Characterization and expression analysis of the Broad-complex (Br-c) gene of the giant tiger shrimp Penaeus monodon

Effects of molting on the expression of ecdysteroid responsive genes in the crustacean molting gland (Y-organ)

Ecdysteroid molting hormones coordinate arthropod growth and development. Binding of 20-hydroxyecdysone (20E) to ecdysteroid receptor EcR/RXR activates a cascade of nuclear receptor transcription factors that mediate tissue responses to hormone. Insect ecdysteroid responsive and Forkhead box class O (FOXO) transcription factor gene sequences were used to extract orthologs from blackback land crab (Gecarcinus lateralis) Y-organ (YO) transcriptome: Gl-Ecdysone Receptor (EcR), Gl-Broad Complex (Br-C), Gl-E74, Gl-Hormone Receptor 3 (HR3), Gl-Hormone Receptor 4 (HR4), Gl-FOXO, and Gl-Fushi tarazu factor-1 (Ftz-f1). Quantitative polymerase chain reaction quantified mRNA levels in tissues from intermolt animals and in YO of animals induced to molt by multiple limb autotomy (MLA) or eyestalk ablation (ESA). Gl-EcR, Gl-Retinoid X Receptor (RXR), Gl-Br-C, Gl-HR3, Gl-HR4, Gl-E74, Gl-E75, Gl-Ftz-f1, and Gl-FOXO were expressed in all 10 tissues, with Gl-Br-C, Gl-E74, Gl-E75, and Gl-HR4 mRNA levels in the YO lower than those in most of the other tissues. In MLA animals, molting had no effect on Gl-Br-C, Gl-E74, and Gl-Ftz-f1 mRNA levels and little effect on Gl-EcR, Gl-E75, and Gl-HR4 mRNA levels. Gl-HR3 and Gl-FOXO mRNA levels were increased during premolt stages, while Gl-RXR mRNA level was highest during intermolt and premolt stages and lowest at postmolt stage. In ESA animals, YO mRNA levels were not correlated with hemolymph ecdysteroid titers. ESA had no effect on Gl-EcR, Gl-E74, Gl-HR3, Gl-HR4, Gl-Ftz-f1, and Gl-FOXO mRNA levels, while Gl-RXR, Gl-Br-C, and Gl-E75 mRNA levels were decreased at 3 days post-ESA. These data suggest that transcriptional up-regulation of Gl-FOXO and Gl-HR3 contributes to increased YO ecdysteroidogenesis during premolt. By contrast, transcriptional regulation of ecdysteroid responsive genes and ecdysteroidogenesis were uncoupled in the YO of ESA animals.

