Two HSP90 genes in mandarin fish Siniperca chuatsi: identification, characterization and their specific expression profiles during embryogenesis and under stresses

Skin transcriptome of lenok trout (Brachymystax lenok) provides new insight on lectin genes and immune response mechanisms to Aeromonas salmonicida infection

Brachymystax lenok is an economically valuable cold-water fish species that has shown lower morbidity during pathogen outbreaks compared to other cold-water species. To elucidate the innate immune mechanisms in B. lenok in response to Aeromonas salmonicida infection, the transcriptome sequencing of the skin was performed. A total of 297,142 unigenes were generated, with 64.21 % (190,809) successfully annotated. Differential expression analysis identified 9238 differentially expressed genes (DEGs), with significant enrichment in immune-related pathways, including NOD-like receptor, C-type lectin receptor, and Toll-like receptor signalling pathways. These pathways may play crucial role in pathogen recognition, immune activation, inflammation, and the induction of adaptive immune responses in B. lenok. Further analysis revealed significant upregulation of pro-inflammatory cytokines, complement system components, and antimicrobial peptides such as hepcidin and cathelicidin, highlighting their pivotal roles in B. lenok's immune defense. Moreover, a notable finding was the dynamic expression of various lectin families, including C-type lectins, plectins, galectin-3, and β-galactoside-binding lectins, which are involved in pathogen recognition, immune modulation, and cell signalling. Lectins may also contribute to resistance mechanisms by affecting bacterial membrane permeability, disrupting vital metabolic processes, and enhancing synergy with antimicrobial peptides. In the pathological experiments, histological examination correlated the upregulation of inflammatory mediators and complement components with tissue damage, immune cell infiltration, and lesion development, further supporting the involvement of these genes in the immune response. These results will enrich the information in understanding the immune response in B. lenok, and provide basic data for the following proteomics and functional assays that can verify the protein-level activity of these immune-related genes and clarify their specific roles in host defense and resistance mechanisms. This comprehensive transcriptome analysis provides insights into the immune response mechanisms of B. lenok, with particular emphasis on the role of lectins in pathogen recognition and resistance. These findings offer a foundation for further research on immune mechanisms in fish and the development of therapeutic strategies to mitigate infections in aquaculture.

Molecular characterization of heat shock protein 70 and 90 genes and their expression analysis in air-breathing magur catfish (Clarias magur) while exposed to zinc oxide nanoparticles

The air-breathing magur catfish (Clarias magur) are frequently challenged with high environmental pollutants, including that of various metal nanoparticles (NPs) in their natural habitats. Heat shock proteins (HSPs) are essential molecular chaperones for preserving intracellular protein homeostasis in eukaryotic cells. In aquatic animals, HSPs are known to play important defensive roles associated with various environmental stress-related cellular damages. In the present investigation, we characterized the molecular and structural organization of distinct HSPs and their potential induction of HSP genes in multiple magur catfish tissues while exposed to ZnO NPs for 14 days. The sequence alignment of four HSP genes (hsp70, hsc70, hsp90a, and hsp90b) of magur catfish demonstrated evolutionary parallels with bony fishes and total conservation of active sites across the amphibia, fish, and mammals. From the architectural analysis of HSP70, HSC70, HSP90a, and HSP90b proteins, a structural similarity with mammals was observed, suggesting the functional resemblances of the studied HSPs in chaperone mechanisms. In the examined tissues, the mRNAs of HSP genes expressed constitutively. Exposure of C. magur to ZnO NPs (10 mg/L) in situ led to a considerable increase in the levels of mRNAs for several HSP genes and translated proteins, with HSP70 exhibiting the highest level of expression. Thus, it can be contemplated that HSPs may be involved in defending the magur catfish against the ZnO NP- and other metal NP-mediated cellular damages. The results provide new insights into the involvement of HSP machinery during adaptation to the ZnO NP-induced stress in magur catfish.

