Molecular cloning and functional characterization of eight galectin genes from Takifugu obscurus

Function of three newly identified galectins in immune response of Takifugu obscurus against bacterial infection

Galectins, a family of β-galactoside-binding proteins, are evolutionarily conserved across diverse organisms. In our research, three galectins were identified from Takifugu obscurus, designated as ToGalec9, ToGalec10, and ToGalec11. Structural analysis revealed that the deduced proteins contain one, one, and two conserved carbohydrate recognition domains, respectively. Transcripts of ToGalec9-11 exhibited ubiquitous expression across all examined tissues, with significant upregulation observed in liver and kidney tissues following challenge with Vibrio harveyi and Staphylococcus aureus. siRNA-mediated knockdown of ToGalec9-11 downregulated four interleukin (IL) genes expression and substantially impaired bacterial clearance capacity. To further elucidate biological functions, the coding regions of ToGalec9-11 were expressed and the proteins were purified. The recombinant ToGalec9-11 proteins demonstrated broad carbohydrate-binding specificity against six tested ligands and displayed potent bacterial agglutination activity against both Gram-negative (V. harveyi) and Gram-positive (S. aureus) pathogens. Furthermore, rToGalec9-11 exhibited significant antimicrobial effects by suppressing bacterial proliferation and biofilm formation. Notably, rToGalec9-11 enhanced the expression of four IL genes and facilitated bacterial clearance in vivo. Our findings collectively demonstrate that ToGalec9-11 function as essential immune mediators in T. obscurus, orchestrating pathogen recognition, antimicrobial defense, and immune modulation through both lectin-mediated interactions and cytokine regulation.

Characterization of a serine protease homolog from Macrobrachium nipponense and its involvement in AMP synthesis and proPO activation

Serine protease homolog (SPH) with a clip domain is crucial for activating prophenoloxidase. In this study, we isolated and characterized an SPH gene from Macrobrachium nipponense, designated as MnSPH. The full-length cDNA sequence of MnSPH was 1709 bp, including an open reading frame of 1383 bp that encoded 460 amino acids. The predicted MnSPH protein contained a signal peptide, two low-density complex regions, and a Tryp_SPc domain. Although SMART was unable to predict a clip domain in MnSPH, it does possess a conserved cysteine pattern that resembles the characteristic pattern of clip domains. Phylogenetic analysis revealed that MnSPH first clustered with SPH of Pacifastacus leniusculus and subsequently formed a clade with other SPHs or prophenoloxidase-activating factors (PPAFs) from crustaceans. MnSPH exhibited high expression levels in the gills and stomach of M. nipponense, with relatively lower expression in other tissues. Upon infection with Vibrio parahaemolyticus and Staphylococcus aureus, the expression levels of MnSPH were significantly upregulated at multiple time points in the hemocytes of M. nipponense. Furthermore, the knockdown of MnSPH in the hemocytes resulted in the inhibition of several antimicrobial peptide (AMP) genes and a significant reduction in phenoloxidase activity. The survival rate of prawns was reduced after MnSPH knockdown. These findings suggested that MnSPH plays a pivotal role in the innate immune response of M. nipponense during pathogen infection.