A Comparative Study on Growth and Metabolism of Eriocheir sinensis Juveniles Under Chronically Low and High pH Stress

Combined effects of low pH stress and bacterial infection on the transcriptional changes of hemocytes in Chinese mitten crab Eriocheir sinensis

Water pH is a critical environmental factor for aquaculture. Acidification is a pressing environmental issue that poses significant threats to the aquaculture industry. Since the outbreaks of disease generally accompany with environmental stress, comparative transcriptome analyses were performed to investigate the combined effects of low pH stress and bacterial infection on the transcriptional changes of hemocytes in the economically important crab Eriocheir sinensis. The results revealed that the immune deficiency (IMD) pathway and prophenoloxidase (proPO) system was activated to defense against Vibro parahaemolyticus even when crabs were subjected to low pH stress, whereas low pH stress resulted in the disorder of Toll-like receptor (TLR) pathway upon V. parahaemolyticus infection. Moreover, low pH stress might weaken crabs' defense against V. parahaemolyticus by inhibiting the up-regulation of crustin and suppressing the expression of lysozyme, and disturb the maintaining of protein homeostasis through the transcriptional decrement of a batch of heat shock proteins (HSPs). It is worth noting that both V. parahaemolyticus infection and low pH stress might suppress the energy metabolism in the hemocytes via inhibiting the expression of critical enzymes, dihydrolipoyllysine-residue acetyltransferase component of pyruvate dehydrogenase complex and fumarase, in the tricarboxylic acid (TCA) cycle. This study provides novel understandings concerning the transcriptional changes of hemocyte in E. sinensis subjected to a combination of low pH stress and V. parahaemolyticus infection as well as contribute to optimize the management strategies for the prevention and control of diseases in E. sinensis farming.

Exploration of Synergistic Regulation Mechanisms of Cerebral Ganglion and Muscle in Eriocheir sinensis Activated in Response to Alkalinity Stress

The cerebral ganglion and muscle are important regulatory tissues in Eriocheir sinensis. Therefore, it is of great significance to explore their synergistic roles in this organism's anti-stress response. In this study, proteomics, metabolomics, and combination analyses of the cerebral ganglion and muscle of E. sinensis under alkalinity stress were performed. The cerebral ganglion and muscle played a significant synergistic regulatory role in alkalinity adaptation. The key regulatory pathways involved were amino acid metabolism, energy metabolism, signal transduction, and the organismal system. They also played a modulatory role in the TCA cycle, nerve signal transduction, immune response, homeostasis maintenance, and ion channel function. In conclusion, the present study provides a theoretical reference for further research on the mechanisms regulating the growth and development of E. sinensis in saline-alkaline environments. In addition, it provides theoretical guidelines for promoting the vigorous development of the E. sinensis breeding industry in saline-alkaline environments in the future.

Comparative transcriptome analysis reveals potential regulatory mechanisms of genes and immune pathways following Vibrio harveyi infection in red drum (Sciaenops ocellatus)

Red drum (Sciaenops ocellatus), as an important economical marine fish, has been affected by various bacterial diseases in recent years. Vibrio harveyi cause fatal vibriosis in S. ocellatus, leading to massive mortality and causing significant setbacks in aquaculture. However, the regulatory mechanisms of S. ocellatus response to V. harveyi infection are poorly understood. In this regard, we performed transcriptomic analysis with head kidney tissues of S. ocellatus after V. harveyi infection from 12 h to 48 h to reveal genes, gene expression profiles, and pathways involved in immune and inflammation responses. Specifically, a total of 9,599, 5,728, and 7144 differentially expressed genes (DEGs) were identified after V. harveyi infection at 12 h, 24 h, and 48 h, respectively, and 1,848 shared DEGs have been identified from the above three comparison groups. Subsequent pathway analysis revealed that the shared DEGs following V. harveyi were involved in complement and coagulation cascades (C1R, C1QC, C3, C4, C5, C7, C8A, C8B, C8G, C9, CFB, CFH, and CFI), MAPK signaling pathway, chemokine signaling pathway (CCL19, CXCL8, CXCL12, CXCL14, CCR4, CCR7, and CXCR2), PPAR signaling pathway (PPAR-α, PPAR-γ and PPAR-β), and TNF signaling pathway. Finally, the expression patterns of DEGs in head kidney tissues and S. ocellatus macrophages were validated by qRT-PCR, suggesting the reliability of RNA sequencing for gene expression analysis. This dynamic transcriptome analyses provided insights into gene expression regulation and immune related pathways involved in S. ocellatus after V. harveyi infection, and provides useful information for further study on the immune defense mechanisms in S. ocellatus as well as other teleost species.

