Molecular characterization, gene expression and transcriptional regulation of cytosolic HSP90 genes in the flatfish Senegalese sole (Solea senegalensis Kaup)

Gene expression responses in different regions of Eisenia fetida with antiparasitic albendazole exposure

Albendazole (ABZ) is a veterinary drug with a high efficiency against parasite. The aim of this research is to investigate and characterize the response of gene expression in different regions of earthworms Eisenia fetida in relation to ABZ exposure. In this research, the earthworms were exposed to ABZ at 0, 10, 30, 90, and 270 mg/kg concentrations for 42 days. Within the initial 14-day exposure, the expression levels of two target genes (mitochondrial large ribosomal subunit (l-rRNA) and heat shock protein (HSP90)) in different regions of earthworms were affected significantly by the different exposure concentrations of ABZ, but the growth rates were similar among the ABZ and control groups. With longer exposure time, growth rates decreased significantly after 28 days of exposure at 90 and 270 mg/kg. These results of target genes expression suggest that, at low ABZ concentrations, the middle region of earthworms is more sensitive to ABZ than the anterior and posterior regions. In the middle region, the l-rRNA expression of the ABZ-exposed groups was significantly lower than the control group, with a reduction to 23%, 25% and 31% for 10, 30 and 90 mg/kg ABZ concentrations, respectively (P<0.01). In contrast, the HSP90 expression of the ABZ groups (full range of 10 to 270 mg/kg) in the middle region increased 4.1-8.7 folds over the control group (P<0.01). In the anterior and posterior regions, the expression of the two target genes at 10mg/kg did not differ significantly among the ABZ and control groups (P>0.05), except for l-rRNA in the posterior region. The characterization and understanding of target genes expression in different regions of earthworms can provide important information on predictive early reading on the pollution of ABZ residue in soils.

Metamorphosis in teleosts

Teleosts are the largest and most diverse group of vertebrates, and many species undergo morphological, physiological, and behavioral transitions, "metamorphoses," as they progress between morphologically divergent life stages. The larval metamorphosis that generally occurs as teleosts mature from larva to juvenile involves the loss of embryo-specific features, the development of new adult features, major remodeling of different organ systems, and changes in physical proportions and overall phenotype. Yet, in contrast to anuran amphibians, for example, teleost metamorphosis can entail morphological change that is either sudden and profound, or relatively gradual and subtle. Here, we review the definition of metamorphosis in teleosts, the diversity of teleost metamorphic strategies and the transitions they involve, and what is known of their underlying endocrine and genetic bases. We suggest that teleost metamorphosis offers an outstanding opportunity for integrating our understanding of endocrine mechanisms, cellular processes of morphogenesis and differentiation, and the evolution of diverse morphologies and life histories.

Overexpression of Hsp90 from grass carp (Ctenopharyngodon idella) increases thermal protection against heat stress

With homologous DNA probes, we had screened a grass carp heat shock protein 90 gene (CiHsp90). The full sequence of CiHsp90 cDNA was 2793 bp, which could code a 798 amino acids peptide. The phylogenetic analysis demonstrated that CiHsp90 shared the high homology with Zebrafish Grp94. Quantitative RT-PCR analysis showed that CiHsp90 was ubiquitously expressed at lower levels in all detected tissues and up-regulated after heat shock at 34 °C or cold stress at 4 °C. To understand the function of CiHsp90 involving in thermal protection, an expression vector containing coding region cDNA was expressed in E. coli BL21 (DE3) plysS. Upon transfer from 37 °C to 42 °C, these cells that accumulated CiHsp90 peptides displayed greater thermoresistance than the control cells. While incubated at 4°C for different periods, it could also improve the cell viability. After transient transfected recombinant plasmid pcDNA3.1/CiHsp90 into mouse myeloma cell line SP2/0, we found that CiHsp90 could contribute to protecting cells against both thermal and cold extremes. On the contrary, the mutant construct ΔN-CiHsp90 (256-798aa) could abolish the protection activity both in prokaryotic cells and eukaryotic cells. Additionally, both CiHsp90 and ΔN-CiHsp90 peptides could reduce the level of citrate synthase aggregation at the high temperature.