The moulting arthropod: a complete genetic toolkit review

Exoskeletons are a defining character of all arthropods that provide physical support for their segmented bodies and appendages as well as protection from the environment and predation. This ubiquitous yet evolutionarily variable feature has been instrumental in facilitating the adoption of a variety of lifestyles and the exploitation of ecological niches across all environments. Throughout the radiation that produced the more than one million described modern species, adaptability afforded by segmentation and exoskeletons has led to a diversity that is unrivalled amongst animals. However, because of the limited extensibility of exoskeleton chitin and cuticle components, they must be periodically shed and replaced with new larger ones, notably to accommodate the growing individuals encased within. Therefore, arthropods grow discontinuously by undergoing periodic moulting events, which follow a series of steps from the preparatory pre-moult phase to ecdysis itself and post-moult maturation of new exoskeletons. Each event represents a particularly vulnerable period in an arthropod's life cycle, so processes must be tightly regulated and meticulously executed to ensure successful transitions for normal growth and development. Decades of research in representative arthropods provide a foundation of understanding of the mechanisms involved. Building on this, studies continue to develop and test hypotheses on the presence and function of molecular components, including neuropeptides, hormones, and receptors, as well as the so-called early, late, and fate genes, across arthropod diversity. Here, we review the literature to develop a comprehensive overview of the status of accumulated knowledge of the genetic toolkit governing arthropod moulting. From biosynthesis and regulation of ecdysteroid and sesquiterpenoid hormones, to factors involved in hormonal stimulation responses and exoskeleton remodelling, we identify commonalities and differences, as well as highlighting major knowledge gaps, across arthropod groups. We examine the available evidence supporting current models of how components operate together to prepare for, execute, and recover from ecdysis, comparing reports from Chelicerata, Myriapoda, Crustacea, and Hexapoda. Evidence is generally highly taxonomically imbalanced, with most reports based on insect study systems. Biases are also evident in research on different moulting phases and processes, with the early triggers and late effectors generally being the least well explored. Our synthesis contrasts knowledge based on reported observations with reasonably plausible assumptions given current taxonomic sampling, and exposes weak assumptions or major gaps that need addressing. Encouragingly, advances in genomics are driving a diversification of tractable study systems by facilitating the cataloguing of putative genetic toolkits in previously under-explored taxa. Analysis of genome and transcriptome data supported by experimental investigations have validated the presence of an "ultra-conserved" core of arthropod genes involved in moulting processes. The molecular machinery has likely evolved with elaborations on this conserved pathway backbone, but more taxonomic exploration is needed to characterise lineage-specific changes and novelties. Furthermore, linking these to transformative innovations in moulting processes across Arthropoda remains hampered by knowledge gaps and hypotheses based on untested assumptions. Promisingly however, emerging from the synthesis is a framework that highlights research avenues from the underlying genetics to the dynamic molecular biology through to the complex physiology of moulting.

Identification of CCCH-type zinc finger antiviral protein 1 (ZAP) gene from Pacific white shrimp (Penaeus vannamei): Characterization and expression analysis in response to viral infection

Zinc-finger proteins (ZFPs) are a huge family that exert multiple roles in the cells. ZFPs could be divided into nine types based on the numbers and positions of conserved Cys and His residues, in which CCCH-type ZFP was one of the most widely studied types. CCCH-type zinc finger antiviral protein 1 (ZAP), a CCCH-type ZFP that can inhibit the replication of certain RNA viruses and DNA viruses by mediating degradation of viral RNA and repressing mRNA translation, plays significant roles in the host innate immune defenses against viral infections. Presently, there have been numerous reports investigating the antiviral ability of ZAP, while no data is available about ZAP gene in the species of shrimps or even crustaceans. In this study, a novel protein containing CCCH-type zinc finger motifs (ZnF-CCCH), CCCH-type zinc finger antiviral protein 1 (ZAP) gene, was identified from Pacific white shrimp (Penaeus vannamei) and its role in antiviral immunity was further investigated. Similar to mammalian ZAPs, in addition to ZnF-CCCH, PvZAP also possesses central WWE domains and C-terminal PARP domain. Phylogenetic analysis showed that PvZAP was close to that of the crustacean Pacific oyster, separating from the cluster of vertebrate ZAP proteins. Upon in vivo infection by IHHNV, gene expression of PvZAP was strongly up-regulated in the hepatopancreas and gills of both adult and juvenile shrimps, where adult individuals showed higher fold changes of up-regulation than in juvenile individuals. These results suggested that PvZAP might play an important role in the innate immune defense of Pacific white shrimp against IHHNV infection. This allows us to gain new insights into the immunological function of ZAP in the innate immunity of shrimp species and even crustaceans.

Roles of Krüppel Homolog 1 and Broad-Complex in the Development of Dendroctonus armandi (Coleoptera: Scolytinae)

