed in hepatopancreas and ovaries of P. monodon. Highest PmE2F-2 expression levels were observed in stage III ovarian development of P. monodon. PmE2F-2 expression levels were significantly augmented in ovaries of P. monodon after 5-hydroxytryptamine injection and eyestalk ablation. RNA interference experiments were conducted to examine PmE2F-2, PmCDK2, and PmCyclin E expression profiles. PmE2F-2 was successfully knocked down in ovaries and hepatopancreas via double-stranded RNA (dsRNA)-E2F-2 injection. In the same organs, PmE2F-2 expression localization and level were investigated through in situ hybridization, which revealed consistent results with those of qRT-PCR. After dsRNA-E2F-2 injection, gonadosomatic index of shrimp was significantly lower than those following dsRNA-GFP and phosphate-buffered solution injections. Therefore, PmE2F-2 may be involved in ovarian maturation in P. monodon.

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.

Molecular cloning, characterization and expression analysis of a novel PDRG1 gene from black tiger shrimp (Penaeus monodon)

P53 And DNA Damage-Regulated Gene 1 (PDRG1) is a novel gene which plays an important role in chaperone-mediated protein folding. In the present study, the full-length complementary DNA (cDNA) sequence of the PDRG1 gene from Penaeus monodon (PmPDRG1) was cloned by the rapid amplification of cDNA ends (RACE) method. The cDNA of PmPDRG1 spans 1,613 bp, interrupted by only one short intron, and encodes a protein of 136 amino acids with calculated molecular weight of 15.49 kDa. The temporal expression profile of PmPDRG1 in different tissues and in different developmental stages of the ovary was investigated by real-time quantitative PCR (RT-qPCR). An RNA interference (RNAi) experiment was performed to study the relationship between P. monodon p53 (Pmp53) and PmPDRG1, and the results showed that the relative expression level of PmPDRG1 mRNA was notably up-regulated from 12 h to 96 h after Pmp53 was silenced both in ovary and hepatopancreas. To further explore the role of PmPDRG1 in ovarian development, dopamine (DA) and 5-hydroxytryptamine (5-HT)-injected shrimps were analyzed by RT-qPCR, indicating that PmPDRG1 may be involved in the regulation of ovarian development of P. monodon.

Identification and evaluation of reference genes for expression studies by RT-qPCR during embryonic development of the emerging model organism, Macrobrachium olfersii

RT-qPCR is a sensitive and highly efficient technique that is widely used in gene expression analysis and to provide insight into the molecular mechanisms underlying embryonic development. The freshwater prawn, Macrobrachium olfersii is an emerging model organism, but, the stable reference genes of this species need to be identified and validated for RT-qPCR analysis. Thus, the aim of this study was to evaluate the expression stability of six genes (β-act, GAPDH, EF-1α, RpL8, RpS6, AK) in embryos and in adult tissues (cerebral ganglia, muscle and hepatopancreas) of M. olfersii. The expression stabilities of these genes were evaluated using geNorm, NormFinder, BestKeeper, ΔCt method and integrated tool RefFinder. In the general ranking, RpL8 and RpS6 were the most stable genes in embryos, while RpS6 and RpL8 were the most stable in a combined adult tissue analysis. Analysis of the adult tissues revealed that β-act and AK were the most stable genes in cerebral ganglia, RpL8 and AK in muscle, and RpS6 and β-act in hepatopancreas. EF-1α and GAPDH were the least stable genes and as normalizer genes in RT-qPCR affected expression of the Distal-less gene during M. olfersii development. This study provides suitable reference genes for RT-qPCR analysis and allows future studies of the gene expression in M. olfersii for understanding the molecular mechanisms of their development. To our knowledge, this is the first published study that identifies and evaluates reference genes for RT-qPCR analysis in M. olfersii and could be useful as basis for evaluations of reference genes in other prawns.

Insights into Sexual Precocity of Female Oriental River Prawn Macrobrachium nipponense through Transcriptome Analysis

Background

The oriental river prawn (Macrobrachium nipponense) is the most prevalent aquaculture species in China. The sexual precocity in this species has received considerable attention in recent years because more and more individuals matured at a small size, which devalues the commercial production. In this study, we developed deep-coverage transcriptomic sequencing data for the ovaries of sexually precocious and normal sexually mature M. nipponense using next-generation RNA sequencing technology and attempted to provide the first insight into the molecular regulatory mechanism of sexual precocity in this species.

Results

A total of 63,336 unigenes were produced from the ovarian cDNA libraries of sexually precocious and normal sexually mature M. nipponense using Illumina HiSeq 2500 platform. Through BLASTX searches against the NR, STRING, Pfam, Swissprot and KEGG databases, 15,134 unigenes were annotated, accounting for 23.89% of the total unigenes. 5,195 and 3,227 matched unigenes were categorized by GO and COG analysis respectively. 15,908 unigenes were consequently mapped into 332 KEGG pathways, and many reproduction-related pathways and genes were identified. Moreover, 26,008 SSRs were identified from 18,133 unigenes. 80,529 and 80,516 SNPs were yielded from ovarian libraries of sexually precocious and normal sexually mature prawn, respectively, and 29,851 potential SNPs between these two groups were also predicted. After comparing the ovarian libraries of sexually precocious and normal sexually mature prawn, 549 differentially expressed genes (DEGs) and 9 key DEGs that may be related to sexual precocity of M. nipponense were identified. 20 DEGs were selected for validation by quantitative real-time PCR (QPCR) and 19 DEGs show consistent expression between QPCR and RNAseq-based differential expression analysis datasets.

Conclusion

This is the first report on the large-scale RNA sequencing of ovaries of sexually precocious and normal sexually mature M. nipponense. The annotated transcriptome data will provide fundamental support for future research into the reproduction biology of M. nipponense. The large number of candidate SNPs and SSRs detected in this study could be used as genetic markers for population genetics and functional genomics in this species. More importantly, many DEGs, especially nine key DEGs between sexually precocious and normal sexually mature prawns were identified, which will dramatically improve understanding of molecular regulatory mechanism of sexual precocity of this species.