Novel Insights into Antiviral Gene Regulation of Red Swamp Crayfish, Procambarus clarkii, Infected with White Spot Syndrome Virus

Antiviral, antioxidant, and anti-inflammatory activities of rhein against white spot syndrome virus infection in red swamp crayfish (Procambarus clarkii)

IMPORTANCE

Aquaculture is essential for ensuring global food security by providing a significant source of animal protein. However, the spread of the white spot syndrome virus (WSSV) has resulted in considerable economic losses in crustacean industries. In this study, we evaluated the antiviral activity of rhein, the primary bioactive component of Rheum palmatum L., against WSSV infection, and many pathological aspects of WSSV were also described for the first time. Our mechanistic studies indicated that rhein effectively arrested the replication of WSSV in crayfish by modulating innate immunity to inhibit viral gene transcription. Furthermore, we observed that rhein attenuated WSSV-induced oxidative and inflammatory stresses by regulating the expression of antioxidant and anti-inflammatory-related genes while enhancing innate immunity by reducing total protein levels and increasing phosphatase activity. Our findings suggest that rhein holds great promise as a potent antiviral agent for the prevention and treatment of WSSV in aquaculture.

Analysis of mRNA and MicroRNA Expression Profiles of Nervous Tissues and Reproductive Tissues in Male Procambarus clarkii After Silencing IAG

The insulin-like androgenic gland hormone gene (IAG), primarily expressed in the androgenic gland (AG), plays a crucial role in controlling male sex differentiation and maintaining male secondary sexual characteristics in decapods. In this study, we investigated the mRNA and microRNA expression profiles of male Procambarus clarkii to understand the transcriptomic regulatory mechanism of IAG after the injection of an efficient siRNA (GsiRNA) designed based on IAG. The results revealed that several differentially expressed genes were enriched in reproduction-related pathways, such as the wnt signaling pathway, MAPK signaling pathway, and GnRH signaling pathway. In the testis (Te), the injection of GsiRNA led to the up-regulation of many ovary-related genes and down-regulation of testis-related genes. Moreover, the brain (Br) and abdominal nerve cord (AN) appeared to be involved in the regulation of IAG, with numerous differentially expressed genes found in Br and AN. Notably, the expression of five neuropeptide genes, Crustacean hyperglycemic hormone, pigment-dispersing hormone, red pigment concentrating hormone precursor, corazonin, and gonadotropin-releasing hormone II receptor isoform X1 in Br/AN, was significantly changed. Additionally, three ovary-related miRNAs (miR-263a, miR-263b, miR-133) highly expressed in Te/AG showed significant up-regulation after GsiRNA injection. Furthermore, the long-term interference of GsiRNA was found to inhibit the development of male external sexual characteristics during the juvenile stage and delay it during the adult stage. This research provides valuable insights into the molecular regulatory mechanism and function of IAG in P. clarkii.

Activity of bovine lactoferrin in resistance to white spot syndrome virus infection in shrimp

White spot syndrome virus (WSSV) is a notorious pathogen that has plagued shrimp farming worldwide for decades. To date, there are no known treatments that are effective against this virus. Lactoferrin (LF) is a protein with many bioactivities, including antiviral properties. In this study, the activities and mechanisms of bovine LF (bLF) against WSSV were analyzed. Our results showed that bLF treatment significantly reduced shrimp mortalities caused by WSSV infection. bLF was found to have the ability to bind to surfaces of both host cells and WSSV virions. These bindings may have been a result of bLF interactions with the host cellular chitin binding protein and F1 ATP synthase β subunit protein and the WSSV structural proteins VP28, VP110, VP150 and VP160B. bLF demonstrated potential for development as an anti-WSSV agent in shrimp culture. Furthermore, these reactionary proteins may play a role in WSSV infection.

Characterization of fibroblast growth factor receptor 4 (FGFR4) from the red swamp crayfish Procambarus clarkii and its role in antiviral and antimicrobial immune responses

