Antimicrobial properties and immune-related gene expression of a C-type lectin isolated from Pinctada fucata martensii

A novel C-type lectin protein (BjCTL5) interacts with apoptosis stimulating proteins of p53 (ASPP) to activate NF-κB signaling pathway in primitive chordate

C-type lectin proteins (CTLs), a group of pattern recognition receptors (PRRs), play pivotal roles in immune responses. However, the signal transduction and regulation of CTLs in cephalochordates have yet to be explored. In this study, we examined the composition of CTLs in Branchiostoma japonicum, identifying a total of 272 CTLs. These CTLs underwent further analysis concerning domain arrangement, tandem and segmental duplication events. A multidomain C-type lectin gene, designated as BjCTL5, encompassing CLECT, KR, CUB, MAM, and SR domains, was the focal point of our investigation. BjCTL5 exhibits ubiquitous expression across all detected tissues and is responsive to stimulation by LPS, mannose, and poly (I:C). The recombinant protein of BjCTL5 can bind to Escherichia coli and Staphylococcus aureus, inducing their agglutination and inhibiting the proliferation of S. aureus. Yeast two-hybrid, CoIP, and confocal immunofluorescence experiments revealed the interaction between BjCTL5 and apoptosis-stimulating proteins of p53, BjASPP. Intriguingly, BjCTL5 was observed to induce the luciferase activity of the NF-κB promoter in HEK293T cells. These results suggested a potential interaction between BjCTL5 and BjASPP, implicating that they involve in the activation of the NF-κB signaling pathway, which provides an evolutionary viewpoint on NF-κB signaling pathway in primitive chordate.

Identification and functional characterization of a superoxide dismutase (CuZnSOD) from Pinctada fucata martensii

Copper/zinc superoxide dismutase (Cu/Zn-SOD) can effectively eliminate reactive oxygen species (ROS)，avoid damage from O2 to the body, and maintain O2 balance. In this study, multi-step high-performance liquid chromatography (HPLC), combined with Mass Spectrometry (MS), was used to isolate and identify Cu/Zn-SOD from the serum of Pinctada fucata martensii (P. f. martensii) and was designated as PmECSOD. With a length of 1864 bp and an open reading frame (ORF) of 1422 bp, the cDNA encodes a 473 amino acid protein. The PmECSOD transcript was detected in multiple tissues by quantitative real-time PCR (qRT-PCR), with its highest expression level being in the gills. Additionally, the temporal expression of PmECSOD mRNA in the hemolymph was highest at 48 h after in vivo stimulation with Escherichia coli and Micrococcus luteus. The results from this study provide a valuable base for further exploration of molluscan innate immunity and immune response.

Molecular cloning, expression, and functional analysis of a putative lectin from the pearl oyster (Pinctada fucata, Gould 1850)

Marine lectins are a group of proteins that possess specific carbohydrate recognition and binding domains. They exhibit various activities, including antimicrobial, antitumor, antiviral, and immunomodulatory effects. In this study, a novel galectin-binding lectin gene named PFL-96 (GenBank: OQ561753.1) was cloned from Pinctada fucata. The PFL-96 gene has an open reading frame of 324 base pairs (bp) and encodes a protein comprising 107 amino acids. The protein has a molecular weight of 11.95 kDa and an isoelectric point of 9.27. It contains an N-terminal signal peptide and a galactose-binding lectin domain. The sequence identity to lectin proteins from fish, echinoderms, coelenterates, and shellfish ranges from 31.90 to 40.00 %. In the phylogenetic analysis, it was found that the PFL-96 protein is closely related to the lectin from Pteria penguin. The PFL-96 recombinant protein exhibited coagulation activity on 2 % rabbit red blood cells at a concentration of ≥8 μg/mL. Additionally, it showed significant hemolytic activity at a concentration of ≥32 μg/mL. The PFL-96 recombinant protein exhibited significant antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Candida albicans, and Vibrio alginolyticus, with minimum inhibitory concentrations (MIC) of 4, 8, 16, and 16 μg/mL, respectively. The minimum bactericidal concentrations (MBC) were determined to be 8, 16, 32, and 32 μg/mL, respectively. Furthermore, the PFL-96 recombinant protein exhibited inhibitory effects on the proliferation of Hela tumor cells, HepG2 tumor cells, and C666-1 tumor cells, with IC50 values of 7.962, 8.007, and 9.502 μg/mL, respectively. These findings suggest that the recombinant protein PFL-96 exhibits significant bioactivity in vitro, contributing to a better understanding of the active compounds found in P. fucata. The present study establishes a fundamental basis for further investigation into the mechanism of action and structural optimization of the recombinant protein PFL-96. The aim is to develop potential candidates for antibacterial and anti-tumor agents.