In insects, metamorphosis is controlled by juvenile hormone (JH) and 20-hydroxyecdysone (20E). Krüppel homolog 1 (Kr-h1), a key JH-early inducible gene, is responsible for the suppression of metamorphosis and the regulation of the Broad-Complex (Br-C) gene, which is induced by 20E and functions as a “pupal specifier”. In this study, we identified and characterized the expression patterns and tissue distribution of DaKr-h1 and DaBr-C at various developmental stages of Dendroctonus armandi. The expression of the two genes was induced by JH analog (JHA) methoprene and 20E, and their functions were investigated by RNA interference. DaKr-h1 and DaBr-C were predominantly expressed in the heads of larvae and were significantly downregulated during the molting stage. In contrast, the DaKr-h1 transcript level was highest in the adult anterior midgut. DaBr-C was mainly expressed in female adults, with the highest transcript levels in the ovaries. In the larval and pupal stages, both JHA and 20E significantly induced DaKr-h1, but only 20E significantly induced DaBr-C, indicating the importance of hormones in metamorphosis. DaKr-h1 knockdown in larvae upregulated DaBr-C expression, resulting in precocious metamorphosis from larvae to pupae and the formation of miniature pupae. DaKr-h1 knockdown in pupae suppressed DaBr-C expression, increased emergence, caused abnormal morphology, and caused the formation of small-winged adults. These results suggest that DaKr-h1 is required for the metamorphosis of D. armandi. Our findings provide insight into the roles of DaKr-h1 and DaBr-C in JH-induced transcriptional repression and highlight DaKr-h1 as a potential target for metamorphosis suppression in D. armandi.

Susceptibility of the Non-Targeted Crustacean Eurytemora affinis to the Endocrine Disruptor Tebufenozide: A Transcriptomic Approach

Copepods are zooplanktonic crustaceans ubiquitously widespread in aquatic systems. Although they are not the target, copepods are exposed to a wide variety of pollutants such as insect growth regulators (IGRs). The aim of this study was to investigate the molecular response of a non-targeted organism, the copepod Eurytemora affinis, to an IGR. Adult males and females were exposed to two sub-lethal concentrations of tebufenozide (TEB). Our results indicate a sex-specific response with a higher sensitivity in males, potentially due to a differential activation of stress response pathways. In both sexes, exposure to TEB triggered similar pathways to those found in targeted species by modulating the transcription of early and late ecdysone responsive genes. Among them were genes involved in cuticle metabolism, muscle contraction, neurotransmission, and gametogenesis, whose mis-regulation could lead to moult, locomotor, and reproductive impairments. Furthermore, genes involved in epigenetic processes were found in both sexes, which highlights the potential impact of exposure to TEB on future generations. This work allows identification of (i) potential biomarkers of ecdysone agonists and (ii) further assessment of putative physiological responses to characterize the effects of TEB at higher biological levels. The present study reinforces the suitability of using E. affinis as an ecotoxicological model.

Gammarid exposure to pyriproxyfen and/or cadmium: what effects on the methylfarnesoate signalling pathway?

Due to expected changes in climate, it is predicted that disease-carrying mosquitoes will expand their geographical range, resulting in increased use of insect growth regulators (IGRs) to face their proliferation. Among IGRs, pyriproxyfen (PXF) is widely used and has been shown to prevent larvae from developing into adults, rendering them unable to reproduce. However, because of the similarity of crustacean and insect endocrine systems, PXF could also impact aquatic crustaceans. In addition, when spreading in the environment, PXF is found in a mixture with other pollutants such as metallic trace elements, which could alter its effect. Consequently, the present work was devoted to analysing the effects of PXF on the methylfarnesoate (MF) hormonal pathway of the freshwater amphipod Gammarus pulex, as well as its combined binary effects with cadmium (Cd), by measuring MF concentration, as well as the relative transcriptional expression of the farnesoic acid O-methyltransferase (FAMeT) (enzyme limiting the MF production), the methoprene-tolerant receptor (Met), and the broad-complex (BrC) as a transcription factor. Results revealed that single exposures to PXF or Cd have mainly overexpressed FAMeT, Met, and BrC but did not significantly affect MF concentration. Conversely, the mixture exposures seemed to suppress these effects and even achieve antagonistic effects. This work confirmed that PXF single exposure could impact non-target organisms such as amphipods through changes in hormonal pathways of MF. In the same way, it highlighted that Cd could also impair the endocrine system of exposed organisms. However, antagonistic effects have been observed in exposure to mixtures, suggesting different long-term consequences on the growth of amphipods under realistic exposure conditions.

