Cloning and molecular modeling of Litopenaeus vannamei (Penaeidae) C-type lectin homologs with mutated mannose binding domain-2

Immunological lectins in shrimp Penaeus vannamei challenged with infectious myonecrosis virus (IMNV) under low-salinity conditions

Lectins are proteins capable of recognizing and binding to glycan in a specific way. In invertebrates, lectins are a crucial group of Pattern Recognition Proteins (PRRs), activating cellular and humoral responses in the innate immune system. The shrimp Penaeus vannamei is the main crustacean cultivated worldwide, however, the productivity of cultures is strongly affected by diseases, mainly viral ones, such as Infectious Myonecrosis (IMN). Thus, we investigated the participation of five lectins (LvAV, LvCTL4, LvCTL5, LvCTLU, and LvLdlrCTL) in IMNV-challenged shrimp. We verified upregulation gene profiles of lectins after IMNV-challenge, especially in hepatopancreas and gills, in addition to an increase in total hemocytes count (THC) after to 12 h post-infection (hpi). The bioinformatics characterization also revealed several sites of post-translational modification (PTM), such as phosphorylation and glycosylation, which possibly influence the action and stabilization of these lectins. We conclude that LvLdlrCTL and LvCTL5 are the lectins with greater participation in the activation of the immune system against IMNV, showing the greatest potential for PTM, higher upregulation levels, and overlapping with the THC and IMNV viral load.

LDLa containing C-type lectin mediates phagocytosis of V.anguillarum and regulates immune effector genes in shrimp

C-type lectins (CTLs) function as pattern recognition receptors (PRRs) by recognizing invading microorganisms, thereby triggering downstream immune events against infected pathogens. In this study, a novel CTL containing a low-density lipoprotein receptor class A (LDLa) domain was obtained from Litopenaeus vannamei, designed as LvLDLalec. Stimulation by the bacterial pathogen Vibrio anguillarum (V. anguillarum) resulted in remarkable up-regulation of LvLDLalec, as well as release of LvLDLalec into hemolymph. The rLvLDLalec protein possessed broad-spectrum bacterial binding and agglutinating activities, as well as hemocyte attachment ability. Importantly, LvLDLalec facilitated the bacterial clearance in shrimp hemolymph and protected shrimp from bacterial infection. Further studies revealed that LvLDLalec promoted hemocytes phagocytosis against V. anguillarum and lysosomes were involved in the process. Meanwhile, LvLDLalec participated in humoral immunity through activating and inducing nuclear translocation of Dorsal to regulate phagocytosis-related genes and antimicrobial peptides (AMPs) genes, thereby accelerated the removal of invading pathogens in vivo and improved the survival rate of L. vannamei. These results unveil that LvLDLalec serves as a PRR participate in cellular and humoral immunity exerting opsonin activity to play vital roles in the immune regulatory system of L. vannamei.

Insight into molecular interaction between shrimp and white spot syndrome virus through MjsvCL-VP28 complex: an in-silico approach

White Spot disease is a devastating disease of shrimps caused by White Spot Syndrome Virus in multifarious shrimp species. At present there is no absolute medication to suppress the disease hence, there is an urgent need for development of drug against the virus. Molecular interaction between viral envelope protein VP28 and shrimp receptor protein especially chitins play a pivotal role in ingression of WSSV. In the present study, we have tried to shed light on structural aspects of lectin protein in Marsupenaeus japonicus (MjsvCL). A structural insight to the CTLD-domain of MjsvCL has facilitated the understanding of the binding mechanism between the two proteins that is responsible for entry of WSSV into shrimps. Further, incorporation of molecular dynamics simulation and MMPBSA studies revealed the affinity of binding and certain hotspot residues, which are critical for association of both the proteins. For the first time we have proposed that these amino acids are quintessential for formation of VP28-MjsvCL complex and play crucial role in entry of WSSV into shrimps. Targeting the interaction between VP28 and CTLD of MjsvCL may possibly serve as a potential drug target. The current study provides information for better understanding the interaction between VP28 and MjsvCL that could be a plausible site for future inhibitors against WSSV in shrimps.Communicated by Ramaswamy H. Sarma.

