Calmodulin is a stress and immune response gene in Chinese mitten crab Eriocheir sinensis

4D-FastDIA proteomic analysis of pedal mucus in Pacific abalone Haliotis discus hannai heat-resistance group

This study aimed to investigate the immune mechanisms of pedal mucus in Pacific abalone Haliotis discus hannai from different populations. Proteomic differences between the pedal mucus of the control group and the heat-resistance group of H. discus hannai were comparatively analyzed, and the proteins were annotated and analyzed to understand the related functions and roles of differentially expressed proteins (DEPs). The results showed that there were 4054 DEPs in total, among which the DEPs in the pedal mucus of the heat-resistance group and the control group were mainly immune-related heat shock proteins, calmodulin, Ig-like and fibronectin type III domain-containing proteins, histones and mucins, etc.; the DEPs related to growth metabolism included glutathione, growth factor receptor-bound protein, alanine aminotransferase, etc. Circadian entrainment signaling pathway and growth hormone synthesis, secretion and action signaling pathway was significantly enriched, cortisol synthesis and secretion signaling pathway was up-regulated in Haliotis discus hannai heat-resistance group. This study provided references for exploring the relationship between the mucus proteome difference in pedal mucus from different abalone populations sources. These results would contribute to further search for proteins related to immunity, growth and stress resistance, and provide theoretical basis for the development of high-quality germplasm resources of Pacific abalone.

Ocean acidification alleviated nickel toxicity to a marine copepod under multigenerational scenarios but at a cost with a loss of transcriptome plasticity during recovery

Marine ecosystem has been experiencing multiple stressors caused by anthropogenic activities, including ocean acidification (OA) and nickel (Ni) pollution. Here, we examined the individual/combined effects of OA (pCO2 1000 μatm) and Ni (6 μg/L) exposure on a marine copepod Tigriopus japonicus for six generations (F1-F6), followed by one-generation recovery (F7) in clean seawater. Ni accumulation and several important phenotypic traits were measured in each generation. To explore within-generation response and transgenerational plasticity, we analyzed the transcriptome profile for the copepods of F6 and F7. The results showed that Ni exposure compromised the development, reproduction and survival of copepods during F1-F6, but its toxicity effects were alleviated by OA. Thus, under OA and Ni combined exposure, due to their antagonistic interaction, the disruption of Ca2+ homeostasis, and the inhibition of calcium signaling pathway and oxytocin signaling pathway were not found. However, as a cost of acclimatization/adaption potential to long-term OA and Ni combined exposure, there was a loss of transcriptome plasticity during recovery, which limited the resilience of copepods to previously begin environments. Overall, our work fosters a comprehensive understanding of within- and transgenerational effects of climatic stressor and metal pollution on marine biota.

Morphologic, cytometric, quantitative transcriptomic and functional characterisation provide insights into the haemocyte immune responses of Pacific abalone (Haliotis discus hannai)

In recent years, the abalone aquaculture industry has been threatened by the bacterial pathogens. The immune responses mechanisms underlying the phagocytosis of haemocytes remain unclear in Haliotis discus hannai. It is necessary to investigate the immune mechanism in response to these bacterial pathogens challenges. In this study, the phagocytic activities of haemocytes in H. discus hannai were examined by flow cytometry combined with electron microscopy and transcriptomic analyses. The results of Vibrio parahaemolyticus, Vibrio alginolyticus and Staphylococcus aureu challenge using electron microscopy showed a process during phagosome formation in haemocytes. The phagocytic rate (PP) of S. aureus was higher than the other five foreign particles, which was about 63%. The PP of Vibrio harveyi was about 43%, the PP peak of V. alginolyticus in haemocyte was 63.7% at 1.5 h. After V. parahaemolyticus and V. alginolyticus challenge, acid phosphatase, alkaline phosphatase, total superoxide dismutase, lysozyme, total antioxidant capacity, catalase, nitric oxide synthase and glutathione peroxidase activities in haemocytes were measured at different times, differentially expressed genes (DEGs) were identified by quantitative transcriptomic analysis. The identified DEGs after V. parahaemolyticus challenge included haemagglutinin/amebocyte aggregation factor-like, supervillin-like isoform X4, calmodulin-like and kyphoscoliosis peptidase-like; the identified DEGs after V. alginolyticus challenge included interleukin-6 receptor subunit beta-like, protein turtle homolog B-like, rho GTPase-activating protein 6-like isoform X2, leukocyte surface antigen CD53-like, calponin-1-like, calmodulin-like, troponin C, troponin I-like isoform X4, troponin T-like isoform X18, tumor necrosis factor ligand superfamily member 10-like, rho-related protein racA-like and haemagglutinin/amebocyte aggregation factor-like. Some immune-related KEGG pathways were significantly up-regulated or down-regulated after challenge, including thyroid hormone synthesis, Th17 cell differentiation signalling pathway, focal adhesion, melanogenesis, leukocyte transendothelial migration, inflammatory mediator regulation of TRP channels, ras signalling pathway, rap1 signalling pathway. This study is the first step towards understanding the H. discus hannai immune system by adapting several tools to gastropods and providing a first detailed morpho-functional study of their haemocytes.

