Cloning of a heat shock protein 90 (HSP90) gene and expression analysis in the ridgetail white prawn Exopalaemon carinicauda

CRISPR/Cas9-mediated gene mutation of EcIAG leads to sex reversal in the male ridgetail white prawn Exopalaemon carinicauda

In the culture of crustaceans, most species show sexual dimorphism. Monosex culture is an effective approach to achieve high yield and economic value, especially for decapods of high value. Previous studies have developed some sex control strategies such as manual segregation, manipulation of male androgenic gland and knockdown of the male sexual differentiation switch gene encoding insulin-like androgenic gland hormone (IAG) in decapods. However, these methods could not generate hereditable changes. Genetic manipulation to achieve sex reversal individuals is absent up to now. In the present study, the gene encoding IAG (EcIAG) was identified in the ridgetail white prawn Exopalaemon carinicauda. Sequence analysis showed that EcIAG encoded conserved amino acid structure like IAGs in other decapod species. CRISPR/Cas9-mediated genome editing technology was used to knock out EcIAG. Two sgRNAs targeting the second exon of EcIAG were designed and microinjected into the prawn zygotes or the embryos at the first cleavage with commercial Cas9 protein. EcIAG in three genetic males was knocked out in both chromosome sets, which successfully generated sex reversal and phenotypic female characters. The results suggest that CRISPR/Cas9-mediated genome editing technology is an effective way to develop sex manipulation technology and contribute to monosex aquaculture in crustaceans.

A Review on the Involvement of Heat Shock Proteins (Extrinsic Chaperones) in Response to Stress Conditions in Aquatic Organisms

Heat shock proteins (HSPs) encompass both extrinsic chaperones and stress proteins. These proteins, with molecular weights ranging from 14 to 120 kDa, are conserved across all living organisms and are expressed in response to stress. The upregulation of specific genes triggers the synthesis of HSPs, facilitated by the interaction between heat shock factors and gene promoter regions. Notably, HSPs function as chaperones or helper molecules in various cellular processes involving lipids and proteins, and their upregulation is not limited to heat-induced stress but also occurs in response to anoxia, acidosis, hypoxia, toxins, ischemia, protein breakdown, and microbial infection. HSPs play a vital role in regulating protein synthesis in cells. They assist in the folding and assembly of other cellular proteins, primarily through HSP families such as HSP70 and HSP90. Additionally, the process of the folding, translocation, and aggregation of proteins is governed by the dynamic partitioning facilitated by HSPs throughout the cell. Beyond their involvement in protein metabolism, HSPs also exert a significant influence on apoptosis, the immune system, and various characteristics of inflammation. The immunity of aquatic organisms, including shrimp, fish, and shellfish, relies heavily on the development of inflammation, as well as non-specific and specific immune responses to viral and bacterial infections. Recent advancements in aquatic research have demonstrated that the HSP levels in populations of fish, shrimp, and shellfish can be increased through non-traumatic means such as water or oral administration of HSP stimulants, exogenous HSPs, and heat induction. These methods have proven useful in reducing physical stress and trauma, while also facilitating sustainable husbandry practices such as vaccination and transportation, thereby offering health benefits. Hence, the present review discusses the importance of HSPs in different tissues in aquatic organisms (fish, shrimp), and their expression levels during pathogen invasion; this gives new insights into the significance of HSPs in invertebrates.

Ovarian development pattern and vitellogenesis of ridgetail white prawn, Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda has the potential to be used as a model organism in crustacean research because it has a transparent body, available draft genome, and short life cycle. However, their ovarian development pattern remains unclear under laboratory culture conditions. This study investigated the changes of ovarian external feature, ovarian histology, gonadosomatic index (GSI), and hepatosomatic index (HSI), as well as the expression and localization of vitellogenin in the ovary and the hepatopancreas during the first ovarian development cycle of E. carinicauda under laboratory-reared condition. The results demonstrated that (1) the first ovarian development cycle of E. carinicauda could be divided into 5 different stages in which the ovary changes its color from white to yellow during the vitellogenesis process in parallel with increasing GSI. (2) After pubertal molt, most females reached ovarian stage II while the females reached stage V after premating molt. (3) During the ovarian development, GSI increased smoothly and HSI relatively stable during the period of stages I to IV, while GSI increased but HSI decreased significantly from stages IV to V. (4) In situ hybridization (ISH) revealed that EcVg was slightly expressed in the oocyte cytoplasm of previtellogenic oocytes. The positive signal was mainly detected in hepatopancreatic fibrillar cells, and a strong signal was found in the hepatopancreas at stage IV. Moreover, the expression level of EcVg-mRNA in the hepatopancreas is stage-specific, and the hepatopancreas contributes majority of vitellin precursor protein to support the ovarian development of E. carinicauda.

