Identification of putative regulatory region of insulin-like androgenic gland hormone gene (IAG) in the prawn Macrobrachium nipponense and proteins that interact with IAG by using yeast two-hybrid system

Identification of Candidate Male-Reproduction-Related Genes from the Testis and Androgenic Gland of Macrobrachium nipponense, Regulated by PDHE1, through Transcriptome Profiling Analysis

The previous publication identified that pyruvate dehydrogenase E1 (PDHE1) positively regulated the process of male reproduction in M. nipponense through affecting the expressions of insulin-like androgenic gland hormone. The present study aimed to identify the potential male-reproduction-related genes that were regulated by PDHE1 through performing the transcriptome profiling analysis in the testis and androgenic gland after the knockdown of the expressions of PDHE1 by the injection of dsPDHE1. Both RNA-Seq and qPCR analysis identified the significant decreases in PDHE1 expressions in the testis and androgenic gland in dsPDHE1-injected prawns compared to those in dsGFP-injected prawns, indicating the efficiency of dsPDHE1 in the present study. Transcriptome profiling analysis identified 56 and 127 differentially expressed genes (DEGs) in the testis and androgenic gland, respectively. KEGG analysis revealed that the energy-metabolism-related pathways represented the main enriched metabolic pathways of DEGs in both the testis and androgenic gland, including pyruvate metabolism, the Citrate cycle (TCA cycle), Glycolysis/Gluconeogenesis, and the Glucagon signaling pathway. Thus, it is predicted that these metabolic pathways and the DEGs from these metabolic pathways regulated by PDHE1 may be involved in the regulation of male reproduction in M. nipponense. Furthermore, four genes were found to be differentially expressed in both the testis and androgenic gland, of which ribosomal protein S3 was down-regulated and uncharacterized protein LOC113829596 was up-regulated in both the testis and androgenic gland in dsPDHE1-injected prawns. The present study provided valuable evidence for the establishment of an artificial technique to regulate the process of male reproduction in M. nipponense.

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

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

Identification of Male Sex-Related Genes Regulated by SDHB in Macrobrachium nipponense Based on Transcriptome Analysis after an RNAi Knockdown

The oriental river prawn (Macrobrachium nipponense) is a commercially important species in Asia. A previous study showed that the succinate dehydrogenase complex iron sulfur subunit B (SDHB) gene participates in testes development in this species through its effect on the expression of the insulin-like androgenic gland hormone gene. This study knocked-down the Mn-SDHB genes in M. nipponense using RNAi. A transcriptome analysis of the androgenic gland and testes was then performed to discover the male sex-related genes regulated by SDHB and investigate the mechanism of male sexual development in this species. More than 16,623 unigenes were discovered in each sample generated. In the androgenic gland, most of the differentially expressed genes were enriched in the hypertrophic cardiomyopathy pathway, while in the testes, they were enriched in the citrate cycle pathway. In addition, after Mn-SDHB knockdown, five genes were found to be downregulated in the androgenic gland in a series of biological processes associated with phosphorylated carbohydrate synthesis and transformations in the glycolysis/gluconeogenesis pathway. Moreover, a total of nine male sex-related genes were identified including Pro-resilin, insulin-like androgenic gland hormone, Protein mono-ADP-ribosyltransferase PAPR11, DNAJC2, C-type Lectin-1, Tyrosine-protein kinase Yes, Vigilin, and Sperm motility kinase Y-like, demonstrating the regulatory effects of Mn-SDHB, and providing a reference for the further study of the mechanisms of male development in M. nipponense.