The P4' Peptide-Carrying Bacillus subtilis in Cottonseed Meal Improves the Chinese Mitten Crab Eriocheir sinensis Innate Immunity, Redox Defense, and Growth Performance

This study developed a recombinant Bacillus subtilis to carry the LGSPDVIVIR peptide (cmP4) isolated from the hydrolyzed products of cottonseed meal with excellent antioxidant and immune-enhancing properties in vitro. It was carried as a tandem of five cmP4 peptides (cmP4') to be stably expressed on a large scale. Then, its effectiveness was evaluated in Chinese mitten crab (Eriocheir sinensis) based on growth performance, redox defense, and innate immunity. A total of 280 crabs (mean body weight: 41.40 ± 0.14) were randomly assigned to seven diets including a control one (without B. subtilis) and six experimental ones with different doses (107,108, and 109 CFU/kg) of unmodified and recombinant B. subtilis, respectively, for 12 weeks. Each diet was tested in four tanks of crabs (10/tank). In terms of bacterial dosages, the final weight (FW), weight gain (WG), hemolymph and hepatopancreatic activities of superoxide dismutase (SOD), catalase (CAT), lysosome (LZM), acid phosphatase (ACP) and alkaline phosphatase (AKP), and hepatopancreatic transcriptions of cat, mitochondrial manganese superoxide dismutase (mtmnsod), thioredoxin-1 (trx1), and prophenoloxidase (propo) all increased significantly with increasing B. subtilis dosages, while hemolymph and hepatopancreatic malondialdehyde (MDA) content and the transcriptions of toll like receptors (tlrs), NF-κB-like transcription factor (relish), and lipopolysaccharide-induced TNF-α factor (litaf) all decreased remarkably. In terms of bacterial species, the recombinant B. subtilis group obtained significantly high values of FW, WG, hemolymph, and hepatopancreatic activities of SOD, CAT, LZM, ACP, and AKP, and the transcriptions of mtmnsod, peroxiredoxin 6 (prx6), and propo compared with the unmodified B. subtilis, while opposite results were noted in hemolymph and hepatopancreatic MDA content and the transcriptions of tlrs, relish, and litaf. These results indicated that dietary supplementation with 109 CFU/kg of recombinant B. subtilis can improve the growth performance, redox defense, and nonspecific immunity of E. sinensis.

Identification of multifunctionality of the PmE74 gene and development of SNPs associated with low salt tolerance in Penaeus monodon

Members of the E74-like factor (ELF) subfamily are involved in the immune stress process of organisms by regulating immune responses and the development of immune-related cells. PmE74 of Penaeus monodon was characterized and functionally analyzed in this study. The full length of PmE74 was 3106 bp, with a 5'-UTR of 297 bp, and a 3'-UTR of 460 bp. The ORF (Open reading frame) was 2349 bp and encoded 782 amino acids. Domain analysis showed that PmE74 contains a typical Ets domain. Multiple sequence alignment and phylogenetic tree analysis showed that PmE74 clustered with Litopenaeus vannamei E74 and displayed significant similarity (98.98%). PmE74 was expressed in all tissues tested in P. monodon, with the highest levels of expression observed in the testis, intestine, and epidermis. Different pathogen stimulation studies have revealed that PmE74 expression varies in response to different pathogen stimuli. A 96-h acute low salt stress study revealed that PmE74 in the hepatopancreas was upregulated and downregulated in the salinity 17 group and considerably downregulated in the salinity 3 group, whereas PmE74 in gill tissue was considerably downregulated in both groups. Further, by knocking down PmE74 and learning the trends of its linkage genes PmAQP1, PmNKA, PmE75, PmFtz-f1, PmEcR, and PmRXR in response to low salt stress, it was further indicated that PmE74 could have a vital role in the regulation of low salt stress. The SNP test revealed that PmE74-In1-53 was significantly associated with low salt tolerance traits in P. monodon (P < 0.05). The findings of this study can aid in the advancement of molecular marker-assisted breeding in P. monodon, as well as provide fundamental data and methodologies for further investigation of its low salt tolerance strains in P. monodon.

Transcriptome analysis reveals fluid shear stress (FSS) and atherosclerosis pathway as a candidate molecular mechanism of short-term low salinity stress tolerance in abalone

BACKGROUND

Transcriptome sequencing is an effective tool to reveal the essential genes and pathways underlying countless biotic and abiotic stress adaptation mechanisms. Although severely challenged by diverse environmental conditions, the Pacific abalone Haliotis discus hannai remains a high-value aquaculture mollusk and a Chinese predominantly cultured abalone species. Salinity is one of such environmental factors whose fluctuation could significantly affect the abalone's cellular and molecular immune responses and result in high mortality and reduced growth rate during prolonged exposure. Meanwhile, hybrids have shown superiority in tolerating diverse environmental stresses over their purebred counterparts and have gained admiration in the Chinese abalone aquaculture industry. The objective of this study was to investigate the molecular and cellular mechanisms of low salinity adaptation in abalone. Therefore, this study used transcriptome analysis of the gill tissues and flow cytometric analysis of hemolymph of H. discus hannai (DD) and interspecific hybrid H. discus hannai ♀ x H. fulgens ♂ (DF) during low salinity exposure. Also, the survival and growth rate of the species under various salinities were assessed.

RESULTS

The transcriptome data revealed that the differentially expressed genes (DEGs) were significantly enriched on the fluid shear stress and atherosclerosis (FSS) pathway. Meanwhile, the expression profiles of some essential genes involved in this pathway suggest that abalone significantly up-regulated calmodulin-4 (CaM-4) and heat-shock protein90 (HSP90), and significantly down-regulated tumor necrosis factor (TNF), bone morphogenetic protein-4 (BMP-4), and nuclear factor kappa B (NF-kB). Also, the hybrid DF showed significantly higher and sustained expression of CaM and HSP90, significantly higher phagocytosis, significantly lower hemocyte mortality, and significantly higher survival at low salinity, suggesting a more active molecular and hemocyte-mediated immune response and a more efficient capacity to tolerate low salinity than DD.