Transcriptome analysis of Chinese sucker (Myxocyprinus asiaticus) head kidney and discovery of key immune-related genes to cold stress after swimming fatigue

For Chinese sucker (Myxocyprinus asiaticus), passing through a dam with fast flow and cold water are always unavoidable, and this process can cause stress, disease or even death. In this study, comparative transcriptome analysis was conducted to investigate the potential immune mechanism in head kidney of M. asiaticus with swimming fatigue stress and cold stress after fatigue. In general, a total of 181,781 unigenes were generated, and 38,545 differentially expressed genes (DEGs) were identified. In these DEGs, 22,593, 7286 and 8666 DEGs were identified among groups of fatigue vs. cold, control vs. cold, and control vs. fatigue, respectively. Enrichment analysis revealed these DEGs were involved in coagulation cascades and complement, natural killer cell mediated cytotoxicity, antigen processing and presentation, Toll-like receptor signaling pathways, and chemokine signaling pathway. Notably, immune genes including heat shock protein 4a (HSP4a), HSP70 and HSP90α genes were significantly up-regulated in fishes with cold stress after fatigue. Differently, more immune genes in control vs. cold compared with that in control vs. fatigue were significantly down-regulated expression, such as claudin-15-like, Toll-like receptor 13, antimicrobial peptide (hepcidin), immunoglobulin, CXCR4 chemokine receptor, T-cell receptor, complement factor B/C2-A3, and interleukin 8. In this study, the number of DEGs in the head kidney was less than that our previous study in the spleen, which we speculated was more sensitive to changes in water temperature than the head kidney. In summary, lots of immune-related genes in the head kidney were down-regulated under cold stress after fatigue, suggesting that M. asiaticus might have experienced severe immunosuppression in the process of passing through the dam.

Comparative Transcriptome Analysis of Eriocheir sinensis from Wild Habitats in Han River, Korea

Eriocheir sinensis is an euryhaline crab found from East Asia to Europe and North America. This species can live in freshwater and seawater due to the unique physiological characteristics of their life cycle, which allows them to adapt and inhabit different habitats in a wide range of environments. Despite the wealth of studies focusing on adaptation mechanism of E. sinensis to specific environmental factors, the adaptation mechanisms to wild habitats with coexisting environmental factors are not well understood. In this study, we conducted a transcriptome analysis to investigate gene expression differences related to habitat adaptation of E. sinensis from two wild habitats with different environmental factors in the Han River, Korea. A total of 138,261 unigenes were analyzed, of which 228 were analyzed as differentially expressed genes (DEGs) between the two wild habitats. Among 228 DEGs, 110 DEGs were annotated against databases; most DEGs were involved in energy metabolism, immunity, and osmoregulation. Moreover, DEG enrichment analysis showed that upregulated genes were related to biosynthesis, metabolism, and immunity in an habitat representing relatively high salinity whereas downregulated genes were related to ion transport and hypoxia response in habitats with relatively low salinity and dissolved oxygen. The present findings can serve as foundation for future E. sinensis culture or conservation approaches in natural conditions.

Exploration of the regulatory mechanisms of regeneration, anti-oxidation, anti-aging and the immune response at the post-molt stage of Eriocheir sinensis

Eriocheir sinensis is widely appreciated by the surrounding population due to its culinary delicacy and rich nutrients. The E. sinensis breeding industry is very prosperous and molting is one of the important growth characteristics. Research on the regulation of molting in E. sinensis is still in the initial stages. There is currently no relevant information on the regulatory mechanisms of heart development following molting. Comparative transcriptome analysis was used to study developmental regulation mechanisms in the heart of E. sinensis at the post-molt and inter-molt stages. The results indicated that many regulatory pathways and genes involved in regeneration, anti-oxidation, anti-aging and the immune response were significantly upregulated after molting in E. sinensis. Aside from cardiac development, the differentially expressed genes (DEGs) were relevant to myocardial movement and neuronal signal transduction. DEGs were also related to the regulation of glutathione homeostasis and biological rhythms in regard to anti-oxidation and anti-aging, and to the regulation of immune cell development and the immune response. This study provides a theoretical framework for understanding the regulation of molting in E. sinensis and in other economically important crustaceans.

Moderate acidification mitigates the toxic effects of phenanthrene on the mitten crab Eriocheir sinensis

Freshwater acidification and phenanthrene may result in complex adverse effects on aquatic animals. Juvenile Chinese mitten crabs (Eriocheir sinensis) were exposed to different pH levels (7.8, 6.5, and 5.5) under phenanthrene (PHE) (0 (control) and 50 μg/L) conditions for 14 days. Antioxidant and transcriptomic responses were determined under stress conditions to evaluate the physiological adaptation of crabs. Under the control pH 7.8, PHE led to significantly reduced activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST), but increased glutathione peroxidase (GSH-Px), 7-ethoxyresorufin-o-deethylase (EROD) activities, and malondialdehyde (MDA) levels. However, moderate acidification (pH 6.5) changed PHE effects by increasing antioxidant enzymes. Acidification generally reduced SOD, GPx, GST and EROD activities, but increased CAT, GR, MDA. Compared with pH7.8 group, pH7.8 × PHE and pH6.5 × PHE groups had 1148 and 1498 differentially expressed genes, respectively, with "Biological process" being the main category in the two experimental groups. pH7.8 × PHE treatment caused significant enrichment of disease and immune-related pathways, while under pH6.5 × PHE, more pathways related to metabolism, detoxification, environmental information processing, and energy supply were significantly enriched. Thus, PHE had a significant inhibitory effect on antioxidant performance in crabs, while moderate acidification (pH6.5) mitigated the toxic effects of PHE. Overall, moderate acidification has a positive effect on the defense against the negative effects of PHE in Chinese mitten crabs, and this study provides insights into the defense mechanism of crustaceans in response to combined stress of acidification and PHE.