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 Inbreeding on Genetic Characteristic, Growth, Survival Rates, and Immune Responses of a New Inbred Line of Exopalaemon carinicauda

The Exopalaemon carinicauda could be a useful crustacean laboratory animal in many research fields. We newly established an inbred line of Exopalaemon carinicauda named EC4 inbred line by brother×sister mating and keeping to F₁₁ generation. Trends in heterozygosity in the process of producing EC4 inbred line were examined through the characterization of polymorphisms based on gene frequencies of SNP and EST-SSR loci. The results demonstrated that the number of alleles (N), observed heterozygosity (Ho), expected heterozygosity (He), and polymorphism information content (PIC) gradually decreased with the increase of inbreeding generations. The genetic detection results indicated that 9 (29.03%, 9/31) of the SNP loci and 15 (32.61%, 15/46) of the EST-SSR loci were homozygous in F₁₁ generation of EC4 inbred line. The variation of the growth-related traits, the immune responses, and antioxidant status were described in experimental full-sibling inbred populations of E. carinicauda at five levels of inbreeding coefficient (F = 0.785, F = 0.816, F = 0.859, F = 0.886, F = 0.908) under controlled laboratory conditions. The body weight, body length, and survival rate in EC4 inbred line of all generations were less than the control population. Inbreeding affected the antibacterial activity, phenoloxidase (PO) activity, and superoxide dismutase (SOD) which decreased at the eleventh generation of EC4 inbred line. This study demonstrated that inbreeding had a negative effect on the economic traits and immune response, but our inbred line was established successfully until F₁₁ and confirmed by genetic detection using SNP and EST-SSR loci.

Genome survey and high-resolution backcross genetic linkage map construction of the ridgetail white prawn Exopalaemon carinicauda applications to QTL mapping of growth traits

BACKGROUND

High-resolution genetic linkage map is critical for QTL mapping, genome sequence assembly and marker-assisted selection in aquaculture species. The ridgetail white prawn Exopalaemon carinicauda is one of the most economic shrimp species naturally distributed in the coasts of eastern China and western Korea. However, quite limited genomics and genetics information have been exploited for genetic improvement of economic traits in this species.

RESULTS

In the present study, we conducted genome survey and constructed high-resolution genetic linkage maps of the ridgetail white prawn with reciprocal-cross mapping family genotyped using next-generation sequencing approaches. The estimated genome size was 9.33 Gb with a heterozygosity of 0.26% and a repeat sequence ratio of 76.62%. 65,772 protein-coding genes were identified by genome annotation. A total of 10,384 SNPs were used to high-throughput genotyping and assigned to 45 linkage groups (LGs) from reciprocal backcross families of E. carinicauda, and the average marker distances were 0.73 cM and 0.55 cM, respectively. Based on the high-resolution linkage map, twenty-three QTLs related to five growth traits were detected. All QTLs could explain 8.8-15.7% of the total growth-traits variation.

CONCLUSIONS

The genome size of E. carinicauda was estimated more accurately by genome survey analysis, which revealed basic genomic architecture. The first high-resolution backcross genetic linkage map and QTLs related to growth traits will provide important information for QTL fine mapping, genome assembly and genetic improvement of E. carinicauda and other palaemon shrimps.

