Functional Characterization of a c-type Lysozyme from Indian Shrimp Fenneropenaeus indicus

Integrated analysis of intestinal microbiota and metabolomic reveals that decapod iridescent virus 1 (DIV1) infection induces secondary bacterial infection and metabolic reprogramming in Marsupenaeus japonicus

In recent years, with global warming and increasing marine pollution, some novel marine viruses have become widespread in the aquaculture industry, causing huge losses to the aquaculture industry. Decapod iridescent virus 1 (DIV1) is one of the newly discovered marine viruses that has been reported to be detected in a variety of farmed crustacean and wild populations. Several previous studies have found that DIV1 can induce Warburg effect-related gene expression. In this study, the effects of DIV1 infection on intestinal health of shrimp were further explored from the aspects of histological, enzymatic activities, microorganisms and metabolites using Marsupenaeus japonicus as the object of study. The results showed that obvious injury in the intestinal mucosa was observed after DIV1 infection, the oxidative and antioxidant capacity of the shrimp intestine was unbalanced, the activity of lysozyme was decreased, and the activities of digestive enzymes were disordered, and secondary bacterial infection was caused. Furthermore, the increased abundance of harmful bacteria, such as Photobacterium and Vibrio, may synergized with DIV1 to promote the Warburg effect and induce metabolic reprogramming, thereby providing material and energy for DIV1 replication. This study is the first to report the changes of intestinal microbiota and metabolites of M. japonicus under DIV1 infection, demonstrating that DIV1 can induce secondary bacterial infection and metabolic reprogramming. Several bacteria and metabolites highly associated with DIV1 infection were screened, which may be leveraged for diagnosis of pathogenic infections or incorporated as exogenous metabolites to enhance immune response.

The potential of antimicrobial peptides isolated from freshwater crayfish species in new drug development: A review

The much-publicised increased resistance of pathogenic bacteria to conventional antibiotics has focused research effort on the characterization of new antimicrobial drugs. In this context, antimicrobial peptides (AMPs) extracted from animals are considered a promising alternative to conventional antibiotics. In recent years, freshwater crayfish species have emerged as an important source of bioactive compounds. In fact, these invertebrates rely on an innate immune system based on cellular responses and on the production of important effectors in the haemolymph, such as AMPs, which are produced and stored in granules in haemocytes and released after stimulation. These effectors are active against both Gram-positive and Gram-negative bacteria. In this review, we summarise the recent progress on AMPs isolated from the several species of freshwater crayfish and their prospects for future pharmaceutical applications to combat infectious agents.

Identification and Functional Analysis of a Lysozyme Gene from Coridius chinensis (Hemiptera: Dinidoridae)

Simple Summary

As a medicinal insect, Coridius chinensis contains many active polypeptides. Extracts from C. chinensis are usually complex and it is not clear which polypeptides are effective medicinal ingredients. In addition, we also need to figure out the functions of various immune effectors in the innate immunity of C. chinensis. To explore the function of lysozyme in C. chinensis, a lysozyme gene CcLys2 was screened and identified from the transcriptome data of C. chinensis. The results showed that CcLys2 had a typical domain of the c-type lysozyme, belonging to the H-branch of the c-type lysozyme. The lysozyme Cclys2 is an effective immune effector in the immune response of C. chinensis and can be stimulated by bacterial infection. Like typical c-type lysozyme, Cclys2 has lytic activity against Gram-positive bacteria. The research holds promise for functional annotation of similar proteins from other dinidoridae insects and provides the theoretical feasibility for the development of medicinal components in C. chinensis. Our results also provide data for further investigating the origin and evolution of insect lysozymes.

Abstract

Coridius chinensis is a valuable medicinal insect resource in China. Previous studies have indicated that the antibacterial and anticancer effects of the C. chinensis extract mainly come from the active polypeptides. Lysozyme is an effective immune effector in insect innate immunity and usually has excellent bactericidal effects. There are two kinds of lysozymes in insects, c-type and i-type, which play an important role in innate immunity and intestinal digestion. Studying lysozyme in C. chinensis will be helpful to further explore the evolutionary relationship and functional differences among lysozymes of various species and to determine whether they have biological activity and medicinal value. In this study, a lysozyme CcLys2 was identified from C. chinensis. CcLys2 contains 223 amino acid residues, and possesses a typical domain of the c-type lysozyme and a putative catalytic site formed by two conserved residues Glu32 and Asp50. Phylogenetic analysis showed that CcLys2 belongs to the H-branch of the c-type lysozyme. The analysis of spatiotemporal expression patterns indicated that CcLys2 was mainly expressed in the fat body of C. chinensis adults and was highly expressed in the second- and fifth-instar nymphs. In addition, CcLys2 was significantly up-regulated after injecting and feeding bacteria. In the bacterial inhibition assay, it was found that CcLys2 had antibacterial activity against Gram-positive bacteria at a low pH. These results indicate that CcLys2 has muramidase activity, involves in the innate immunity of C. chinensis, and is also closely related to the bacterial immune defense or digestive function of the intestine.