RNAi Analysis of Potential Functions of Cyclin B3 in Reproduction of Male Oriental River Prawns (Macrobrachium nipponense)

Cyclin B3 (CycB3) is involved in the metabolic pathway of the cell cycle, playing essential roles in the regulation of cell proliferation and mitosis. CycB3 is also predicted to be involved in the reproduction of male oriental river prawns (Macrobrachium nipponense). In this study, the potential functions of CycB3 in M. nipponense were investigated using quantitative real-time PCR, RNA interference, and histological observations. The full-length DNA sequence of CycB3 in M. nipponense was 2147 base pairs (bp) long. An open reading frame of 1500 bp was found, encoding 499 amino acids. A highly conserved destruction box and two conserved cyclin motifs were found in the protein sequence of Mn-CycB3. Phylogenetic tree analysis revealed that this protein sequence was evolutionarily close to that of CycB3s of crustacean species. Quantitative real-time PCR analysis results suggested that CycB3 was involved in the process of spermiogenesis, oogenesis, and embryogenesis in M. nipponense. RNA interference analysis showed that CycB3 had a positive regulatory relationship with insulin-like androgenic gland hormone (IAG) in M. nipponense. In addition, sperm were rarely observed in the testis of double-stranded CycB3-injected prawns after 14 days of treatment, and sperm abundance was dramatically lower than that in the double-stranded GFP-injected prawns on the same day. This result indicated that CycB3 can regulate the testis reproduction in M. nipponense through inhibiting the IAG expressions. Overall, these results indicated that CycB3 plays essential roles in the regulation of male reproduction in M. nipponense, which may promote the studies of male reproduction in other crustacean species.

RNA interference analysis of potential functions of cyclin A in the reproductive development of male oriental river prawns (Macrobrachium nipponense)

Cyclin A (CycA) plays essential roles in regulating multiple steps of the cell cycle, and it affects gonad development in mammals and invertebrates. Previous RNA interference (RNAi) analysis revealed that knocking-down the expression of CycA in female oriental river prawns (Macrobrachium nipponense) inhibited ovarian development. CycA was also predicted to have regulatory roles in reproductive development of male M. nipponense based on significant changes of Mn-CycA expression after eyestalk ablation. The goal of this study was to investigate the potential functions of CycA in the reproductive development of male M. nipponense using RNAi and histological observations. Quantitative real-time PCR analysis revealed that both single-side and double-side eyestalk ablation stimulated the expressions of Mn-CycA, and the expression was higher in prawns with double-side eyestalk ablation (p < 0.05). Mn-CycA expression was significantly higher in the testis and androgenic gland during the reproductive season than during the non-reproductive season (p < 0.05). In the RNAi analysis, Mn-CycA expression significantly decreased after prawns were injected with dsCycA, and the expression of insulin-like androgenic gland hormone (Mn-IAG) also decreased as Mn-CycA expression decreased. This result indicated that CycA positively regulated the expression of IAG in M. nipponense. Histological observations revealed that the number of sperm decreased dramatically to <5% of the total cells in the testis of the dsCycA-treated group compared to that of control group on day 14, indicating that knockdown of Mn-CycA expression inhibited testis development by affecting the expression of Mn-IAG in M. nipponense. These results highlighted the functions of CycA in male reproductive development of M. nipponense, which can be applied to future studies of male reproduction in other crustacean species.

RNA Interference Analysis of the Functions of Cyclin B in Male Reproductive Development of the Oriental River Prawn (Macrobrachium nipponense)

Cyclin B (CycB) plays essential roles in cell proliferation and promotes gonad development in many crustaceans. The goal of this study was to investigate the regulatory roles of this gene in the reproductive development of male oriental river prawns (Macrobrachium nipponense). A phylo-genetic tree analysis revealed that the protein sequence of Mn-CycB was most closely related to those of freshwater prawns, whereas the evolutionary distance from crabs was much longer. A quantitative PCR analysis showed that the expression of Mn-CycB was highest in the gonad of both male and female prawns compared to that in other tissues (p < 0.05), indicating that this gene may play essential roles in the regulation of both testis and ovary development in M. nipponense. In males, Mn-CycB expression in the testis and androgenic gland was higher during the reproductive season than during the non-reproductive season (p < 0.05), implying that CycB plays essential roles in the reproductive development of male M. nipponense. An RNA interference analysis revealed that the Mn-insulin-like androgenic gland hormone expression decreased as the Mn-CycB expression decreased, and that few sperm were detected 14 days after the dsCycB treatment, indicating that CycB positively affects testis development in M. nipponense. The results of this study highlight the functions of CycB in M. nipponense, and they can be applied to studies of male reproductive development in other crustacean species.

