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
or mammalian counterparts. Understanding the interplay between pathogens and shrimp NF-κB pathways may provide new opportunities for disease-prevention strategies in the future.
As invertebrates, shrimps rely on multiple innate defense reactions, including humoral immunity and cellular immunity to recognize and eliminate various invaders, such as viruses. White spot syndrome ...virus (WSSV) causes the most prevalent and devastating viral disease in penaeid shrimps, which are the most widely cultured species in the coastal waters worldwide. In the last couple of decades, studies about WSSV implicate a dual role of the immune system in protecting shrimps against the infection; these studies also explore on the pathogenesis of WSSV infection. Herein, we review our current knowledge of the innate immune responses of shrimps to WSSV, as well as the molecular mechanisms used by this virus to evade host immune responses or actively subvert them for its own benefit. Deciphering the interactions between WSSV and the shrimp host is paramount to understanding the mechanisms that regulate the balance between immune-mediated protection and pathogenesis during viral infection and to the development of a safe and effective WSSV defensive strategy.
•We summarized some innate immune pathways that are very important for the host to counteract virus infection.•We propose an updated molecular view of the dual role of the immune system in protecting shrimps against the WSSV infection.•We reported some novelties concerning nucleic acid-induced nonspecific antiviral immunity in shrimp.•We outlined WSSV induced metabolic reprogramming.
The Upper Triassic Chang 7 Member lacustrine organic-rich shale of the Yanchang Formation of the Ordos Basin is a significant hydrocarbon source rock containing abundant of tuff intervals ranging ...from millimeters to tens of centimeters thick. The present study relies upon petrographic and geochemical data of Chang 7 tuff intervals and organic-rich shale to consider fertilization of the lake surface by volcanic debris as a triggering mechanism of black shale sedimentation. Paleoproductivity proxies, including P/Al, Ni/Al, and Cu/Al, display elevated values in association with tuff intervals, suggesting increased productivity induced by volcanic nutrient seeding of the lake surface. Moreover, vertical variations of TOC mimic trends of paleoproductivity proxies, indicating that primary productivity was critical to organic carbon enrichment of the Chang 7 Member. Previous studies have postulated that lake bottom redox conditions were predominantly oxic-suboxic during deposition of the Chang 7 and that these deposits accumulated slowly, neither of which would have favored the export and preservation of organic matter in the absence of enhanced productivity. Accumulation of the organic-rich Chang 7 shale demonstrates the critical role that intensified primary productivity triggered by volcanism can play in the accumulation of carbonaceous sediment.
The function of Toll pathway defense against bacterial infection has been well established in shrimp, however how this pathway responds to viral infection is still largely unknown. In this study, we ...report the Toll4-Dorsal-AMPs cascade restricts the white spot syndrome virus (WSSV) infection of shrimp. A total of nine Tolls from Litopenaeus vannamei namely Toll1-9 are identified, and RNAi screening in vivo reveals the Toll4 is important for shrimp to oppose WSSV infection. Knockdown of Toll4 results in elevated viral loads and renders shrimp more susceptible to WSSV. Furthermore, Toll4 could be a one of upstream pattern recognition receptor (PRR) to detect WSSV, and thereby leading to nuclear translocation and phosphorylation of Dorsal, the known NF-κB transcription factor of the canonical Toll pathway. More importantly, silencing of Toll4 and Dorsal contributes to impaired expression of a specific set of antimicrobial peptides (AMPs) such as anti-LPS-factor (ALF) and lysozyme (LYZ) family, which exert potent anti-WSSV activity. Two AMPs of ALF1 and LYZ1 as representatives are demonstrated to have the ability to interact with several WSSV structural proteins to inhibit viral infection. Taken together, we therefore identify that the Toll4-Dorsal pathway mediates strong resistance to WSSV infection by inducing some specific AMPs.
