Cloning of three heat shock protein genes (HSP70, HSP90α and HSP90β) and their expressions in response to thermal stress in loach (Misgurnus anguillicaudatus) fed with different levels of vitamin C

Effects of Chronic Heat Stress on Growth, Apoptosis, Antioxidant Enzymes, Transcriptomic Profiles, and Immune-Related Genes of Hong Kong Catfish (Clarias fuscus)

Chronic heat stress can have detrimental effects on the survival of fish. This study aimed to investigate the impact of prolonged high temperatures on the growth, antioxidant capacity, apoptosis, and transcriptome analysis of Hong Kong catfish (Clarias fuscus). By analyzing the morphological statistics of C. fuscus subjected to chronic high-temperature stress for 30, 60, and 90 days, it was observed that the growth of C. fuscus was inhibited compared to the control group. The experimental group showed a significant decrease in body weight and body length compared to the control group after 60 and 90 days of high-temperature stress (p < 0.05, p < 0.01). A biochemical analysis revealed significant alterations in the activities of three antioxidant enzymes superoxide dismutase activity (SOD); catalase activity (CAT); glutathione peroxidase activity (GPx), the malondialdehyde content (MDA), and the concentrations of serum alkaline phosphatase (ALP); Aspartate aminotransferase (AST); and alanine transaminase (ALT) in the liver. TUNEL staining indicated stronger apoptotic signals in the high-temperature-stress group compared to the control group, suggesting that chronic high-temperature-induced oxidative stress, leading to liver tissue injury and apoptosis. Transcriptome analysis identified a total of 1330 DEGs, with 835 genes being upregulated and 495 genes being downregulated compared to the control group. These genes may be associated with oxidative stress, apoptosis, and immune response. The findings elucidate the growth changes in C. fuscus under chronic high temperature and provide insights into the underlying response mechanisms to a high-temperature environment.

The Direct Effects of Climate Change on Tench (Tinca tinca) Sperm Quality under a Real Heatwave Event Scenario

Global aquaculture growth will most probably face specific conditions derived from climate change. In fact, the most severe impacts of these changes will be suffered by aquatic populations in restrictive circumstances, such as current aquaculture locations, which represent a perfect model to study global warming effects. Although the impact of temperature on fish reproduction has been characterized in many aspects, this study was focused on recreating more realistic models of global warming, particularly considering heatwave phenomena, in order to decipher its effects on male gametes (spermatozoa). For this purpose, thermal stress via a heatwave simulation (mimicking a natural occurring heatwave, from 24 to 30 °C) was induced in adult tench (Tinca tinca) males and compared with a control group (55.02 ± 16.44 g of average body wet weight). The impact of the thermal stress induced by this climate change event was assessed using cellular and molecular approaches. After the heatwave recreation, a multiparametric analysis of sperm quality, including some traditional parameters (such as sperm motility) and new ones (focus on redox balance and sperm quality biomarkers), was performed. Although sperm concentration and the volume produced were not affected, the results showed a significant deleterious effect on motility parameters (e.g., reduced progressive motility and total motility during the first minute post-activation). Furthermore, the sperm produced under the thermal stress induced by this heatwave simulation exhibited an increased ROS content in spermatic cells, confirming the negative effect that this thermal stress model (heatwave recreation) might have had on sperm quality. More importantly, the expression of some known sperm quality and fertilization markers was decreased in males exposed to thermal stress. This present study not only unveils the potential effects of climate change in contemporary and future fish farming populations (and their underlying mechanisms) but also provides insights on how to mitigate and/or avoid thermal stress due to heatwave events.

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.

Mitotic defects lead to unreduced sperm formation in cdk1-/- mutants

Unreduced gametes, that are important for species evolution and agricultural development, are generally believed to be formed by meiotic defects. However, we found that male diploid loach (Misgurnus anguillicaudatus) could produce not only haploid sperms, but also unreduced sperms, after cyclin-dependent kinase 1 gene (cdk1, one of the most important kinases in regulating cell mitosis) deletion. Observations on synaptonemal complexes of spermatocyte in prophase of meiosis and spermatogonia suggested that the number of chromosomes in some spermatogonia of cdk1^-/- loach doubled, leading to unreduced diploid sperm production. Then, transcriptome analysis revealed aberrant expressions of some cell cycle-related genes (such as ppp1c and gadd45) in spermatogonia of cdk1^-/- loach relative to wild-type loach. An in vitro and in vivo experiment further validated that Cdk1 deletion in diploid loach resulted in mitotic defects, leading to unreduced diploid sperm formation. In addition, we found that cdk1^-/- zebrafish could also produce unreduced diploid sperms. This study provides important information on revealing the molecular mechanisms behind unreduced gamete formation through mitotic defects, and lays the foundation for a novel strategy for fish polyploidy creation by using cdk1 mutants to produce unreduced sperms, which can then be used to obtain polyploidy, proposed to benefit aquaculture.

