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Abstract Thymosins β are actin-binding proteins that play a variety of different functions in inflammatory responses, wound healing, cell migration, angiogenesis, and stem cell recruitment and differentiation. In crayfish, thymosins participate in antiviral immunology. However, the roles of thymosin during bacterial infection in shrimp remain unclear. In the present study, four thymosins were identified from kuruma shrimp, Marsupenaeus japonicus , and named as Mj thymosin2, Mj thymosin3, Mj thymosin4, and Mj thymosin5 according the number of their thymosin beta actin-binding motifs. Mj thymosin3 was selected for further study because its expression level was the highest in hemocytes. Expression analysis showed that Mjthymosin3 was upregulated in hemocytes after challenged by Vibrio anguillarum or Staphylococcus aureus. The recombinant Mj thymosin3 protein could inhibit the growth of certain bacteria in an in vitro antibacterial test. Mj thymosins could facilitate external bacterial clearance in shrimp, and were beneficial to shrimp survival post V. anguillarum or S. aureus infection. The results suggested that Mj thymosins played important roles in the antibacterial immune response of kuruma shrimp. Highlights • Four thymosins were identified from kuruma shrimp, Marsupenaeus japonicus. • Mjthymosin3 was upregulated in hemocytes after challenge by V. anguillarum or S. aureus. • R Mj thymosin3 could inhibit the growth of certain bacteria. • Mj thymosins could facilitate external bacterial clearance in shrimp. • Mj thymosins were beneficial to shrimp survival post V. anguillarum or S. aureus infection. [ABSTRACT FROM AUTHOR]

Myeloid leukemia factor (MLF) plays an important role in development, cell cycle, myeloid differentiation, and regulates the RUNX transcription factors. However, the function of MLF in immunity is still unclear. In this study, an MLF was identified and characterized in kuruma shrimp Marsupenaeus japonicus , and named as Mj MLF. The full-length cDNA of Mj MLF contained 1111 nucleotides, which had an opening reading frame of 816 bp encoding a protein of 272 amino acids with an MLF1-interacting protein domain. MjMLF could be ubiquitously detected in different tissues of shrimp at the transcriptional level. The expression pattern analysis showed that MjMLF could be upregulated in shrimp hemocytes and hepatopancreas after white spot syndrome virus challenge. The RNA interference and protein injection assay showed that Mj MLF could inhibit WSSV replication in vivo. Flow cytometry assay showed that Mj MLF could induce hemocytes apoptosis which functioned in the shrimp antiviral reaction. All the results suggested that Mj MLF played an important role in the antiviral immune reaction of kuruma shrimp. The research indicated that Mj MLF might function as a novel regulator to inhibit WSSV replication in shrimp. [ABSTRACT FROM AUTHOR]

Leucine rich repeat (LRR) motif exists in many immune receptors of animals and plants. Most LRR containing (LRRC) proteins are involved in protein-ligand and protein-protein interaction, but the exact functions of most LRRC proteins were not well-studied. In this study, an LRRC protein was identified from kuruma shrimp Marsupenaeus japonicus , and named as Mj LRRC1. MjLRRC 1 was consistently expressed in different tissues of normal shrimp with higher expression in gills and stomach. At the transcriptional level, there were no significant changes of MjLRRC 1 after injection of Vibrio anguillarum or Staphylococcus aureus in gills and hepatopancreas. While in V. anguillarum oral infection, MjLRRC 1 was upregulated in stomach but not in intestine. The recombinant Mj LRRC1 protein could bind to Gram-positive and Gram-negative bacteria, bacterial cell wall components including peptidoglycan, lipoteichoic acid, and lipopolysaccharide. Mj LRRC1 regulated the expression of some antimicrobial peptide (AMP) genes and participated in bacteria clearance of stomach. All these results suggested that Mj LRRC1 might play important roles in antibacterial immune response of kuruma shrimp. [ABSTRACT FROM AUTHOR]

Lysin motif (LysM) is a peptidoglycan and chitin-binding motif with multiple functions in bacteria, plants, and animals. In this study, a novel LysM and putative peptidoglycan-binding domain-containing protein was cloned from kuruma shrimp ( Marsupenaeus japonicus ) and named as Mj LPBP. The cDNA of Mj LPBP contained 1010 nucleotides with an open reading frame of 834 nucleotides encoding a protein of 277 amino acid residues. The deduced protein contained a Lysin motif and a transmembrane region, with a calculated molecular mass of 31.54 kDa and isoelectric point of 8.61. MjLPBP was ubiquitously distributed in different tissues of shrimp at the mRNA level. Time course expression assay showed that MjLPBP was upregulated in hemocytes of shrimp challenged with Vibrio anguillarum or Staphylococcus aureus . MjLPBP was also upregulated in hepatopancreas after white spot syndrome virus and bacteria challenge. The recombinant protein of Mj LPBP could bind to some Gram-positive and Gram-negative bacteria and yeast. Further study found that r Mj LPBP bound to bacterial cell wall components, including peptidoglycans, lipoteichoic acid, lipopolysaccharide, and chitin. The induction of several antimicrobial peptide genes and phagocytosis-related gene, such as anti-lipopolysaccharide factors and myosin, was depressed after knockdown of MjLPBP . Mj LPBP could facilitate V. anguillarum clearance in vivo. All the results indicated that Mj LPBP might play an important role in the innate immunity of shrimp. [ABSTRACT FROM AUTHOR]