Immune response of Exopalaemon carinicauda infected with an AHPND-causing strain of Vibrio parahaemolyticus

To investigate the immune response of Exopalaemon carinicauda infected with an AHPND-causing strain of Vibrio parahaemolyticus (VP_AHPND), three-generation breeding of shrimp selected for their survival to VP_AHPND infection was applied to explore the relationship between immune parameters and AHPND-resistant capacity of E. carinicauda. In this study, the LD₅₀ dose of 48 h and survival rates at 144 h of shrimp to VP_AHPND increased from 10^6.0 to 10^6.6 cfu ml^-1 and from 26.67% to 36.67% by three successive generations selection, respectively, while there was no significant difference between the first and second generation (p > .05). Then the immune parameters including vibrio density, total hemocyte counts (THCs), hemocyanin (HEM) concentration, antibacterial activity, activities of four immune enzymes, and expressions of eight immune-related genes were determined in the shrimp of the first (G1) and the third selective generation (G3). The results showed that the shrimp in G1 and G3 generation cleared most of VP_AHPND infecting hepatopancreas during 24 h and 6 h post injection, respectively. The levels of THCs, HEM concentration, antibacterial activity, immune enzymes including lysozyme (LZM) activity, alkaline phosphatase (AKP) activity in cell-free hemolymph, and the expression levels of Tollip, ALF, cathepsin B in hemocytes and hepatopancreas, crustin, LZM, SR in hepatopancreas and LGBP in hemocytes were higher in G3 generation than in G1 generation after infection with VP_AHPND, suggesting that these parameters may serve as potential disease-resistant indicators for evaluating the physiological status and disease-resistant capability of shrimp when infected with VP_AHPND. To further test the role of above genes in the shrimp immune response, RNAi was used to suppress their expressions and a significant decrease in survival was observed in knockdown shrimp infected with VP_AHPND as compared to controls.

The anti-stresses capability of GRP78 in Penaeus monodon: Evidence from in vitro and in vivo studies

Glucose-regulated protein 78 (GRP78) is an important member of the heat shock protein 70 (HSP70) family, which plays important roles in the response to stimulation from various external environmental stimuli. In this study, the full-length cDNA of GRP78 (PmGRP78) was cloned from Penaeus monodon. The qRT-PCR analysis showed that PmGRP78 was ubiquitously expressed in all the tested shrimp tissues, and the expression pattern of PmGRP78 in the gill and hepatopancreas tissues after a pH challenge, osmotic stress, and heavy metal exposure was also detected. A chaperone activity assay was performed to study the function of PmGRP78, and the results showed that the recombinant PmGRP78 possesses biological activity and could protect alcohol dehydrogenase (ADH) from denaturing in vitro. To further explore the role played by PmGRP78 in vivo, RNA interference (RNAi) technology was adopted to silence the expression of PmGRP78 in P. monodon, and a cumulative mortality rate assay was carried out. In conclusion, we inferred that PmGRP78 may play important roles in the defence against environmental stresses in P. monodon.

CRISPR/Cas9-Mediated Genome Editing and Mutagenesis of EcChi4 in Exopalaemon carinicauda

The development of the type II clustered regularly interspaced short palindromic repeats (CRISPR) system has resulted in the revolution of genetic engineering, and this technology has been applied in the genome editing of various species. However, there are no reports about target-specific genome editing in shrimp. In this research, we developed a microinjection method for the ridgetail white prawn Exopalaemon carinicauda and successfully applied CRISPR/Cas9 technology to the genome editing of E. carinicauda Through coinjection of mRNA of Cas9 nuclease and gRNA specialized for E. carinicauda chitinase 4 (EcChi4), shrimps with indel mutations were obtained. Further analysis showed that the mutations could be transmitted to the next generation. This is the first time that site-specific genome editing has been successfully demonstrated in a decapod, and will further contribute to the study of functional genomics in decapods.

Characterization of ADP ribosylation factor 1 gene from Exopalaemon carinicauda and its immune response to pathogens challenge and ammonia-N stress