Effects of Dietary Vitamin C on the Growth Performance, Biochemical Parameters, and Antioxidant Activity of Coho Salmon Oncorhynchus kisutch (Walbaum, 1792) Postsmolts

Vitamin C (VC) plays an essential role in fish physiological function and normal growth. However, its effects and requirement of coho salmon Oncorhynchus kisutch (Walbaum, 1792) are still unknown. Based on the influences on growth, serum biochemical parameters, and antioxidative ability, an assessment of dietary VC requirement for coho salmon postsmolts (183.19 ± 1.91 g) was conducted with a ten-week feeding trial. Seven isonitrogenous (45.66% protein) and isolipidic (10.76% lipid) diets were formulated to include graded VC concentrations of 1.8, 10.9, 50.8, 100.5, 197.3, 293.8, and 586.7 mg/kg, respectively. Results showed that VC markedly improved the growth performance indexes and liver VC concentration, enhanced the hepatic and serum antioxidant activities, and increased the contents of serum alkaline phosphatase (AKP) activity, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and total cholesterol (TC) whereas decreased the serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities, and triglyceride (TG) level. Polynomial analysis showed that the optimal VC levels in the diet of coho salmon postsmolts were 188.10, 190.68, 224.68, 132.83, 156.57, 170.12, 171.00, 185.50, 142.77, and 93.08 mg/kg on the basis of specific growth rate (SGR), feed conversion ratio (FCR), liver VC concentration, catalase (CAT), hepatic superoxide dismutase (SOD) activities, malondialdehyde (MDA) content, and serum total antioxidative capacity (T-AOC), AKP, AST, and ALT activities, respectively. The dietary VC requirement was in the range of 93.08-224.68 mg/kg for optimum growth performance, serum enzyme activities, and antioxidant capacity of coho salmon postsmolts.

Heat shock protein 70 gene expression and stress response of red-spotted (Epinephelus akaara) and hybrid (E. akaara female × E. lanceolatus male) groupers to heat and cold shock exposure

The importance of the temperature tolerance of fish is increasing due to climate change caused by global warming. This study examined the expression of the heat shock protein 70 (HSP70) gene, and plasma cortisol and glucose levels, as a stress response in red-spotted and hybrid groupers during exposure to heat and cold shock. Temperature in the tank where fishes acclimated at 20℃ was gradually increased or decreased, respectively, to examine the survival rate of fish. The result showed a higher survival rate of the hybrid than that of the red-spotted grouper upon exposure to a higher temperature. To further analyze the factors associated with temperature-associated stress, fishes were collected from different temperatures which changed from 20 to 30℃ or 10℃, respectively, and then back to 20℃. The expression levels of the gene encoding heat shock protein 70 (HSP70) were analyzed by qPCR using cDNA prepared from RNA extracted from the brain. A higher level of HSP70 transcript was detected in the hybrid during heat shock exposure. Analysis of cortisol and glucose from the blood of fish collected during the acclimation periods clearly indicated that the level of cortisol was increased upon temperature shift although a slight difference in the degrees of changes timing was slightly different between red-spotted grouper and hybrid. The results showed a correlation between the level of HSP70 and survival rate upon exposure to higher temperature shock. This study provides basic information regarding whether HSP70 expression increases the survival rate of fish subjected to rapid temperature changes.