Inspired by the remarkable photochemical and photophysical properties of novel 2-(2′-hydroxyphenyl)benzothiazole (HBT) derivatives that could be potentially applied across various disciplines, in ...this work, effects of solvent polarity on excited state hydrogen bond effects and excited state intramolecular proton transfer (ESIPT) reaction of 5-{2-2-(4-amino-phenyl)-2,3-dihydro-benzofuran-6-yl-vinyl}-2-benzothiazol-2-yl-phenol (E-HBT) are focused. By comparing the structural changes and infrared (IR) vibrational spectra of the E-HBT fluorophore in polar acetonitrile, moderate polar dichloromethane and nonpolar cyclohexane solvents, combined with the preliminary detection of hydrogen bond interaction by core-valence bifurcation (CVB) index, we can conclude that the hydrogen bond could be strengthened in
S
1
state, which is favorable for the occurrence of ESIPT reactions. The charge recombination behavior of hydrogen bond induced by photoexcitation also further illustrates this point. Via constructing potential energy curves (PECs) based on restrictive optimization and searching transition state (TS) form, we confirm change of surrounding solvent polarity has a regulatory effect on the ESIPT behavior for E-HBT, that is, the higher the polarity of the solvent, the more favorable it is for the ESIPT reaction.
Phenoloxidases (POs) are a family of enzymes including tyrosinases, catecholases and laccases, which play an important role in immune defences of various invertebrates. Whether or not laccase exists ...in shrimp and its function is still poorly understood. In this study, a laccase (LvLac) was cloned and identified from Litopenaeus vannamei for the first time. The full length of LvLac is 3406 bp, including a 2034 bp open reading frame (ORF) coding for a putative protein of 677 amino acids with a signal peptide of 33 aa. LvLac contains three Cu-oxidase domains with copper binding centers formed by 10 histidines, one cysteine and one methionine, respectively. Phylogenetic analysis revealed that LvLac was close to insects laccase 1 family. LvLac expression was most abundant in heart and the crude LvLac protein could catalyze the oxidation of hydroquinone. Real-time PCR showed that LvLac expression was responsive to Vibrio parahaemolyticus, Micrococcus lysodeikticus and white spot syndrome virus (WSSV) infection. Knockdown of LvLac enhanced the sensitivity of shrimps to V. parahaemolyticus and M. lysodeikticus challenge, suggesting that LvLac may play a positive role against bacterial pathogens.
•A laccase (LvLac) is identified from Litopenaeus vannamei for the first time.•The crude LvLac protein can catalyze the oxidation of hydroquinone.•LvLac expression is responsive to V. parahaemolyticus and M. lysodeikticus infection.•LvLac may play a positive role against bacterial pathogens.
There is a debate on whether invertebrates possess an antiviral immunity similar to the interferon (IFN) system of vertebrates. The Vago gene from arthropods encodes a viral-activated secreted ...peptide that restricts virus infection through activating the JAK-STAT pathway and is considered to be a cytokine functionally similar to IFN. In this study, the first crustacean IFN regulatory factor (IRF)-like gene was identified in Pacific white shrimp, Litopenaeus vannamei. The L. vannamei IRF showed similar protein nature to mammalian IRFs and could be activated during virus infection. As a transcriptional regulatory factor, L. vannamei IRF could activate the IFN-stimulated response element (ISRE)-containing promoter to regulate the expression of mammalian type I IFNs and initiate an antiviral state in mammalian cells. More importantly, IRF could bind the 5'-untranslated region of L. vannamei Vago4 gene and activate its transcription, suggesting that shrimp Vago may be induced in a similar manner to that of IFNs and supporting the opinion that Vago might function as an IFN-like molecule in invertebrates. These suggested that shrimp might possess an IRF-Vago-JAK/STAT regulatory axis, which is similar to the IRF-IFN-JAK/STAT axis of vertebrates, indicating that invertebrates might possess an IFN system-like antiviral mechanism.