FGFRs involved multiple physiological processes, such as endocrine homeostasis, wound repair, and cellular behaviors including proliferation, differentiation and survival. In the present study, the homologs of fibroblast growth factor receptor 4 (FGFR4) were identified and characterized from the red swamp crayfish Procambarus clarkii for the first time. The full-length cDNAs of pcFGFR4 were 2878 bp with 2451 bp open reading frame (ORF), respectively. The deduced pcFGFR4 protein contained an immunoglobulin, two immunoglobulin C-2 Type, a transmembrane region and a catalytic domain. Real-time PCR analysis showed that pcFGFR4 were highly expressed in muscle and hemocyte. Moreover, the expression levels of pcFGFR4 in the hepatopancreas and hemocyte were positively stimulated after challenge with Aeromonas hydrophila and WSSV, implying the involvement of pcFGFR4 against bacterial and viral infections in innate immune responses. While pcFGFR4 were silenced in vivo, the expression levels of antimicrobial peptide (AMP) genes (pcALF1-5,8 and pcCrustin1-2) and NF-κB signaling components (pcDrosal and pcRelish) were significantly reduced. Additionally, NF-κB signaling could be markedly activated by overexpression of pcFGFR4 in HEK293T cells. Finally, our results indicated that pcFGFR4 regulated crayfish's innate immunity by modulating NF-κB signaling. These findings may provide new insights into pcFGFR4-mediated signaling cascades in crustaceans and provide a better understanding of crustacean innate immune system.

Effects of air exposure stress on crustaceans: Histopathological changes, antioxidant and immunity of the red swamp crayfish Procambarus clarkii

Air exposure stress may result in oxidative damage and ultimately disease or death in crustaceans. Using the Procambarus clarkia, one of the main commercial aquaculture species in China, as a study model, the molecular mechanism including histopathological changes, antioxidant capacity and immunity response under the air exposure stress were firstly evaluated. Results showed that the surfaces of gill were wrinkled while the morphologies of the nuclei and mitochondria in the hepatopancreas were altered after 48 h of air exposure stress, and the damage of mitochondria was more serious after additional bacterial infection. Moreover, the activity of antioxidant enzymes increased at first and then decreased along with increasement of air exposure time. The concentration of malondialdehyde (MDA) in hepatopancreas was significantly increased under the air exposure stress, while the bacterial infection further aggravated such oxidative damage. The transcriptome analysis exhibited that the stress- and immunity-related genes in hepatopancreas altered when response to the air exposure stress. This study could help uncover the mechanisms of aerial exposure stress responses in Procambarus clarkii.

Transcriptome profiles of red swamp crayfish Procambarus clarkii hematopoietic tissue in response to WSSV challenge

The crayfish Procambarus clarkii could achieve a high cumulative mortality after WSSV infections. To better understand the immune response to WSSV in hematopoietic tissue, the present study investigated the immunological response of P. clarkii and analyzed the expression of some hematopoietic cytokines. After assembly, there was an average of 47,712,411 clean reads were obtained in control and treatment groups. A total of 35,945 unigenes were discovered with N50 length of 1554 bp. Under functional classification, enrichment, and pathway analysis using different database, there were about 257 differentially expressed genes (DEGs) identified, of which 139 were up-regulated and 118 were down-regulated. The GO function analysis of these DEGs were mostly participated in activation of immune response, complement activation, complement binding, negative regulation of humoral immune response and secretory granule membrane. Under KEGG analysis, these DEGs were involved in ECM-receptor interaction, HIF-1 signaling pathway, Glycolysis/Gluconeogenesis, Thyroid hormone signaling pathway and Glucagon signaling pathway. The real-time quantitative PCR (RT-qPCR) analysis of 9 selected genes confirmed the reliability of RNA-Seq results. The present research provide for the first time the transcriptomic profile of P. clarkii hematopoietic tissue in response to WSSV infection and reveals the astakines may play important roles in antiviral immune response. The results of the present study will further enrich the theoretical basis of the crayfish immune system and provide new ideas for disease prevention and control.

Comparative transcriptomic analysis of the different developmental stages of ovary in red swamp crayfish Procambarus clarkii

Background

The red swamp crayfish Procambarus clarkii is a freshwater species that possesses high adaptability, environmental tolerance, and fecundity. P. clarkii is artificially farmed on a large scale in China. However, the molecular mechanisms of ovarian development in P. clarkii remain largely unknown. In this study, we identified four stages of P. clarkii ovary development, the previtellogenic stage (stage I), early vitellogenic stage (stage II), middle vitellogenic stage (stage III), and mature stage (stage IV) and compared the transcriptomics among these four stages through next-generation sequencing (NGS).