Preliminary investigation of the immune activity of PmH2A-derived antimicrobial peptides from the pearl oyster Pinctada fucata martensii

Antimicrobial peptides (AMPs) play important roles in the immune defense against pathogenic microorganisms. For instance, histone 2A (H2A)-derived AMPs is an antimicrobial peptide involved in the host's innate immune defense and immunoregulation. AMPs have been isolated from the pearl oyster Pinctada fucata martensii but their role in host defense remains poorly understood. To elucidate the structural features of P. f. martensii H2A (PmH2A)-derived AMPs and their potential immune functions, we synthesized a series of laboratory-designed synthetic analogs of PmH2A and examined their antimicrobial properties, as well as their mechanisms of action. This analysis revealed inhibitory effects on the growth of Gram-positive and Gram-negative bacteria. Further assessment by transmission electron microscopy (TEM) of two of the three peptides, PmH2A-AMP and PmH2A-AMP(5-13)[KLLK]₃, confirmed that it exerted an anti-bacterial activity through membrane lysis. Finally, we found that the hemocytes and gills of P. f. martensii released antimicrobial H2A histones in response to LPS exposure, mimicking tissue damage and infection. This immune response is reminiscent of the neutrophil extracellular traps (NETs) recently described in oysters. Thus, the LPS challenge is sufficient to induce histone-derived peptide accumulation in pearl oyster P.f. martensii.

Molecular Cloning and Characteristics of a Lectin from the Bivalve Glycymeris yessoensis

C-type lectins (CTLs) are a family of carbohydrate-binding proteins that mediate multiple biological events, including adhesion between cells, the turnover of serum glycoproteins, and innate immune system reactions to prospective invaders. Here, we describe the cDNA cloning of lectin from the bivalve Glycymeris yessoensis (GYL), which encodes 161 amino acids and the C-type carbohydrate recognition domain (CRD) with EPN and WND motifs. The deduced amino acid sequence showed similarity to other CTLs. GYL is a glycoprotein containing two N-glycosylation sites per subunit. N-glycans are made up of xylose, mannose, D-glucosamine, 3-O-methylated galactose, D-quinovoses, and 3-O-methylated 6-deoxy-D-glucose. The potential CRD tertiary structure of the GYL adopted CTL-typical long-form double-loop structure and included three disulfide bridges at the bases of the loops. Additionally, when confirming the GYL sequence, eight isoforms of this lectin were identified. This fact indicates the presence of a multigene family of GYL-like C-type lectins in the bivalve G. yessoensis. Using the glycan microarray approach, natural carbohydrate ligands were established, and the glycotope for GYL was reconstructed as "Galβ1-4GlcNAcβ obligatory containing an additional fragment", like a sulfate group or a methyl group of fucose or N-acetylgalactosamine residues.

Members of the histone-derived antimicrobial peptide family from the pearl oyster Pinctada fucata martensii: Inhibition of bacterial growth

