Selenium mitigated cadmium-induced ovarian retardation in female Procambarus clarkii by regulating vitellogenin synthesis and transfer in the hepatopancreas

Cadmium (Cd) is prevalent in aquatic ecosystems and accumulates in various tissues of aquatic organisms, leading to severe biological toxicity. Selenium (Se) is recognized for mitigating heavy metal toxicity, though its protective effects against Cd in aquatic crustaceans remain underexplored. This study, therefore, assessed the effects of dietary Cd (15 mg/kg) exposure and Se (6 mg/kg) supplementation on the hepatopancreas and ovaries of female crayfish to uncover the mechanisms of Cd toxicity and the protective role of Se. The results showed that Cd accumulation in the hepatopancreas caused a reduced hepatopancreas index (HPI), decreased protein content, histopathological damage, and oxidative stress, while Se supplementation reduced Cd levels, mitigated damage, and restored tissue integrity and antioxidant defenses. Transcriptomic analysis further revealed significant alterations in gene expression related to detoxification, lipid metabolism, and energy production in response to Cd exposure, which were partially or fully restored by Se supplementation. Additionally, Se alleviated Cd-induced inhibition of ovarian development, as evidenced by improved ovary index, enhanced oocyte development, and normalization of essential trace element levels. Mechanistically, Se restored the Cd-disrupted vitellogenin (Vtg) synthesis in the hepatopancreas via regulating the mRNA expression of hsp70 and genes related to the molt-inhibiting hormone (MIH) (mih, rxr, and ecr). Overall, these findings indicate that Se supplementation mitigated Cd-induced hepatopancreatic dysfunction, restored Vtg synthesis, and consequently counteracted the inhibition of ovarian development in adult female crayfish.

Comparative transcriptomic analysis of ovaries from high and low egg-laying Lingyun black-bone chickens

Egg‐laying rate is mainly determined by ovarian function and regulated by the hypothalamic‐pituitary‐gonadal axis; however, the mechanism by which the ovary regulates the egg‐laying rate is still poorly understood. The purpose of this study was to compare the differences in the transcriptomes of the ovary of Lingyun black‐bone chickens with relatively high and low egg‐laying rates and screen candidate genes related to the egg‐laying rate. RNA‐sequencing (RNA‐Seq) was conducted to explore the chicken transcriptome from the ovarian tissue of six Lingyun black‐bone chickens with high (group G, n = 3) and low (group D, n = 3) egg‐laying rates. The results showed that 235 differentially expressed genes (DEGs) were identified between the chickens with high and low egg‐laying rates; among them, 209 DEGs were up‐regulated and 26 DEGs were down‐regulated. Gene Ontology analysis showed that the up‐regulated 209 DEGs were enriched in 50 GO terms and the down‐regulated 26 DEGs were enriched in 40 GO terms. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that up‐regulated DEGs were significantly enriched in 25 pathways and down‐regulated DEGs were significantly enriched in three pathways. Among the pathways, we found the longevity regulating pathway‐multiple species pathway, Estrogen signalling pathway and PPAR signalling pathway may have an essential function in regulating the egg‐laying rate. The results highlighted DEGs in the ovarian tissues of relatively high and low laying Lingyun black‐bone chicken and identified essential candidate genes related to the egg‐laying rate, thereby providing a theoretical basis for improving the egg‐laying rate of Lingyun black‐bone chicken.

A serpin from the tick Rhipicephalus haemaphysaloides: Involvement in vitellogenesis

Tick serpins are involved in enzyme activity, food digestion, blood-feeding, immune response and anticoagulation. Little is known about the potential roles of serpins in tick reproduction. RHS8, a serpin from the tick Rhipicephalus haemaphysaloides, has an open reading frame 1212 bp long and encodes a protein that has 404 amino acids and a predicted molecular weight of 45 kDa. RHS8 exhibits 89.58 % amino acid identity with RmS15 in Rhipicephalus microplus. RHS8 was expressed primarily in larvae and nymphs. RHS8 mRNA expression in the ovaries, fat bodies and salivary glands were up-regulated from feeding to ovipositing ticks. RNAi results showed that RHS8 dsRNA-injected ticks had a lower body weight, longer feeding time, fewer eggs laid and lower egg hatchability. Tick reproduction, such as egg laying and hatching, was disrupted by RNAi. Compared with the control group, ovaries of the RHS8 interference group were light brown color, indicating a reduction in yolk granule accumulation. Western blot results showed that the expression of RHVg3 and RHVg4 proteins in ovaries was reduced in the RHS8 dsRNA-injected group. These results indicate that RHS8 is related to tick reproduction and its interference affects vitellogenesis.