Higher acclimation temperature affects growth of rohu (Labeorohita) through suppression of GH and IGFs genes expression actuating stress response

Water temperature alone can affect the growth, metabolic rates and physiological responses of aquatic organisms. Our earlier study reported that higher temperature affects cellular and hemato-biochemical responses in rohu, Labeo rohita. In this backdrop, the present study assessed the effect of higher acclimation temperature on the regulatory mechanisms of growth and stress responses of juvenile L. rohita acclimatized in three temperature conditions (30 °C, 33 °C, and 36 °C) for a period of 30 days. The relative expression of genes for growth hormone (GH), insulin-like growth factors (IGF-1 and IGF-2) and heat shock proteins (hsp70 and hsp90) were measured by real-time quantitative PCR. The results revealed that the highest acclimation temperature (36 °C) significantly decreased the weight gain (WG) and specific growth rate (SGR), and increased the feed conversion ratio (FCR) compared to 30 °C (control), while increased WG, SGR and lowered FCR were observed in fish reared at the intermediate temperature (33 °C) compared to 30 °C. Similarly, the GH gene expression in the pituitary was significantly decreased and increased at 36 °C and 33 °C, respectively as compared to 30 °C. A significantly lower expression of IGF-1 and IGF-2, and higher expression of hsp70 and hsp90 were observed in the liver of fish at 36 °C. The results of the present study indicate that although slightly elevated temperature promotes the growth of juvenile L. rohita, the higher acclimation temperature may induce stress response and impair growth performance by suppressing GH/IGF system.

Molecular cloning, expression HSP70 and its response to bacterial challenge and heat stress in Microptenus salmoides

The gene encoding HSP70 was isolated from Microptenus salmoides by homologous cloning and rapid amplification of cDNA ends (RACE). The HSP70 transcripts were 2116 bp long and contained 1953 open reading frames encoding proteins of 650 amino acids with a molecular mass of 71.2 kDa and theoretical isoelectric point of 5.22. The qRT-PCR analysis showed that the HSP70 gene was differentially expressed in various tissues under normal conditions, and the highest HSP70 level was observed in the spleen and the lowest levels in the muscle and heart. The clear time-dependent expression level of HSP70 was observed after bacterial challenge and heat stress. A significant increase in HSP70 expression level was detected and reached a maximum at 3 h and 6 h in liver, spleens and gill tissues after Aeromonas hydrophila infection and heat stress, respectively (P < 0.05). As time progressed, the expression of HSP70 transcript was downregulated and mostly dropped back to the original level at 48 h. The concentration of cortisol, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) increased as the time of stress progressed, with the highest level found on 3 h and later declined rapidly and reached to the control levels at the 48 h. Those results suggested that HSP70 was involved in the immune response to bacterial challenge and heat stress. The cloning and expression analysis of the HSP70 provide theoretical basis to further study the mechanism of anti-adverseness in Microptenus salmoides.

Expression of HSP70 family mRNAs in albino northern snakehead, Channa argus: Response to extreme temperature stress and bacterial infection

The wild albino northern snakehead, Channa argus, has only been found in Jialing Rivers System of China so far. It is easy to be affected by the environmental factors such as temperature changes and bacterial infection, thus causing a huge economic loss. Therefore, this study cloned a 2,213 bp cDNA that encodes a protein of heat shock protein 70 (CaHSP70), which has an open reading frame (ORF) that encodes 639 amino acids and the corresponding polypeptides of 70.50 kDa. And the oretical isoelectric point (pI) of CaHSP70 is 5.79. Additionally, we also cloned a cDNA for heat shock cognate protein 70 (CaHSC70) with a total length of 2,300 bp. And the ORF of CaHSC70 encodes 648 amino acids and 71.18 kDa peptides. The pI of CaHSC70 is 5.22. Moreover, the cDNA length of stress-70 protein mitochondrial (CaHSPA9) is 2,944 bp with an ORF that encodes 679 amino acids, polypeptides of 73.74 kDa, and a pI of 6.68. The quantitative real-time PCR (qRT-PCR) analysis showed that the mRNA expression levels of CaHSP70, CaHSC70, and CaHSPA9 genes were tissue-specific in the control groups. After the heat shock at 37 °C, the mRNA expression levels of CaHSP70 were extremely significantly upregulated in the kidney, liver, spleen, and brain tissues, while fewer mRNA expression levels of CaHSC70 and CaHSPA9 showed a relatively induction in these tissues. In contrast, after the cold shock at 8.5 °C, fewer mRNA expression levels of CaHSP70, CaHSC70, and CaHSPA9 showed the changes of expression in all the tissues, compared to heat shock. In addition, CaHSP70, CaHSC70, and CaHSPA9 mRNA expression levels showed an overall trend of first upregulating and then falling after Edwardsiella tarda (strain No. DL1,476) challenge. In conclusion, this study demonstrated that temperature had a great effect on the mRNA expression levels of CaHSP70, CaHSC70, and CaHSPA9, and the mRNA expression levels of these three genes were also sensitive to pathogen infection, especially CaHSP70 in the albino C. argus.