ADP ribosylation factors (Arf), as highly conserved small guanosine triphosphate (GTP)-binding proteins, participates in intracellular trafficking and organelle structure. In this study, a full-length cDNA of Arf1 (designated EcArf1) was cloned from Exopalaemon carinicauda by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EcArf1 was 1428 bp, which contains an open reading frame (ORF) of 549 bp, encoding a 182 amino-acid polypeptide with the predicted molecular weight of 20.69 kDa and estimated isoelectric point was 7.24. Sequence analysis revealed that the conserved Arf protein family signatures were identified in EcArf1. The deduced amino acid sequence of EcArf1 shared high identity (95%-98%) with that of other species and clustered together with Arf1 of other shrimp in the NJ phylogenetic tree, indicating that EcArf1 should be a member of the Arf1 family. Quantitative real-time RT-qPCR analysis indicated that EcArf1 was expressed in hemocytes, hepatopancreas, gills, muscle, ovary, intestine, stomach and heart, and the most abundant level was in hemocytes and gills, which were also the two main target tissues of pathogen infection and environmental stress. After Vibrio parahaemolyticus challenge, EcArf1 transcripts level significantly increased in hemocytes and hepatopancreas at 3 h and 6 h, respectively. The expression of EcArf1 in hemocytes and hepatopancreas significantly up-regulated at 12 h and 6 h respectively, and down-regulated at 72 h and 48 h, respectively. EcArf1 expression in hepatopancreas and gills both significantly increased at 6 h and decreased at 24 h under ammonia-N stress. The results suggested that EcArf1 might be involved in immune responses to pathogens (V. parahaemolyticus and WSSV) challenge and ammonia-N stress in E. carinicauda.

Characterization and function analysis of Hsp60 and Hsp10 under different acute stresses in black tiger shrimp, Penaeus monodon

Heat shock proteins (Hsps) are a class of highly conserved proteins produced in virtually all living organisms from bacteria to humans. Hsp60 and Hsp10, the most important mitochondrial chaperones, participate in environmental stress responses. In this study, the full-length complementary DNAs (cDNAs) of Hsp60 (PmHsp60) and Hsp10 (PmHsp10) were cloned from Penaeus monodon. Sequence analysis showed that PmHsp60 and PmHsp10 encoded polypeptides of 578 and 102 amino acids, respectively. The expression profiles of PmHsp60 and PmHsp10 were detected in the gills and hepatopancreas of the shrimps under pH challenge, osmotic stress, and heavy metal exposure, and results suggested that PmHsp60 and PmHsp10 were involved in the responses to these stimuli. ATPase and chaperone activity assay indicated that PmHsp60 could slow down protein denaturation and that Hsp60/Hsp10 may be combined to produce a chaperone complex with effective chaperone and ATPase activities. Overall, this study provides useful information to help further understand the functional mechanisms of the environmental stress responses of Hsp60 and Hsp10 in shrimp.

The role of oncoprotein NM23 gene from Exopalaemon carinicauda is response to pathogens challenge and ammonia-N stress

Oncoprotein NM23, as a family of genes encoding the nucleoside diphosphate (NDP) kinase, plays important roles in bioenergetics, DNA replication, differentiation and tumor metastasis. In this study, a full-length cDNA of NM23 (designated EcNM23) was cloned from Exopalaemon carinicauda by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EcNM23 was 755 bp, which contains an open reading frame (ORF) of 518 bp, encoding a 175 amino-acid polypeptide with the predicted molecular weight of 19.60 kDa and estimated isoelectric point of 7.67. The deduced amino acid sequence of EcNM23 shared high identity (86%-93%) with that of other crustaceans. a NDP kinase super family signature was identified in E. carinicauda EcNM23. Quantitative real-time RT-qPCR analysis indicated that EcNM23 was expressed in all the examined tissues with the high expression level in hemocytes and ovary. The EcNM23 expression in immune-related tissues changed rapidly and reached peak at different time after pathogens (Vibrio parahaemolyticus and WSSV) challenge and ammonia-N stress treatment. The results suggested that EcNM23 might be associated with the immune defenses to pathogens infection and ammonia-N stress in E. carinicauda.

The polymorphisms in the promoter of HSP90 gene and their association with heat tolerance of bay scallop