Effects of Density Stress During Transportation on the Antioxidant Activity and Immuno-Related Gene Expression in Yellowfin Seabream (Acanthopagrus latus Houttuyn, 1782)

Background/Objectives: Maintaining an optimum transport density is essential for protecting water quality, lowering stress levels, and increasing fish survival rates. Transporting marine fish fry involves major dangers. The purpose of this study was to evaluate the impact of transport stress at varying densities on the immune-related gene expression, antioxidant capacity, and survival rate of yellowfin seabream (Acanthopagrus latus) fry. Methods: A 12 h simulated transport experiment was conducted with A. latus fry divided into six density groups. For 1-2 cm fry, densities of 900, 1200, and 1500 fry per pouch were used to assess antioxidant enzyme activity; and for 4-5 cm fry, densities of 100, 125, and 150 fry per pouch were used for gene expression analysis. The key parameters measured included survival rates, antioxidant enzyme activities in liver and intestinal tissues, and expression levels of HSP90α and caspase-3 genes. Results: The findings showed that recovery time and density both affected the observed responses and that transport density had a substantial effect on antioxidant enzyme activity in all tissues. The intestinal and liver tissues showed a considerable decrease in antioxidant enzyme activity, suggesting that these tissues may be able to respond to oxidative stress. Moreover, under high-density transport conditions, there were notable increases in the expression of caspase-3 and HSP90α, suggesting the activation of immune response systems. This research offers valuable new understandings into the relationship between transport density and immunological and antioxidant modulation in A. latus fry. Conclusions: The results provide a scientific foundation for enhancing aquaculture transport conditions, which will ultimately lead to decreased fish mortality and improved general health during transit, resulting in more sustainable and effective aquaculture methods.

Genetic dissection of crayfish (Procambarus clarkii) high temperature tolerance and assessment of the potential application in breeding of the HSP genes

Red swamp crayfish (Procambarus clarkii) is an important freshwater aquaculture species in China. In the process of crayfish aquaculture, high temperature stress is common, which seriously affects its yield and quality. It is urgently recommended to improve these traits in the breed. However, the application of high-temperature tolerance genes in molecular breeding of crayfish has not been reported. In this study, transcriptome analysis was used to explore the high-temperature tolerance genes of crayfish. The results showed that genes related to energy metabolism, antioxidant, immunity and body restoration were involved in high temperature adaptation of crayfish. Based on the selected high temperature tolerance genes Heat Stress Protein 70 and Heat Stress Protein 90 (HSP70 and HSP90), the genetic variation of their open reading frames was investigated. Totally, three and four SNPs of HSP70 and HSP90, were obtained respectively. In addition, three high-temperature stress experiments were conducted on crayfish to identify favoured haplotypes. HSP70-1 and HSP90-1 are the favoured haplotypes of HSP70 and HSP90, respectively. Furthermore, a series of molecular markers were developed to identify the favoured haplotype combinations of HSP70 and HSP90. Finally, we propose a molecular breeding strategy to improve crayfish tolerance to high temperature, thereby providing a potential to increase crayfish yield. Together, this study provides a theoretical basis and molecular markers for the breeding of high-temperature tolerant crayfish.

Transcriptomic profiling of the thermal tolerance in two subspecies of the bay scallop Argopecten irradians

The bay scallop is a eurythermal species with high economic value and now represents the most cultured bivalve species in China. Two subspecies of the bay scallop, the northern subspecies Argopecten irradians irradians Korean population (KK) and the southern subspecies Argopecten irradians concentricus (MM), exhibited distinct adaptations to heat stress. However, the molecular mechanism of heat resistance of the two subspecies remains unclear. In this study, we compared the transcriptomic responses of the two subspecies to heat stress and identified the involved differentially expressed genes (DEGs) and pathways. More DEGs were found in the KK than in the MM when exposed to high temperatures, indicating elevated sensitivity to thermal stress in the KK. Enrichment analysis suggests that KK scallops may respond to heat stress more swiftly by regulating GTPase activity. Meanwhile, MM scallops exhibited higher resistance to heat stress mainly by effective activation of their antioxidant system. Chaperone proteins may play different roles in responses to heat stress in the two subspecies. In both subspecies, the expression levels of antioxidants such as GST were significantly increased; the glycolysis process regulated by PC and PCK1 was greatly intensified; and both apoptotic and anti-apoptotic systems were significantly activated. The pathways related to protein translation and hydrolysis, oxidoreductase activity, organic acid metabolism, and cell apoptosis may also play pivotal roles in the responses to heat stress. The results of this study may provide a theoretical basis for marker-assisted breeding of heat-resistant strains.