Results

The total numbers of clean reads of the four stages ranged from 42,013,648 to 62,220,956. A total of 216,444 unigenes were obtained, and the GC content of most unigenes was slightly less than the AT content. Principal Component Analysis (PCA) and Anosim analysis demonstrated that the grouping of these four stages was feasible, and each stage could be distinguished from the others. In the expression pattern analysis, 2301 genes were continuously increase from stage I to stage IV, and 2660 genes were sharply decrease at stage IV compared to stages I-III. By comparing each of the stages at the same time, four clusters of differentially expressed genes (DEGs) were found to be uniquely highly expressed in stage I (136 genes), stage II (43 genes), stage III-IV (49 genes), and stage IV (22 genes), thus exhibiting developmental stage specificity. Moreover, in comparisons between adjacent stages, the number of DEGs between stage III and IV was the highest. GO enrichment analysis demonstrated that nutrient reservoir activity was highest at stage II and that this played a foreshadowing role in ovarian development, and the GO terms of cell, intracellular and organelle participated in the ovary maturation during later stages. In addition, KEGG pathway analysis revealed that the early development of the ovary was mainly associated with the PI3K-Akt signaling pathway and focal adhesion; the middle developmental period was related to apoptosis, lysine biosynthesis, and the NF-kappa B signaling pathway; the late developmental period was involved with the cell cycle and the p53 signaling pathway.

Conclusion

These transcriptomic data provide insights into the molecular mechanisms of ovarian development in P. clarkii. The results will be helpful for improving the reproduction and development of this aquatic species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07537-x.

Structure, gene expression, and putative functions of crustacean heat shock proteins in innate immunity

Heat shock proteins (HSPs) are molecular chaperones with critical roles in the maintenance of cellular proteostasis. HSPs, which regulate protein folding and refolding, assembly, translocation, and degradation, are induced in response to physiological and environmental stressors. In recent years, HSPs have been recognized for their potential role in immunity; in particular, these proteins elicit a variety of immune responses to infection and modulate inflammation. This review focuses on delineating the structural and functional roles of crustacean HSPs in the innate immune response. Members of crustacean HSPs include high molecular weight HSPs (HSP90, HSP70, and HSP60) and small molecular weight HSPs (HSP21 and HSP10). The sequences and structures of these HSPs are highly conserved across various crustacean species, indicating strong evolutionary links among this group of organisms. The expression of HSP-encoding genes across different crustacean species is significantly upregulated upon exposure to a wide range of pathogens, emphasizing the important role of HSPs in the immune response. Functional studies of crustacean HSPs, particularly HSP70s, have demonstrated their involvement in the activation of several immune pathways, including those mediating anti-bacterial resistance and combating viral infections, upon heat exposure. The immunomodulatory role of HSPs indicates their potential use as an immunostimulant to enhance shrimp health for control of disease in aquaculture.

Cloning and characterization of chst11 from Procambarus clarkii involved in the host immune response of white spot syndrome virus and Aeromonas hydrophila

Carbohydrate sulfotransferases 11 (chst11) is one of the enzymes that synthesize chondroitin sulfate (CS), which has extensive immune functions in vitro and plays a critical role in mediating the infection of host by pathogenic microorganisms. However, whether it has immune functions in crayfish is still poorly understood. In our previous study of transcriptome, chst11 was differentially expressed in susceptible individuals and resistant individuals of Procambarus clarkii after white spot syndrome virus (WSSV) injection. Thus, in this study, the sequence of chst11 was obtained from P. clarkii for the first time and analyzed, and the expression pattern of chst11 was investigated. Besides, the purified recombinant protein of chst11 effect in protection in WSSV infection was explored. The full length of chst11 was 1536 bp with an 831-bp open reading frame (ORF), which encoding 276 amino acids residues with a calculated molecular mass of 33.1 kDa. The chst11 contains a Sulfotransfer_2 domain, one N-glycosylation site and three O-glycosylation sites. Phylogenetic analysis results showed that chst11 had the highest similarity to Penaeus vannamei (79.93%). The expression pattern of chst11 in different tissues indicated that chst11 was expressed highest in gut, gill and hypodermis, lowest in testicular duct, periesophageal nerve and hemocytes. The chst11 had different expression patterns in different tissues when the crayfish was challenged by WSSV, Aeromonas hydrophila and CpG ODN. Recombinant chst11 protein significantly reduced the amount of WSSV copy number in hepatopancreas at 6 h and 12 h post injection compared to the control group injected with bovine serum albumin (BSA). It was found that chst11 protein enhanced the expression of peroxinectin, proPO in hepatopancreas and midgut and the C-type lectin (ctl) in hemocytes and hepatopancreas. Intramuscularly injection of juvenile crayfish with chst11 protein decreased 60% mortality compared to the control group with BSA. This study is the first report on the antiviral function of chst11 in the immune system of crustacean.