The heat shock protein 90 (HSP90) is a highly abundant and ubiquitous molecular chaperone which plays essential roles in many cellular processes. In the present study, the messenger RNA (mRNA) expressions of HSP90 after acute heat stress were investigated in two bay scallop populations (Argopecten irradians irradians and Argopecten irradians concentricus). The heat-resistant scallop A. i. concentricus, which is distributed in Zhanjiang, China, exhibited significantly higher induction of HSP90 compared with that of the heat-sensitive scallop A. i. irradians, which is distributed in Qinhuangdao, China. The promoter sequence of HSP90 gene from bay scallop (AiHSP90) was cloned, and the polymorphisms within this region were investigated by sequencing to analyze their association with heat tolerance. A total of six single nucleotide polymorphisms (SNPs), including -1167 T-C, -1023 A-C, -799 C-T, -774 A-G, -686 C-T, and -682 A-C, were identified in the amplified promoter region, and most of them affected the putative transcription factor binding sites except for locus -1167. All the six SNP sites were found to be associated with heat tolerance after Hardy-Weinberg equilibrium (HWE) and association analysis. Moreover, haplotypes CACACC and TCTATC were also found to be associated with heat tolerance based on the result of linkage disequilibrium and association analysis. The results provided insights into the molecular mechanisms underlying the thermal adaptation of different congener endemic bay scallops, which suggested that the increased heat tolerance of A. i. concentricus (compared with A. i. irradians) was associated with the higher expression of AiHSP90. Meanwhile, the six genotypes (-1167 TT, -1023 CC, -799 TT, -774 GG, -686 CC, and -682 AA) and two haplotypes (CACACC and TCTATC) could be used as potential markers for scallop selection breeding with higher heat tolerance.

The roles of Na⁺/K⁺-ATPase α-subunit gene from the ridgetail white prawn Exopalaemon carinicauda in response to salinity stresses

Na(+)/K(+)-ATPase (NAK) is one important transporter protein and plays a key role in maintaining osmotic homeostasis in low and high salinity acclimation in variety of crustacean species. The ridgetail white prawn Exopalaemon carinicauda is an euryhaline and economic shrimp species in China, but it remains unclear about its mechanism of salinity adaption. In this study, a full-length of Na(+)/K(+)-ATPase α-subunit (α-NAK) cDNA was cloned from E. carinicauda by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of α-NAK was of 3680 bp, containing an open reading frame (ORF) of 3030 bp encoding a polypeptide of 1009 amino acids with the predicted molecular weight of 112.27 kDa. Eight transmembrane domains and two sites of phosphorylation and ATP binding were identified in E. carinicauda α-NAK. BLAST analysis revealed that the sequence of α-NAK amino acids of E. carinicauda shared more than 75% homologies with those of other crustacean. Real time quantitative RT-PCR analysis indicated that E. carinicauda α-NAK gene could be detected in all the tested tissues with highest expression level in gill. The expression profiles of E. carinicauda α-NAK transcripts were analyzed in gill and hepatopancreas tissues after salinity stresses. The results showed that the expression level of E. carinicauda α-NAK gene in both gill and hepatopancreas reached peak at different time after low and high salinity stresses, and showed different expression profiles. The expression profiles of proPO transcripts in gills after salinity stresses also indicated α-NAK and proPO played synergistic actions for salinity responses in E. carinicauda. These results indicated that E. carinicauda α-NAK involved in stress responses against salinity.

Transcriptome analysis of eyestalk and hemocytes in the ridgetail white prawn Exopalaemon carinicauda: assembly, annotation and marker discovery

The ridgetail white prawn Exopalaemon carinicauda is one of major economic mariculture species in eastern China. The deficiency of genomic and transcriptomic data is becoming the bottleneck of further researches on its good traits. In the present study, 454 pyrosequencing was undertaken to investigate the transcriptome profiles of E. carinicauda. A collection of 1,028,710 sequence reads (459.59 Mb) obtained from cDNA prepared from eyestalk and hemocytes was assembled into 162,056 expressed sequence tags (ESTs). Of these, 29.88 % of 48,428 contigs and 70.12 % of 113,628 singlets possessed high similarities to sequences in the GenBank non-redundant database, with most significant (E value <1e(-10)) unigenes matches occurring with crustacean and insect sequences. KEGG analysis of unigenes identified putative members of biological pathways related to growth and immunity. In addition, we obtained a total of putative 125,112 SNPs and 13,467 microsatellites. These results will contribute to the understanding of the genome makeup and provide useful information for future functional genomic research in E. carinicauda.