CONCLUSIONS

Our study argues that the abalone CaM gene might be necessary to maintain ion equilibrium while HSP90 can offset the adverse changes caused by low salinity, thereby preventing damage to gill epithelial cells (ECs). The data reveal a potential molecular mechanism by which abalone responds to low salinity and confirms that hybridization could be a method for breeding more stress-resilient aquatic species.

The Innate Immune Response to Infection by Polyascus gregaria in the Male Chinese Mitten Crab (Eriocheir sinensis), Revealed by Proteomic Analysis

The Chinese mitten crab (Eriocheir sinensis) is a representative catadromous invertebrate of the Yangtze River and a commercial species widely cultivated in China. Both cultivated and wild crabs suffer from a variety of parasites and pathogens, which can result in catastrophic economic losses in aquaculture revenue. Polyascus gregaria, a parasitic barnacle with a highly derived morphology, is specialized in invading these crabs. This study examines the immunological mechanism in E. sinensis infected with P. gregaria. Tandem mass tags (TMT), a specialized method of mass-spectrometry, was used to analyze the infection by P. gregaria resistance at the protein level. In the hepatopancreas of infected crabs, 598 proteins differentially expressed relating to physiological change, of which, 352 were upregulated and 246 were downregulated. Based on this differential protein expression, 104 GO terms and 13 KEGG pathways were significantly enriched. Differentially expressed proteins, such as ATG, cathepsin, serpin, iron-related protein, Rab family, integrin, and lectin, are associated with the lysosome GO term and the autophagy-animal KEGG pathways, both of which likely relate to the immune response to the parasitic P. gregaria infection. These results show the benefit of taking a detailed, protein-level approach to understanding the innate immune response of aquatic invertebrates to macroparasite infection.

A calmodulin targeted by miRNA scaffold659_26519 regulates IL-17 expression in the early immune response of oyster Crassostrea gigas

Calmodulin (CaM) is a highly conserved second messenger protein transducing calcium signals by binding and modulating intracellular calcium ions (Ca²⁺), and involves in the Ca²⁺-dependent physical processes including host defense in vertebrates. In the present study, a CaM homologue (designated as CgCaM) was identified from Pacific oyster Crassostrea gigas. The open reading frame of CgCaM cDNA was of 471 bp encoding a polypeptide of 156 amino acid residues. There were four EFh domains predicted in CgCaM, which shared high homologies with those in CaMs from oyster C. virginica and other invertebrates. The mRNA transcripts of CgCaM were constitutively expressed in all the tested tissues including labellum, mantle, gonad, gills, adductor muscle, haemocytes and hepatopancreas, with the highest expression level in haemocytes. The mRNA expression level of CgCaM in haemocytes decreased significantly (0.31-fold of that in blank, p < 0.05) at 3 h after LPS stimulation, while the intracellular Ca²⁺ (1.57-fold of that in blank, p < 0.05) and the mRNA expression of cytokine CgIL17-1 (4.87-fold of that in blank, p < 0.05) both increased in haemocytes. Meanwhile, an oyster miRNA scaffold659_26519 was identified, and it was proved to target the 3'-untranslated regions (3'-UTR) of CgCaM mRNA by luciferase reporter assay. The expression of scaffold659_26519 increased significantly at 3 h (43.523-fold of that of blank, p < 0.05) and 6 h (55.91-fold of that of blank, p < 0.05) after LPS stimulation. When the expression of scaffold659_26519 was inhibited by transfection with its inhibitor in vitro, the expression of CgIL17-1 declined significantly to 0.58-fold of that in LPS stimulation group. These findings indicated that the miRNA scaffold659_26519 targeted CaM was involved in the early inflammatory response of oyster immunity, and provided a new evidence for CaM-mediated immune mechanism in molluscs.

Modulatory function of calmodulin on phagocytosis and potential regulation mechanisms in the blood clam Tegillarca granosa

Unlike vertebrate species, invertebrates lack antigen-antibody mediated immune response and mainly rely on haemocyte phagocytosis to fight against pathogen infection. Recently, studies conducted in model vertebrates demonstrated that the multifunctional protein calmodulin (CaM) plays an important role in regulating immune responses. However, the intrinsic relation between CaM and phagocytosis process remains poorly understood in invertebrate species such as bivalve mollusks. Therefore, in the present study, the immunomodulatory function of CaM on haemocyte phagocytosis was verified in the blood clam, Tegillarca granosa, using the CaM-specific inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7). Results obtained show that CaM inhibition significantly suppressed the phagocytic activity of haemocytes. In addition, CaM inhibition constrained intracellular Ca²⁺ elevation, hampered actin cytoskeleton assembly, suppressed calcineurin (CaN) activity, and disrupted NF-κB activation in haemocytes upon LPS induction. Furthermore, expression of seven selected genes from the actin cytoskeleton regulation- and immune-related pathways were significantly downregulated whereas those of CaM and CaN from the Ca²⁺-signaling pathway were significantly upregulated by in vitro incubation of haemocytes with W-7. For the first time, the present study demonstrated that CaM play an important role in phagocytosis modulation in bivalve species. In addition, the intracellular Ca²⁺ and downstream Ca²⁺-signaling-, actin cytoskeleton regulation-, and immune-related pathways offer candidate routes through which CaM modulates phagocytosis.