Structural and functional diversity of lectins associated with immunity in the marine shrimp Litopenaeusvannamei

Lectins are important pattern recognition receptors (PRRs) and their immunological action is related to the recognition of glycans present in the pathogen cells surface. The lectins described for Litopenaeus vannamei are divided into C-type, L-type and galectin, which are mainly expressed in hepatopancreas and hemocytes. They are involved in several immune response pathways, such as phagocytosis, hemocytes recruitment, prophenoloxidase activation, and gene regulation. Although lectins have multiple immune functions, most experimental challenges focus only on WSSV and Vibrio sp. This article is a detailed review on the role of lectins in L. vannamei immune system, bringing together information on molecular structure, temporal and special expression and immune function, highlighting the wide participation of these molecules in shrimp innate immune system.

A single-CRD C-type lectin from Haliotis discus hannai acts as pattern recognition receptor enhancing hemocytes opsonization

C-type lectins (CTLs), as a member of the Ca²⁺-dependent carbohydrate recognition protein superfamily, play multiple roles in non-self recognition and the elimination of invading pathogens. In this study, a C-type lectin was identified and characterized from the Pacific abalone Haliotis discus hannai (designed as HdClec), and its open reading frame (ORF) encoded a polypeptide of 163 amino acids containing a typical signal peptide and only one carbohydrate-recognition domain (CRD). The deduced amino acid sequence of CRD in HdClec shared identities ranging from 22.4% to 39.8% with that of other identified CRDs of CTLs. A novel NPN motif was found in Ca²⁺-binding site 2 of HdClec. The mRNA transcripts of HdClec were detectable in all the examined tissues of non-stimulated abalones, with the highest expression in hepatopancreas (224.13-fold of that in gills). The expression of HdClec mRNA in hemocytes was significantly up-regulated after Vibrio harveyi challenge. Recombinant HdClec protein (rHdClec) could bind lipopolysaccharide (LPS) and peptidoglycan (PGN) in vitro in the presence of Ca²⁺. Coinciding with the PAMPs binding assay, rHdClec displayed broad agglutination activities towards Gram-negative bacteria V. splendidus, V. anguillarum, V. parahaemolyticus, V. harveyi, Escherichia coli, and Gram-positive bacteria Micrococcus luteus. Moreover, rHdClec could significantly elicit the chemotactic response of hemocytes in vitro. And the phagocytosis and encapsulation ability of hemocytes could be significantly enhanced by rHdClec. All these results showed that HdClec could function as pattern recognition receptors (PRRs) and further enhance the opsonization of hemocytes, which might play a crucial role in the innate immune responses of Pacific abalone.

A Hint of Primitive Mucosal Immunity in Shrimp through Marsupenaeus japonicus Gill C-Type Lectin

Lectins are found in most living organisms, providing immune surveillance by binding to carbohydrate ligands. In fishes, C-type lectins were isolated from mucus of respiratory organs (skin and gills), where they aid the mucosal immune response in regulating microbiota and suppressing pathogens. In shrimp, however, no mucosal immunity or any form of gill-specific immune defense has been reported, and most identified C-type lectins are associated with hemocyte cellular and humoral responses. Interestingly, our microarray analysis revealed the localization of highly expressed novel biodefense genes in gills, among which is Marsupenaeus japonicus gill C-type lectin (MjGCTL), which we previously reported. Gill mucus collected from M. japonicus displayed similar bacterial agglutination ability as observed with recombinant MjGCTL. This agglutinating ability can be attributed to endogenous MjGCTL (nMjGCTL) detected in gill mucus, which was confirmed with an agglutination assay using purified nMjGCTL from gills. In addition, nMjGCTL also promoted in vivo bacterial phagocytosis by hemocytes. In vivo knockdown of MjGCTL resulted in a compromised immune system, which was manifested by impaired agglutination capacity of gill mucus and downregulation of the gill antimicrobial peptides, crustin and penaeidin. Shrimp immunocompromised by MjCGTL knockdown, apparently lost the ability to respond to attaching and penetrating bacteria. This was evident as increased total bacteria and Vibrio counts in both gills and hemolymph, which were correlated with low survival during a bacterial challenge. These results reveal immune defense by shrimp gills resembling a primitive form of mucosal immunity.