The gene expression response of the catadromous perciform barramundi Lates calcarifer to an acute heat stress

The acute heat-shock response of the tropical estuarine fish species barramundi Lates calcarifer as indicated by the expression of genes within stress (hsp 90AA, hsp 90AB, hsp 70 and hsc 70), metabolic (cisy, cco II and ldh) and growth (igf1 and mstn 1) related pathways was examined following an increase in water temperature from 28 to 36° C over 30 min. Lates calcarifer were maintained at the acute stress temperature of 36° C for 1 h before being returned to 28° C and allowed to recover at this temperature for a further 2 weeks. Muscle tissue sampling over the experimental period allowed for the expression quantification of stress, metabolic and growth-related genes via quantitative real-time polymerase chain reaction (qrt-PCR) where a robust and reliable normalization approach identified both α-tub and Rpl8 as appropriate genes for the analysis of gene expression in response to an acute heat stress. hsp90AA and hsp70 of the inducible heat-shock response pathway showed a massive up-regulation of gene expression in response to heat stress, whilst the constitutive heat-shock genes hsp90AB and hsp70 showed no change over the course of the experiment and a small increase after 2 weeks of recovery, respectively. Of the three genes representing the metabolic pathway (cisy, cco II and ldh) only cco II changed significantly showing a decrease in gene expression, which may suggest a small suppression of aerobic metabolism. igf1 of the growth pathway showed no significant differences in response to an acute heat stress, whilst mstn1 increased at the beginning of the heat stress but returned to basal levels soon after. Overall, the results demonstrate that an acute heat stress in L. calcarifer caused a significant increase in the expression of genes from the stress response pathway and a possible decrease in aerobic metabolism with only relatively minor changes to the growth pathway highlighting the hardy nature of L. calcarifer and its resilience in coping with sudden temperature changes routinely encountered within its natural environment.

Cloning and characterization of the HSP90 beta gene from Tanichthys albonubes Lin (Cyprinidae): effect of copper and cadmium exposure

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone important in the maturation of a broad spectrum of proteins. In order to evaluate the effect of copper (Cu(2+)) and cadmium (Cd(2+)) on the expression of HSP90 from Tanichthys albonubes (designated TaHSP90), the full-length complementary DNA (cDNA) of TaHSP90 was cloned using reverse transcription PCR and rapid amplification of cDNA ends (RACE) techniques. A 2,687-bp sequence was sequenced and consisted of an open reading frame (ORF) of 2,181 bp encoding a polypeptide of 727 amino acids with five HSP90 family signatures. Homologous analysis revealed that TaHSP90 gene shared high similarity with other known HSP90 genes and belonged to HSP90β subtype. Fluorescent real-time quantitative PCR was used to examine the expression pattern of TaHSP90β mRNA in different tissues (liver, muscle, gill, fin, eye, ovary, intestine and brain), and the result indicated that TaHSP90β was widely expressed in all examined tissues at different levels. Sensitivity of TaHSP90β to copper and cadmium was examined by exposing fish to different concentrations of Cu(2+) (0, 13.50 and 27.00 μg/L) and Cd(2+) (0, 1.15, 2.31 mg/L) for 24, 48, 72 and 96 h, respectively. The copper treatment induced TaHSP90β expression slight increase only at 24 and 48 h, while cadmium treatment caused slight down-regulation of TaHSP90β only 72 and 96 h. Our data suggest that the cloning and expression analysis of T. albonubes HSP90β gene provided useful molecular information of T. albonubes responses in stress conditions and potential ways to monitor the chronic stressors in T. albonubes culture environments.

Dexamethasone modulates expression of genes involved in the innate immune system, growth and stress and increases susceptibility to bacterial disease in Senegalese sole (Solea senegalensis Kaup, 1858)

