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A β-GALACTOSIDE BINDING LECTIN FROM ROCK BREAM Oplegnathus fasciatus IS INVOLVED IN MICROBIAL RECOGNITION

William Shanthakumar Thulasitha*, Navaneethaiyer Umasuthan and Jehee Lee
 
Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Special Self-Governing Province, Republic of Korea.
E.mail: thulasiwilliam@gmail.com  
 

 

Pattern recognition receptors (PRRs) are one of the significant components in the innate immune system which recognize the pathogen associated molecular patterns of microbial pathogens. Galectins are galactoside binding lectins, identified as PPRs in many vertebrates. In the present study, we identified a β-galactoside binding lectin from rock bream cDNA database designated as Ofβ-Gal and reported its genomic organization, molecular characterization, transcriptional profile and functional properties.

The genomic structure of Ofβ-Gal has four exons interrupted by three introns. The cDNA (692 bp) of Ofβ-Gal consisted of a 396 bp coding sequence, 34 bp 5´ UTR and a 262 bp 3´ UTR. The coding sequence encoded a putative peptide of 131 amino acids, (15.1 kDa) in which a single carbohydrate recognition domain with all seven critical residues important for carbohydrate binding (-H-N-P-, -N-, -W--E-R-) was detected and classified as a proto type galectin. Homology studies indicated that rock bream Ofβ-Gal showed highest identity 89.4%) and similarity (93.2 %) with Larimichthys crocea (XP_010736226). Comparison of genomic structure, homology and multiple sequence analysis revealed that Ofβ-Gal is an evolutionary conserved galectin family member.

Ubiquitous pattern of mRNA expression was detected under normal physiological conditions with the highest expression in intestine followed by blood, liver, skin, muscle and gill. Temporal expression in liver under pathological conditions revealed that Ofβ-Gal was significantly up-regulated by bacterial (Streptococcus iniae and Edwardsiella tarda), viral (rock bream irido virus) and immune-stimulants (LPS and poly I:C). Purified recombinant Ofβ-Gal showed high affinity towards D-galactose and lactose. Recombinant Ofβ-Gal showed agglutination with Gram-positive (S. iniae, S. parauberis, Listeria monocytogenes) and Gram-negative (Vibrio anguillarum, Vibrio tapetis and Escherichia coli) bacteria as well as with a ciliate parasite Miamiensis avidus. Recognition of both Gram-positive and Gram-negative bacteria were confirmed by Western blot. Results from the present study indicate that Ofβ-Gal involved in pathogen recognition and function as PRR in the innate immune system of rock bream.

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