The responsive expression of a chitinase gene in the ridgetail white prawn Exopalaemon carinicauda against Vibrio anguillarum and WSSV challenge

Chitinases are essential enzymes for crustaceans and participates in several biological processes, such as nutrient digestion, morphogenesis, pathogenesis, and pathogen defense. In the present study, the full-length cDNA of Chi (named EcChi) was cloned from the hemocytes of ridgetail white prawn Exopalaemon carinicauda by rapid amplification of cDNA ends methods. The full-length cDNA of EcChi was 1,319 bp, including contains a 5'-untranslated region (UTR) of 42 bp, 3'-UTR of 101 bp with a poly (A) tail, an open-reading frame of 1,176 bp, encoding a 391-amino acid polypeptide with the predicted molecular weight of 43.71 kDa and estimated isoelectric point of 4.78. Sequence analysis revealed that the conserved chitinases family 18 active site was predicted in the amino acid sequence of EcChi. BLAST analysis revealed that amino acids of EcChi shared high identity (61-77 %) with that of other crustaceans. Quantitative real-time PCR analysis indicated that EcChi could be detected in all the tested tissues, and strongly expressed in hepatopancreas of E. carinicauda. After challenged with Vibrio anguillarum and WSSV, EcChi transcripts both in hemocytes and hepatopancreas increased significantly in the first 3 h, respectively. These results indicated that EcChi might be involved in the innate immune responses to V. anguillarum and WSSV in E. carinicauda.

Sexual dimorphism in Grp78 and Hsp90A heat shock protein expression in the estuarine copepod Eurytemora affinis

Aquatic organisms are constantly exposed to both natural and anthropogenic stressors. Under stress conditions, they elicit a cellular stress response, involving heat shock proteins (HSPs). HSPs are essential to protect proteins against aggregation and to help in the folding of native proteins or refolding of damaged ones. Because of their conservation among taxons and their inducibility after environmental/chemical stress, HSPs are commonly used as ecological and ecotoxicological biomarkers. However, the appropriate use of such molecular tools requires the investigation of the influence of biotic factors on their basal levels. As a first step in biomarker characterization, the present study aims to evaluate the impact of the reproductive cycle on the expression of the two major HSPs, Grp78 and Hsp90A in the estuarine copepod Eurytemora affinis. The constitutive expression of both genes in males was weak when compared to female levels suggesting gender-specific stress tolerance. Transcript levels gradually increased during oogenesis and maximal levels were recorded in ovigerous females. The present data support the view that the reproductive condition of individuals has to be considered as a confounding factor in stress evaluation by HSP quantification.

A copper-induced metallothionein gene from Exopalaemon carinicauda and its response to heavy metal ions

A full-length copper-induced metallothionein (EcMT-Cu) cDNA was obtained from Exopalaemon carinicauda (Holthuis) and it contained a 198 bp open reading frame that encoded a peptide with 65 amino acid residues. Twenty-one cysteines were found in deduced amino acid sequence and the cysteine (Cys)-rich characteristic was also reported in different types of metallothioneins from other species. EcMT-Cu mRNA expression profile showed that it is the hepatopancreas specific gene. The expression of EcMT-Cu was extremely different when shrimp were exposed to seawater containing 50 μM CuSO4 or 2.5 μM CdCl2. The expression of EcMT-Cu in shrimp was significantly up-regulated at 12 and 24 h after exposure to CuSO4, however, its expression was not induced compared to that of pretreatment (p>0.05) when shrimp were exposed to CdCl2. The transcript of EcMT-Cu was found to be extremely low at gastrula and nauplius stage and expression of EcMT-Cu could be detected from egg protozoa stage.

A farnesoic acid O-methyltransferase (FAMeT) from Exopalaemon carinicauda is responsive to Vibrio anguillarum and WSSV challenge

Methyl farnesoate (MF), an analogue of the insect juvenile hormone III, is believed to play important roles in the regulation of the growth and reproductive development in crustaceans. Farnesoic acid O-methyltransferase (FAMeT) is the key enzyme in the juvenile hormone biosynthetic pathway, involved in the conversion of farnesoic acid (FA) to MF in the final step of MF synthesis. In this study, a FAMeT cDNA (named EcFAMeT) was cloned from the hemocytes of ridgetail white prawn Exopalaemon carinicauda by rapid amplification of cDNA ends (RACE) methods. The full-length cDNA of EcFAMeT was 1,620 bp, including contains a 5'-untranslated region (UTR) of 75 bp, 3'-UTR of 714 bp with a poly (A) tail, an open reading frame (ORF) of 831 bp, encoding a 276-amino-acid polypeptide with the predicted molecular weight of 31.57 kDa and estimated isoelectric point of 4.67. BLAST analysis revealed that amino acids of EcFAMeT shared high identity (75-90 %) with that of other crustaceans. Two conserved signatures domains of Methyltransf-FA superfamily were also identified in EcFAMeT. Real time quantitative RT-PCR analysis indicated that EcFAMeT could be detected in all the tested tissues and strongly expressed in hepatopancreas and ovary of E. carinicauda. After Vibrio anguillarum and WSSV challenge, EcFAMeT transcripts both in hemocytes and hepatopancreas increased significantly in the first 3 h, respectively. The results indicated that EcFAMeT might be associated with the immune defenses to V. anguillarum and WSSV in E. carinicauda.