Cortisol, the main glucocorticoid in fish, undertakes pleiotropic biological effects in response to stressors to maintain homeostasis. It can exert several actions on the immune system, growth and cellular metabolism, establishing a fine-tune regulation stress response and cross-talk interactions with other regulatory pathways. In this study, we investigated a causal relationship between high levels of glucocorticoids and susceptibility to pathogens and modification of gene expression profiles in Senegalese sole. For this purpose, we carried out two experiments using post-metamorphic individuals (21 days after hatching) that were exposed to dexamethasone (DXM), a potent glucocorticoid, in order to mimic cortisol effects. We quantified transcript levels of a wide set of genes involved in innate immune system (g-type lysozyme and hepcidin (hamp1)), HPI axis (crf, crfbp, pomcα, pomcβ, gr1 and gr2), HPT axis (tgb), cellular stress defense system (hsp70 and hsp90aa), GH/IGF axis (igf-I and igf-Ir) and the neuropeptide trh. Short-term exposure to 0.1, 1 and 10 ppm DXM provoked a reduction of pomcβ transcripts and an increase of crfbp mRNAs in a dose-dependent manner at 48 and 72 h after treatment. Moreover, g-type lysozyme transcript levels decreased significantly at 72 h whereas hamp1 mRNA levels increased at 48 h after exposure. Long-term DXM treatment (10 ppm DXM) affected negatively weight of soles (~20% lower than controls). Moreover, reduced mRNA levels were observed for pomcβ after 1 week and igf-I and hamp1 after 2 weeks. In contrast, crfbp and crf increased mRNA levels after 2 weeks. hsp70 exhibited a dual response increasing transcript levels at 1 week after treatment and reducing thereafter. No significant changes in gene expression were observed at any time during this study for tgb, trh, hsp90aa, pomcα, gr1 and gr2. Finally, a challenge experiment using the pathogen Photobacterium damselae subsp piscicida confirmed earlier and higher mortalities in DXM-treated animals. Taken together, these data indicate that a prolonged exposure to DXM increases the susceptibility to pathogens and reduces growth. Moreover, DXM can trigger a wide cellular response modulating the expression of genes involved in the innate immune system, HPI and GH/IGF axes as well as cellular stress defense. These results are highly valuable to evaluate responses associated to aquaculture stressful conditions and discriminate specific glucocorticoid-mediated effects.

Expression analysis of heat shock genes in the skin, spleen and blood of common carp (Cyprinus carpio) after cadmium exposure and hypothermia

Heat shock proteins are chaperones that play a pivotal role in controling multiple regulatory pathways such as stress defense, hormone signaling, cell cycle control, cell proliferation and differentiation, and apoptosis. In this study, the expression patterns of four well-known heat shock genes (hsp70, hsc70-1, hsc70-2 and hsp90α) were characterized in the skin, spleen and blood cells of the common carp, under unstressed conditions and after Cd2+ treatment or hypothermia. The examined genes were expressed in a tissue-specific manner: hsc70-2 was expressed constitutively, and was at best only slightly inducible; hsp90α exhibited a high basic expression in all three tissues, whereas hsc70-1 did so only in the blood cells, the expression of hsp70 proved to be below the level of detection in unstressed fish. Cold shock induced the expression of hsp genes in the spleen (hsp90α) and blood cells (hsp70, hsc70-1 and hsp90α), while Cd2+ treatment has no effect on the expression pattern. The highest inducibilities were detected in the skin: for hsp70 an induction of at least 20-fold after cadmium exposure, for hsc70-1 of at least 30-fold and for hsp90α of 3-fold after hypothermia.

Can the integration of multiple biomarkers and sediment geochemistry aid solving the complexity of sediment risk assessment? A case study with a benthic fish

Surveying toxicity of complex geochemical media as aquatic sediments often yields results that are either difficult to interpret or even contradictory to acknowledged theory. Multi-level biomarkers were investigated in a benthic fish exposed to estuarine sediments through laboratory and in situ bioassays, to evaluate their employment either in ecological risk assessment or in more mechanistic approaches to assess sediment-bound toxicity. Biomarkers reflecting lesions (such as genotoxicity or histopathology), regardless of their low or absent specificity to contaminants, are efficient in segregating exposure to contaminated from uncontaminated sediments even when classical biomarkers like CYP1A and metallothionein induction are inconclusive. Conversely, proteomics and gene transcription analyses provided information on the mechanics of toxicity and aided explaining response variation as a function of metabolic imbalance and impairment of defences against insult. In situ bioassays, although less expedite and more affected by confounding factors, produced data better correlated to overall sediment contamination.