Transcriptional changes of Pacific oyster Crassostrea gigas reveal essential role of calcium signal pathway in response to CO2-driven acidification

There is increasing evidence that ocean acidification (OA) has a significant impact on marine organisms. However, the ability of most marine organisms to acclimate to OA and the underlying mechanisms are still not well understood. In the present study, whole transcriptome analysis was performed to compare the impacts of short- (7 days, named as short group) and long- (60 days, named as long group) term CO₂ exposure (pH 7.50) on Pacific oyster Crassostrea gigas. The responses of C. gigas to short- and long-term CO₂ exposure shared common mechanisms in metabolism, membrane-associated transportation and binding processes. Long-term CO₂ exposure induced significant expression of genes involved in DNA or RNA binding, indicating the activated transcription after long-term CO₂ exposure. Oysters in the short-term group underwent significant intracellular calcium variation and oxidative stress. In contrast, the intracellular calcium, ROS level in hemocytes and H₂O₂ in serum recovered to normal levels after long-term CO₂ exposure, suggesting the compensation of physiological status and mutual interplay between calcium and oxidative level. The compensation was supported by the up-regulation of a series of calcium binding proteins (CBPs) and calmodulins (CaMs) related signal pathway. The results provided valuable information to understand the molecular mechanism underlying the responses of Pacific oyster to the acidified ocean and might have implications for predicting the possible effects of global climate changes on oyster aquaculture.

-Omic Analysis of the Sepia officinalis White Body: New Insights into Multifunctionality and Haematopoiesis Regulation

Cephalopods, like other protostomes, lack an adaptive immune system and only rely on an innate immune system. The main immune cells are haemocytes (Hcts), which are able to respond to pathogens and external attacks. First reports based on morphological observations revealed that the white body (WB) located in the optic sinuses of cuttlefish was the origin of Hcts. Combining transcriptomic and proteomic analyses, we identified several factors known to be involved in haematopoiesis in vertebrate species in cuttlefish WB. Among these factors, members of the JAK-STAT signaling pathway were identified, some of them for the first time in a molluscan transcriptome and proteome. Immune factors, such as members of the Toll/NF-κB signaling pathway, pattern recognition proteins and receptors, and members of the oxidative stress responses, were also identified, and support an immune role of the WB. Both transcriptome and proteome analyses revealed that the WB harbors an intense metabolism concurrent with the haematopoietic function. Finally, a comparative analysis of the WB and Hct proteomes revealed many proteins in common, confirming previous morphological studies on the origin of Hcts in cuttlefish. This molecular work demonstrates that the WB is multifunctional and provides bases for haematopoiesis regulation in cuttlefish.

Dietary reduced glutathione supplementation can improve growth, antioxidant capacity, and immunity on Chinese mitten crab, Eriocheir sinensis

Eriocheir sinensis is an important aquaculture species in China, and its yield and quality are threatened by oxidative stress caused by deteriorating water conditions. Reduced glutathione (GSH) is an endogenous antioxidant, but whether dietary GSH can increase the resistance of E. sinensis to environmental stress remains unclear. Therefore, in this study, crabs were fed with dietary GSH (0, 300, 600, 900, and 1200 mg/kg diet weight) for up to 10 weeks to determine the effects of different dietary GSH concentrations on growth, antioxidant capacity, and immunity of E. sinensis. The results showed that the weight gain rate and survival rate increased significantly as dietary GSH levels increased from 0 to 900 mg/kg, but decreased at 1200 mg/kg. Compared with the control group, the diet supplemented with 900 mg/kg GSH not only increased the concentration of GSH in the haemolymph and hepatopancreas, but also enhanced the activity of glutathione peroxidase (GSH-Px) (p < 0.05). Diets supplemented with 600 or 900 mg/kg GSH significantly increased the enzymes activities of superoxide dismutase (SOD), lysozyme (LZM), alkaline phosphatase, and acid phosphatase, and significantly decreased the content of malondialdehyde. To understand the changes in the activity of these enzymes further, the expression of related genes was detected. Diets supplemented with 600 or 900 mg/kg GSH significantly upregulated the genes expressions of cytosolic manganese SOD, mitochondrial manganese SOD, copper, zinc-SOD, GSH-Px, LZM, and prophenoloxidase activating factor, and significantly down regulated the expression of Toll-like receptor 1, Toll-like receptor 2, Dorsal, and the myeloid differentiation factor 88. However, a diet supplemented with 1200 mg/kg GSH decreased those positive indicators. Overall, our results demonstrated that an appropriate diet supplemented with 600 or 900 mg/kg GSH enhances antioxidant capacity and immunity, which will enhance the general health of E. sinensis.