Single or Combined Dietary Supply of Psidium guajava and Phyllanthus amarus Extracts Differentially Modulate Immune Responses and Liver Proteome in Striped Catfish (Pangasianodon hyphophthalmus)

Guava Psidium guajava L (Pg) and bhumi amla Phyllanthus amarus Schum. et Thonn (Pa) are well-known plants in traditional medicine. However, the capacity of these plants for improving the immune system of aquatic species has received less attention so far. This study aimed to investigate the effects of single supply or mixture of Pg and Pa extracts on immune responses, disease resistance and liver proteome profiles in striped catfish Pangasianodon hypophthalmus. Fish were fed diets including basal diet 0% or one of three doses of each plant extract, either alone or in mixture, 0.08, 0.2, or 0.5% Pg, Pa or mixture (Pg:Pa, v/v) for 6 weeks. The immune parameters (respiratory burst activity (RBA); nitric oxide synthase (NOS), total immunoglobulin, lysozyme, and complement activities) were examined at W3, W6 post-feeding, and after challenge test. The growth parameters and the challenge test with Edwardsiella ictaluri were done at W6. The liver proteome profiles were analyzed in W6 at 0.08 and 0.5% of each extract. The results showed that extract-based diets significantly improved growth parameters in the Pg0.2 group compared to control. The cellular immune responses in spleen and the humoral immune responses in plasma were significantly improved in a dose and time-dependent manner. Diets supplemented with single Pg and Pa extracts, and to lesser extent to combined extracts, could significantly decrease the mortality of striped catfish following bacterial infection compared to control. The proteomic results indicated that some pathways related to immune responses, antioxidant and lipid metabolism were enriched in liver at W6. Several proteins (i.e., CD8B, HSP90AA1, HSP90AB1, PDIA3, CASP8, TUBA1C, CCKAR, GNAS, GRIN2D, PLCG1, PRKCA, SLC25A5, VDAC2, ACTN4, GNAI2, LCK, CARD9, NLRP12, and NLRP3) were synergistically upregulated in mixture of Pg and Pa-based diets compared to control and single dietary treatments. Taken together, the results revealed that single Pg and Pa extracts at 0.2 and 0.5% and their mixture at 0.08 and 0.5% have the potential to modulate the immune mechanisms and disease resistance of striped catfish. Moreover, the combination of Pg and Pa in diets suggested positive synergistic effects liver proteome profile related to immune system processes.

Transcriptome analysis of acute exposure of the Manila clam, Ruditapes philippinarum to perfluorooctane sulfonate (PFOS)

Perfluorooctane sulfonate (PFOS) is an increasingly important environmental pollutant, which has been detected almost everywhere in the environment. Despite the widespread presence of PFOS, much less notice is taken of its toxicology effects on marine bivalves. Thus, the transcriptome response to PFOS treatment (nominal concentration of 20 mg/L) in hepatopancreas of a sentinel organism, Ruditapes philippinarum was examined. Compared with the control group, 32,149 unigenes were up-regulated and 26,958 unigenes down-regulated. Notably, significant gene expression changes were found in carbohydrate metabolism, energy metabolism, amino acid metabolism, lipid metabolism and protein biosynthesis, indicating the metabolic disruptions caused by PFOS in R. philippinarum. Additionally, numerous other differentially expressed genes were involved in immune system, antioxidant defense system and detoxification metabolism. In summary, transcriptome profiling of R. philippinarum after exposure to PFOS provided molecular support for our current understanding of the detrimental toxicity of PFOS on marine bivalves.