2-Transmembrane C-type lectin from oriental river prawn Macrobrachium nipponense participates in antibacterial immune response

As a type of pattern-recognition proteins (PRRs), C-type lectins (CTLs) perform important functions in non-self recognition and clearance of pathogens in innate immunity. In this study, a unique 2-transmembrane CTL (designated as Mn-2TM-cLec) with a single carbohydrate recognition domain (CRD) was isolated from Macrobrachium nipponense. The full-length cDNA of Mn-2TM-cLec consisted of 3265 bp with an 837 bp open reading frame encoding a protein with 278 amino acids. Mn-2TM-cLec was ubiquitously distributed in various tissues of normal prawn, particularly in the hemocytes, hepatopancreas, and gills. The expression of Mn-2TM-cLec was significantly up-regulated in the gills and hepatopancreas after the prawns were challenged with Staphylococcus aureus and Vibrio parahaemolyticus. RNA interference knock-down of Mn-2TM-cLec gene decreased the transcription levels of three antimicrobial peptides (anti-lipopolysaccharide factor (ALF) 1, ALF2, and Crustin (Crus) 1) after V. parahaemolyticus infection. The recombinant CRD of Mn-2TM-cLec could bind lipopolysaccharide, peptidoglycans, and diverse bacterial strains and agglutinate S. aureus and V. parahaemolyticus in a Ca²⁺-dependent manner. In addition, the rCRD enhanced the clearance of V. parahaemolyticus injected in prawns. In summary, Mn-2TM-cLec might act as a PRR to participate in the prawn immune defense against pathogens through its antimicrobial activity.

Genomes of trombidid mites reveal novel predicted allergens and laterally transferred genes associated with secondary metabolism

Background

Trombidid mites have a unique life cycle in which only the larval stage is ectoparasitic. In the superfamily Trombiculoidea ("chiggers"), the larvae feed preferentially on vertebrates, including humans. Species in the genus Leptotrombidium are vectors of a potentially fatal bacterial infection, scrub typhus, that affects 1 million people annually. Moreover, chiggers can cause pruritic dermatitis (trombiculiasis) in humans and domesticated animals. In the Trombidioidea (velvet mites), the larvae feed on other arthropods and are potential biological control agents for agricultural pests. Here, we present the first trombidid mites genomes, obtained both for a chigger, Leptotrombidium deliense, and for a velvet mite, Dinothrombium tinctorium.

Results

Sequencing was performed using Illumina technology. A 180 Mb draft assembly for D. tinctorium was generated from two paired-end and one mate-pair library using a single adult specimen. For L. deliense, a lower-coverage draft assembly (117 Mb) was obtained using pooled, engorged larvae with a single paired-end library. Remarkably, both genomes exhibited evidence of ancient lateral gene transfer from soil-derived bacteria or fungi. The transferred genes confer functions that are rare in animals, including terpene and carotenoid synthesis. Thirty-seven allergenic protein families were predicted in the L. deliense genome, of which nine were unique. Preliminary proteomic analyses identified several of these putative allergens in larvae.

Conclusions

Trombidid mite genomes appear to be more dynamic than those of other acariform mites. A priority for future research is to determine the biological function of terpene synthesis in this taxon and its potential for exploitation in disease control.