Transcriptomic analysis of oligochaete immune responses to myxosporeans infection: Branchiura sowerbyi infected with Myxobolus cultus

The Myxozoa are endoparasites characterized by a two-host life cycle that typically involves invertebrates and vertebrates as definitive and intermediate hosts, respectively. However, little is known about invertebrate-myxosporean interactions, particularly about patterns of host immune defense. We used RNA-sequencing to identify genes that are possibly involved in the immune responses of the oligochaete Branchiura sowerbyi naturally infected with Myxobolus cultus. De novo assembly of the B. sowerbyi transcriptome yielded 119,031 unigenes, with an average length of 896 bp and an N50 length of 1754 bp. Comparative transcriptome analysis revealed 4059 differentially expressed genes (DEGs) between M. cultus-infected and uninfected B. sowerbyi groups, including 3802 upregulated genes and 257 downregulated genes. Among the B. sowerbyi immune factors implicated in the responses to M. cultus infection, DEGs related to lectins, ubiquitin-mediated proteolysis, phagocytosis, oxidative-antioxidative responses, proteases, and protease inhibitors were upregulated. The expression of some immune-related molecules such as calmodulin, heat shock proteins, antimicrobial peptides, lysenin, and serum amyoid A protein were also significantly upregulated. The expression patterns of 14 immune-related DEGs identified by RNA-seq were validated by quantitative real-time polymerase chain reaction. This study is the first attempt to characterize the B. sowerbyi transcriptome and identify immune-related molecules possibly associated with M. cultus infection. It is also the first report of invertebrate host-myxosporean interactions at the transcriptomic level. Our results will facilitate the elucidation of adaptive evolution mechanisms of myxosporean parasites in the definitive host and the genetic basis for differences in resistance of invertebrate hosts of different genotypes to a myxosporean species.

Differential proteomic profiles and characterizations between hyalinocytes and granulocytes in ivory shell Babylonia areolata

The haemocytes of the ivory shell, Babylonia areolata are classified by morphologic observation into the following types: hyalinocytes (H) and granulocytes (G). Haemocytes comprise diverse cell types with morphological and functional heterogene and play indispensable roles in immunological homeostasis of invertebrates. In the present study, two types of haemocytes were morphologically identified and separated as H and G by Percoll density gradient centrifugation. The differentially expressed proteins were investigated between H and G using mass spectrometry. The results showed that total quantitative proteins between H and G samples were 1644, the number of up-regulated proteins in G was 215, and the number of down-regulated proteins in G was 378. Among them, cathepsin, p38 MAPK, toll-interacting protein-like and beta-adrenergic receptor kinase 2-like were up-regulated in G; alpha-2-macroglobulin-like protein, C-type lectin, galectin-2-1, galectin-3, β-1,3-glucan-binding protein, ferritin, mega-hemocyanin, mucin-17-like, mucin-5AC-like and catalytic subunit of protein kinase A were down-regulated in G. The results showed that the most significantly enriched KEGG pathways were the pathways related to ribosome, phagosome, endocytosis, carbon metabolism, protein processing in endoplasmic reticulum and oxidative phosphorylation. For phagosome and endocytosis pathway, the number of down-regulation proteins in G was more than that of up-regulation proteins. For lysosome pathway, the number of up-regulation proteins in G was more than that of down-regulation proteins. These results suggested that two sub-population haemocytes perform the different immune functions in B. areolata.

Proteomic and structural differences in lumpfish skin among the dorsal, caudal and ventral regions

Fish skin is a vital organ that serves a multitude of functions including mechanical protection, homeostasis, osmoregulation and protection against diseases. The expression of skin proteins changes under different physiological conditions. However, little is known about differences in protein expression among various body sites in naïve fish. The objectives of this work is to study potential differences in protein and gene expression among dorsal, caudal and ventral regions of lumpfish skin employing 2D gel based proteomics and real-time PCR and to assess structural differences between these regions by using Alcian blue and Periodic acid Schiff stained skin sections. The proteins collagen alfa-1, collagen alfa-2, heat shock cognate 71 kDa, histone H4, parvalbumin, natterin-2, 40S ribosomal protein S12, topoisomerase A and topoisomerase B were differentially expressed among the three regions. mRNA expression of apoa1, hspa8 and hist1h2b showed significant differences between regions. Skin photomicrographs showed differences in epidermal thickness and goblet cell counts. The ventral region showed relatively high protein expression, goblet cell count and epidermal thickness compared to dorsal and caudal regions. Overall, this study provides an important benchmark for comparative analysis of skin proteins and structure between different parts of the lumpfish body.

Dietary fructooligosaccharide can mitigate the negative effects of immunity on Chinese mitten crab fed a high level of plant protein diet

An 8-week feeding trial was carried out under controlled condition to evaluate the effect of dietary fructooligosaccharide (FOS) on growth performance, whole body composition, antioxidant status and immunity of crabs fed high levels of plant protein diets. Thus, six experimental diets were formulated (designated as F₀P₅₀, F₀P₆₀, F₀P₇₀, F_0.2P₅₀, F_0.2P₆₀ and F_0.2P₇₀), which contain two FOS levels (0 or 0.2%) and three plant protein levels (50, 60, or 70%) according to a 2 × 3 factorial design. The results showed that weight gain increased significantly as dietary plant protein level decreased from 70% to 50%. At 50% plant protein level, the addition of 0.2% FOS can significantly elevate weight gain (WG) (P < 0.05). The highest value in survival rate was observed in crabs fed F_0.2P₅₀ and F_0.2P₆₀ diet. Crabs fed F_0.2P₅₀ diet showed significantly higher crude protein content (P < 0.05) compared with those in other groups, but there were no significant differences in the contents of moisture, crude lipid and ash among all groups (P > 0.05). Catalase (CAT) activity in crabs fed F_0.2P₅₀ increased significantly (P < 0.05) compared with crabs fed F₀P₆₀, F₀P₇₀, F_0.2P₆₀ and F_0.2P₇₀, but malondialdehyde (MDA) concentrations decreased significantly (P < 0.05). Meanwhile, nitric oxide (NO) concentration, acid phosphatase (ACP) and alkaline phosphatase (AKP) activities of crabs fed 0.2% FOS diets increased significantly (P < 0.05) compared with crabs fed 0% FOS diets. The expressions of prophenoloxidase (propo) was significantly (P < 0.05) affected only by dietary plant protein levels with the highest values observed in 50% plant protein diet, whereas the opposite was true for Myeloid differentiation factor 88 (myd88). The mRNA expressions of mitochondrial manganese superoxide dismutase (mtmnsod), lipopolysaccharide-induced TNF-α factor (litaf) and toll like receptors (tlrs) were significantly affected (P < 0.05) by both FOS and plant protein levels. The cytosolic manganese superoxide dismutase (cytmnsod) mRNA expressions in F_0.2P₅₀ and F_0.2P₆₀ groups were significantly higher than those in F₀P₇₀ and F_0.2P₇₀ groups. The results in this study indicated that supplementation with 0.2% FOS can enhance growth performance in crabs fed lower plant protein diets and as well improve immunity in those fed with higher plant protein diets.