A new antimicrobial peptide isoform, Pc-crustin 4 involved in antibacterial innate immune response in fresh water crayfish, Procambarus clarkii

The main advantage of antimicrobial peptides (AMPs) used as the effectors in the innate immunity system of invertebrates is that the high specificity is not indispensable. And they play important roles in the systemic defenses against microbial invasion. In this study, a new full-length cDNA of the crustins molecule was identified in red swamp crayfish, P. clarkii (named Pc-crustin 4). The ORF of Pc-crustin 4 contained 369 bp which encoded a protein of 122 amino acids, with a 20-amino-acid signal peptide sequence. On the base of the classification method established by Smith et al., Pc-crustin 4 belonged to Type Ⅰ crustin molecule. The Pc-crustin 4 transcripts were expressed in hemocytes at relatively high level, and relatively low level in hepatopancreas, gills, and intestine in normal crayfish. After respectively challenged with S. aureus or E. ictaluri, the expression levels of Pc-crustin 4 showed up-regulation trends at different degrees in the hemocytes, hepatopancreas, gills, and intestine tissues. Besides, the results of liquid antibacterial assay showed that rPc-crustin 4 inhibited obviously the growth of S. aureus and E. ictaluri. The results of bacteria binding assay showed that rPc-crustin 4 could bind strongly to S. aureus and E. ictaluri. Finally, RNAi assay was performed to study the immunity roles of Pc-crustin 4 in crayfish in vivo. Taken together, Pc-crustin 4 is an important immunity effector molecule, which plays crucial roles in defending against bacterial infection in crayfish.

The Two NF-κB Pathways Regulating Bacterial and WSSV Infection of Shrimp

The outbreak of diseases ordinarily results from the disruption of the balance and harmony between hosts and pathogens. Devoid of adaptive immunity, shrimp rely largely on the innate immune system to protect themselves from pathogenic infection. Two nuclear factor-κB (NF-κB) pathways, the Toll and immune deficiency (IMD) pathways, are generally regarded as the major regulators of the immune response in shrimp, which have been extensively studied over the years. Bacterial infection can be recognized by Toll and IMD pathways, which activate two NF-κB transcription factors, Dorsal and Relish, respectively, to eventually lead to boosting the expression of various antimicrobial peptides (AMPs). In response to white-spot-syndrome-virus (WSSV) infection, these two pathways appear to be subverted and hijacked to favor viral survival. In this review, the recent progress in elucidating microbial recognition, signal transduction, and effector regulation within both shrimp Toll and IMD pathways will be discussed. We will also highlight and discuss the similarities and differences between shrimps and their Drosophila or mammalian counterparts. Understanding the interplay between pathogens and shrimp NF-κB pathways may provide new opportunities for disease-prevention strategies in the future.

Identification and functional characterization of a c-type lysozyme from Fenneropenaeus penicillatus

Lysozyme is an important defense molecule of the innate immune system and possess high antimicrobial activities. In this study, a full-length c-type lysozyme cDNA (Fplysc) was cloned and characterized from Fenneropenaeus penicillatus. The cDNA contains an open reading frame of 477 bp encoding 158 amino acids, with 53-94% identity with those of other crustaceans. The recombinant Fplysc had antibacterial activities against Gram-positive bacteria (Streptococcus agalactiae and Micrococcus luteus) and Gram-negative bacteria (Vibrio alginolyticus and Escherichia coli), and showed antiviral activity against WSSV and IHHNV. The qRT-PCR analysis showed that Fplysc expression levels were most abundant in hemocytes and less in eyestalk. The expression levels of Fplysc were significantly upregulated in gill, intestine and hemocytes when challenged with WSSV and V. alginolyticus. Fplysc-silencling suppressed Fplysc expression in cephalothoraxes and increased mortality caused by WSSV and V. alginolyticus, and exogenous rFplysc led to a significant decrease of shrimp mortality by injecting rFplysc into Fplysc silenced shrimp, suggesting Fplysc is the important molecule in shrimp antimicrobial and antiviral response. In conclusion, the results provide some insights into the function of Fplysc in shrimp against bacterial and viral infection.