Crustin is an antimicrobial peptide (AMP) that plays a key role in the innate immunity of crustaceans. This study cloned a new crustin from Pacific white shrimp Litopenaeus vannamei, which we ...designated as LvCrustinB, using rapid amplification of cDNA ends (RACE). The full-length cDNA of LvCrustinB is 751 bp with an open reading frame (ORF) of 591 bp encoding a peptide of 196 amino acids that includes a putative signal sequence. LvCrustinB is a type II crustin that has a glycine-rich region and a single whey acidic protein domain (WAP) domain. The mRNA transcript of LvCrustinB was detected in all examined tissues and was found to be most abundantly expressed in the epithelium and muscle. The expression of LvCrustinB in hemocytes was significantly upregulated after L. vannamei was challenged with LPS, Vibrio parahaemolyticus, and white spot syndrome virus (WSSV). When LvCrustinB was knocked down with RNAi, the mortality rate of L. vannamei significantly increased after V. parahaemolyticus or WSSV infection. Recombinant LvCrustinB was produced using Pichia pastoris GS115 and was shown to bind to 2 g-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and 2 g-negative bacteria (Escherichia coli and V. parahaemolyticus) via polysaccharides, which included PGN, LTA, and LPS. In vivo, the recombinant LvCrustinB remarkably protected L. vannamei from V. parahaemolyticus infection. These results suggest that LvCrustinB plays an important role in innate immunity and may be potentially utilized as antibacterial agents in shrimp.
•A new crustin gene (LvCrustinB) from pacific white shrimp Litopenaeus vannamei.•LvCrustinB is ubiquitously distributedand its expression is up-regulated by V. parahaemolyticus or WSSV infection.•LvCrustinB directly bind to polysaccharides, which included PGN, LTA, and LPS.•LvCrustinB is involved in antibacterial immune defense against V. parahaemolyticus in vivo.
Inspired by the brilliant photochemical and photophysical properties of organic molecule containing the halide substitution that could be potentially applied across various disciplines, in this work, ...effects of atomic electronegativity of halogen (F, Cl, and Br) on excited state hydrogen bond effects and excited state intramolecular proton transfer (ESIPT) reaction. We present the characteristic 4-chloro-2-1-(4-methoxy-phenyl)-4,5-diphenyl-1H-imidazol-2-yl-phenol (CMDIP) that is the main objective of this study to explore in detail the influence of the change of atomic electronegativity by photoexcitation. By comparing the structural changes and infrared (IR) vibrational spectra of the CMDIP derivatives (CMDIP-F, CMDIP-Cl, and CMDIP-Br) fluorophores in S
0
and S
1
states, combined with the preliminary detection of hydrogen bond interaction by core-valence bifurcation (CVB) index, we can conclude that the hydrogen bond could be strengthened in S
1
state, which is favorable for the occurrence of ESIPT reactions. The charge recombination behavior of hydrogen bond induced by photoexcitation also further illustrates this point. Via constructing potential energy curves (PESs) based on restrictive optimization and searching transition state (TS) form, we confirm the change of atomic electronegativity has a regulatory effect on the ESIPT behavior for CMDIP derivatives, that is, the higher the atomic electronegativity is more conducive to the ESIPT reaction.
Stimulator of interferon genes (STING) is crucial for the innate immune to defend against pathogenic infections. Our previous study showed that a STING homolog from Litopenaeus vannamei (LvSTING) was ...involved in antibacterial response
via
regulating antimicrobial peptides (AMPs). Nevertheless, how LvSTING induces AMPs expression to inhibit bacterial infection remains unknown. Herein, we revealed that the existence of a STING–IKKβ–Relish–AMPs axis in shrimp that was essential for opposing to Vibrio parahaemolyticus invasion. We observed that LvRelish was essential for host defense against V. parahaemolyticus infection
via
inducing several AMPs, such as LvALF1, LvCRU1, LvLYZ1 and LvPEN4. Knockdown of LvSTING or LvIKKβ
in vivo
led to the attenuated phosphorylation and diminished nuclear translocation of LvRelish, as well as the impaired expression levels of LvRelish-regulated AMPs. Accordingly, shrimps with knockdown of LvSTING or LvIKKβ or both were vulnerable to V. parahaemolyticus infection. Finally, LvSTING could recruit LvRelish and LvIKKβ to form a complex, which synergistically induced the promoter activity of several AMPs
in vitro
. Taken together, our results demonstrated that the shrimp STING–IKKβ–Relish–AMPs axis played a critical role in the defense against bacterial infection, and provided some insights into the development of disease prevention strategies in shrimp culture.
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