Multiple calmodulin genes of the Pacific abalone, Haliotis discus hannai (Mollusca: Vetigastropoda: Haliotidae)

In this study, we identified four canonical calmodulin genes in the Pacific abalone, Haliotis discus hannai. Their full-length cDNAs were variable in the 5' and 3' untranslated regions, but highly similar (91-97%) in the coding region. Each of the genes encoded 149 amino acids, with 93-97% similarity among themselves and 94-98% similarity with human CAM I. There were 54 substitutions distributed unevenly throughout the coding regions, found mostly in the third codon position. Gene structure analysis revealed that each of the calmodulin genes comprised five exons and four introns. The intron positions and phases were identical and there were no introns in the fourth exon. The corresponding introns differed in their sequences and sizes. Expression profiles of nine tissues from abalone revealed that the calmodulin genes were transcribed in common in gill and mantle tissue, but differentially in the other tissues. A phylogenetic analysis based on the amino acid sequences revealed that calmodulin C was the most common isoform in Gastropoda and calmodulin was the most diverged isoform. An in silico analysis of the calmodulin genes identified paralogous genes in other Haliotis species, indicating that gene duplication might have occurred in the last common ancestor of Haliotis. Abbreviations: ORF: open reading frame; RACE: random amplification of cDNA end; TSA: transcriptome shotgun assembly; UTR: untranslated region.

Stress-Induced Mucus Secretion and Its Composition by a Combination of Proteomics and Metabolomics of the Jellyfish Aurelia coerulea

BACKGROUND

Jellyfish respond quickly to external stress that stimulates mucus secretion as a defense. Neither the composition of secreted mucus nor the process of secretion are well understood.

METHODS

Aurelia coerulea jellyfish were stimulated by removing them from environmental seawater. Secreted mucus and tissue samples were then collected within 60 min, and analyzed by a combination of proteomics and metabolomics using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS), respectively.

RESULTS

Two phases of sample collection displayed a quick decrease in volume, followed by a gradual increase. A total of 2421 and 1208 proteins were identified in tissue homogenate and secreted mucus, respectively. Gene Ontology (GO) analysis showed that the mucus-enriched proteins are mainly located in extracellular or membrane-associated regions, while the tissue-enriched proteins are distributed throughout intracellular compartments. Tryptamine, among 16 different metabolites, increased with the largest-fold change value of 7.8 in mucus, which is consistent with its involvement in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway 'tryptophan metabolism'. We identified 11 metalloproteinases, four serpins, three superoxide dismutases and three complements, and their presence was speculated to be related to self-protective defense.

CONCLUSIONS

Our results provide a composition profile of proteins and metabolites in stress-induced mucus and tissue homogenate of A. coerulea. This provides insight for the ongoing endeavors to discover novel bioactive compounds. The large increase of tryptamine in mucus may indicate a strong stress response when jellyfish were taken out of seawater and the active self-protective components such as enzymes, serpins and complements potentially play a key role in innate immunity of jellyfish.

Characterization and function of a novel calmodulin-like protein from crayfish Procambarus clarkii

Calmodulin plays an important role in calcium-dependent signal transduction pathways. In this experiment, a novel calmodulin-like gene (Pc-CaM-L) was identified in the crayfish Procambarus clarkii; it encodes a polypeptide of 145 amino acids. Quantitative real-time PCR analysis revealed that Pc-CaM-L was expressed in all examined tissues, including hepatopancreas, hemocytes, heart, gill, intestine and muscle; the highest Pc-CaM-L expression level was detected in the hepatopancreas. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blot analysis demonstrated that a recombinant Pc-CaM-L protein was successfully expressed in Escherichia coli. The calcium-binding activity of the purified Pc-CaM-L protein was confirmed by gel mobility shift assay. The expression of Pc-CaM-L was significantly upregulated in gut, gill and hemocytes after lipopolysaccharide or polyinosinic:polycytidylic acid induction. These results suggest that Pc-CaM-L plays a role in the immune response of P. clarkii.

