Immunological characterization and expression of lily-type lectin in response to environmental stress in turbot (Scophthalmus maximus)

Immunological characterization and function analysis of L-type lectin from spotted knifejaw, Oplegnathus punctatus

Lily-type lectin (LTL) plays significant roles in innate immune response against pathogen infection. LTL in animals and plants has received widespread attention. In the present study, an LTL (OppLTL) was identified from spotted knifejaw Oplegnathus punctatus. The OppLTL encoded a typical Ca²⁺-dependent carbohydrate-binding protein containing a CRD domain. The qRT-PCR showed that it was mainly expressed in the gill and was significantly upregulated after Vibrio anguillarum challenge. The agglutination analysis showed that the recombinant OppLTL could bind and agglutinate Gram-negative and Gram-positive bacteria in a Ca²⁺-dependent manner. However, the binding activity was different. Meanwhile, the recombinant OppLTL could hemagglutinate mammalian and teleost erythrocytes. Subcellular localization revealed that OppLTL was mainly detected in the cytoplasm of HEK293T cells. The dual-luciferase analysis revealed that OppLTL could inhibit the activity of the NF-κB signal pathway in HEK293T cells after OppLTL overexpression. These findings collectively demonstrated that OppLTL could be involved in host innate immune response and defense against bacterial infection in spotted knifejaw.

Scuticociliatosis caused by Philasterides dicentrarchi

The ciliate Philasterides dicentrarchi has been previously identified as a new agent of scuticociliatosis in marine fish. The parasite can cause high mortalities in fish reared on farms or kept in aquariums. P. dicentrarchi is usually a free-living protozoan but can become an opportunistic histophagous parasite causing rapid lethal systemic infections in cultured fish. This review provides information about the morphology and biology of the scuticociliate P. dicentrarchi, as well as information about the pathological and immunological reactions of the host in response to the infection with the parasite. The epidemiology and the control strategies of the disease are also reviewed.

An Update of Lectins from Marine Organisms: Characterization, Extraction Methodology, and Potential Biofunctional Applications

Lectins are a unique group of nonimmune carbohydrate-binding proteins or glycoproteins that exhibit specific and reversible carbohydrate-binding activity in a non-catalytic manner. Lectins have diverse sources and are classified according to their origins, such as plant lectins, animal lectins, and fish lectins. Marine organisms including fish, crustaceans, and mollusks produce a myriad of lectins, including rhamnose binding lectins (RBL), fucose-binding lectins (FTL), mannose-binding lectin, galectins, galactose binding lectins, and C-type lectins. The widely used method of extracting lectins from marine samples is a simple two-step process employing a polar salt solution and purification by column chromatography. Lectins exert several immunomodulatory functions, including pathogen recognition, inflammatory reactions, participating in various hemocyte functions (e.g., agglutination), phagocytic reactions, among others. Lectins can also control cell proliferation, protein folding, RNA splicing, and trafficking of molecules. Due to their reported biological and pharmaceutical activities, lectins have attracted the attention of scientists and industries (i.e., food, biomedical, and pharmaceutical industries). Therefore, this review aims to update current information on lectins from marine organisms, their characterization, extraction, and biofunctionalities.

Dissection of genotype × tissue interactions for immunological factors in turbot (Scophthalmus maximus) infected with Vibrio anguillarum

Seven immune factors, lysozyme, hepcidin, heat-shock protein (HSP) 70, HSP90, immunoglobulin M, C-type lectin, and Lily-type lectin, were measured by PCR in the livers, spleens, and head kidneys of turbot infected with Vibrio anguillarum. Additive main effects and multiplicative interaction (AMMI) and genotype main effects and genotype × environment interaction (GGE) biplot analysis were used to analyze genotype × tissue interactions for immunological factors. The AMMI analysis revealed that immune factor expression was significantly affected by genotype, tissue, and genotype × tissue interactions. Genotype (65.85%) was the major contributor to the total variation in immune factor expression in comparison to tissue effects (7.54%) and genotype × tissue interactions (12.52%). GGE biplot analysis revealed differences in the ranking of the seven immune factors in the three tissues; head kidney possessed the strongest ability to distinguish the seven immune factors. The test tissue locations were divided into liver-spleen and head kidneys regions; HSP70 was expressed the highest in the liver-spleen regions, and lysozyme had the highest expression in the head kidney region. Overall, HSP70 and HSP90 had the best expression and stability in the three tissues.