Expression of heat shock protein 70 and Annexin A1 in serum of patients with acutely severe traumatic brain injury

Trends of early expression levels of heat shock protein 70 (Hsp70) and Annexin A1 (ANXA1) in serum of patients with acutely severe traumatic brain injury and the effects on clinical prognosis were investigated. Eighty-four patients with severe traumatic brain injury admitted to Binzhou Center Hospital from June 2014 to July 2017 were selected as the experimental group. Glasgow coma scale and acute physiology and chronic health evaluation II (APACHE II) score were obtained after admission. A further 75 healthy subjects were selected as the control group. Serum expression of Hsp70 and ANXA1 in the two groups was detected by enzyme-linked immunosorbent assay on the 1st, 2nd, 3rd and 4th day after admission. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic value of Hsp70 and ANXA1 for the death of patients with acutely severe traumatic brain injury. Compared with the control group, expression of Hsp70 in the experimental group was significantly increased on the 1st, 2nd, 3rd and 4th day after admission (P<0.05), while expression of ANXA1 was significantly decreased (P<0.05). Expression levels of serum Hsp70 in the experimental group reached the peak on the 3rd day after admission, and the difference was statistically significant compared with the 1st, 2nd and 4th day (P<0.05). Expression of ANXA1 was the lowest on the 3rd day, and the difference was statistically significant compared with the 1st, 2nd and 4th day (P<0.05). The ROC curve analysis showed that the area under the curve of serum Hsp70 and ANXA1 was, respectively, 0.721 (95% CI: 0.611-0.829) and 0.684 (95% CI: 0.569-0.799). In conclusion, Hsp70 and ANXA1 may be involved in the occurrence and progression of acutely severe traumatic brain injury. The detection of serum Hsp70 and ANXA1 has certain diagnostic value for the death of patients with acutely severe traumatic brain injury.

Effects of Ascorbic Acid and β-1,3-Glucan on Survival, Physiological Response and Flesh Quality of Cultured Tiger Grouper (Epinephelus fuscoguttatus) during Simulated Transport in Water

Transport in water is the most common method for achieving high survival rates when transporting cultured fish in China; yet, transport success relies on proper water quality and conditions. This research was designed to explore the effects of ascorbic acid and β-1,3-glucan on survival, physiological responses, and flesh quality of farmed tiger grouper (Epinephelus fuscoguttatus) during simulated transport. The transport water temperature for live tiger grouper was 15 °C, which had the highest survival rate, the lowest stress response, and metabolic rate, and this will reduce the susceptibility to diseases. It is stated that β-1,3-glucan influences the changes of cortisol content, heat shock protein 70, IL-1β, and IgM transcription levels during simulated transport. Rather than using ascorbic acid alone (the A-group), β-1,3-glucan (3.2 mg/L) in the presence of ascorbic acid (25 mg/L) can effectively reduce the increase of transport-induced serum cortisol content, heat shock protein 70, and IL-1β, but stimulated IgM. 25 mg/L ascorbic acid and 3.2 mg/L β-1,3-glucan had no obvious effect on the nutritional indexes and flavor of live tiger grouper; however, these can effectively reduce the stress response, improve the innate immune activity, and ensure a higher survival rate.

Cloning and expression of three heat shock protein genes in the gills of Cherax quadricarinatus responding to bacterial challenge

Cherax quadricarinatus is seriously affected by multiple types of pathogens, including bacteria and viruses, and has been widely transplanted around the world. Heat shock proteins (Hsps) are a group of molecular chaperones that play important roles in promoting the proper refolding and blocking the aggregation of denatured proteins. In this study, CqHsp60, CqHsp70 and CqHsp90 from C. quadricarinatus were cloned, and their expression patterns were analysed. The CDS (coding sequence) lengths of the CqHsp60, CqHsp70 and CqHsp90 genes were 1731 bp, 1932 bp and 2199 bp, encoding 576, 643 and 732 amino acids, respectively. CqHsp60 was 99.13%, 98.78% and 88.63% identical to the corresponding sequences of Cherax cainii, Cherax destructor and Eriocheir sinensis, respectively. CqHsp70 showed 99.84%, 92.73% and 91.58% identity to the corresponding sequences of C. cainii, C. destructor and E. sinensis, while CqHsp90 was 98.25%, 98.51% and 91.41% identical with those of C. cainii, C. destructor and E. sinensis, respectively. The expression patterns of the three CqHsps were different between males and females. CqHsp60 and CqHsp70 exhibited the highest expression in the hepatopancreas of males and the gonads of females, and CqHsp90 presented the highest expression in the gonads of males and hepatopancreas of females. After pathogenic inoculation, the death trend of C. quadricarinatus at different time points was the same in association with different pathogens, with most deaths occurring within 6 h post-inoculation. The trend of CqHsp transcription at different time points was the same among the groups treated with Vibrio alginolyticus, Vibrio parahemolyticus and Aeromonas hydrophila, exhibiting upregulation first and then downregulation. The expression of CqHsp60 and CqHsp70 in the gills of living C. quadricarinatus was less than 3.5 times that in the PBS group, but in the gills of dead C. quadricarinatus under A. hydrophila inoculation, its expression was more than 5-9 times that in the PBS group. CqHsp90 expression changed dramatically in the V. alginolyticus, V. parahemolyticus and A. hydrophila groups, in which it exceeded 50 times the level in the PBS group. These results indicated that CqHsps could induce the activation of the immune system within a short time and that CqHsp90 could be used as a more effective molecular biomarker than CqHsp70 and CqHsp60 in a pathogenic bacterium-polluted environment.