Novel C-type lectin from razor clam Sinonovacula constricta agglutinates bacteria and erythrocytes in a Ca2+-dependent manner

Among its other physiological roles, C-type lectins functioned as pattern recognition receptors (PRR) in innate immunity received much attention. In the present study, a novel C-type lectin was identified and characterized from the invertebrate razor clam Sinonovacula constrict and designated as ScCTL. The complete cDNA sequence of ScCTL was 828 bp in length and coded a secreted polypeptide of 158 amino acids with a typical CRD domain. Multiple sequence alignments combined with phylogenetic analysis both collectively confirmed that ScCTL was a novel member belong to lectin family. Spatial expression distribution analysis revealed that ScCTL was extensively expressed in all of the examined tissues, and the highest expression was detected in the hepatopancreas. After 1 × 10⁷ CFU/mL Vibrio parahaemolyticus challenge by immersion infection, the ScCTL transcript in hepatopancreas and gill were markedly upregulated and arrived the maximum levels at 24 or 12 h after challenge, respectively. Recombinant ScCTL could agglutinate not only all tested bacteria but sheep and mouse erythrocyte in the presence of Ca²⁺. All of our studies suggested that ScCTL performed important roles in protecting cells from pathogenic infection in S. constrict.

The functional characterization and comparison of two single CRD containing C-type lectins with novel and typical key motifs from Portunus trituberculatus

C-type lectins are a superfamily of Ca²⁺-dependent carbohydrate-recognition proteins, which play crucial roles in innate immunity including nonself-recognition and pathogen elimination. In the present study, two single-CRD containing C-type lectins were identified from swimming crab Portunus trituberculatus (designated as PtCTL-2 and PtCTL-3). The open reading frame (ORF) of PtCTL-2 encoded polypeptides of 485 amino acids with a signal peptide and a single carbohydrate-recognition domain (CRD), while PtCTL-3's ORF encoded polypeptides of 241 amino acids with a coiled-coil region and a single-CRD. The key motifs determining carbohydrate binding specificity in PtCTL-2 and PtCTL-3 were EPR (Glu-Pro-Arg) and QPD (Gln-Pro-Asp). EPR is a motif being identified for the first time, whereas QPD is a typical motif in C-type lectins. Different PAMPs binding features of the two recombinant proteins - PtCTL-2 (rPtCTL-2) and PtCTL-3 (rPtCTL-3) have been observed in our experiments. rPtCTL-2 could bind three pathogen-associated molecular patterns (PAMPs) with relatively high affinity, including glucan, lipopolysaccharide (LPS) and peptidoglycan (PGN), while rPtCTL-3 could barely bind any of them. However, rPtCTL-2 could bind seven kinds of microbes and rPtCTL-3 could bind six kinds in microbe binding assay. Moreover, rPtCTL-2 and rPtCTL-3 exhibited similar agglutination activity against Gram-positive bacteria, Gram-negative bacteria and fungi in agglutination assay. All these results illustrated that PtCTL-2 and PtCTL-3 could function as important pattern-recognition receptors (PRR) with broad nonself-recognition spectrum involved in immune defense against invaders. In addition, the results of carbohydrate binding specificity showed that PtCTL-2 with novel key motif had broad carbohydrate binding specificity, while PtCTL-3 with typical key motif possessed different carbohydrate binding specificity from the classical binding rule. Furthermore, PtCTL-2 and PtCTL-3 could also function as opsonin to enhance encapsulation of hemocytes against Ni-NTA beads.