Two Short Repeats in the 5′ Untranslated Region of Insulin-like Androgenic Gland Factor in Procambarus clarkii (PcIAG) That Regulate PcIAG Expression

Insulin-like androgenic gland factor (IAG) plays an important role in sex manipulation in decapods. Understanding the molecular regulation mechanism of IAG in Procambarus clarkii (PcIAG) is important for realizing its sex control. In this study, the promoter and gene structure of PcIAG, mRNA, and miRNA expression profiles after interfering with two siRNAs synthesized according to the two short repeats in the 5′ untranslated regions (5′UTR) of PcIAG were analyzed, and miRNAs of exosomes were investigated to explore the role of repeated sequences with tandem two short repeats located in the 5′UTR of PcIAG isolated from the androgenic gland (AG) in the regulation of IAG expression. The results showed that the repeated sequences of 5′UTR only occurred completely in the cDNA from AG, and the function of the two repeats was different in regulating the expression of PcIAG, in which the Wnt signaling pathway may be involved. Furthermore, we found that six miRNAs including miR-133, miR-193, miR-34, miR-1, miR-100, and let-7 might be involved in the regulation of the expression of PcIAG, wherein miR-133 might directly be related with the repeated sequences of 5′UTR.

Molecular identification and putative role of insulin growth factor binding protein-related protein (IGFBP-rp) in the swimming crab Portunus trituberculatus

The insulin-like growth factor/insulin-like polypeptide (IGF/ILP) signaling is vital for growth, physiological metabolism, development, and reproduction. Insulin-like growth factor-binding protein (IGFBP) is involved in the insulin signaling pathway in both vertebrates and invertebrates and is critical for various physiology functions. Herein, we cloned and characterized the full-length cDNA of IGFBP-rp in the swimming crab, Portunus trituberculatus (PtIGFBP-rp). The deduced amino acid sequence of PtIGFBP-rp was found to contain three key domains (insulin-like binding (IB) domain, the kazale-type serine protease inhibitor (KAZAL) domain, and the immunoglobulin-like C2 (IGc2) domain). Results showed that PtIGFBP-rp shared the same expression pattern as P. trituberculatus insulin androgenic gland hormone (PtIAG) transcripts during the embryonic larval, juvenile crab stage and the androgenic gland (AG) developmental cycle. Moreover, PtIGFBP-rp transcripts were also present in high abundance in hepatopancreas, muscle, and androgenic glands. The regulatory relationship between PtIGFBP-rp and PtIAG was investigated by RNA interference and co-localization assays, which showed a co-localization relationship and feedback regulation between them. Bilateral eye stalk ablation (ESA) increased the expression of PtIGFBP-rp in the AG at 7 d after surgery. These results demonstrate the involvement of PtIGFBP-rp in the signaling regulatory network of IAG in P. trituberculatus.

RNA Interference Analysis Reveals the Positive Regulatory Role of Ferritin in Testis Development in the Oriental River Prawn, Macrobrachium nipponense

Ferritin plays an essential role in organismic and cellular iron homeostasis in Macrobrachium nipponense. In this study, we aimed to investigate the role of ferritin in the sexual development of male M. nipponense. According to the qPCR analysis of different tissues and developmental stages, ferritin exhibited high expression levels in the testis and androgenic gland, from post-larval developmental stage 5 (PL5) to PL15, indicating that it may be involved in gonad differentiation and development, especially in male sexual development. In situ hybridization and qPCR analysis in various reproductive cycles of the testis indicated that ferritin may play an essential role in spermatogonia development in M. nipponense. RNAi analysis revealed that ferritin positively affected mRNA expression of the insulin-like androgenic gland (Mn-IAG) and the secretion of testosterone, and thus positively affected testis development in M. nipponense. This study highlighted the functions of ferritin in the sexual development of male M. nipponense and provided important information for the establishment of a technique to regulate the process of testis development in M. nipponense.