FoxO signaling and mitochondria-related apoptosis pathways mediate tsinling lenok trout (Brachymystax lenok tsinlingensis) liver injury under high temperature stress

Tsinling lenok trout (Brachymystax lenok tsinlingensis) is a typical cold water fish. High temperature has been shown to damage the liver of fish. However, few studies have investigated the liver apoptosis induced by high temperature stress in fish from the perspective of gene expression and metabolic function. Therefore, we investigated the changes caused by high temperature stress (24 °C) on the liver tissue structure, antioxidant capacity, liver gene expression, and the metabolome of tsinling lenok trout. The transcriptomic results showed that genes associated with apoptosis, such as CASP8, CASP3, PERK, Bcl-6 and TRAIL, were upregulated under high temperature stress. Metabolomic analysis showed that the metabolic pathway of nucleotide synthesis was significantly downregulated, while that of oxygen radical synthesis was significantly upregulated. Integrated analysis showed that after high temperature stress, immune-related signaling pathways in trout were activated and their apoptosis level increased, which might be related to hepatopancreas injury. In addition, abnormalities in the tricarboxylic acid cycle and mitochondrial function were observed, suggesting that functional hypoxia caused by high temperature might be involved fish cell apoptosis. These results provide new insights into the process of cell apoptosis in fish under high temperature stress.

Characterising the Physiological Responses of Chinook Salmon (Oncorhynchus tshawytscha) Subjected to Heat and Oxygen Stress

In New Zealand, during the hottest periods of the year, some salmon farms in the Marlborough Sounds reach water temperatures above the optimal range for Chinook salmon. High levels of mortality are recorded during these periods, emphasising the importance of understanding thermal stress in this species. In this study, the responses of Chinook salmon (Oncorhynchus tshawytscha) to chronic, long-term changes in temperature and dissolved oxygen were investigated. This is a unique investigation due to the duration of the stress events the fish were exposed to. Health and haematological parameters were analysed alongside gene expression results to determine the effects of thermal stress on Chinook salmon. Six copies of heat shock protein 90 (HSP90) were discovered and characterised: HSP90AA1.1a, HSP90AA1.2a, HSP90AA1.1b, HSP90AA1.2b, HSP90AB1a and HSP90AB1b, as well as two copies of SOD1, named SOD1a and SOD1b. The amino acid sequences contained features similar to those found in other vertebrate HSP90 and SOD1 sequences, and the phylogenetic tree and synteny analysis provided conclusive evidence of their relationship to other vertebrate HSP90 and SOD1 genes. Primers were designed for qPCR to enable the expression of all copies of HSP90 and SOD1 to be analysed. The expression studies showed that HSP90 and SOD1 were downregulated in the liver and spleen in response to longer term exposure to high temperatures and lower dissolved oxygen. HSP90 was also downregulated in the gill; however, the results for SOD1 expression in the gill were not conclusive. This study provides important insights into the physiological and genetic responses of Chinook salmon to temperature and oxygen stress, which are critical for developing sustainable fish aquaculture in an era of changing global climates.

Genomic organization and hypoxia inducible factor responsive regulation of teleost hsp90β gene during hypoxia stress

BACKGROUND

The physiological significance of a large family of heat-shock proteins (HSPs), comprised of the cytosolic HSP90A and the endoplasmic reticulum component of HSPB, is evident in prokaryotes and eukaryotes. The HSP90A is believed to play critical roles in diverse physiological functions of cell viability and chromosomal stability including stress management. Heightened abundance of hsp90β transcript was documented in Channa striatus, a freshwater fish, which is capable of surviving within an extremely hypoxic environment.