The evolution of insect metamorphosis: a developmental and endocrine view

Developmental, genetic and endocrine data from diverse taxa provide insight into the evolution of insect metamorphosis. We equate the larva–pupa–adult of the Holometabola to the pronymph–nymph–adult of hemimetabolous insects. The hemimetabolous pronymph is a cryptic embryonic stage with unique endocrinology and behavioural modifications that probably served as preadaptations for the larva. It develops in the absence of juvenile hormone (JH) as embryonic primordia undergo patterning and morphogenesis, the processes that were arrested for the evolution of the larva. Embryonic JH then drives tissue differentiation and nymph formation. Experimental treatment of pronymphs with JH terminates patterning and induces differentiation, mimicking the processes that occurred during the evolution of the larva. Unpatterned portions of primordia persist in the larva, becoming imaginal discs that form pupal and adult structures. Key transcription factors are associated with the holometabolous life stages: Krüppel-homolog 1 (Kr-h1) in the larva, broad in the pupa and E93 in the adult. Kr-h1 mediates JH action and is found whenever JH acts, while the other two genes direct the formation of their corresponding stages. In hemimetabolous forms, the pronymph has low Broad expression, followed by Broad expression through the nymphal moults, then a switch to E93 to form the adult.

This article is part of the theme issue ‘The evolution of complete metamorphosis’.

Ecdysone inducible gene E75 from black tiger shrimp Penaeus monodon: Characterization and elucidation of its role in molting

Molting is controlled by ecdysteroids, which are synthesized and secreted by the Y-organ in crustaceans. Ecdysone inducible gene, E75, is an early-response gene in the 20-hydroxyecdysone (20E) signaling pathway, with crucial roles in arthropod development. Complementary DNA (cDNA) encoding Penaeus monodon E75 (PmE75) was cloned using RT-PCR and RACE. PmE75 cDNA was 3526 bp long and encoded a 799-amino acid protein. Tissue distribution analysis showed that PmE75 was expressed ubiquitously in selected tissues, and was relatively abundant in the epidermis, muscle, and hepatopancreas. Developmental expression revealed that PmE75 was expressed throughout its life cycle. Silencing PmE75 significantly decreased PmE75 expression. Shrimps injected with PBS and dsGFP started molting on Day 7 and had almost completed molting on Day 9, whereas dsPmE75-injected shrimp presented no signs of molting. These results suggested that PmE75 might be involved in molting. In situ hybridization results support this hypothesis. To explore the role of 20E and eyestalks in the regulation of molting in P. monodon, exogenous 20E injection and eyestalk ablation (ESA) were performed, and showed that 20E can induce the transcription and expression of PmE75 in the hepatopancreas, epidermis, and muscle, which were significantly elevated after ESA. These results provide further insights into our understanding of molting.

The crustacean ecdysone cassette: A gatekeeper for molt and metamorphosis

Arthropods have long been utilized as models to explore molecular function, and the findings derived from them can be applied throughout metazoa, including as a basis for medical research. This has led to the adoption of many representative insect models beyond Drosophila, as each lends its own unique perspective to questions in endocrinology and genetics. However, non-insect arthropods are yet to be realised for the potential insight they may provide in such studies. The Crustacea are among the most ancient arthropods from which insects descended, comprising a huge variety of life histories and ecological roles. Of the events in a typical crustacean development, metamorphosis is perhaps the most ubiquitous, challenging and highly studied. Despite this, our knowledge of the endocrinology which underpins metamorphosis is rudimentary at best; although several key molecules have been identified and studied in depth, the link between them is quite nebulous and leans heavily on well-explored insect models, which diverged from the Pancrustacea over 450 million years ago. As omics technologies become increasingly accessible, they bring the prospect of explorative molecular research which will allow us to uncover components and pathways unique to crustaceans. This review reconciles known components of crustacean metamorphosis and reflects on our findings in insects to outline a future search space, with focus given to the ecdysone cascade. To expand our knowledge of this ubiquitous endocrine system not only aids in our understanding of crustacean metamorphosis, but also provides a deeper insight into the adaptive capacity of arthropods throughout evolution.