Identification of Important Genes Involved in the Sex-Differentiation Mechanism of Oriental River Prawn, Macrobrachium nipponense, During the Gonad Differentiation and Development Period

Identification of important genes, involved in the gonad differentiation and development, plays essential roles in the establishment of the artificial technique to regulate the process of testis development in M. nipponense. In this study, we aimed to determine the sensitive period of gonad differentiation and development through hematoxylin and eosin (HE) staining. The important genes involved in the gonad differentiation and development of M. nipponense were then identified through transcriptome profiling analysis during the sensitive period of gonad differentiation and development. HE staining analysis revealed that the sensitive period of gonad differentiation and development was from the post–larval developmental stages 5 (PL5) to PL25, which was dramatically faster than was for the other identified aquatic animals. The transcriptome profiling analysis predicted that phagosome, lysosome, oxidative phosphorylation, and glycolysis/gluconeogenesis play essential roles in the mechanism of gonad differentiation and development in M. nipponense. A total of 29 genes were further identified as the candidate genes, involved in the process of gonad differentiation and development in M. nipponense, based on the gene annotation and gene expression pattern. The qPCR analysis of Mn-JHEH, Mn-DHP, Mn-ALY, and Mn-SMA6 during the whole developmental process revealed that all of these four genes showed high expression levels during the sensitive period of gonad differentiation and development in M. nipponense. Mn-JHEH, Mn-DHP, and Mn-ALY showed higher expressions at PL25F than at PL25M, while Mn-SMA6 showed a higher expression at PL25M. The RNA interference (RNAi) analysis was further used to investigate the potential functions of SMA6 in male sexual development of M. nipponense. The RNAi analysis revealed that SMA6 positively regulated the testis development in M. nipponense by affecting the expression of Mn-IAG. This study provided valuable evidences for the establishment of the technique to regulate the process of gonad development in M. nipponense.

Identification of potential functions of polo-like kinase 1 in male reproductive development of the oriental river prawn (Macrobrachium nipponense) by RNA interference analysis

Polo-like kinase 1 (Plk1) has multiple functions in the cell cycle, including in the maturation of centrosomes during the G2/M transition, the separation of centrosomes, and the activation of cyclin-dependent kinase 1 expression and spindle assembly. In this study, we investigated the potential regulatory roles of Plk1 in the reproductive development of the male oriental river prawn (Machrobrachium nipponense). The full cDNA sequence of Mn-Plk1 was 2360 base pairs long, with an open reading frame of 1836 base pairs encoding 611 amino acids. Protein sequence alignment identified a conserved serine/threonine kinase domain and two Polo-boxes. Phylogenetic tree analysis revealed that Mn-Plk1 had the closest evolutionary distance with Plk1s of freshwater prawns and then with those of crustacean species, whereas the evolutionary distance with mollusks was much more distant. Quantitative PCR analysis predicted that Mn-Plk1 plays essential roles in the regulation of gonad development. RNA interference analysis and histological observations showed that expression of insulin-like androgenic gland hormone decreased as the expression of Mn-Plk1 decreased, and fewer than 5% of cells were sperm cells at day 14 in the dsPlk1 injected prawns. This result indicated that Plk1 positively regulated testis development in M. nipponense by affecting the expression of this hormone. Our results highlight the functions of Plk1 in M. nipponense and provide valuable information that can be applied to establish artificial techniques to regulate testis development in this species.

Identification of candidate genes from androgenic gland in Macrobrachium nipponense regulated by eyestalk ablation

The eyestalk of crustaceans, such as Macrobrachium nipponense, contains many neurosecretory hormones affecting the process of reproduction, molting, metabolism of glucose, and other functions. In this study, important metabolic pathways and candidate genes involved in male sexual development were selected from M. nipponense. The methodology involved performing long-read and next generation transcriptome sequencing of genes from the androgenic gland after eyestalk ablation. qPCR analysis revealed that the mRNA expression of Mn-IAG was significantly increased after ablation of both the single-side (SS) and double-side (DS) eyestalk, compared with the control group (CG). The long-read transcriptome generated 49,840 non-redundant transcripts. A total of 1319, 2092 and 4351 differentially expressed genes (DEGs) were identified between CG versus SS, SS versus DS and CG versus DS, respectively. These data indicated that ablation of the double-sided eyestalk played stronger regulatory roles than the single-side ablation on male sexual development in M. nipponense. This was consistent with the qPCR analysis. Cell Cycle, Cellular Senescence, Oxidative Phosphorylation, Glycolysis/Gluconeogenesis and Steroid Hormone Biosynthesis were the primary enriched metabolic pathways in all three comparisons, and the important genes from these metabolic pathways were also selected. qPCR permitted secondary confirmation of ten DEGs identified through RNA-seq. RNAi-mediated silencing analyses of Hydroxysteroid dehydrogenase like 1 (HSDL1) revealed that HSDL1 has a positive regulatory effect on testes development. This study provides valuable insight into male sexual development in M. nipponense, including metabolic pathways and genes, paving the way for advanced studies on male sexual development in this species and in other crustaceans.