METHODS AND RESULTS

To better understand the mechanism of hsp90β gene expression, we investigated its genomic organization. Eleven exons were identified, including a long upstream intron with a remarkable similarity with human, but not with chicken counterpart. Dual-luciferase assays identified promoter activity in a 1366 bp 5'-flanking segment beyond the transcription initiation site. Examination detected a minimal promoter of 754 bp containing a TATA-box, CAAT-enhancer in addition to providing clues regarding other enhancer and repressor elements. The driving capability of this minimal promoter was further validated by its binding ability with TATA-box binding protein and the generation of GFP expressing transgenic zebrafish (F₂). Further, deletion of an inverted HIF (hypoxia inducible factor) motif RCGTG (upstream of the TATA-box) dramatically reduced luciferase expression in a hypoxic environment (CoCl₂ treated cultivable cells) and was identified as a cis-acting HIF responsive element, necessary for the hypoxia-induced expression.

CONCLUSIONS

The results obtained herein provide an insight regarding how hsp90β gene expression is controlled by HIF responsive element in teleost both during hypoxia stress management and normal physiological functions, and suggested that the hsp90β gene promoter could be used as a potential candidate for generating ornamental and food-fish transgenics.

Hypoxia-induced oxidative stress and transcriptome changes in the mud crab (Scylla paramamosain)

Mud crab (Scylla paramamosain) is an economically important cultured species in China. Hypoxia is a major environmental stressor during mud crab culture. In the present study, we investigated the oxidative stress and transcriptome changes in the gills of mud crab after intermediate hypoxia stress with dissolved oxygen (DO) 3.0 ± 0.2 mg/L (named as "DO3") and acute hypoxia stress with DO 1.0 ± 0.2 mg/L (named as "DO1") for 0, 3, 6, 12 and 24 h. The superoxide dismutase (SOD) activity of DO1 increased significantly at 3, 6 and 24 h after hypoxia stress, while SOD activity of DO3 increased significantly at 6 and 24 h. The total antioxidant capacity (T-AOC) increased significantly at 6, 12 and 24 h after hypoxia stress. The malondialdehyde (MDA) concentration of DO1 increased significantly at 6, 12 and 24 h after hypoxia stress, while MDA concentration of DO3 only increased significantly at 6 h. The lactate dehydrogenase (LDH) activity of DO1 increased significantly at 3, 6, 12 and 24 h after hypoxia stress, while LDH activity of DO3 increased significantly at 12 and 24 h. Transcriptomic analysis was conducted at 24 h of gill tissues after hypoxia stress. A total of 1052 differentially expressed genes (DEGs) were obtained, including 394 DEGs between DO1 and DO3, 481 DEGs between DO1 and control group, 177 DEGs between DO3 and control group. DEGs were enriched in the pathways related to metabolism, immune functions, ion transport, and signal transduction. Transcriptional analysis showed that glycolysis and tricarboxylic acid cycle genes were the key factors in regulating the adaptation of mud crab to hypoxia stress.

Abundances of vitellogenin and heat shock protein 90 during ovarian and embryonic development of Exopalaemon carinicauda

To evaluate functions of vitellogenin (Vg) and heat shock protein 90 (Hsp90) during ovarian and embryonic development of Exopalaemon carinicauda, the cDNA of Vg (Ec-Vg) was cloned, and the abundances of Ec-Vg and heat shock protein 90 (Hsp90) (Ec-Hsp90) were determined during ovarian and embryonic development. During ovarian development, the concentration of Vg protein in hemolymph was markedly greater than in the ovary and hepatopancreas, and was greatest at sexual maturity. The relative abundance of Ec-Vg mRNA transcript was greatest in the hepatopancreas and almost undetectable in hemocytes. By combining mRNA transcript relative abundances with morphological results, a model was developed to explain the mRNA transcript relative abundance of Ec-Hsp90 and Ec-Vg during ovarian and embryonic development. The relative abundance of Ec-Vg mRNA transcript was greatest during the recovery period after reproduction had occurred (Stage V) and mature stage (Stage IV) in the ovary or hepatopancreas, respectively. There were marked associations of the patterns of Ec-Hsp90 and Ec-Vg mRNA transcript abundances both in hepatopancreas and ovary. During embryonic development, the relative abundance of the two mRNA transcripts were greatest at the metazoea and protozoea stages, respectively. These results indicate that Ec-Vg is produced primarily in the hepatopancreas, secreted into the hemolymph and transported into growing oocytes. It, therefore, is believed that Ec-Vg has an important function in the overall ovarian development and late embryonic development of E. carinicauda. In contrast, Ec-Hsp90 is a regulatory factor for Vg transcription and is important during early organogenesis in E. carinicauda.