Genetic parameters of seven immune factors in turbot (Scophthalmus maximus) infected with Vibrio anguillarum

In this study, 1,800 turbot (Scophthalmus maximus) individuals from 30 full-sib families were experimentally infected with Vibrio anguillarum, and the expression levels of the immune factors lysozyme, hepcidin, heat-shock protein 70 (HSP70), HSP90, immunoglobulin M (IgM), C-type lectin and Lily-type lectin in the liver were measured by real-time PCR. Heritability values of the seven immune factors were 0.289 ± 0.087, 0.092 ± 0.024, 0.282 ± 0.043, 0.244 ± 0.027, 0.343 ± 0.081, 0.092 ± 0.011 and 0.084 ± 0.009, respectively. The ranges of phenotypic, genetic and environmental correlations were -0.889 to 0.759, -0.841 to 0.888 and -0.919 to 0.883, respectively. The heritability values of HSP70, HSP90 and IgM were moderate, and the genetic correlations between HSP70, HSP90 and IgM were moderate to highly positive, which suggests that the immunocompetence of turbot against V. anguillarum can be improved by genetically improving these three immune characters via multi-trait integrated breeding technology or indirect selection.

Transcriptome analysis provides insights into the effects of myo-inositol on the turbot Scophthalmus maximus

Myo-inositol is an essential vitamin for most animals, and it can modulate multiple physiological functions. In this study, we performed transcriptome gene expression profiling of gill tissue from turbot Scophthalmus maximus fed different concentrations of myo-inositol (0, 300, 600, 900, 1200 mg/kg). Results of expression tendency analysis, Weighted Gene Co-Expression Network Analysis (WGCNA), integrated transcriptome analyses, and KEGG annotation analysis of all differentially expressed genes (DEGs) demonstrated that the cytokine-cytokine receptor interaction played a core role in effects of myo-inositol on turbot, which was followed by the Jak-STAT signaling pathway. The results of qRT-PCR also showed myo-inositol mediated the gene expression of the cytokine-cytokine receptor interaction and the Jak-STAT signaling pathway in turbot. The ELISA assay indicated that myo-inositol affected the concentration change of interleukins (IL-2 and IL-10). Consequently, the interleukins associated with immune functions in the cytokine-cytokine receptor interaction played a core role in the effects of myo-inositol on turbot, which was followed by the Jak-STAT signaling pathway. Additionally, 10 hub genes associated with myo-inositol-traits were identified via WGCNA.

Molecular cloning, characterization and expression analysis of p53 from turbot Scophthalmus maximus and its response to thermal stress

The tumor suppressor protein, p53 plays a crucial role in protecting genetic integrity. Once activated by diverse cell stresses, p53 reversibly activates downstream target genes to regulate cell cycle and apoptosis. However, few studies have investigated the effects of thermal stress in turbot, specifically the p53 signaling pathway. In this study, the rapid amplification of cDNA ends was used to obtain a full-length cDNA of the turbot p53 gene (Sm-p53) and perform bioinformatics analysis. The results showed that the cDNA of the Sm-p53 gene was 2928 bp in length, encoded a 381 amino acid protein, with a theoretical isoelectric point of 6.73. It was composed of a DNA binding and a tetramerization domain. Expression of Sm-p53 in different tissues was detected and quantified by qRT-PCR, and was highest in the liver. We also investigated the expression profiles of Sm-p53 in different tissue and TK cells after thermal stress. These result suggested that Sm-p53 plays a key role, and provides a theoretical basis for Sm-p53 changes in environmental stress responses in the turbot.