Characterize and Gene Expression of Heat Shock Protein 90 in Marine Crab Charybdis japonica following Bisphenol A and 4-Nonylphenol Exposures

OBJECTIVES

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone important in the maturation of a broad spectrum of protein. In this study, an HSP90 gene was isolated from Asian paddle crab, Charybdis japonica, as a bio-indicator to monitor the marine ecosystem.

METHODS

This work reports the responses of C. japonica HSP90 mRNA expression to cellular stress by endocrine disrupting chemicals (EDCs), such as bisphenol A (BPA) and 4-nonylphenol (NP) using real-time. reverse transcription polymerase chain reaction.

RESULTS

The deduced amino acid sequence of HSP90 from C. japonica shared a high degree of homology with their homologues in other species. In a phylogenetic analysis, C. japonica HSP90 is evolutionally related with an ortholog of the other crustacean species. The expression of HSP90 gene was almost distributed in all the examined tissues of the C. japonica crab but expression levels varied among the different body parts of the crabs. We examined HSP90 mRNA expression pattern in C. japonica crabs exposed to EDCs for various exposure times. The expression of HSP90 transcripts was significantly increased in C. japonica crabs exposed to BPA and NP at different concentrations for 12, 24, 48 and 96 hours. The mRNA expression of HSP90 gene was significantly induced in a concentration- and time-dependent manner after BPA or NP exposures for 96 hours.

CONCLUSIONS

Taken together, expression analysis of Asian paddle crab HSP90 gene provided useful molecular information about crab responses in stress conditions and potential ways to monitor the EDCs stressors in marine environments.

Molecular responses of calreticulin gene to Vibrio anguillarum and WSSV challenge in the ridgetail white prawn Exopalaemon carinicauda

Calreticulin (CRT), as a highly conserved endoplasmic reticulum luminal resident protein, plays important roles in Ca(2+) homeostasis, molecular chaperoning and response to viral infection. In this study, a full-length cDNA of CRT (designated EcCRT) was cloned from hemocytes of the ridgetail white prawn Exopalaemon carinicauda by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EcCRT was 1725 bp, which contains a 5'-untranslated region (UTR) of 57 bp, 3'-UTR of 453 bp with a poly (A) tail, an open reading frame (ORF) of 1215 bp, encoding a 404 amino-acid polypeptide with the predicted molecular weight of 46.51 kDa and estimated isoelectric point of 4.32. The deduced amino acid sequence of EcCRT shared high identity (82%-85%) with that of other crustaceans. Phylogenetic analysis showed that EcCRT of E. carinicauda was clustered together with CRT of other shrimps, indicating that EcCRT should be a member of the CRT family. Quantitative real-time RT-qPCR analysis indicated that EcCRT was expressed in hemocytes, gill, hepatopancreas, muscle, ovary, intestine, stomach and eyestalk, with the highest expression level in hemocytes. After Vibrio anguillarum and WSSV challenge, the expression level of EcCRT transcripts both in the hemocytes and hepatopancreas of E. carinicauda were up-regulated in the first 6 h, respectively. The results suggested that EcCRT might be associated with the immune defenses to V. anguillarum and WSSV in E. carinicauda.

cDNA cloning, characterization and expression analysis of peroxiredoxin 5 gene in the ridgetail white prawn Exopalaemon carinicauda