Because it is difficult to isolate standard antimicrobial peptides (AMPs) using traditional biochemical approaches, we designed, synthesized, and evaluated a series of structurally altered histone-derived AMPs (HDAPs) from the pearl oyster Pinctada fucata martensii using molecular cloning approaches. Four histone-homolog genes (PmH2A, PmH2B, PmH3, and PmH4-1) were identified, of which PmH2A and PmH2B had yet to be described. PmH2A and PmH2B were therefore cloned using Rapid Amplification of cDNA Ends (RACE) and characterized. Constitutive PmH2A and PmH2B mRNA expression was detected in all six pearl oyster tissues tested, with comparatively greater transcript abundance in the gonads. Because α-helical content, hydrophilicity index, and the presence of a proline hinge may be the three important factors influencing the antimicrobial efficacy of HDAPs, we synthesized a series of eight N- and C-terminally truncated or amino acid-substituted synthetic candidate HDAP analogs derived from PmH2A, PmH2B, PmH3, and PmH4-1. Only the PmH2A- and PmH4-derived AMPs inhibited bacterial growth. The PmH2A-derived AMPs were α-helical proteins, while the PmH4-derived AMPs were extended strand/random coil proteins. Our results suggested that having an α-helical structure was particularly important for the antibacterial efficacy of the PmH2A-derived peptides; amphipathic structures (hydrophilic index, 0.3 to -0.3) may enhance the antimicrobial function of both the PmH2A- and PmH4-derived peptides. The high antibacterial efficacy of one of the HDAP analogs studied, PmH2A-AMP (5-13) [KLLK]₃, indicated that this protein may represent a promising candidate for the treatment of bacterial infections in aquaculture mollusk species. This first study of HDAPs from the pearl oyster P. f. martensii provides new insights into the design and function of highly effective antimicrobial peptides.

Gene cloning and functional study of PmKSPI from Pinctada fucata martensii

Kunitz-type serine protease inhibitors (KSPI) are a family of serine protease inhibitors (SPIs) and are extensively found in animals, plants, and microbes. SPI can inhibit proteases that may be harmful or unwanted to its cells. Here, a four-domain Kunitz-type SPI, PmKSPI, was cloned by RACE in the pearl oyster Pinctada fucata martensii. The full-length cDNA sequence of PmKSPI was 1318 bp, including the 5' UTR (25 bp), the 3' UTR (96 bp) and ORF (1197 bp). Homology analysis indicated that PmKSPI had the highest resemblance (30.14%) with its homolog in Crassostrea gigas. Phylogenetic analysis revealed that PmKSPI clustered with homologs in other molluscs. We found that PmKSPI mRNA expression in P. f. martensii was distributed in all six tissues, with the highest level in the mantle, and almost no expression in other tissues. After PAMPs challenge, expression of PmKSPI mRNA in the mantle was significantly up-regulated. The recombinant protein rPmKSPI significantly inhibited the growth of 5 kinds of Gram-negative bacteria but had little effect on Gram-positive bacterial activity. Transmission electron microscopy showed that plasmolysis occurred in two Gram-negative bacteria species when treated with rPmKSPI. rPmKSPI may thus have a bactericidal effect by destroying the bacterial cell membrane or cell walls and releasing its contents. Therefore, our results suggest that PmKSPI is tightly associated with the immunological defence of P. f. martensii.

Comprehensive analysis of the lncRNAs, mRNAs, and miRNAs implicated in the immune response of Pinctada fucata martensii to Vibrio parahaemolyticus

Non-coding RNAs (ncRNAs) have been implicated in a variety of biological processes. However, most ncRNAs are of unknown function and are as-yet unannotated. The immune-related functions of ncRNAs in the pearl oyster Pinctada fucata martensii were explored based on transcriptomic differences in the expression levels of long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) in the hemocytes of P.f. martensii after challenge by the pathogenic bacterium Vibrio parahaemolyticus. Across the challenged and control pearl oysters, 144 miRNAs and 14,571 lncRNAs were identified. In total, 13,375 ncRNAs were differentially expressed between the challenged and control pearl oysters; in the challenged pearl oysters as compared to the controls, 15 miRNAs and 5147 lncRNAs were upregulated, while 51 miRNAs and 8162 lncRNAs were downregulated. The sequencing results were validated using quantitative real-time polymerase chain reaction (qRT-PCR) analysis. GO and KEGG pathway analysis showed that genes targeted by the differentially expressed ncRNAs were associated with the vascular endothelial growth factor (VEGF) signaling pathway and the nuclear factor kappa-B (NF-κB) signaling pathway. An lncRNA-mRNA-miRNA network that was developed based on the transcriptomic results of this study suggested that lncRNAs may compete with miRNAs for mRNA binding sites. This study may provide a useful framework for the detection of additional novel ncRNAs, as well as new insights into the pathogenic mechanisms underlying the response of P.f. martensii to V. parahaemolyticus.