Identification and characterization of a B-type mannose-binding lectin from Nile tilapia (Oreochromis niloticus) in response to bacterial infection

Lectins are a group of carbohydrate-binding proteins, which play an important role in innate immune system against pathogen infection. In this study, a B-type mannose-binding lectin (OnBML) was identified from Nile tilapia (Oreochromis niloticus), and characterized at expression patterns against bacterial infection and capability to promote phagocytosis by macrophages. The open reading frame of OnBML is 354 bp of nucleotide sequence encoding polypeptides of 117 amino acids. The deduced protein is highly homologous to other teleost BMLs, containing two repeats of the conserved mannose-binding motif QXDXNXVXY. Expression of OnBML was widely exhibited in all examined tissues, with the most abundance in spleen and following gill, peripheral blood, and head kidney. The OnBML expressions were significantly up-regulated following two major bacterial infections including a Gram-positive bacterium (Streptococcus agalactiae) and a Gram-negative bacterium (Aeromonas hydrophila) in vivo and in vitro. Recombinant OnBML protein possessed capacities of mannose-binding and calcium-dependent agglutination to S. agalactiae and A. hydrophila, and promoted the phagocytosis by macrophages. Taken together, the present study indicated that OnBML is likely to get involved in host defense against bacterial infection in Nile tilapia.

Turbot (Scophthalmus maximus) Nk-lysin induces protection against the pathogenic parasite Philasterides dicentrarchi via membrane disruption

P. dicentrarchi is one of the most threatening pathogens for turbot aquaculture. This protozoan ciliate is a causative agent of scuticociliatosis, which is a disease with important economic consequences for the sector. Neither vaccines nor therapeutic treatments are commercially available to combat this infection. Numerous antimicrobial peptides (AMPs) have demonstrated broad-spectrum activity against bacteria, viruses, fungi, parasites and even tumor cells; an example is Nk-lysin (Nkl), which is an AMP belonging to the saposin-like protein (SAPLIP) family with an ability to interact with biological membranes. Following the recent characterization of turbot Nkl, an expression plasmid encoding Nkl was constructed and an anti-Nkl polyclonal antibody was successfully tested. Using these tools, we demonstrated that although infection did not clearly affect nkl mRNA expression, it induced changes at the protein level. Turbot Nkl had the ability to inhibit proliferation of the P. dicentrarchi parasite both in vivo and in vitro. Moreover, a shortened peptide containing the active core of turbot Nkl (Nkl71-100) was synthesized and showed high antiparasitic activity with a direct effect on parasite viability that probably occurred via membrane disruption. Therefore, the nkl gene may be a good candidate for genetic breeding selection of fish, and either the encoded peptide or its shortened analog is a promising antiparasitic treatment in aquaculture.

Identification and characterization of a calcium-dependent lily-type lectin from black rockfish (Sebastes schlegelii): Molecular antennas are involved in host defense via pathogen recognition

Lily-type lectins (LTLs) are soluble pathogen recognition receptors (PRRs) that contain one or more characteristic carbohydrate recognition domains (CRDs), through which LTLs bind reversibly and specifically to cognate sugar moieties present on the invading pathogen membrane and trigger the host innate immune responses. In this study, we identified a LTL homolog (SsLTL) from black rockfish (Sebastes schlegelii) transcriptome database and its functional roles in innate immunity was investigated in vitro and in vivo. Three mannose-binding sites were found in the protein sequence of SsLTL, among which two sites are conserved with those in mannose-binding lectins of monocotyledonous plants. SsLTL were highly expressed in both the external and internal mucosal tissues of healthy rockfish. During the immune challenge, early up-regulation of SsLTL mRNA expression showed in gill and blood upon both poly I:C and S. iniae challenges. In contrast, the challenge with lipopolysaccharide significantly down-regulated SsLTL expression in both examined tissues. Recombinant SsLTL showed a hemagglutination activity toward fish erythrocytes, which could be enhanced by the addition of calcium ions. Furthermore, strong agglutination activity of SsLTL was also observed with a broad range of fish pathogenic bacteria. Our results implied the crucial role of SsLTL as a PRR molecule in the black rockfish defense mechanism against invading microbial pathogens.