Insulin-like androgenic gland hormone from the shrimp Fenneropenaeus merguiensis: Expression, gene organization and transcript variants

Male sex differentiation in the crustacean is best known to be controlled by the insulin-like androgenic gland hormone (IAG). In this report, the cDNA and gene of the shrimp Fenneropenaeus merguiensis FmIAG were studied and characterized. FmIAG gene shares a high sequence identity in the coding region as well as the promoter region with that of F. chinensis. FmIAG gene is most likely consists of 5 exons and 4 introns. The cDNA reported here is the most abundant transcript that retained cryptic intron 4. The use of different splicing acceptor sites in exon 2 can produce a long-form FmIAG transcript variant with 6 additional amino acids inserted. Splicing of cryptic intron 4 would produce a transcript variant with a different C-terminal end. Therefore 4 different FmIAG transcripts can be produced from the FmIAG gene. During the molt cycle, the expression level of FmIAG was low in the early intermolt, increase steadily towards the late premolt and decreased rapidly in the early postmolt. In addition to the androgenic gland, FmIAG is also expressed in the hepatopancreas and ovary of adult females. Unilateral eyestalk ablation caused a significant increase in FmIAG transcript suggesting that the eyestalk consists of inhibiting factor(s) that suppressesFmIAGexpression. To explore the function of FmIAG in males, injection of FmIAG dsRNA knock-down the expression of FmIAG and up-regulated the expression of the vitellogenin gene in the testis and hepatopancreas. Interestingly a CHH-like gene identified in the androgenic gland was down-regulated. CHH-like gene knock-down resulted in altered expression of FmIAG in males suggesting that the CHH-like may be involved in FmIAG's regulation. RT-PCR with specific primers to the different transcript variant were used to determine if there is an association of different sizes of male and the type of IAG transcript. Results indicated that a high percentage of the large male shrimp expressed the long-form of FmIAG. The results suggested that FmIAG may be useful as a size marker for male shrimp aquaculture. In summary, the results of this study have expanded our knowledge of shrimp insulin-like androgenic gland hormone in male sex development and its potential role as a marker gene for growth regulation in shrimp.

A chromosome-level genome assembly of the oriental river prawn, Macrobrachium nipponense

BACKGROUND

The oriental river prawn, Macrobrachium nipponense, is an economically important shrimp in China. Male prawns have higher commercial value than females because the former grow faster and reach larger sizes. It is therefore important to reveal sex-differentiation and development mechanisms of the oriental river prawn to enable genetic improvement.

RESULTS

We sequenced 293.3 Gb of raw Illumina short reads and 405.7 Gb of Pacific Biosciences long reads. The final whole-genome assembly of the Oriental river prawn was ∼4.5 Gb in size, with predictions of 44,086 protein-coding genes. A total of 49 chromosomes were determined, with an anchor ratio of 94.7% and a scaffold N50 of 86.8 Mb. A whole-genome duplication event was deduced to have happened 109.8 million years ago. By integration of genome and transcriptome data, 21 genes were predicted as sex-related candidate genes.

CONCLUSION

The first high-quality chromosome-level genome assembly of the oriental river prawn was obtained. These genomic data, along with transcriptome sequences, are essential for understanding sex-differentiation and development mechanisms in the oriental river prawn, as well as providing genetic resources for in-depth studies on developmental and evolutionary biology in arthropods.