Genomic characterization, phylogeny and gene regulation of g-type lysozyme in sole (Solea senegalensis)

The g-type lysozyme is a key protein of the innate immune system to fight bacterial infections. In this study we cloned and characterized the gene encoding for g-type lysozyme in Senegalese sole (Solea senegalensis). The deduced amino acid sequence comprised 195 residues containing the three conserved catalytic residues and two cysteines. A BAC analysis revealed that the gene is structured in 5 exons and 4 introns. Also, two polyadenylation signals that generate two cDNAs differing in 3'-UTR length were detected. Promoter analysis showed the presence of the main cis-acting elements involved in the transcriptional regulation of the gene. At genomic level, the g-type lysozyme was associated with mucolipin 1 and the peptidoglycan recognition protein 2 conforming a cluster of antidefensive genes with a well-conserved synteny across Percomorpha. FISH analysis using the BAC clone revealed a single hybridization signal located in an acrocentric chromosome pair. The phylogenetic analysis confirmed that the g-type lysozyme represents a complex group in fish that has been shaped by gene duplications and diversification with several positions under Darwinian selection. Expression analysis in juvenile tissues indicated that transcript levels were higher in gills, spleen and heart. During development, gene expression activated just at the beginning of metamorphosis, increasing progressively until climax. Hormonal treatments demonstrated that this gene was regulated positively by thyroid hormones during development and negatively by dexamethasone. In contrast, no response was observed after all-trans retinoic acid or 4-diethylaminobenzaldehyde treatments. Finally, treatments using lipopolysaccharide, lipoteichoic acid, peptidoglycan, zymosan and poly(I:C) activated gene expression in a time- and tissue-specific manner. Taken together, data indicate that g-type lysozyme is a high evolutionary conserved gene that diversified to adapt to changing environment and pathogen conditions. Gene expression can be activated by diverse pathogen stimuli and modulated by physiological factors with important consequences for the aquaculture of this species.

Molecular characterization and transcriptional regulation of the sodium-dependent vitamin C transporter genes (slc23a1 and slc23a2) in a teleost fish, the Senegalese sole (Solea senegalensis)

Vitamin C (ascorbic acid, AA) is an antioxidant that acts as a free radical scavenger and cofactor for several important enzymatic reactions, thus being important for normal cellular functions, growth and development. Accumulation of AA in cells depends on two types of sodium-dependent vitamin C transporters (SVCTs), designed as SVCT1 and SVCT2. In human, they are the products of SLC23A1 and SLC23A2 genes, respectively. In the present work, the molecular cloning of the cDNAs corresponding to slc23a1 and slc23a2 in a teleost fish, the Senegalese sole (Solea senegalensis Kaup, 1858) is first described. Sequence analysis of the predicted polypeptides revealed a conserved topology with those of mammals with important motifs involved in structure and function, being also present in svct1 and svct2. Phylogenetic analyses including a range of vertebrate SVCTs suggest that both transporters are the result of an ancient gene duplication event that occurred prior to the divergence of tetrapods and teleosts, which took place 450 million years ago. Expression profiles in juvenile tissues and during larval development were analyzed using a real-time PCR approach. In juvenile fish, slc23a1 was strongly expressed in intestine, whereas slc23a2 exhibited a widespread distribution in tissues. Transcripts of both genes were detected at early developmental stages, probably representing mRNAs of maternal origin. A possible regulation by their own substrate was detected after first uptakes of AA from diet in both genes. During metamorphosis, both slc23a1 and slc23a2 were down-regulated, the former in a thyroid hormone (TH) dependent way. This pattern coincided with a significant reduction in the AA content of larvae during metamorphosis. These results are interpreted in a physiological context of general reduction in the metabolism of metamorphic larvae. Data presented here provide the first step toward a better understanding of the physiological role of SVCTs in teleost fish.

Expression of hsp70, hsp90 and hsf1 in the reef coral Acropora digitifera under prospective acidified conditions over the next several decades

Ocean acidification is an ongoing threat for marine organisms due to the increasing atmospheric CO₂ concentration. Seawater acidification has a serious impact on physiologic processes in marine organisms at all life stages. On the other hand, potential tolerance to external pH changes has been reported in coral larvae. Information about the possible mechanisms underlying such tolerance responses, however, is scarce. In the present study, we examined the effects of acidified seawater on the larvae of Acropora digitifera at the molecular level. We targeted two heat shock proteins, Hsp70 and Hsp90, and a heat shock transcription factor, Hsf1, because of their importance in stress responses and in early life developmental stages. Coral larvae were maintained under the ambient and elevated CO₂ conditions that are expected to occur within next 100 years, and then we evaluated the expression of hsps and hsf1 by quantitative real-time polymerase chain reaction (PCR). Expression levels of these molecules significantly differed among target genes, but they did not change significantly between CO₂ conditions. These findings indicate that the expression of hsps is not changed due to external pH changes, and suggest that tolerance to acidified seawater in coral larvae may not be related to hsp expression.