Pathogen recognition of a novel C-type lectin from Marsupenaeus japonicus reveals the divergent sugar-binding specificity of QAP motif

C-type lectins (CTLs) are calcium-dependent carbohydrate-binding proteins known to assist the innate immune system as pattern recognition receptors (PRRs). The binding specificity of CTLs lies in the motif of their carbohydrate recognition domain (CRD), the tripeptide motifs EPN and QPD bind to mannose and galactose, respectively. However, variants of these motifs were discovered including a QAP sequence reported in shrimp believed to have the same carbohydrate specificity as QPD. Here, we characterized a novel C-type lectin (MjGCTL) possessing a CRD with a QAP motif. The recombinant MjGCTL has a calcium-dependent agglutinating capability against both Gram-negative and Gram-positive bacteria, and its sugar specificity did not involve either mannose or galactose. In an encapsulation assay, agarose beads coated with rMjGCTL were immediately encapsulated from 0 h followed by melanization at 4 h post-incubation with hemocytes. These results confirm that MjGCTL functions as a classical CTL. The structure of QAP motif and carbohydrate-specificity of rMjGCTL was found to be different to both EPN and QPD, suggesting that QAP is a new motif. Furthermore, MjGCTL acts as a PRR binding to hemocytes to activate their adherent state and initiate encapsulation.

Comparative study of two single CRD C-type lectins, CgCLec-4 and CgCLec-5, from pacific oyster Crassostrea gigas

C-type lectins (CTLs), a superfamily of Ca²⁺-dependent carbohydrate-recognition proteins, are involved in nonself-recognition and pathogen elimination, and play crucial roles in the innate immunity. In the present study, two single CRD C-type lectins, CgCLec-4 and CgCLec-5, were identified from oyster Crassostrea gigas. The open reading frame (ORF) of CgCLec-4 and CgCLec-5 encoded polypeptides of 152 and 150 amino acids, respectively. Both CgCLec-4 and CgCLec-5 contained one CRD with six conserved cysteines to form three disulfide bridges. The motif in Ca²⁺-binding site 2 of CgCLec-4 was QPE, while it was QYE, a non-a typical motif in CgCLec-5. CgCLec-4 was a secreted lectin with a signal peptide which was highly expressed in hepatopancreas, mantle and hemocytes. CgCLec-5 was an intracellular lectin which was mostly expressed in hemocytes. The lipopolysaccharide stimulation could induce the expressions of CgCLec-4 and CgCLec-5. The recombinant proteins of CgCLec-4 and CgCLec-5 (rCgCLec-4 and rCgCLec-5) could bind to various PAMPs including LPS, PGN, GLU and mannan, while the binding affinity of rCgCLec-5 was stronger than that of rCgCLec-4. Meanwhile, rCgCLec-4 and rCgCLec-5 could bind to different kinds of microorganisms, including Staphylococcus aureus, Escherichia coli and Vibro anguillarum and Yarrowia lipolytica, and the microbial agglutinating ability of rCgCLec-4 was stronger than that of CgCLec-5. Moreover, rCgCLec-4 exhibited anti-microbial activity against bacteria and fungi, but anti-microbial activity of CgCLec-5 was not obvious. All these results suggested that CgCLec-4 and CgCLec-5 could function as an important PRR involved in immune defense against invading pathogen in oyster, and the diversity and complexity of motifs in Ca²⁺ binding site 2 in CRDs determined their comprehensive recognition spectrum and multiple immune functions.

Microarray Analysis of Immunity Against WSSV in Response to Injection of Non-specific Long dsRNA in Kuruma Shrimp, Marsupenaeus japonicus

Injection of shrimp with non-specific double-stranded RNA (dsRNA) of diverse lengths, sequences, and base compositions is known to induce non-specific immunity and protect against lethal disease, although the mechanisms are unclear. Previous shrimp studies examined the effects of non-specific RNA on particular pathways, while their global effects have not been examined. To understand the global effects of non-specific RNA in shrimp, we injected kuruma shrimp (Marsupenaeus japonicus) with a dsRNA and a small interfering RNA (siRNA) that is not specific to any gene in the shrimp genome and then examined global gene expression at 24 and 48 h with a microarray. For the non-specific RNA, we chose double-stranded green fluorescent protein (dsGFP) and siGFP because they are commonly used as mock controls and their effects on shrimp have not yet been studied. Injection of PBS was used as a control. The microarray results showed that many genes were up-regulated and some were down-regulated by dsGFP. In addition, dsGFP injection increased survival following WSSV challenge. The changes in expression for several genes were confirmed by quantitative PCR. The up-regulated genes included genes for eight immune-related proteins: c-type lectin 2, hemocyte homeostasis-associated protein, viral responsive protein, fibrinogen-related protein 1, sid-1 like protein, argonaute 2, Dicer 2, and heat shock protein 90. These results show that injection of shrimp with non-specific dsRNA hinders viral accumulation and prevents significant mortalities.