Lysine acetylation plays a role in the allograft-induced stress response of the pearl oyster (Pinctada fucata martensii)

Implanting a spherical nucleus into a recipient oyster is a critical step in artificial pearl production using the pearl oyster Pinctada fucata martensii. However, little is known about the role of post-translational modifications (PTMs) in the response of the pearl oyster to this operation. Lysine acetylation, a highly conserved PTM, may be an essential adaptive strategy to manage multiple biotic or abiotic stresses. We conducted the first lysine acetylome analysis of the P. f. martensii gill 12 h after nucleus implantation, using tandem mass tags (TMT) labeling and K^ac affinity enrichment. We identified 2443 acetylated sites in 1301 proteins, and 1511 sites on 895 proteins were quantitatively informative. We found 25 conserved motifs from all of the identified lysine sites, particularly motifs K^ac H, K^ac S, and K^ac Y were strikingly conserved, of which K^ac Y, K^ac H, Y K^ac, K^ac K, K^ac *K, K^ac R, and K^ac F which have been observed in other species and are therefore highly conserved. We identified 58 sites that were significantly differently acetylated in P. f. martensii in response to allograft (|fold change|>1.2, P-value ≤ 0.05); 38 newly acetylated and 20 deacetylated. According to GO functional analysis, subcellar location, and KOG classIfication, these proteins were divided into four categories: cytoskeleton, response to stimulus, metabolism, and other. The differentially acetylated proteins (DAPs) enriched pathways include aminoacyl-tRNA biosynthesis, salmonella infection, and longevity regulating pathway-worm-Caenorhabditis elegans (nematode). Parallel reaction-monitoring (PRM) validation of the differential acetylation of 10 randomly selected differentially acetylated sites from the acetylome analysis. These results indicated that our acetylome analysis results were sufficiently reliable and reproducible. These results provide an essential resource for in-depth exploration of the stress responses and adaptation mechanisms associated with lysine acetylation in marine invertebrates and P. f. martensii.

The succinylome of Pinctada fucata martensii implicates lysine succinylation in the allograft-induced stress response

Lysine succinylation is a novel protein post-translational modification associated with the regulation of a variety of cellular processes. Post-translational modifications may regulate the immune response of Pinctada fucata martensii, a marine bivalve used to produce cultured pearls, in response to the surgical implantation of the seed pearl. This allograft-induced stress response may lead to transplant rejection or host death. However, the regulatory effects of post-translational modifications following nucleus insertion surgery in P.f. martensii remain largely unknown. Here, we used 4D label-free quantitative proteomics (4D-LFQ) with LC-MS/MS to explore the effects of nucleus implantation on lysine succinylation in P.f. martensii. We identified 4430 succinylated sites on 964 succinylated proteins in P.f. martensii after nucleus insertion surgery, and seven conserved motifs were identified upstream and downstream of these sites. In total, 269 succinylation sites were differentially expressed in response to implantation (|fold-change| > 1.5 and FDR <1%; 211 upregulation and 58 downregulation), corresponding to 163 differentially expressed succinylated proteins (DESPs; 124 upregulated and 39 downregulated). The terms over-enriched in the DESPs included "cellular processes", "metabolic pathways", and "binding activity", while the significantly enriched pathways included "ECM-receptor interaction", "PI3K-Akt signaling", and "focal adhesion". "EGF-like structural domains", "platelet-responsive protein type 1 structural domains", and "laminin EGF-like (domains III and V) domains" were overrepresented in the DESPs. Parallel reaction-monitoring (PRM) analysis validated 13 DESPs from the proteomics data. The succinylome of P.f. martensii (generated here for the first time) helps to clarify the biological role of large-scale succinylation in this bivalve after nucleus insertion surgery, providing a theoretical basis for further investigations of stress-induced post-translational modifications in other mollusks and extending our knowledge of the molluscan succinylated proteome.