Skin mucus proteins of lumpsucker (Cyclopterus lumpus)

Fish skin mucus serves as a first line of defense against pathogens and external stressors. In this study the proteomic profile of lumpsucker skin mucus was characterized using 2D gels coupled with tandem mass spectrometry. Mucosal proteins were identified by homology searches across the databases SwissProt, NCBInr and vertebrate EST. The identified proteins were clustered into ten groups based on their gene ontology biological process in PANTHER (www.patherdb.org). Calmodulin, cystatin-B, histone H2B, peroxiredoxin1, apolipoprotein A1, natterin-2, 14-3-3 protein, alfa enolase, pentraxin, warm temperature acclimation 65 kDa (WAP65kDa) and heat shock proteins were identified. Several of the proteins are known to be involved in immune and/or stress responses. Proteomic profile established in this study could be a benchmark for differential proteomics studies.

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A proteome reference map of lumpsucker skin mucus was established.

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Proteins involved in immune and stress responses were identified in skin mucus of Cyclopterus lumpus.

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Mucosal proteins identified could be potential biomarkers.

Comparison of Integrated Responses to Nonlethal and Lethal Hypothermal Stress in Milkfish (Chanos chanos): A Proteomics Study

Milkfish is an important aquaculture species in Taiwan, and its high mortality during cold snaps in winter usually causes huge economic losses. To understand the effect of hypothermal stress and the corresponding compensatory stress response in milkfish, this study aimed to compare liver and gill protein levels between milkfish exposed to nonlethal (18°C), lethal (16°C), and control (28°C) temperatures. Using a proteomics approach based on two-dimensional electrophoresis and nano-LC-MS/MS analysis, this study identified thirty unique protein spots from milkfish livers and gills for which protein abundance was significantly different between nonlethal, lethal, and control temperature groups. Proteins identified in the liver were classified into three different categories according to their cellular function: (1) anti-oxidative stress, (2) apoptotic pathway, and (3) cytoskeleton. Similarly, proteins identified in the gill were sorted in five different functional categories: (1) cytoskeleton, (2) immune response, (3) protein quality control, (4) energy production, and (5) intracellular homeostasis. Based on functional information derived from the identified proteins, we assumed that different levels of hypothermal stress had a different effect and induced a different cellular response. Upon nonlethal hypothermal stress, the identified proteins were involved in anti-oxidative stress and anti-inflammation pathways, suggesting that milkfish had high levels of oxidative stress in the liver and exhibited inflammation response in the gill. Upon lethal hypothermal stress, however, identified proteins were associated with apoptosis in the liver and regulation of intracellular homeostasis in the gill. The present study provided evidence to illustrate different multi-physiological responses to nonlethal and lethal hypothermal stress in milkfish livers and gills.

Cloning, characterization, and expression of the macrophage migration inhibitory factor gene from the black tiger shrimp (Penaeus monodon)

Macrophage migration inhibitory factor (MIF) is an ancient cytokine that engages in innate immune system of vertebrates and invertebrates. In this study, the MIF gene homologue (PmMIF) was cloned from the black tiger shrimp, Penaeus monodon. The full-length cDNA sequence of PmMIF was 838 bp and contained 78 bp 5' untranslated region (UTR) and 397 bp 3' UTR, and an open reading frame (ORF) of 363 bp which coded 120 amino acids (aa). Multiple alignment analysis showed that the deduced amino acid sequence shared 98% identities with MIF from closely related species of Litopenaeus vannamei. Quantitative real-time PCR (qRT-PCR) analysis indicated that PmMIF was highly expression observed in hepatotpancreas and gills. After Vibrio harveyi challenge, PmMIF mRNA level in hepatopancreas and gills were sharply up-regulated at 6 h post-injection, and reached the maximum at 12 h. PmMIF expression level in the hepatopancreas and gills were up-regulated markedly under low (2.3%) and high (4.3%) salinity exposure, respectively. PmMIF expression level in gills increased significantly at 12 h and reached peak values (2.5- fold, 6.4-fold and 1.8-fold compared with the control) at 12 h, 48 h and 12 h after zinc, cadmium and copper exposure, respectively. In the hepatopancreas, the expression of PmMIF reached maximum levels (8.5- fold, 6.2-fold and 2.1-fold compared with the control) at 24 h, 6 h and 48 h after zinc, cadmium and copper exposure, respectively. All the results indicate that PmMIF plays an important role in responding in the innate immune system of shrimps.

Identification and characterization of nascent polypeptide-associated complex alpha from Chinese mitten crab (Eriocheir sinensis): A novel stress and immune response gene in crustaceans

Disease in aquatic animals is tightly linked to environmental challenges and their immune responses are greatly modified by their external environment. The chaperone protein nascent polypeptide-associated complex alpha (NACA) has been suggested to play important roles in the cellular response to stress and immune challenges, while the related biological functions remain largely unknown in invertebrates. In the present study we identified a NACA gene (termed EsNACA) from Chinese mitten crab Eriocheir sinensis and analyzed its expression changes in response to ambient (salinity and pH) stresses and immune challenges. The EsNACA protein is comprised of 209 amino acid residues with a conserved DNA binding domain, a C-Jun binding domain, a NAC domain and an ubiquitin-associated domain and shows the highest sequence identity (87%) with its counterpart in shrimp Penaeus monodon. EsNACA mRNA transcripts are presented in all tested normal tissues with predominant expression in hepatopancreas and lower expression in hemocytes. In addition, EsNACA expression was significantly altered in response to the ambient salinity (15‰ and 30‰ salinities) and pH (pH 6 and 8.5) stresses in gill, hepatopancreas, muscle, hemocytes and intestine tissues. Furthermore, EsNACA gene expression was substantially induced upon LPS and Poly(I:C) immune stimulations in E. sinensis hemocytes in vitro. Finally, EsNACA expression was up-regulated in E. sinensis hemocytes, gill, hepatopancreas, intestine and muscle tissues in response to Vibrio anguillarum challenges in vivo. Taken together, our findings for the first time show that EsNACA is an inducible gene involved in stress and immune response in crustaceans.