Transcriptomic analyses in a benthic fish exposed to contaminated estuarine sediments through laboratory and in situ bioassays

The transcription of contaminant response-related genes was investigated in juvenile Senegalese soles exposed to sediments from three distinct sites (a reference plus two contaminated) of a Portuguese estuary (the Sado, W Portugal) through simultaneous 28-day laboratory and in situ bioassays. Transcription of cytochrome P450 1A (CYP1A), metallothionein 1 (MT1), glutathione peroxidase (GPx), catalase (CAT), caspase 3 (CASP3) and 90 kDa heat-shock protein alpha (HSP90AA) was surveyed in the liver by real-time PCR. CASP3 transcription analysis was complemented by surveying apoptosis through the TUNEL reaction. After 14 days of exposure, relative transcription was either reduced or decreased in fish exposed to the contaminated sediments, revealing a disturbance stress phase during which animals failed to respond to insult. After 28 days of exposure all genes' transcription responded to contamination but laboratory and in situ assays depicted distinct patterns of regulation. Although sediments revealed a combination of organic and inorganic toxicants, transcription of the CYP1A gene was consistently correlated to organic contaminants. Metallothionein regulation was found correlated to metallic and organic xenobiotic contamination in the laboratory and in situ, respectively. The transcription of oxidative stress-related genes can be a good indicator of general stress but caution is mandatory when interpreting the results since regulation may be influenced by multiple factors. As for MT1, HSP90 up-regulation has potential to be a good indicator for total contamination, as well as the CASP3 gene, even though hepatocyte apoptosis depicted values inconsistent with sediment contamination, showing that programmed cell death did not directly depend on caspase transcription alone.

Expression pattern of heat shock protein 90 gene of humphead snapper Lutjanus sanguineus during pathogenic Vibrio harveyi stress

The full-length cDNA of heat shock protein 90 (HSP90) of humphead snapper Lutjanus sanguineus, designated as rsHSP90, was cloned by rapid amplification of complementary (c)DNA ends (RACE) techniques with the primers designed from the known expressed sequence tag (EST) sequence identified from the subtracted cDNA library of the head kidney of L. sanguineus. Sequence analysis showed that the full-length cDNA of rsHSP90 was 2745 bp, containing a 5' terminal untranslated region (UTR) of 99 bp, a 3' terminal UTR of 471 bp and an open reading frame (ORF) of 2175 bp encoding a polypeptide of 725 amino acids. On the basis of the deduced amino acid sequence, the theoretical molecular mass of rsHSP90 was calculated to be 83·18 kDa with an isoelectric point of 4·79. Moreover, five classical HSP90 family signatures were found in the amino acids sequence of rsHSP90 by PredictProtein. Basic local-alignment search-tool (BLAST) analysis revealed that the amino acids sequence of rsHSP90 had the highest similarity of 97% when compared with other HSP90s. Fluorescent real-time quantitative reverse-transcription (RT)-PCR was used to examine the expression pattern of rsHSP90 in eight kinds of tissues and organs of L. sanguineus challenged with Vibrio harveyi. There was a clear time-dependent expression pattern of rsHSP90 in head kidney, spleen and thymus after bacterial challenge and the expression of messenger (m)RNA reached the maximum level at the time points of 9, 15 and 24 h, respectively. The up-regulated mRNA expression of rsHSP90 in L. sanguineus after bacterial challenge indicated that rsHSP90 was inducible and might be involved in immune response.