Impact of Aeromonas hydrophila and infectious spleen and kidney necrosis virus infections on susceptibility and host immune response in Chinese perch (Siniperca chuatsi)

Co-infections with pathogenic microorganisms are common in aquaculture, resulting in more serious economic losses than single-pathogen infection. Infection of Aeromonas hydrophila (A. hydrophila) often occurs together with infectious spleen and kidney necrosis virus (ISKNV) in Chinese perch (Siniperca chuatsi) culture ponds. In this study, A. hydrophila and ISKNV were inoculated into Chinese perch to mimic individual infection, secondary infection, and mixed infection. The effects of concurrent infections on the susceptibility and the immune response of the host and changes in bacterial and viral load were studied. The results showed relatively complex interaction between ISKNV and A. hydrophila for different infection modes, acting in an antagonistic or synergistic manner. The experimental groups infected with a mixture of ISKNV and A. hydrophila showed higher mortality rate than groups infected with single-pathogen or secondary infection groups, suggesting a synergistic lethal effect of A. hydrophila and ISKNV co-infection. Serious clinical symptoms and obvious histopathological changes were observed in moribund fish under the mixed-infection condition. In addition, obviously higher mortalities were caused by secondary bacterial infections than the number caused by secondary viral infections. ISKNV-primary infection increased the mortality caused by secondary bacterial infections, but A. hydrophila-primary infection did not significantly increase the mortality caused by secondary viral infections. Co-infected fish showed high expression levels of IRF1, Mx, Viperin, Hepcidin, TNFα, and IL-1β mRNAs relative to the levels in healthy fish, which suggested that the co-infection of these two pathogens activated the host immune system and caused host inflammation. These results of infection with A. hydrophila and ISKNV provided the theoretical basis to analyze the pathogenic effects and interaction between pathogens, and could facilitate design of strategies for clinical prevention and control measures of outbreak of fulminant hemorrhagic disease and bacterial sepsis in Chinese perch.

Expression analysis of the heat shock protein genes and cellular reaction in dojo loach (Misgurnus anguillicaudatus) under the different pathogenic invasion

As molecular chaperones, heat shock proteins (HSPs) play essential roles in cells in response to stress conditions. Recent studies about immune functions of HSPs in fish have also been reported. In this study, based on the reported cDNA sequences of the four HSP genes, HSP70, HSC70, HSP90α and HSP90β, the temporal expression patterns of the four genes during embryonic development of dojo loach(Misgurnus anguillicaudatus) was assayed with qRT-PCR. All of the four genes were ubiquitously expressed in all detected embryonic developmental stages. Among of them, HSP70, HSC70 and HSP90β were highly expressed in the organ formation stage, while HSP90α was the highest expressed in myotome formation stage. Further, the immune responses of the four HSP genes were assayed when loach were infected with three different pathogens, bacterium (Flavobacterium cloumnare G4), parasite (Ichthyophthirius multifiliis) and fungus (Saprolegnia). All of the four genes were differentially expressed in four tissues such as skin, gills, spleen and kidney in response to the pathogenic invasion, but both HSP70 and HSP90α expressions were dramatically up-regulated. Further, the cellular responses of the loach skinand gill tissues were observed, in which the number of the skin goblet cells were significantly increased, and the gill lamellae became shorter and wider after infected. Thus, our work indicated that the HSPs may directly or indirectly involved in immune defense in fish, at least in the loach.