Identification, expression, and endocrine-disruption of three ecdysone-responsive genes in the sentinel species Gammarus fossarum

Taking advantage of a large transcriptomic dataset recently obtained in the sentinel crustacean amphipod Gammarus fossarum, we developed an approach based on sequence similarity and phylogenetic reconstruction to identify key players involved in the endocrine regulation of G. fossarum. Our work identified three genes of interest: the nuclear receptors RXR and E75, and the regulator broad-complex (BR). Their involvement in the regulation of molting and reproduction, along with their sensitivity to chemical contamination were experimentally assessed by studying gene expression during the female reproductive cycle, and after laboratory exposure to model endocrine disrupting compounds (EDCs): pyriproxyfen, tebufenozide and piperonyl butoxide. RXR expression suggested a role of this gene in ecdysis and post-molting processes. E75 presented two expression peaks that suggested a role in vitellogenesis, and molting. BR expression showed no variation during molting/reproductive cycle. After exposure to the three EDCs, a strong inhibition of the inter-molt E75 peak was observed with tebufenozide, and an induction of RXR after exposure to pyriproxyfen and piperonyl butoxide. These results confirm the implication of RXR and E75 in hormonal regulation of female reproductive cycles in G. fossarum and their sensitivity towards EDCs opens the possibility of using them as specific endocrine disruption biomarkers.

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.

Optimizing Hybrid de Novo Transcriptome Assembly and Extending Genomic Resources for Giant Freshwater Prawns (Macrobrachium rosenbergii): The Identification of Genes and Markers Associated with Reproduction

The giant freshwater prawn, Macrobrachium rosenbergii, a sexually dimorphic decapod crustacean is currently the world’s most economically important cultured freshwater crustacean species. Despite its economic importance, there is currently a lack of genomic resources available for this species, and this has limited exploration of the molecular mechanisms that control the M. rosenbergii sex-differentiation system more widely in freshwater prawns. Here, we present the first hybrid transcriptome from M. rosenbergii applying RNA-Seq technologies directed at identifying genes that have potential functional roles in reproductive-related traits. A total of 13,733,210 combined raw reads (1720 Mbp) were obtained from Ion-Torrent PGM and 454 FLX. Bioinformatic analyses based on three state-of-the-art assemblers, the CLC Genomic Workbench, Trans-ABySS, and Trinity, that use single and multiple k-mer methods respectively, were used to analyse the data. The influence of multiple k-mers on assembly performance was assessed to gain insight into transcriptome assembly from short reads. After optimisation, de novo assembly resulted in 44,407 contigs with a mean length of 437 bp, and the assembled transcripts were further functionally annotated to detect single nucleotide polymorphisms and simple sequence repeat motifs. Gene expression analysis was also used to compare expression patterns from ovary and testis tissue libraries to identify genes with potential roles in reproduction and sex differentiation. The large transcript set assembled here represents the most comprehensive set of transcriptomic resources ever developed for reproduction traits in M. rosenbergii, and the large number of genetic markers predicted should constitute an invaluable resource for future genetic research studies on M. rosenbergii and can be applied more widely on other freshwater prawn species in the genus Macrobrachium.

How Did Arthropod Sesquiterpenoids and Ecdysteroids Arise? Comparison of Hormonal Pathway Genes in Noninsect Arthropod Genomes