Effects of thermal stress on mortality and HSP90 expression levels in the noble scallops Chlamys nobilis with different total carotenoid content

The noble scallop Chlamys nobilis is an economically important marine bivalve cultivated in the southern sea of China since the 1980s. Unfortunately, mass mortality of this scallop species often occurs in summer. The present study was conducted to investigate whether the expression of heat shock protein 90 (HSP90) and level of carotenoids could enhance high-temperature stress resistance in scallop. First, the HSP90 homolog of C. nobilis (designated CnHSP90) was identified and cloned. The complete cDNA sequence of CnHSP90 was 2631 bp, including a 2181-bp open reading frame (ORF) encoding a 726 amino acid polypeptide with five HSP90 family signatures, and sharing high homology with members of the HSP90 family. CnHSP90 was ubiquitously expressed in all examined tissues including the intestine, kidney, adductor, mantle, gill, and gonad, with the highest in the gonad. Golden and brown scallops, which contain significantly different total carotenoid content (TCC), were subjected to acute thermal challenge, and the LTE50 (semi-lethal temperature at 36 h heat shock) and LTI50 (semi-lethal time after heat shock) as well as the correlation between CnHSP90 gene expression and TCC were determined. The LTE50 of golden scallop (32.14 °C) was higher than that of brown scallops (31.19 °C), with longer LTI50 at all tested temperatures, indicating that golden scallops were more resistant to thermal stress than brown scallops. Similarly, the mRNA expression levels of CnHSP90 in gill of golden scallops were significantly higher (P < 0.05) than that of brown scallops at 6, 12, 24, and 36 h, with a strong positive correlation between CnHSP90 expression level and TCC. This suggests that both carotenoids and HSP90 levels could improve thermal resistance in the noble scallops.

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.

Alterations to transcriptomic profile, histopathology, and oxidative stress in liver of pikeperch (Sander lucioperca) under heat stress

Pikeperch (Sander lucioperca) is an economically important cool-water fish. In recent years, its cultivation has become threatened by higher temperatures in summer. We previously investigated the effects of heat stress on pikeperch liver under different temperatures, but the molecular mechanism of the heat-stress response is still unknown. This study applied consistent heat stress (29 °C, 0-48 h) to pikeperch juveniles, and a transcriptomic profile of pikeperch liver under heat stress (29 °C, 0 h) was performed by RNA-Seq. The antioxidant status, changes in liver histology, and antioxidant gene expression at different time points were examined. We identified 403 differentially expressed genes (DEGs), many of which were enriched in KEGG pathways, including protein processing in endoplasmic reticulum (ER), insulin signaling, and immune-related pathways. Among these, the most significant heat-stress-related pathway was protein processing in ER, indicating that this pathway is critical for the heat-stress response. After consistent heat stress at 29 °C, the total antioxidant capacity (T-AOC), the activities of total superoxide dismutase (T-SOD) and catalase (CAT), and the mRNA expression of manganese SOD (Mn-SOD), CAT, and glutathione peroxidase 1 and 7 (GPx1 and GPx7) in the treated groups showed the same trend of first increasing and then decreasing. Levels of malondialdehyde (MDA) content did not show significant differences between samples at 0 h and 3 h, but significantly increased by 6 h, and thereafter decreased. The liver tissue was normal at 0 h (29 °C); however, it suffered histological damage with increased duration of the heat stress. Above all, heat stress at 29 °C seemed to cause oxidative damage and dysfunction in pikeperch liver between 3 h and 48 h. The present results indicate that pikeperch have the capacity to defend against heat stress and maintain relative balance of oxidation-reduction reactions mainly through activating the antioxidant system, protein processing in ER, the insulin-signaling pathway, and immune-related pathways.