Intensive herbicide use has selected for constitutively elevated levels of stress-responsive mRNAs and proteins in multiple herbicide-resistant Avena fatua L

BACKGROUND

Intensive use of herbicides has led to the evolution of two multiple herbicide-resistant (MHR) Avena fatua (wild oat) populations in Montana that are resistant to members of all selective herbicide families available for A. fatua control in US small grain crops. We used transcriptome and proteome surveys to compare constitutive changes in MHR and herbicide-susceptible (HS) plants associated with non-target site resistance.

RESULTS

Compared to HS plants, MHR plants contained constitutively elevated levels of differentially expressed genes (DEGs) with functions in xenobiotic catabolism, stress response, redox maintenance and transcriptional regulation that are similar to abiotic stress-tolerant phenotypes. Proteome comparisons identified similarly elevated proteins including biosynthetic and multifunctional enzymes in MHR plants. Of 25 DEGs validated by RT-qPCR assay, differential regulation of 21 co-segregated with flucarbazone-sodium herbicide resistance in F₃ families, and a subset of 10 of these were induced or repressed in herbicide-treated HS plants.

CONCLUSION

Although the individual and collective contributions of these DEGs and proteins to MHR remain to be determined, our results support the idea that intensive herbicide use has selected for MHR populations with altered, constitutively regulated patterns of gene expression that are similar to those in abiotic stress-tolerant plants. © 2017 Society of Chemical Industry.

Transcriptomic profiling analysis of tilapia (Oreochromis niloticus) following Streptococcus agalactiae challenge

Innate immune system is the primary defense mechanism against pathogen infection in teleost, which are living in pathogen-rich aquatic environment. It has been long hypothesized that the disease resistance in teleost are strongly correlated to the activities of innate immune genes. Tilapia is an important economical fish around the world, especially in China, where the production accounts for nearly half of the global production. Recently, S. agalactiae has become one of the most serious bacterial diseases in southern China, resulted in high cumulative mortality and economic loss to tilapia industry. Therefore, we sought here to characterize the expression profiles of tilapia against S. agalactiae infection at whole transcriptome level by RNA-seq technology. A total of 2822 genes were revealed significantly expressed in tilapia spleen with a general trend of induction. Notably, most of the genes were rapidly the most induced at the early timepoint. The significantly changed genes highlighted the function of pathogen attachment and recognition, antioxidant/apoptosis, cytoskeletal rearrangement, and immune activation. Collectively, the induced expression patterns suggested the strong ability of tilapia to rapidly recognize the invasive bacteria, and activation of downstream immune signaling pathways to clear the bacteria and prevent the tissue damage and bacteria triggered cell apoptosis. Our results heighted important roles of novel candidate genes which were often missed in previous tilapia studies. Further studies are needed to characterize the molecular relationships between key immune genes and disease resistance, and to identify the candidate genes for molecular-assistant selection of disease-resistant broodstock and evaluation of disease prevention and treatment measures.

Molecular identification and functional analysis of KLF2 in Plecoglossus altivelis (ayu): It's regulatory role in monocyte/macrophage activation

Monocytes/macrophages (MO/MФ) play an important role in the response to infection in Plecoglossus altivelis (ayu). However, the role of transcription factors in the function of ayu MO/MФ is poorly understood. Here, we cloned the cDNA sequence of the Kruppel-like factor 2 (PaKLF2) gene from ayu. Phylogenetic analysis indicated that PaKLF2 was closest to that of Atlantic salmon (Salmo salar). Real time quantitative PCR (RT-qPCR) revealed that the PaKLF2 mRNA level was highest in the peripheral blood mononuclear cells among all tested tissues. The mRNA expression of PaKLF2 was upregulated in the head kidney, liver, spleen, and brain after Listonella anguillarum infection. Subsequently, PaKLF2 was expressed and purified to prepare anti-PaKLF2 antibodies. After L. anguillarum challenge, the PaKLF2 mRNA and protein levels were significantly upregulated in ayu MO/MФ. Moreover, PaKLF2 knockdown in MO/MФ resulted in the enhancement of cytokine production as well as phagocytotic and bactericidal capability. Therefore, PaKLF2 may modulate the immune response in ayu by suppressing the function of MO/MФ.