Insights into carbohydrate metabolism from an insulin-like peptide in Macrobrachium rosenbergii

This study identified an insulin-like peptide (ILP) in Macrobrachium rosenbergii termed Mr-ILP and further investigated its function through glucose injection and RNAi. With the analysis of five other glucose metabolism related genes, this study shed light on the molecular mechanism of carbohydrate metabolism in crustaceans. Mr-ILP shared the typical skeleton with six conserved cysteine and mainly expressed in neuroendocrine system. In M. rosenbergii, the elevated hemolymph glucose concentration after glucose injection returned to basal levels in short time, implying an efficient regulatory system in carbohydrate metabolism. Hyperglycemic related genes answered the elevated hemolymph glucose concentration quickly with significant decreased expression level, while Mr-ILP showed delayed response. Instead, glycolysis increased after glucose injection, which indicated glycolysis might play an important role in lowering the abnormally high glucose level. In vivo silencing of Mr-ILP, by injecting the prawns with double-stranded RNA (dsRNA) for 21 days reduced its expression by approximately 75%. Accordingly, glycogen synthase decreased and the trehalose and glycogen level in the hepatopancreas were significantly reduced, indicating the function of Mr-ILP in oligosaccharide and polysaccharide accumulation. When Mr-ILP was silenced, the expression of hyperglycemic related genes were enhanced, but the hemolymph glucose level was not elevated significantly, which might attribute to the increased glycolysis to keep a balanced glucose level in hemolymph.

De novo gonad transcriptome analysis of the common littoral shrimp Palaemon serratus: novel insights into sex-related genes

BACKGROUND

The common littoral shrimp Palaemon serratus is an economically important decapod resource in some European communities. Aquaculture practices prevent the genetic deterioration of wild stocks caused by overfishing and at the same time enhance the production. The biotechnological manipulation of sex-related genes has the proved potential to improve the aquaculture production but the scarcity of genomic data about P. serratus hinders these applications. RNA-Seq analysis has been performed on ovary and testis samples to generate a reference gonadal transcriptome. Differential expression analyses were conducted between three ovary and three testis samples sequenced by Illumina HiSeq 4000 PE100 to reveal sex-related genes with sex-biased or sex-specific expression patterns.

RESULTS

A total of 224.5 and 281.1 million paired-end reads were produced from ovary and testis samples, respectively. De novo assembly of ovary and testis trimmed reads yielded a transcriptome with 39,186 transcripts. The 29.57% of the transcriptome retrieved at least one annotation and 11,087 differentially expressed genes (DEGs) were detected between ovary and testis replicates. Six thousand two hundred seven genes were up-regulated in ovaries meanwhile 4880 genes were up-regulated in testes. Candidate genes to be involved in sexual development and gonadal development processes were retrieved from the transcriptome. These sex-related genes were discussed taking into account whether they were up-regulated in ovary, up-regulated in testis or not differentially expressed between gonads and in the framework of previous findings in other crustacean species.

CONCLUSIONS

This is the first transcriptome analysis of P. serratus gonads using RNA-Seq technology. Interesting findings about sex-related genes from an evolutionary perspective (such as Dmrt1) and for putative future aquaculture applications (Iag or vitellogenesis genes) are reported here. We provide a valuable dataset that will facilitate further research into the reproductive biology of this shrimp.

Identification of potentially novel functions of DNA polymerase zeta catalytic subunit in oriental river prawn, Macrobrachium nipoponense: cloning, qPCR, in situ hybridization and RNAi analysis