Two novel C-type lectins with a low-density lipoprotein receptor class A domain have antiviral function in the shrimp Marsupenaeus japonicus

C-type lectins (CTLs) are pattern-recognition receptors (PRRs) that play important roles in immune response. In this study, two new CTLs containing a low-density lipoprotein receptor class A domain (LDLR) and a carbohydrate recognition domain (CRD) were identified in Marsupenaeus japonicus and designated as LdlrLec1 and LdlrLec2. The two CTLs expressed in all the tested tissues of shrimp, however, LdlrLec1 was mainly expressed in hemocytes, heart, gill and intestines, whereas LdlrLec2 was expressed in hepatopancreas and heart. The expression patterns of both LdlrLec1 and LdlrLec2 mRNA were obviously upregulated upon white spot syndrome virus (WSSV) challenge. Injection of recombinant LdlrLec1 or LdlrLec2 into shrimp inhibited WSSV replication, whereas knocking down the expression of LdlrLec1 and LdlrLec2 by RNA interference increased WSSV replication in vivo. The infection rates of WSSV incubated with LdlrLecs were reduced significantly compared with the control group. The LdlrLec proteins could interact with VP28, a major envelope protein of WSSV, which is necessary for the attachment and penetration of WSSV into shrimp cells. These results indicate that LdlrLec1 and LdlrLec2 may function in antiviral response by binding to WSSV and inhibiting their pervasion and replication in shrimp.

A novel C-type lectin from Eriocheir sinensis functions as a pattern recognition receptor with antibacterial activity

As pattern recognition receptors (PRRs), C-type lectins (CTLs) play significant roles in recognizing and eliminating pathogens in innate immunity. In this study, a novel CTL (EsLecD) was identified from the crustacean Eriocheir sinensis. The cloning of full-length EsLecD cDNA was based on the initial expressed sequence tags (ESTs) isolated from a hepatopancreatic cDNA library. The full-length EsLecD cDNA of 686 bp with an open reading frame of 468 bp encodes a putative protein of 155 aa residues, including an N-terminal signal peptide and a single carbohydrate-recognition domain (CRD). By quantitative RT-PCR analysis, the EsLecD transcript was mainly detected in the hepatopancreas but rarely in other tissues, and it was significantly upregulated in the hepatopancreas after immune challenge with lipopolysaccharides. The recombinant EsLecD protein (rEsLecD) exhibited the ability to bind to all tested microorganisms, including bacteria and yeast. Meanwhile, calcium significantly increased the binding affinity of rEsLecD toward microorganisms, but it was not essential. The binding of rEsLecD induced the aggregation of microbial pathogens. Moreover, rEsLecD was capable of inhibiting the growth of microorganisms and even directly killing bacteria. Interestingly, rEsLecD could stimulate cellular encapsulation in vitro. In conclusion, results of this study suggest that EsLecD acts as an antibacterial PRR participating in the innate immunity of invertebrates.

Diversity and multiple functions of lectins in shrimp immunity

Lectins play important roles in many biological processes, including protein trafficking, cell signaling, pathogen recognition, as effector molecules, and so on, because of their capacity to bind carbohydrates. Presently, seven groups of lectins have been identified in shrimp: C-type, L-type, P-type, M-type, fibrinogen-like domain lectins, galectins, and calnexin/calreticulin. These lectins have different structures, diverse expression patterns, and multiple functions in the shrimp immune response. This review summarizes the research progress and analyzes the diversity of shrimp lectins, focusing mainly on the C-type lectin family. Shrimp C-type lectins show considerable diversity in their domain architectures, sugar substrates, tissue distributions, expression patterns responding to pathogen challenge and functions in shrimp immunity.