Cloning and functional analysis of a trypsin-like serine protease from Pinctada fucata martensii

Trypsin-like serine proteases (TLSs) play various roles in dietary protein digestion, hemolymph coagulation, antimicrobial peptide synthesis, and, in particular, the rapid immune pathways activated in response to pathogen detection. The cultured pearl industry, of which Pinctada fucata martensii is one of the most important species, is plagued by disease, thus leading to large economic losses. Herein, the molecular mechanisms underlying the innate immune response of P.f. martensii were explored. First, immune effector molecules from the P.f. martensii genome were screened and a TLS-like gene encoding a protein with a trypsin domain, herein designated as PmTLS, was identified. A multi-sequence alignment indicated a low sequence homology between PmTLS and other mollusk TLS-like proteins. Furthermore, a neighbor-joining phylogenetic analysis indicated that PmTLS has the closest genetic relationship to a Crassostrea gigas TLS. Additionally, real-time quantitative PCR (qPCR) analysis showed that PmTLS mRNA is constitutively expressed in all of the 6 examined P.f. martensii tissues, with significantly higher expression noted in hemocytes relative to the other tissues examined (p < 0.05). P.f. martensii samples were then challenged with various pathogen-associated molecular patterns (PAMPs), including lipopolysaccharide, peptidoglycan, and polyinosinic acid. In the challenge groups, PmTLS was significantly upregulated in hemocytes at 48 h post-challenge when compared to the unchallenged controls. Furthermore, treatment with recombinant PmTLS (rPmTLS) also significantly inhibited the growth of most of the examined gram-negative bacteria tested in vitro (p < 0.05), but it had little effect on the growth of the examined gram-positive bacteria. When examining morphological changes via transmission electron microscopy, rPmTLS treated bacteria exhibited morphological changes such as plasma wall separation. Thus, rPmTLS appears to play a bactericidal role by destroying bacterial cell membranes or cell walls, which subsequently leads to a release of the cellular contents and cell death. The findings presented herein have enabled further characterization of the immune defense mechanisms in P.f. martensii and may lead to improved disease control methods for the pearl cultivation industry.

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.

Role of peroxinectin in the antibacterial immune response of the Chinese mitten crab, Eriocheir sinensis

To elucidate the antibacterial role of peroxinectin (referred to as PXN) and its molecular mechanism in Chinese mitten crab Eriocheir sinensis, we analyzed the bacterial binding and removal of the peroxinectin recombinant protein in vitro and the interaction of peroxinectin with integrin and CuZn-SOD through GST-pulldown and bimolecular fluorescence complementation methods. Concurrently, the effect of peroxinectin interference on the expression of other immune-related genes was studied using RNA interference. The results showed that the recombinant peroxinectin protein could bind to Bacillus subtilis, Staphylococcus aureus, Aeromonas hydrophila, and Vibrio parahaemolyticus with different affinities in vitro and could eliminate Vibrio parahaemolyticus in vivo. The findings also indicated that peroxinectin could establish interactions with integrin and CuZn-SOD in vitro. Furthermore, 48 h after the injection of the peroxinectin gene siRNA in vivo, the expression of peroxinectin mRNA decreased significantly (P < 0.05), integrin mRNA expression decreased by 16.8%, and CuZn-SOD mRNA expression decreased by 62.84% (P < 0.01). The expression levels of Dorsal, GPx, GST, PPAF, and Relish (P < 0.01), as well as that of lectin (P < 0.001) were significantly decreased. When peroxinectin siRNA was injected in vivo for 48 h and Aeromonas hydrophila was injected into mitten crabs, the expression of immune-related genes significantly increased. All data indicate that the recombinant peroxinectin protein in Chinese mitten crabs can recognize and bind different bacteria and promote the elimination of Vibrio parahaemolyticus from the body. Furthermore, peroxinectin may establish interactions with integrin and CuZn-SOD to activate the expression of related immune genes to elicit responses to bacterial infections and achieve immune protection.