Validation of housekeeping genes for gene expression studies in Symbiodinium exposed to thermal and light stress

Unicellular photosynthetic algae (dinoflagellate) from the genus Symbiodinium live in mutualistic symbiosis with reef-building corals. Cultured Symbiodinium sp. (clade C) were exposed to a range of environmental stresses that included elevated temperatures (29°C and 32°C) under high (100 μmol quanta m(-2) s(-1) Photosynthetic Active Radiation) and low (10 μmol quanta m(-2) s(-1)) irradiances. Using real-time RT-PCR the stability of expression for the nine selected putative housekeeping genes (HKGs) was tested. The most stable expression pattern was identified for cyclophilin and S-adenosyl methionine synthetase (SAM) followed by S4 ribosomal protein (Rp-S4), Calmodulin (Cal), and Cytochrome oxidase subunit 1 (Cox), respectively. Thermal stress alone resulted in the highest expression stability for Rp-S4 and SAM, with a minimum of two reference genes required for data normalization. For Symbiodinium exposed to both, light and thermal stresses, at least five reference genes were recommended by geNorm analysis. In parallel, the expression of Hsp90 for Symbiodinium in culture and in symbiosis within coral host (Acropora millepora) was evaluated using the most stable HKGs. Our results revealed a drop in Hsp90 expression after an 18 h-period and a 24 h-period of exposure to elevated temperatures indicating the similar Hsp90 expression profile in symbiotic and non-symbiotic environments. This study provides the first list of the HKGs and will provide a useful reference in future gene expression studies in symbiotic dinoflagellates.

Validation of reference genes for quantitative RT-qPCR studies of gene expression in Atlantic cod (Gadus morhua l.) during temperature stress

Background

One important physiological response to environmental stress in animals is change in gene expression. To obtain reliable data from gene expression studies using RT-qPCR it is important to evaluate a set of possible reference genes as normalizers for expression. The expression of these candidate genes should be analyzed in the relevant tissues during normal and stressed situations. To find suitable reference genes it was crucial that the genes were stably expressed also during a situation of physiological stress. For poikilotermic animals like cod, changes in temperature are normal, but if the changes are faster than physiological compensation, the animals respond with typical stress responses. It has previously been shown that Atlantic cod show stress responses when elevation of water temperature is faster than 1 degree/day, for this reason we chose hyperthermia as stress agent for this experiment.

Findings

We here describe the expression of eight candidate reference genes from Atlantic cod (Gadus morhua l.) and their stability during thermal stress (temperature elevation of one degree C/day for 5 days). The genes investigated were: Eukaryotic elongation factor 1 alpha, ef1a; 18s ribosomal RNA; 18s, Ubiquitin conjugate protein; ubiq, cytoskeletal beta-actin; actb, major histcompatibility complex I; MHC-I light chain, beta-2 -microglobulin; b2m, cytoskeletal alpha-tubulin; tba1c, acidic ribosomal phosphoprotein; rplp1, glucose-6-phosphate dehydrogenase; g6pd. Their expression were analyzed in 6 tissues (liver, head kidney, intestine, spleen, heart and gills) from cods exposed to elevated temperature and compared to a control group. Although there were variations between tissues with respect to reference gene stability, four transcripts were more consistent than the others: ubiq, ef1a, 18s and rplp1. We therefore used these to analyze the expression of stress related genes (heat shock proteins) induced during hyperthermia. We found that both transcripts were significantly upregulated in several tissues in fish exposed to increased temperature.

Conclusion

This is the first study comparing reference genes for RT-qPCR analyses of expression during hyperthermia in Atlantic cod. ef1a, 18s, rplp1 and ubiq transcripts were found to be well suited as reference genes during these experimental conditions.

Expression of hsp90 mediates cytoprotective effects in the gastrodermis of planarians

Heat shock proteins (HSPs) play a crucial role in the protection of cells. In the present study, we have identified an hsp90-related gene (Djhsp90) encoding a cytosolic form of HSP90 that is primarily expressed in gastrodermis of the planarian Dugesia japonica. Djhsp90 becomes significantly induced after traumatic amputation or other stress stimuli, such as exposure to X-ray or ultraviolet radiations, heat shock, or prolonged starvation. When Djhsp90 is silenced by ribonucleic acid interference (RNAi), planarians dramatically decrease in size, becoming unable to eat, and die in a few weeks. Our results indicate that this gene plays an essential cytoprotective role in the gastrodermis of planarians and suggest that this chaperone can be involved in autophagic processes that are activated by this tissue.