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

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

Comparative transcriptome reveals the potential modulation mechanisms of estradiol affecting ovarian development of female Portunus trituberculatus

Estradiol is an important sex steroid hormone that is involved in the regulation of crustacean ovarian development. However, the molecular regulatory mechanisms of estradiol on ovarian development are largely unknown. This study performed transcriptome sequencing of ovary, hepatopancreas, brain ganglion, eyestalk, and mandibular organ of crabs after estradiol treatment (0.1μg g^-1 crab weight). A total of 23, 806 genes were annotated, and 316, 1300, 669, 142, 383 genes were expressed differently in ovary, hepatopancreas, brain ganglion, eyestalk, and mandibular organ respectively. Differentially expressed gene enrichment analysis revealed several crucial pathways including protein digestion and absorption, pancreatic secretion, insect hormone biosynthesis, drug metabolism-cytochrome P450 and signal transduction pathway. Through this study, some key genes in correlation with the ovarian development and nutrition metabolism were significantly affected by estradiol, such as vitelline membrane outer layer 1-like protein, heat shock protein 70, Wnt5, JHE-like carboxylesterase 1, cytochrome P302a1, crustacean hyperglycemic hormone, neuropeptide F2, trypsin, carboxypeptidase B, pancreatic triacylglycerol lipase-like, and lipid storage droplet protein. Moreover, RT-qPCR validation demonstrated that expression of transcripts related to ovarian development (vitelline membrane outer layer 1-like protein and cytochrome P302a1) and nutrition metabolism (trypsin, glucose dehydrogenase and lipid storage droplet protein) were significantly affected by estradiol treatment. This study not only has identified relevant genes and several pathways that are involved in estradiol regulation on ovarian development of P. trituberculatus, but also provided new insight into the understanding of the molecular function mechanisms of estradiol in crustacean.

Effects of environmental stress on shrimp innate immunity and white spot syndrome virus infection

The shrimp aquaculture industry is plagued by disease. Due to the lack of deep understanding of the relationship between innate immune mechanism and environmental adaptation mechanism, it is difficult to prevent and control the diseases of shrimp. The shrimp innate immune system has received much recent attention, and the functions of the humoral immune response and the cellular immune response have been preliminarily characterized. The role of environmental stress in shrimp disease has also been investigated recently, attempting to clarify the interactions among the innate immune response, the environmental stress response, and disease. Both the innate immune response and the environmental stress response have a complex relationship with shrimp diseases. Although these systems are important safeguards, allowing shrimp to adapt to adverse environments and resist infection, some pathogens, such as white spot syndrome virus, hijack these host systems. As shrimp lack an adaptive immune system, immunization therapy cannot be used to prevent and control shrimp disease. However, shrimp diseases can be controlled using ecological techniques. These techniques, which are based on the innate immune response and the environmental stress response, significantly reduce the impact of shrimp diseases. The object of this review is to summarize the recent research on shrimp environmental adaptation mechanisms, innate immune response mechanisms, and the relationship between these systems. We also suggest some directions for future research.

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

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

Broad-complex Z3 contributes to the ecdysone-mediated transcriptional regulation of the vitellogenin gene in Bombus lantschouensis

During reproduction, vitellogenin (Vg), as an egg yolk precursor, is critical in sexually mature females of oviparous species including some insects. The transcription of Vg is usually mediated by hormones such as juvenile hormone (JH), ecdysteroids and some neuropeptides. In this study, the structure of the Vg gene from the bumblebee Bombus lantschouensis, (BlVg) was determined by sequencing and assembly. BlVg was found to be expressed at higher levels in reproductive queens than in virgins by quantitative real-time PCR analysis. Tissue-specific expression analysis showed that BlVg was expressed at the highest levels in the fat bodies of both virgin and reproductive queens. Prediction of the BlVg promoter revealed the presence of ecdysteroid-responsive cis-regulatory elements (CREs) containing one Broad-Complex zinc-finger isoform 3 (BR-C Z3), and one ecdysone-induced protein 74A (E74A). In addition, luciferase reporter expression, driven by the 5' -regulatory region of the BlVg gene, from -1517 bp to +895 bp downstream of the start codon, was induced by treatment with 20-hydroxyecdysone (20-E). Moreover, the luciferase activity of the BlVg promoter was elevated by only BlBrC-Z3 when Sf9 cells were cotransfected with four BlBrC isoforms respectively. BlVg promoter-mediated luciferase activation was significantly reduced when the putative BrC-Z3 CRE in the promoter was mutated. In summary, this report describes the first study of vitellogenin gene regulation at the transcriptional level in bumblebees and demonstrates that the ecdysone-induced transcription of the BlVg gene is mediated by the binding of BlBrC-Z3 to the BrC-Z3 CRE in the BlVg promoter in bumblebees.

Characterization, expression profile, and promoter analysis of the Rhodeus uyekii vitellogenin Ao1 gene

The fish Vitellogenin (Vg) gene has been applied as a biomarker for exposure to estrogenic compounds in the aquatic environment. In this study, we cloned and characterized Vg cDNA from the Korean rose bitterling Rhodeus uyekii (Ru-Vg). The Ru-Vg cDNA encodes a 1424-amino-acid polypeptide that belongs to the VgAo1 family and contains a putative signal peptide, lipovitellin I, phosvitin, and lipovitellin II, but does not contain the vWFD domain or the C-terminal peptide. The deduced Ru-Vg protein has high amino acid identity (73.97%–32.17%) with fish Vg proteins. Pairwise alignment and phylogenetic analysis revealed that Ru-Vg is most closely related to Acheilognathus yamatsutae Vg. Ru-Vg transcripts were detected using quantitative polymerase chain reaction in all tissues tested, with the highest level of expression observed in the ovary. Ru-Vg mRNA was upregulated in R. uyekii hepatopancreas cells in response to treatment with 17β-estradiol (E2) or 17α-ethinylestradiol (EE2). Luciferase reporter expression, driven by the 5'-regulatory region of the Ru-Vg gene spanning from −1020 bp to the start codon was induced by the estrogen receptor and was synergistically activated by treatment with E2 or EE2. These results suggest that R. uyekii and the Ru-Vg gene may be useful as biomarkers for exposure to E2 or EE2.