The phylum Arthropoda contains the largest number of described living animal species, with insects and crustaceans dominating the terrestrial and aquatic environments, respectively. Their successful radiations have long been linked to their rigid exoskeleton in conjunction with their specialized endocrine systems. In order to understand how hormones can contribute to the evolution of these animals, here, we have categorized the sesquiterpenoid and ecdysteroid pathway genes in the noninsect arthropod genomes, which are known to play important roles in the regulation of molting and metamorphosis in insects. In our analyses, the majority of gene homologs involved in the biosynthetic, degradative, and signaling pathways of sesquiterpenoids and ecdysteroids can be identified, implying these two hormonal systems were present in the last common ancestor of arthropods. Moreover, we found that the “Broad-Complex” was specifically gained in the Pancrustacea, and the innovation of juvenile hormone (JH) in the insect linage correlates with the gain of the JH epoxidase (CYP15A1/C1) and the key residue changes in the binding domain of JH receptor (“Methoprene-tolerant”). Furthermore, the gain of “Phantom” differentiates chelicerates from the other arthropods in using ponasterone A rather than 20-hydroxyecdysone as molting hormone. This study establishes a comprehensive framework for interpreting the evolution of these vital hormonal pathways in these most successful animals, the arthropods, for the first time.

Identification of putative ecdysteroid and juvenile hormone pathway genes in the shrimp Neocaridina denticulata

Although the sesquiterpenoid juvenile hormone (JH) and the steroidal ecdysteroids are of vital importance to the development and reproduction of insects, our understanding of the evolution of these crucial hormonal regulators in other arthropods is limited. To better understand arthropod hormone evolution and regulation, here we describe the hormonal pathway genes (e.g. those involved in hormone biosynthesis, degradation, regulation and signal transduction) of a new decapod model, the shrimp Neocaridina denticulata. The majority of known insect sesquiterpenoid and ecdysteroid pathway genes and their regulators are contained in the N. denticulata genome. In the sesquiterpenoid pathway, these include biosynthetic pathway components: juvenile hormone acid methyltransferase (JHAMT); hormone binding protein: juvenile hormone binding protein (JHBP); and degradation pathway components: juvenile hormone esterase (JHE), juvenile hormone esterase binding protein (JHEBP) and juvenile hormone epoxide hydrolase (JHEH), with the JHBP, JHEBP and JHEH genes being discovered in a crustacean for the first time here. Ecdysteroid biosynthetic pathway genes identified include spook, phantom, disembodied, shadow and CYP18. Potential hormonal regulators and signal transducers such as allatostatins (ASTs), Methoprene-tolerant (Met), Retinoid X receptor (RXR), Ecdysone receptor (EcR), calponin-like protein Chd64, FK509-binding protein (FKBP39), Broad-complex (Br-c), and crustacean hyperglycemic hormone/molt-inhibiting hormone/gonad-inhibiting hormone (CHH/MIH/GIH) genes are all present in the shrimp N. denticulata. To our knowledge, this is the first report of these hormonal pathways and their regulatory genes together in a single decapod, providing a vital resource for further research into development, reproduction, endocrinology and evolution of crustaceans, and arthropods in general.

Proteomic analysis of ovarian proteins and characterization of thymosin-β and RAC-GTPase activating protein 1 of the giant tiger shrimp Penaeus monodon

Cellular proteomics of total proteins in ovaries of domesticated and wild giant tiger shrimp (Penaeus monodon) were examined using GeLC-MS/MS. In total, 1638 proteins matched those previously deposited in databases and 1253 (76.50%) of these significantly matched known proteins. Several reproduction-related proteins (e.g. Cdc2, Cyclin B, Cdc25, 14-3-3, thymosin-β and Rac-GTPase activating protein 1) were identified. In addition, the full-length cDNA of P. monodon thymosin-β (PmTmsb; 1084 bp with an ORF of 387 bp and 128 deduced aa) and Rac-GTPase activating protein 1 (PmRacgap1; an ORF of 1881 bp and 626 deduced aa) were further characterized. PmTmsb was constitutively expressed in all tissues. In contrast, PmRacgap1 was more abundantly expressed in gonads than in several non-reproductive tissues (e.g. subcuticular epithelium, hepatopancreas, intestine, pleopods, stomach and thoracic ganglion). The expression levels of PmTmsb and PmRacgap1 in ovaries of wild adult broodstock were significantly greater than those in ovaries of juveniles (P<0.05). However, their expression levels did not vary significantly during ovarian development stages in intact broodstock. However, eyestalk ablation resulted in a significant reduction in PmTmsb expression at stages I and III ovaries (P<0.05), although it did not affect PmRacgap1 transcription significantly at these stages. On the other hand, use of polyclonal antibodies derived from recombinant PmTmsb and PmRacgap1 revealed that levels of both proteins decreased at the late stage (IV) of ovarian development. Our results suggested that PmTmsb and PmRacgap1 may act as negative effectors during ovarian development in P. monodon.