Engineering Pichia pastoris for Efficient Production of a Novel Bifunctional Strongylocentrotus purpuratus Invertebrate-Type Lysozyme

Lysozymes are known as ubiquitously distributed immune effectors with hydrolytic activity against peptidoglycan, the major bacterial cell wall polymer, to trigger cell lysis. In the present study, the full-length cDNA sequence of a novel sea urchin Strongylocentrotus purpuratus invertebrate-type lysozyme (sp-iLys) was synthesized according to the codon usage bias of Pichia pastoris and was cloned into a constitutive expression plasmid pPIC9K. The resulting plasmid, pPIC9K-sp-iLys, was integrated into the genome of P. pastoris strain GS115. The bioactive recombinant sp-iLys was successfully secreted into the culture broth by positive transformants. The highest lytic activity of 960 U/mL of culture supernatant was reached in fed-batch fermentation. Using chitin affinity chromatography and gel-filtration chromatography, recombinant sp-iLys was produced with a yield of 94.5 mg/L and purity of > 99%. Recombinant sp-iLys reached its peak lytic activity of 8560 U/mg at pH 6.0 and 30 °C and showed antimicrobial activities against Gram-negative bacteria (Vibrio vulnificus, Vibrio parahemolyticus, and Aeromonas hydrophila) and Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis). In addition, recombinant sp-iLys displayed isopeptidase activity which reached the peak at pH 7.5 and 37 °C with the presence of 0.05 M Na⁺. In conclusion, this report describes the heterologous expression of recombinant sp-iLys in P. pastoris on a preparative-scale, which possesses lytic activity and isopeptidase activity. This suggests that sp-iLys might play an important role in the innate immunity of S. purpuratus.

Molecular characterization, expression and antimicrobial activities of two c-type lysozymes from manila clam Venerupis philippinarum

Lysozymes play an important role in the innate immune responses with which mollusks respond to bacterial invasion through its lytic activity. In the present study, two c-type lysozymes (designed as VpCLYZ-1 and VpCLYZ-2, respectively) were identified and characterized from the manila clam Venerupis philippinarum. The full-length cDNA of VpCLYZ-1 and VpCLYZ-2 was of 629 and 736 bp, encoding a polypeptide of 156 and153 amino acid residues, respectively. The deduced amino acid sequences of VpCLYZs showed high similarity to other known invertebrate c-type lysozymes. Multiple alignments and phylogenetic relationship strongly suggested that VpCLYZ-1 and VpCLYZ-2 belonged to the c-type lysozyme family. Both VpCLYZ-1 and VpCLYZ-2 transcripts were constitutively expressed in a wide range of tissues with different levels. The VpCLYZ-1 transcript was dominantly expressed in hepatopancreas and hemocytes, while VpCLYZ-2 transcript was mainly expressed in the tissues of hepatopancreas and gills. Both the mRNA expression of VpCLYZ-1 and VpCLYZ-2 was significantly up-regulated at 12 h post Vibrio anguillarum challenge. The recombinant VpCLYZ-1 and VpCLYZ-2 (designed as rVpCLYZ-1 and rVpCLYZ-2) exhibited lytic activity against all tested bacteria, and rVpCLYZ-1 showed higher activities than rVpCLYZ-2 in killing Micrococcus luteus and V. anguillarum. Overall, our results suggested that VpCLYZ-1 and VpCLYZ-2 belonged to the c-type lysozyme family, and played important roles in the immune responses of manila clam, especially in the elimination of pathogens.

Molecular cloning, inducible expression and antibacterial analysis of a novel i-type lysozyme (lyz-i2) in Pacific white shrimp, Litopenaeus vannamei

The full-length cDNA coding for a novel invertebrate (i-type) lysozyme was identified in Pacific white shrimp (Litopenaeus vannamei). The newly obtained L. vannamei lysozyme is similar to the Penaeus monodon i-type lysozyme 2, but it is distant from the known L. vannamei c-type lysozyme and i-type lysozyme 1 in protein sequence; therefore, it was defined as L. vannamei i-type lysozyme 2 (lyz-i2). Expression of L. vannamei lyz-i2 transcripts were ubiquitously detected in all tissues we selected, with the highest abundance observed in the hemolymph. Challenge with Vibrio harveyi might elicit L. vannamei lyz-i2 mRNA expression in the hepatopancreas, intestine, muscle, gill and hemolymph. In the themolymph, specifically, the stimulatory effects of Vibrio and lipopolysaccharide (LPS) on lyz-i2 transcript levels were durable and transient, respectively; while Polyinosinic:polycytidylic acid [Poly (I:C)] treatment did not affect lyz-i2 expression. L. vannamei lyz-i2 recombinant protein was generated in an Escherichia coli system. By lysoplate and turbidimetric assays, the L. vannamei lyz-i2 recombinant protein showed a broad spectrum of antimicrobial properties with high activities against Micrococcaceae lysodeikticus and various Vibrio species and relatively low activity against E. coli. In conclusion, L. vannamei lyz-i2 might be a potent antibacterial protein with a role in innate immunity in Penaeid shrimp.