The goal of this study was to analyze the functions of DNA polymerase zeta catalytic subunit (Rev3) in the oriental river prawn Macrobrachium nipponense (Mn-Rev3) with a focus on its potential roles in sex differentiation and development. The full length of Mn-Rev3 cDNA sequence was 6832 base pairs (bp) with an open reading frame of 6102 bp encoding 2033 amino acids. Mn-Rev3 showed the closest evolutionary relationship with Penaeus vannamei. The highest expression level of Mn-Rev3 occurred in the hepatopancreas and strong signals were observed in hepatopancreas cells, suggesting that Mn-Rev3 played a role in the immune system. Expression levels of Mn-Rev3 also were relatively high in the androgenic gland and testis, suggesting its potential roles in male sexual differentiation and development. During development, expression of Mn-Rev3 was highest on larval day 15 and relatively high from post-larval day 1 (PL1) to PL15, indicating that it played essential roles in promoting metamorphosis and gonad differentiation and development in M. nipponense. Strong Mn-Rev3 signals were detected in spermatids, spermatocytes, and sperm in the testes, and Mn-Rev3 expression was higher in the testes during the reproductive season than in the non-reproductive season. This result indicated that Rev3 promoted whole testis development, and especially sperm development, in M. nipponense. The expression level of Mn-Rev3 was high from ovary V to ovary II stages, indicating that Rev3 may be involved in yolk deposition. The expression level of Mn-insulin-like androgenic gland hormone (Mn-IAG) and the content of testosterone showed the same expression pattern as that of Mn-Rev3 after injection of double-stranded RNA of Mn-Rev3, which indicated that Rev3 had positive effects on male sexual differentiation and development in M. nipponense. The results of this study advance our understanding of male sexual development in M. nipponense and provide the basis for further studies of male sexual differentiation and development in crustaceans.

Potential Functions of Gem-Associated Protein 2-Like Isoform X1 in the Oriental River Prawn Macrobrachium nipponense: Cloning, qPCR, In Situ Hybridization, and RNAi Analysis

Gem-associated protein 2-like isoform X1 (GEM) was previously predicted to be involved in the sexual development of male Macrobrachium nipponense. In this study, we analyze the GEM functions in depth using quantitative polymerase chain reaction (qPCR), in situ hybridization, and RNA interference (RNAi). The full-length Mn-GEM cDNA sequence was 1018 base pairs (bp) long with an open reading frame of 777 bp encoding 258 amino acids. qPCR analysis of Mn-GEM in different tissues and developmental stages showed that Mn-GEM was highly expressed in the gonad and from post-larval developmental stage day 5 (PL5) to PL15, which indicated that GEM has potential roles in gonad differentiation and development in M. nipponense. In situ hybridization and qPCR analysis of various stages of the reproductive cycle of the testis and ovary indicated that GEM may promote spermatid development and gametogenesis in M. nipponense. After injecting with double-stranded RNA (dsRNA) of Mn-GEM, mRNA expression of Mn-insulin-like androgenic gland hormone (Mn-IAG) and the content of testosterone increased with the decrease of Mn-GEM expression, indicating that GEM has negative effects on the male sexual differentiation and development in M. nipponense. Results of this study highlight the functions of GEM in M. nipponense, which can be applied to future studies of male sexual development in M. nipponense and other crustacean species.

Identification of Carassius auratus gibelio liver cell proteins interacting with the GABAA receptor γ2 subunit using a yeast two-hybrid system

The γ-aminobutyric acid type A (GABA_A) receptor is an important pentameric inhibitory neurotransmitter receptor, and the γ2 subunit of this receptor plays a key role in potentiation of the GABA_A response. We previously detected that the expression of GABA_A receptor in the livers of Carassius auratus gibelio significantly increased after medication (avermectin and difloxacin treatment). In order to better understand the mechanism of action of the GABA_A receptor γ2 subunit in the livers of C. auratus gibelio, we constructed a C. auratus gibelio liver cDNA library (the titer value of 1.2 × 10⁶ cfu/mL) and identified the proteins that interact with the GABA_A receptor γ2 subunit by using a yeast two-hybrid assay. The yeast two-hybrid screening yielded seven positive clones, namely, prelid3b, cdc42, sgk1, spg21, proteasome, chia.5, and AP-3 complex subunit beta-1, all of which have been annotated by the NCBI database. The functions of these proteins are complex; therefore, additional studies are required to determine the specific interactions of these proteins with the GABA_A receptor γ2 subunit in the liver of C. auratus gibelio. Although the interactions identified by the yeast two-hybrid system should be considered as preliminary results, the findings of this study may provide further direction and a foundation for future research focusing on the mechanisms of the GABA_A receptor γ2 subunit in C. auratus gibelio livers.