Characterization and expression of cell division cycle 2 (Cdc2) mRNA and protein during ovarian development of the giant tiger shrimp Penaeus monodon

The meiotic maturation of oocytes is regulated by the maturation-promoting factor (MPF), a complex of Cdc2 (Cdk1) and Cyclin B. Here, the complete open reading frame (ORF) of Cdc2 in Penaeus monodon was characterized. PmCdc2 were 900bp in length corresponding to a polypeptide of 299 amino acids with the conserved Thr14, Tyr15 and Thr161 residues. Quantitative real-time PCR indicated that the expression level of PmCdc2 in wild intact broodstock was significantly increased in stages II (vitellogenic) and III (early cortical rod) ovaries relative to stage I (previtellogenic) ovaries and peaked in stage IV (mature) ovaries (P<0.05). The expression level of PmCdc2 in stages I-IV ovaries of eyestalk-ablated broodstock was greater than that of the same ovarian developmental stages in intact broodstock (P<0.05). Expression levels of PmCdc2 in ovaries of 18-month-old P. monodon upon 5-HT injection (50μg/g body weight) were significantly increased at 1hour post injection (hpi, P<0.05). Recombinant PmCdc2 protein and its polyclonal antibody were successfully produced. Western blot analysis revealed the expected 34kDa band (PmCdc2) along with a smaller band of 23kDa (ribosomal protein S3) in ovaries of juveniles and various ovarian stages of broodstock. Using phospho-Cdc2 (Thr161) polyclonal antibody, the positive signal of 34kDa was observed in all ovarian stages but the most intense signal was found in stage IV ovaries. Results in the present study indicated that PmCdc2 gene/protein plays an important role in the development and maturation of oocytes/ovaries in P. monodon.

Characterization, expression and localization of valosin-containing protein in ovaries of the giant tiger shrimp Penaeus monodon

Valosin-containing protein (VCP), a member of the ATPase-associated with diverse cellular activity (AAA) family, was identified from the giant tiger shrimp (Penaeus monodon). The full-length cDNA of the PmVCP mRNA consisted of 2,724 bp containing an ORF of 2,367 bp corresponding to a deduced polypeptide of 788 amino acids. The deduced PmVCP protein contained two putative Cdc48 domains (positions 17-103, E-value=2.00e-36 and 120-186, E-value=3.60e-11) and two putative AAA domains (positions 232-368, E-value=3.67e-24 and 505-644, E-value=3.73e-25). PmVCP mRNA expression in ovaries was greater than that in testes in both juveniles and broodstock. PmVCP was significantly up-regulated in stages II and IV ovaries in intact wild broodstock (P<0.05) but it was not differentially expressed during ovarian development in eyestalk-ablated broodstock (P>0.05). The expression level of PmVCP mRNA in ovaries of 14-month-old shrimp was not affected by progesterone injection (0.1μg/g body weight, P>0.05). In contrast, exogenous 5-HT administration (50μg/g body weight) resulted in an increase of PmVCP mRNA in ovaries of 18-month-old shrimp at 6 and 24h post-injection (hpi) (P<0.05). The rPmCdc48-VCP protein and its polyclonal antibody were successfully produced. Cellular localization revealed that PmVCP was localized in the ooplasm of previtellogenic oocytes. Subsequently, it was translocated into the germinal vesicle of vitellogenic oocytes. Interestingly, PmVCP was found in nucleo-cytoplasmic compartments, in the cytoskeletal architecture and in the plasma membrane of mature oocytes in both intact and eyestalk-ablated broodstock.