Comparative proteomics and transcriptomics illustrate the allograft-induced stress response in the pearl oyster (Pinctada fucata martensii)

Implantation of a spherical nucleus into a recipient oyster is a critical step in artificial pearl production. However, the molecular mechanisms underlying the response of the pearl oyster to this operation are poorly understood. In this research, we used transcriptomic and proteomic analyses to examine allograft-induced changes in gene/protein expression patterns in Pinctada fucata martensii 12 h after nucleus implantation. Transcriptome analysis identified 688 differential expression genes (DEGs) (FDR<0.01 and |fold change) ＞ 2). Using a 1.2-fold increase or decrease in protein expression as a benchmark for differentially expressed proteins (DEPs), 108 DEPs were reliably quantified, including 71 up-regulated proteins (DUPs) and 37 down-regulated proteins (DDPs). Further analysis revealed that the GO terms, including "cellular process", "biological regulation" and "metabolic process" were considerably enriched. In addition, the transcriptomics analysis showed that "Neuroactive ligand-receptor interaction", "NF-kappa B signaling pathway", "MAPK signaling pathway", "PI3K-Akt signaling pathway', "Toll-like receptor signaling pathway", and "Notch signaling pathway" were significantly enriched in DEGs. The proteomics analysis showed that "ECM-receptor interaction", "Human papillomavirus infection", and "PI3K-Akt signaling pathway" were significantly enriched in DEPs. The results indicate that these functions could play an important role in response to pear oyster stress at nucleus implantation. To assess the potential relevance of quantitative information between mRNA and proteins, using Ward's hierarchical clustering analysis clustered the protein/gene expression patterns across the experimental and control samples into six groups. To investigate the biological processes associated with the protein in each cluster, we identified the significantly enriched GO terms and KEGG pathways in the proteins in each cluster. Gene set enrichment analysis (GSEA) was used to reveal the potential protein or transcription pathways associated with the response to nuclear implantation. Thus, the study of P. f. martensii is essential to enhance our understanding of the molecular mechanisms involved in pearl biosynthesis and the biology of bivalve molluscs.

A review on the antimicrobial properties of lectins

Lectins are biologically versatile biomolecules with remarkable antimicrobial effects, notably against bacteria, fungi and protozoa, in addition to modulating host immunity. For this, the lectins bind to carbohydrates on the surface of the pathogen, which can cause damage to the cell wall and prevent the attachment of microorganisms to host cells. Thus, this study intends to review the biological activities of lectins, with an emphasis on antimicrobial activity. Lectins of plant stood out for its antimicrobial effects, demonstrating that they act against a variety of strains, where in vitro were able to inhibit their development and affect their morphology. In vivo, they modulated host immunity, signaling and activating defense cells. Some of these lectins were capable to modulate the action of antibiotics, indicating their potential to minimize the antibiotic resistance. The results suggest that lectins have antimicrobial activity with potential to be used in drug development.

Identification and Characterization of a Novel Lectin from the Clam Glycymeris yessoensis and Its Functional Characterization under Microbial Stimulation and Environmental Stress

Lectin from the bivalve Glycymeris yessoensis (GYL) was purified by affinity chromatography on porcine stomach mucin-Sepharose. GYL is a dimeric protein with a molecular mass of 36 kDa, as established by SDS-PAGE and MALDI-TOF analysis, consisting of 18 kDa subunits linked by a disulfide bridge. According to circular dichroism data, GYL is a β/α-protein with the predominance of β-structure. GYL preferentially agglutinates enzyme-treated rabbit erythrocytes and recognizes glycoproteins containing O-glycosidically linked glycans, such as porcine stomach mucin (PSM), fetuin, thyroglobulin, and ovalbumin. The amino acid sequences of five segments of GYL were acquired via mass spectrometry. The sequences have no homology with other known lectins. GYL is Ca2+-dependent and stable over a range above a pH of 8 and temperatures up to 20 °C for 30 min. GYL is a pattern recognition receptor, as it binds common pathogen-associated molecular patterns, such as peptidoglycan, LPS, β-1,3-glucan and mannan. GYL possesses a broad microbial-binding spectrum, including Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli, Vibrio proteolyticus), but not the fungus Candida albicans. Expression levels of GYL in the hemolymph were significantly upregulated after bacterial challenge by V. proteolyticus plus environmental stress (diesel fuel). Results indicate that GYL is probably a new member of the C-type lectin family, and may be involved in the immune response of G. yessoensis to bacterial attack.