Peroxiredoxin is a superfamily of antioxidative proteins that play important roles in protecting organisms against the toxicity of reactive oxygen species. In this study, a full-length of peroxiredoxin 5 (designated EcPrx5) cDNA was cloned from the ridgetail white prawn Exopalaemon carinicauda by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of the EcPrx5 was of 827 bp, containing a 5′ untranslated region (UTR) of 14 bp, a 3′ UTR of 228 bp with a poly (A) tail, and an open reading frame of 585 bp encoding a polypeptide of 194 amino acids with the predicted molecular weight of 20.83 kDa and estimated isoelectric point of 7.62. BLAST analysis revealed that amino acids of EcPrx5 shared 89, 68, 66, 65, 53 and 51 % identity with that of Macrobrachium rosenbergii, Megachile rotundata, Harpegnathos saltator, Acromyrmex echinatior, Danio rerio, and Homo sapiens counterparts, respectively. The conserved Prx domain and the signature of peroxiredoxin catalytic center identified in EcPrx5 suggested that EcPrx5 belonged to the atypical 2-Cys Prx subgroup. Real time quantitative RT-PCR analysis indicated that EcPrx5 could be detected in all the tested tissues with highest expression level in hepatopancreas. As time progressed, the expression level of EcPrx5 both in hemocytes and hepatopancreas increased in the first 6 h after Vibrio anguillarum and white spot syndrome virus challenge, and showed different expression profiles. The results indicated that EcPrx5 involved in immune response against bacterial and viral infection in E. carinicauda.

Expression profiles of selenium dependent glutathione peroxidase and glutathione S-transferase from Exopalaemon carinicauda in response to Vibrio anguillarum and WSSV challenge

A selenium-dependent glutathione peroxidase cDNA was obtained from the ridgetail white prawn Exopalaemon carinicauda (EcGPx) by rapid amplification of cDNA ends (RACE) methods. The full-length cDNA of EcGPx was 946 bp, which contains a 5'-untranslated region (UTR) of 105 bp, 3'-UTR of 280 bp with a poly (A) tail, an open reading frame (ORF) of 561 bp, encoding a 186 amino-acid polypeptide with the predicted molecular weight of 21.35 kDa and estimated isoelectric point of 7.65. It involves a putative selenocysteine (U39) residue which is encoded by an opal codon, (220)TGA(222), and forms an active site with residues Q73 and W141. Sequence analysis revealed that a GPx signature motif 2 ((63)LAFPCNQF(70)), an extra active site motif ((151)WNFEKF(156)), two putative N-glycosylation site ((75)NNT(77) and (107)NGS(109)), and two arginine residues (R89 and R167) were observed in the EcGPx sequence. Comparison of amino acid sequences showed that white shrimp GPx is more closely related to GPx1 and GPx2 subgroups. Quantitative real-time RT-PCR analysis indicated that two glutathione antioxidant enzymes of E. carinicauda, glutathione peroxidase (designated EcGPx) and glutathione S-transferase (designated EcGST) were widely expressed in all the tested tissues, but showed different expression patterns. After Vibrio anguillarum and WSSV challenge, EcGPx and EcGST transcripts both in hemocytes and hepatopancreas increased in the first 6 h and 3 h, respectively. The results suggested that EcGPx and EcGST might be associated with the immune defenses to V. anguillarum and WSSV in E. carinicauda.

Immune gene discovery by expressed sequence tag (EST) analysis of hemocytes in the ridgetail white prawn Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda is one of the most important commercial species in eastern China. However, little information of immune genes in E. carinicauda has been reported. To identify distinctive genes associated with immunity, an expressed sequence tag (EST) library was constructed from hemocytes of E. carinicauda. A total of 3411 clones were sequenced, yielding 2853 ESTs and the average sequence length is 436 bp. The cluster and assembly analysis yielded 1053 unique sequences including 329 contigs and 724 singletons. Blast analysis identified 593 (56.3%) of the unique sequences as orthologs of genes from other organisms (E-value < 1e-5). Based on the COG and Gene Ontology (GO), 593 unique sequences were classified. Through comparison with previous studies, 153 genes assembled from 367 ESTs have been identified as possibly involved in defense or immune functions. These genes are categorized into seven categories according to their putative functions in shrimp immune system: antimicrobial peptides, prophenoloxidase activating system, antioxidant defense systems, chaperone proteins, clottable proteins, pattern recognition receptors and other immune-related genes. According to EST abundance, the major immune-related genes were thioredoxin (141, 4.94% of all ESTs) and calmodulin (14, 0.49% of all ESTs). The EST sequences of E. carinicauda hemocytes provide important information of the immune system and lay the groundwork for development of molecular markers related to disease resistance in prawn species.