Lactobacillus acidophilus and L. plantarum improve health status, modulate gut microbiota and innate immune response of marron (Cherax cainii)

This study aimed to investigate the combined effects of two most potent probiotic bacteria Lactobacillus acidophilus and Lactobacillus plantarum on overall health and immune status of freshwater crayfish, marron under laboratory conditions. A total of 36 marron were distributed into six different tanks and two different feeding groups, control and probiotic-fed group. After acclimation, control group was fed with basal diet while probiotic group was fed 109 CFU/mL per kg of bacterial supplemented feed for 60 days. The results showed no significant differences in weight gain, however, probiotic feed significantly enhanced some hemolymph parameters and biochemical composition of tail muscle. Histology data revealed better hepatopancreas health and higher microvilli counts in the marron gut fed probiotic diet. The probiotic bacteria triggered significant shift of microbial communities at different taxa level, mostly those reported as beneficial for crayfish. The probiotic diet also enriched the metabolic functions and genes associated with innate immune response of crayfish. Further correlation analysis revealed significant association of some taxa with increased activity for hemolymph and immune genes. Therefore, dietary Lactobacillus supplementation can modulate the overall health and immunity as well as gut microbial composition and interaction network between gut microbiota and immune system in crayfish.

The Complete Genome of an Endogenous Nimavirus (Nimav-1_LVa) From the Pacific Whiteleg Shrimp Penaeus (Litopenaeus) Vannamei

White spot syndrome virus (WSSV), the lone virus of the genus Whispovirus under the family Nimaviridae, is one of the most devastating viruses affecting the shrimp farming industry. Knowledge about this virus, in particular, its evolution history, has been limited, partly due to its large genome and the lack of other closely related free-living viruses for comparative studies. In this study, we reconstructed a full-length endogenous nimavirus consensus genome, Nimav-1_LVa (279,905 bp), in the genome sequence of Penaeus (Litopenaeus) vannamei breed Kehai No. 1 (ASM378908v1). This endogenous virus seemed to insert exclusively into the telomeric pentanucleotide microsatellite (TAACC/GGTTA)n. It encoded 117 putative genes, with some containing introns, such as g012 (inhibitor of apoptosis, IAP), g046 (crustacean hyperglycemic hormone, CHH), g155 (innexin), g158 (Bax inhibitor 1 like). More than a dozen Nimav-1_LVa genes are involved in the pathogen-host interactions. We hypothesized that g046, g155, g158, and g227 (semaphorin 1A like) were recruited host genes for their roles in immune regulation. Sequence analysis indicated that a total of 43 WSSV genes belonged to the ancestral/core nimavirus gene set, including four genes reported in this study: wsv112 (dUTPase), wsv206, wsv226, and wsv308 (nucleocapsid protein). The availability of the Nimav-1_LVa sequence would help understand the genetic diversity, epidemiology, evolution, and virulence of WSSV.

Modeling Modulation of the Tick Regulome in Response to Anaplasma phagocytophilum for the Identification of New Control Targets

Ticks act as vectors of pathogens affecting human and animal health worldwide, and recent research has focused on the characterization of tick-pathogen interactions using omics technologies to identify new targets for developing novel control interventions. The regulome (transcription factors-target genes interactions) plays a critical role in cell response to pathogen infection. Therefore, the application of regulomics to tick-pathogen interactions would advance our understanding of these molecular interactions and contribute to the identification of novel control targets for the prevention and control of tick infestations and tick-borne diseases. However, limited information is available on the role of tick regulome in response to pathogen infection. In this study, we applied complementary in silico approaches to modeling how Anaplasma phagocytophilum infection modulates tick vector regulome. This proof-of-concept research provided support for the use of network analysis in the study of regulome response to infection, resulting in new information on tick-pathogen interactions and potential targets for developing interventions for the control of tick infestations and pathogen transmission. Deciphering the precise nature of circuits that shape the tick regulome in response to pathogen infection is an area of research that in the future will advance our knowledge of tick-pathogen interactions, and the identification of new antigens for the control of tick infestations and pathogen infection/transmission.

Proliferation dynamics of WSSV in crayfish, Procambarus clarkii, and the host responses at different temperatures