Inefficient ATP synthesis by inhibiting mitochondrial respiration causes lipids to decrease in MSTN-lacking muscles of loach Misgurnus anguillicaudatus

Myostatin (MSTN) lacking could lead to enhanced muscle growth and lipid metabolism disorder in animals. Plenty of researches have been performed to warrant a better understanding of the mechanisms underlying the enhanced muscle growth; however, mechanisms for lipid metabolic changes are poorly understood. In this study, MSTN-depletion loaches Misgurnus anguillicaudatus (MU for short) were firstly generated by CRISPR/Cas9 technique. Based on histological observation, we found that skeletal muscle fat accumulation in MU sharply reduced compared with wild-type loaches (WT for short). To further investigate the fat change, muscle lipidomic analysis was performed. There were no significant differences in three membrane phospholipid contents between WT and MU. The contents of six other major lipid species in MU muscles were all significantly lower than those in WT muscles, indicating that MSTN deficiency could obviously decrease muscle lipid production in the loach. Meanwhile, it was also supported by results of three lipogenesis-related genes' expressions. And then combined with muscle ATP determination and gene expression profiles of the five mitochondrial respiration chain complexes, we speculated that MSTN lacking may cause the weak of mitochondrial respiration functions in the loach muscles, leading to ATP synthesis decreasing and finally reducing the production of lipids.

Effects of exogenous salicylic acid and pH on pathogenicity of biotrophy-associated secreted protein 1 (BAS1)-overexpressing strain, Magnaporthe oryzae

Abiotic stress can influence the interactions between a pathogen and its host. In this paper, we analyzed the effects of salicylic acid (SA) and pH on the morphological development and pathogenicity of Magnaporthe oryzae, the pathogen that causes rice (Oryza sativa) blast. A strain of rice blast that overexpresses biotrophy-associated secreted protein 1 (BAS1) and a wild-type (WT) strain were pretreated with different levels of pH and different concentrations of SA to analyze M. oryzae colony growth, sporulation, spore germination, dry weight of hypha, and appressorium formation. Disease incidence and the expression of defense-related genes in infected rice were analyzed after pretreatment with pH 5.00 or pH 8.00 and 200 μM SA. The results showed that both SA and pH had some influence on morphological development, including sporulation and appressorium formation of the BAS1-overexpression strain. In the 200 μM SA pretreatment, there was a lower incidence of disease and higher expression levels of the rice defense-related genes PR1a, PAL, HSP90, and PR5 on leaves inoculated with the BAS1-overexpession strain compared with the WT strain, whereas, LOX2 appeared to be downregulated in the BAS1-overexpession strain compared with the WT. In both pH treatments, disease incidence and expression of HSP90 were higher and the expression of PR1a and PR10a and LOX2 and PAL was lower in leaves inoculated with the BAS1-overexpression strain compared with leaves inoculated with the WT strain. We conclude that SA and pH affect morphological development of the BAS1-overexpression blast strain, but that these factors have little influence on the pathogenicity of the strain, indicating that BAS1-overexpression may have enhanced the tolerance of this rice blast strain to abiotic stressors. This work suggests new molecular mechanisms that exogenous SA and pH affect the interactions between M. oryzae and rice.