Molecular characterization and gene expression of thyrotropin receptor (TSHR) and a truncated TSHR-like in Senegalese sole

Thyroid hormones (THs) play a key role in larval development, growth and metamorphosis in flatfish. Their synthesis is tightly regulated by the hypothalamic-pituitary-thyroid axis. Thyroid-stimulating hormone receptor (TSHR) is a key protein in the control of thyroid function stimulating TH synthesis after binding its ligand, the thyrotropin. In teleost fish, numerous reports have associated the TSHR with gametogenesis. However, little information about its role during larval development is available. In this study, we report the cloning of two different cDNAs with high similarity to TSHR. Phylogenetic analysis clustered both cDNAs separately. One of them (referred to TSHR) grouped with TSHR orthologs in tetrapods and teleost fish and possessed the three typical conserved domains and regulatory motifs. The second receptor (referred to as TSHRtr-like) represented a novel truncated cDNA bearing the extracellular and part of the transmembrane domain. TSHRtr-like orthologs were only found in teleosts, which suggests that it could have appeared after fish-specific 3R genome duplication. Expression profiles of both genes are analyzed in juvenile tissues and during larval development using a real-time PCR approach. In juvenile fish, TSHR and TSHRtr-like are expressed ubiquitously although transcript levels varied between organs. In both cases, the highest mRNAs levels are detected in brain. During larval development, both genes are expressed to a high level during the first stages (2-3days after hatching) reducing progressively their abundance in the whole larvae during metamorphosis. This reduction in mRNA abundance is more accentuated for the TSHRtr-like gene. To evaluate the possible regulation of both receptors by T4 during sole metamorphosis, larvae are exposed to the goitrogen thiourea (TU). Only TSHRtr-like modifies its expression, increasing its transcripts at 11days after treatment. Moreover, adding exogenous T4 hormone to TU-treated larvae restores the TSHRtr-like steady-state levels similar to the untreated control. Overall, these results demonstrate the existence of two thyrotropin receptors differentially regulated by THs in teleosts.

MnHSP90 cDNA characterization and its expression during the ovary development in oriental river prawn, Macrobrachium nipponense

Heat shock protein 90 (HSP90) is not only involved in environmental stress but also plays roles in the ovary development in some vertebrates. To understand its role in crustacean, we examined the HSP90 cDNA for the first time in the ovary and hepatopancreas of the oriental river prawn, Macrobrachium nipponense and designated this protein as MnHSP90 in this study. The MnHSP90 was cloned by the methods of degenerated oligonucleotide primers and rapid amplification of the cDNA ends (RACE). Bioinformatics analysis showed that the MnHSP90 cDNA was 2,684 bp in length, containing a 126 bp 5' untranslated region (UTR), a 359 bp 3' UTR, and an open reading frame (ORF) of 2,199 bp encoding a 732-amino acid polypeptide with predicted molecular mass of 84.3 KDa. Sequence alignment showed that the MnHSP90 shared 72-79% identity with other animals. Real-time quantitative PCR (qPCR) analysis demonstrated that the MnHSP90 mRNA was ubiquitously detected in all tested tissues, with the highest expression in the thoracic ganglia, the mediate in heart, muscle and intestine, and the lowest in haemocytes and gills. The MnHSP90 mRNA levels in the hepatopancreas and ovary of M. nipponense reached a maximum at the stage III (early vitellogenic stage) and stage IV (later vitellogenic stage) ovaries, respectively, and then decreased significantly in both tissues as the ovarian development proceeded. The level of MnHSP90 expression in the hepatopancreas was higher than that in the ovary when compared with in the same ovarian developmental stage. Our results indicate that MnHSP90 is involved in ovarian development in oriental river prawn and may play a regulatory role in ovary maturation.