The replication profile of white spot syndrome virus (WSSV) in crayfish, Procambarus clarkii, at different water temperature was investigated in this study. The WSSV detections were negative at 15 ± 1°C, and the natural infection ratio increased at 19 ± 1°C (24.2% ± 2.25%), reached 100% at 25 ± 1°C and decreased at 30 ± 1°C (93.2% ± 3.37%). The WSSV genome copies number was much higher at 25 ± 1°C (≥5 × 10^{6.45 ± 0.35} /mg) than at 15 ± 1°C (≤5 × 10^{1.13 ± 0.12} /mg), 19 ± 1°C (≤5 × 10^{2.74 ± 0.48} /mg) and 32 ± 1°C (≤5 × 10^{3.18 ± 0.27} /mg). Meanwhile, the significant transcription signals of immediate early gene ie1 and late gene vp28 and a large number of virus particles were detected in epitheliums of stomach, gut and gill, hepatopancreas, heart and muscle cells at 25 ± 1°C by using in situ hybridization (ISH) and transmission electron microscopy. The experimental infection of P. clarkii with WSSV infection showed reduced mortality and lower virus copies number at 19 ± 1°C (23.51% ± 0.84%, ≤5 × 10^{3.41 ± 0.11} /mg) and 32 ± 1°C (38.42% ^±  1.21%, ≤5 × 10^{3.72 ± 0.13} /mg) compared to 25 ± 1°C (100%, ≥5 × 10^{4.99 ± 0.24} /mg). The water temperature regulated the transcription of immune-related genes (crustin2, prophenoloxidase (proPO) and heat shock protein70 (Hsp70)), with some differences between WSSV treatments and control treatments. These results demonstrate that water temperature has effect on WSSV proliferation, which may due to transcriptional response of immune-related genes to temperature.

Cloning and expression of the lectin gene from the mushroom Agrocybe aegerita and the activities of recombinant lectin in the resistance of shrimp white spot syndrome virus infection

Lectin is a protein with multiple functions. In this study, the full-length cDNA of the Agrocybe aegerita lectin (AAL) gene was cloned, recombinant AAL (AAL-His) was expressed, and the activities of AAL-His were analyzed. Northern blot analysis showed that the major AAL transcript is approximately 900 bp. Sequence analysis showed that the coding region of AAL is 489 bp with a transcription start site located 39 nucleotides upstream of the translation initiation codon. In an agglutination test, AAL-His agglutinated rabbit erythrocytes at 12.5 μg/ml. AAL-His also showed antiviral activity in protecting shrimp from white spot syndrome virus (WSSV) infection. This anti-WSSV effect might be due to the binding of AAL-His on WSSV virions via the direct interactions with four WSSV structural proteins, VP39B, VP41B, VP53A and VP216. AAL demonstrates the potential for development as an anti-WSSV agent for shrimp culture. It also implies that these four AAL interaction WSSV proteins may play important roles in virus infection.

Genome survey sequencing of red swamp crayfish Procambarus clarkii

Red swamp crayfish, Procambarus clarkii, presently is an important aquatic commercial species in China. The crayfish is a hot area of research focus, and its genetic improvement is quite urgent for the crayfish aquaculture in China. However, the knowledge of its genomic landscape is limited. In this study, a survey of P. clarkii genome was investigated based on Illumina's Solexa sequencing platform. Meanwhile, its genome size was estimated using flow cytometry. Interestingly, the genome size estimated is about 8.50 Gb by flow cytometry and 1.86 Gb with genome survey sequencing. Based on the assembled genome sequences, total of 136,962 genes and 152,268 exons were predicted, and the predicted genes ranged from 150 to 12,807 bp in length. The survey sequences could help accelerate the progress of gene discovery involved in genetic diversity and evolutionary analysis, even though it could not successfully applied for estimation of P. clarkii genome size.

Antibacterial activity of hemocyanin from red swamp crayfish (Procambarus clarkii)

Hemocyanins (HMC): the copper-containing respiratory proteins present in invertebrate hemolymph, which plays many essential roles in the immune system. Currently, little is known about the HMC domains of Procambarus clarkii (P. clarkii) and their function in antimicrobial immune response. In this present study, we comparatively studied the expression pattern of native PcHMC with the three recombinant proteins of variable domains of crayfish hemocyanin (PcHMC-N, N-terminal domain of hemocyanin; PcHMC-T, tyrosinase domain of hemocyanin; PcHMC-C, C-terminal domain of hemocyanin). The results showed that three purified recombinant proteins had a strong binding to various bacteria and lipopolysaccharides that further highly agglutinated. The HMCs recombinant proteins showed strong antibacterial activity against V. parahaemolyticus and S. aureus by bacterial growth inhibition, phenoloxidase (PO) and phagocytosis assays. Specifically, rPcHMC1-T and rPcHMC1-C inhibited both the bacteria efficiently, rPcHMC1-T was highly upregulated the PO activity than the other recombinant proteins. Whereas, recombinant proteins pretreated crayfish hemocytes participated in phagocytosis activity, rPcHMC1-N and rPcHMC1-C proteins had a profound effect than the rPcHMC1-T on S. aureus and V. parahaemolyticus phagocytosis. The crayfish hemocyanin domains clearly exhibited antibacterial and phagocytic activities against both the bacteria, suggesting that its variable domains of hemocyanin have the different function on specific pathogen during the assault of pathogens.