Effects of exogenous salicylic acid and pH on pathogenicity of biotrophy-associated secreted protein 1 (BAS1)-overexpressing strain, Magnaporthe oryzae

Abiotic stress can influence the interactions between a pathogen and its host. In this paper, we analyzed the effects of salicylic acid (SA) and pH on the morphological development and pathogenicity of Magnaporthe oryzae, the pathogen that causes rice (Oryza sativa) blast. A strain of rice blast that overexpresses biotrophy-associated secreted protein 1 (BAS1) and a wild-type (WT) strain were pretreated with different levels of pH and different concentrations of SA to analyze M. oryzae colony growth, sporulation, spore germination, dry weight of hypha, and appressorium formation. Disease incidence and the expression of defense-related genes in infected rice were analyzed after pretreatment with pH 5.00 or pH 8.00 and 200 μM SA. The results showed that both SA and pH had some influence on morphological development, including sporulation and appressorium formation of the BAS1-overexpression strain. In the 200 μM SA pretreatment, there was a lower incidence of disease and higher expression levels of the rice defense-related genes PR1a, PAL, HSP90, and PR5 on leaves inoculated with the BAS1-overexpession strain compared with the WT strain, whereas, LOX2 appeared to be downregulated in the BAS1-overexpession strain compared with the WT. In both pH treatments, disease incidence and expression of HSP90 were higher and the expression of PR1a and PR10a and LOX2 and PAL was lower in leaves inoculated with the BAS1-overexpression strain compared with leaves inoculated with the WT strain. We conclude that SA and pH affect morphological development of the BAS1-overexpression blast strain, but that these factors have little influence on the pathogenicity of the strain, indicating that BAS1-overexpression may have enhanced the tolerance of this rice blast strain to abiotic stressors. This work suggests new molecular mechanisms that exogenous SA and pH affect the interactions between M. oryzae and rice.

Transcriptomic and cortisol analysis reveals differences in stress alleviation by different methods of anesthesia in Crucian carp (Carassius auratus)

Stress response has negative effect on fish in aquaculture and research, which can be alleviated with anesthetic. To determine the optimal anesthetic, we investigated the physiological response of crucian carp (Carassius auratus) treated with three different anti-stress treatments: MS-222, eugenol and percussive stunning. Stress responses were evaluated by analyzing serum cortisol level and gene expression in blood. We determined the optimal concentrations of MS-222 (100 mg L^-1) and eugenol (20 mg L^-1) by dose selection. We found that the control group had significantly higher cortisol levels (172.78 ± 19.95 ng mL^-1) compared to the MS-222 treated group (46.85 ± 3.22 ng mL^-1), the eugenol treated group (72.78 ± 9.07 ng mL^-1), and the stunning treatment group (82.78 ± 8.16 ng mL^-1). Transcriptome analysis revealed 1572 differentially expressed genes (DEGs), including 155 DEGs related to the stress response, mainly involved in oxidative-stress response, heat shock proteins, and cold shock domain-containing protein. The heat shock protein genes were the primary DEGs in response to stress. RT-qPCR analysis confirmed differential expression of Hsps. We analyzed the function of the DEGs, which were enriched in genes involved in cellular response to stress and antigen processing and presentation. Combining the results from biochemical, transcriptome, and gene expression analysis, our data suggest that eugenol is more effective than MS-222 and percussive stunning in alleviating stress in crucian carp.

HSP60 and HSP90β from blunt snout bream, Megalobrama amblycephala: Molecular cloning, characterization, and comparative response to intermittent thermal stress and Aeromonas hydrophila infection

Heat shock proteins (HSPs) play critical roles in the process of anti-stress and immunity and are implicated in autoimmune diseases. In order to understand the comparative stress responses of HSP60 and HSP90β under intermittent thermal stress and Aeromonas hydrophila infection, we cloned their full-length cDNAs from Megalobrama amblycephala liver, predicted their secondary and tertiary structure, and examined their tissue-specific expression patterns. The full length of HSP60 and HSP90β cDNAs indicated that they included all signature sequences of corresponding protein families. They showed high homology to their counterparts in other species, and were consistent with the known classification of fishes based on phylogenetic analysis. HSP60 showed the highest expression in head-kidney, brain, and gill, while HSP90β presented higher in hindgut, liver, and brain. Significant mRNA expression differences were determined between HSP60 and HSP90β in tissues of bladder, liver, heart, and gill. During thermal stress and recovery phase, the highest expression of them were observed at the first recovery for 2 d and 1 d, respectively. The expression between them were extremely significant difference during the first recovery and second stress period. After A. hydrophila infection, their expressions were extremely significantly upregulated. The significant upregulation and rapid response indicated that they were sensitive to thermal stress and bacterial challenge. This study demonstrated that HSP60 and HSP90β might participate in innate immune and environmental responses of M. amblycephala. It indicated that they could be used as biomarkers to test the stress caused by local aquaculture environment.