A novel lectin domain-containing protein (LvCTLD) associated with response of the whiteleg shrimp Penaeus (Litopenaeus) vannamei to yellow head virus (YHV)

When using mRNA from gills of normal whiteleg shrimp Penaeus (Litopenaeus) vannamei as the tester and mRNA from yellow head virus (YHV)-infected shrimp as the driver, subtractive suppression hybridization (SSH) revealed that a novel EST clone of 198 bp with a putative C-type lectin-like domain (CTLD) was downregulated in YHV-infected shrimp. The clone nucleotide sequence had 99% identity with one contig MGID1052359 (1,380 bp) reported in an EST database of P. vannamei, and the presence of this target in normal shrimp was confirmed by RT-PCR using primers designed from the MGID1052359 sequence. Analysis of the primary structure of the deduced amino acid (a.a.) sequence of the contig revealed a short portion (40 a.a. residues) at its N-terminus with high similarity to a low density lipoprotein receptor (LDLR) class A domain and another 152 a.a. residues at its C-terminus with high similarity to a C-type lectin domain. Thus, the clone was named LvCTLD and three recombinant proteins (LvCTLD, the LDLR domain and the CTLD domain) were synthesized in a bacterial system based on its sequence. An in vitro encapsulation assay revealed that Sepharose 4B beads coated with rLvCTLD were encapsulated by shrimp hemocytes and that melanization followed by 24 h post-encapsulation. The encapsulation activity of rLvCTLD was inhibited by 100 mM galactose, but not mannose or EDTA. In vivo injection of rLvCTLD or rLvCTLD plus YHV resulted in a significant elevation of PO activity in the hemolymph of the challenged shrimp when compared to shrimp injected with buffer, suggesting that rLvCTLD could activate the proPO system. An ELISA test revealed that rLvCTLD could bind to YHV particles in the presence of shrimp hemolymph. Phylogenetic analysis suggested that the LvCTLD sequence was more closely related to an antiviral gene found in Penaeus monodon (PmAV) than to other reported shrimp lectins. Taken together, we conclude that a novel shrimp LvCTLD is a host recognition molecule involved in the shrimp defense mechanism against YHV via recruitment of hemocytes, probably at the site of viral infection, and via activation of the proPO system.

Identification of differentially transcribed genes in shrimp Litopenaeus vannamei exposed to osmotic stress and challenged with WSSV virus

The effects of hyposmotic stress and white spot syndrome virus (WSSV) challenge in expression was studied in the marine shrimp Litopenaeus vannamei. Messenger RNA from gills of shrimp submitted to osmotic stress was isolated to identify genes differentially expressed through the suppressive subtractive hybridization (SSH) method. Two subtractive libraries forward and two reverse were constructed to identify up and down-regulated genes under these conditions. About 192 clones were sequenced, of which 46 genes were identified. These genes encode proteins corresponding to a wide range of biological roles, including defense, cell signaling, electron transfer, cell proliferation and differentiation, apoptosis, intermediary metabolism, cytoskeleton and digestion. Among the identified genes, 19 were up-regulated and 27 were down-regulated in the animals kept at a lower ion concentration. We evaluated the expression of eight genes by RT-qPCR in shrimp submitted to hyposmotic conditions with and without WSSV challenge. The SSH enabled the identification of genes that are influenced by hyposmotic stress. A significant up-regulation was observed in lectin-C, QM, TGF beta inducible nuclear protein 1, ciclophilin, malate dehydrogenase, mitochondrial ATP synthase F chain and ATP synthase subunit 9 precursor transcripts. However, the expression of these genes in L. vannamei was not affected by WSSV infection both at isosmotic and hyposmotic conditions.