Molecular characterization and expression analysis of a heat shock protein 90 gene from disk abalone (Haliotis discus)

Heat shock protein 90s (hsp90s) are chaperones that contribute to the proper folding of cellular proteins and help animals cope with the cellular protein damages in stress conditions. In this study, an hsp90 gene was isolated from disc abalone (Haliotis discus). The complete nucleotide sequence of the hsp90 gene contains an open reading frame of 2,184 base pairs, encoding an 84 kDa protein. Disk abalone hsp90 shares high sequence similarity with other hsp90 family proteins. Although the phylogenetic analysis did not classify it into the hsp90α group, the inductivity of this gene was confirmed by heat shock and lipopolysaccharide (LPS) challenge test. Disk abalone hsp90 gene displayed a rapid and reversible induction response to both an exposure of typical heat shock and the LPS challenge. Once given the sublethal heat shock treatment, the transcription of disk abalone hsp90 gene was significantly up-regulated. With a recovery of 12 h, the transcription of disk abalone hsp90 gene gradually attenuated to the control level. These observations reflected the feedback regulation of abalone heat shock responses faithfully. In response to LPS challenge, the transcription of disk abalone hsp90 gene was significantly increased within 2 h and it approached maximum induction at 4 h later and recovered finally the reference level in 24 h. Take all together, the cloning and expression analysis of disk abalone hsp90 gene provided useful molecular information of abalone responses in stress conditions and potential ways to monitor the chronic stressors in abalone culture environments and diagnose the animal health status.

Effects of stocking density and feed ration on growth and gene expression in the Senegalese sole (Solea senegalensis): potential effects on the immune response

Stocking density and ration size are two major factors influencing aquaculture production. To evaluate their effects on growth and immune system in Senegalese sole (Solea senegalensis) juveniles, a 2 x 2 experimental design using two rations (1.0% and 0.25% of the total fish biomass) and two different initial stocking densities (7 and 30 kg m(-2)) was performed throughout a 60 days culture period. Soles fed 1.0% showed a higher specific growth rate (SGR) than those fed 0.25% (3.3-fold). No differences in SGR at 60 days were found between densities in spite of reduced values were detected at high density after 20 days (soles fed 0.25%) and 40 days (soles fed 1%) suggesting a compensatory growth. Physiologically, plasma cortisol levels were elevated in soles at high density (45-fold higher than at 7 kg m(-2)) whereas no differences associated to the feeding ration were observed. To assess the effects at a molecular level, the mRNA levels of genes involved in cellular stress (heat shock proteins HSP70 and HSP90), growth (insulin-like growth factors IGF-I, the spliced variants IGF-Ia and IGFI-b, and IGF-II) and innate immune system (g-type lysozyme and hepcidin (HAMP1)) were quantified. No differences in HSP90 expression were detected between densities or rations. In contrast, IGF-I, IGF-Ia and IGF-II showed reduced transcript levels in liver and HSP70 in liver and kidney at high density. Finally, g-type lysozyme and HAMP1 expression was greatly affected by both factors exhibiting an important reduction in the transcript levels at high density and low ration. Overall, our results show that S. senegalensis juveniles might exhibit satisfactory SGR at high density although the high plasma cortisol levels indicate a crowding stress that could negatively affect the expression levels of some of the genes studied.

Molecular characterization, gene expression and transcriptional regulation of thyroid hormone receptors in Senegalese sole

Thyroid hormones (THs) play a key role in larval development, growth and metamorphosis in flatfish. Their genomic effects are mediated by thyroid hormone receptors (TRs). In this study, cDNAs encoding for TRalphaA, TRalphaB, and TRbeta have been sequenced in Senegalese sole (Soleasenegalensis). Main domains and conserved motifs were identified. Also, a truncated TRalphaB isoform (referred to as TRalphaBtr) and a spliced TRbeta variant (referred to as TRbetav) were detected. A phylogenetic analysis grouped both TRalpha and TRbeta genes into two separate clusters with their fish and mammalian counterparts. Expression profiles during larval development and in juvenile tissues were analyzed using a real-time PCR approach. In juvenile fish, TRalphaA, TRalphaB, TRbetav, and TRbeta showed distinct transcript levels in tissues. During metamorphosis, only TRbetav and TRbeta modified their mRNA levels in a similar way to the T4 contents. To evaluate the possible regulation of TRs by their cognate ligand T4 during sole metamorphosis, larvae were exposed to the goitrogen thiourea (TU). TRbeta transcripts decreased significantly at 11 and 15 days after treatment. Moreover, adding exogenous T4 hormone to TU-treated larvae restored the steady-state levels or even increased TRbeta and TRbetav mRNAs with respect to the untreated control. Overall, these results demonstrate that TRbeta transcription is up-regulated by THs playing a major role during metamorphosis in Senegalese sole.