Calmodulin of the tropical sea cucumber: Gene structure, inducible expression and contribution to nitric oxide production and pathogen clearance during immune response

Calmodulin (CaM) is an essential second messenger protein that transduces calcium signals by binding calcium ions (Ca(2+)) and modulating its interactions with various target proteins. In contrast to vertebrates, where CaM is well established as a cofactor for Ca(2+)-dependent physiological and cellular functions including host defense, there is a paucity of understanding on CaM in invertebrates (such as echinoderms) in response to immune challenge or microbial infections. In this study, we obtained and described the gene sequence of CaM from the tropical sea cucumber Stichopus monotuberculatus, a promising yet poorly characterized aquacultural species. mRNA expression of StmCaM could be detected in the intestine and coelomic fluid after Vibrio alginolyticus injection. Transcriptional and translational expression of StmCaM was inducible in nature, as evidenced by the expression patterns in primary coelomocytes following Vibrio challenge. This response could be mimicked by the Vibrio cells membrane components or lipopolysaccharides (LPS), and blocked by co-treatment of the LPS-neutralizing agent polymyxin B (PMB). Furthermore, inhibition of CaM activity by incubation with its inhibitor trifluoroperazine dihydrochloride (TFP) blunted the production of Vibrio-induced nitric oxide (NO) and augmented the survival of invading Vibrio in coelomocytes. Collectively, our study here supplied the first evidence for echinoderm CaM participation in innate immunity, and provided a functional link between CaM expression and antibacterial NO production in sea cucumber.

Characterization and identification of calmodulin and calmodulin binding proteins in hemocyte of the black tiger shrimp (Penaeus monodon)

Calmodulin (CaM), a ubiquitous intracellular calcium (Ca(2+)) sensor in all eukaryotic cells, is one of the well-known signaling proteins. Previously, CaM gene has shown a high transcriptional level in hemocyte of the pathogen infected shrimp, suggesting that shrimp CaM does not only regulate Ca(2+) metabolism, but is also involved in immune response cascade. In the present study, the CaM gene of shrimp Penaeus monodon was identified and the recombinant P.monodon CaM (rPmCaM) was produced and biochemically characterized. The identification of CaM-binding proteins was also performed. The PmCaM cDNA consisted of an open reading frame of 447 bp encoding for 149 amino acid residues with a calculated mass of 16,810 Da and an isoelectric point of 4.09. Tissue distribution showed that the PmCaM transcript was expressed in all examined tissues. The results of gel mobility shift assay, circular dichroism spectroscopy and fluorescence spectroscopy all confirmed that the conformational changes of the rPmCaM were observed after the calcium binding. According to the gene silencing of PmCaM transcript levels, the shrimp's susceptibility to pathogenic Vibrio harveyi infection increased in comparison with that of the control groups. Protein pull-down assay and LC-MS/MS analysis were performed to identify rPmCaM-binding proteins involved in shrimp immune responses and transglutaminase, elongation factor 1-alpha, elongation factor 2 and actin were found. However, by computational analysis, only the first three proteins contained CaM-binding domain. These findings suggested that PmCaM may play an important role in regulation of shrimp immune system.

Identification and characterization of the cDNAs encoding the two subunits of Chinese mitten crab (Eriocheir sinensis) calcineurin: their implications in stress and immune response

Calcineurin (CN), the only Ca(2+)/calmodulin-activated serine/threonine protein phosphatase, is a key effector participating in Ca(2+)-dependent signal transduction pathways in a number of cellular processes under normal, stress and pathological conditions. However, the expression and the relevance of CN in stress and immune response have not been characterized in crustaceans. Here, we identified the cDNAs that encode the two subunits of CN (termed EsCN-A and EsCN-B, respectively) in Chinese mitten crab Eriocheir sinensis and analysed their expression patterns in response to stress and immune challenges. The catalytic subunit EsCN-A is comprised of 511 amino acids with a theoretical molecular mass of 57.5 kDa and shows 80% sequence identity with human beings CN-A alpha isoform, while the regulatory subunit EsCN-B protein is composed of 170 amino acids with an estimated molecular mass of 19.3 kDa and shares 88% sequence identity with human beings CN-B type 1. Tissue distribution analysis reveals that both EsCN-A and EsCN-B mRNA transcripts are expressed in all tested tissues with the greatest expression in hepatopancreas and the lowest expression in haemocytes. In addition, both EsCN-A and EsCN-B genes could be significantly up-regulated but with different expression patterns by ambient salinity (15‰ and 30‰ salinities) and pH (pH 6 and 8.5) stresses in gill, hepatopancreas, haemocytes, intestine and muscle. Furthermore, EsCN-A and EsCN-B were up-regulated by LPS and Poly(I:C) immune stimulations in E. sinensis haemocytes in vitro. Moreover, EsCN-A and EsCN-B mRNA were significantly up-regulated in haemocytes, gill, hepatopancreas, intestine and muscle in response to Edwardsiella tarda challenge in vivo. Finally, we revealed the importance of EsCN in LPS-induced nitric oxide production in E. sinensis haemocytes. Together our observations suggest that EsCN, the important downstream effector of CaM-mediated signalling pathway(s), may possess vital roles in stress and immune response in the Chinese mitten crab.