Identification, characterization, and antimicrobial activity of a novel big defensin discovered in a commercial bivalve mollusc, Tegillarca granosa

Sanghyok Ri; Shanjie Zha; Tongchol Kim; Kwangjin Ju; Weishang Zhou; Wei Shi; Myongsik Wu; Chunmi Kim; Yongbo Bao; Changsen Sun; Guangxu Liu

doi:10.1016/j.fsi.2022.04.003

Identification, characterization, and antimicrobial activity of a novel big defensin discovered in a commercial bivalve mollusc, Tegillarca granosa

Fish Shellfish Immunol. 2022 May:124:174-181. doi: 10.1016/j.fsi.2022.04.003. Epub 2022 Apr 7.

Authors

Sanghyok Ri¹, Shanjie Zha², Tongchol Kim¹, Kwangjin Ju³, Weishang Zhou⁴, Wei Shi⁴, Myongsik Wu⁵, Chunmi Kim⁵, Yongbo Bao², Changsen Sun², Guangxu Liu⁶

Affiliations

¹ College of Animal Sciences, Zhejiang University, Hangzhou, 310058, PR China; College of Life Science, Kim Hyong Jik University of Education, Pyongyang, 99903, D.P.R, North Korea.
² Zhejiang Key Laboratory of Aquatic Germplasm Resources, College of Biological & Environmental Sciences, Zhejiang Wanli University, Ningbo, 315100, PR China; Ninghai Institute of Mariculture Breeding and Seed Industry, Zhejiang Wanli University, Ninghai, 315604, PR China.
³ College of Animal Sciences, Zhejiang University, Hangzhou, 310058, PR China; College of Aquaculture, Wonsan Fisheries University, Wonsan, 999093, D.P.R, North Korea.
⁴ College of Animal Sciences, Zhejiang University, Hangzhou, 310058, PR China.
⁵ College of Life Science, Kim Hyong Jik University of Education, Pyongyang, 99903, D.P.R, North Korea.
⁶ College of Animal Sciences, Zhejiang University, Hangzhou, 310058, PR China. Electronic address: guangxu_liu@zju.edu.cn.

PMID: 35398526
DOI: 10.1016/j.fsi.2022.04.003

Abstract

Molluscs, the second largest animal phylum on earth, primarily rely on cellular and humoral immune responses to fight against pathogen infection. Although antimicrobial peptides (AMPs) such as big defensin play crucial roles in the humoral immune response, it remains largely unknown in the ecological and economic important blood clam (Tegillarca granosa). In this study, a novel big defensin gene (TgBD) was identified in T. granosa through transcripts and whole genome searching. Bioinformatic analyses were conducted to explore the molecular characteristics of TgBD, and comparisons of TgBD with those reported in other molluscs were performed by multiple alignments and phylogenetic analysis. In addition, the expression patterns of TgBD in various tissues and upon bacterial challenge were investigated while the antimicrobial activity of synthetic N-terminal domain of TgBD was confirmed in vitro by radial diffusion experiment. Results obtained showed TgBD had an open reading frame (ORF) of 369 bp, encoding a prepropeptide containing a signal peptide and a propeptide. Similar to big defensins reported in other species, TgBD consists of a hydrophobic N-terminal domain containing β1-α1-α2-β2 folds and a cysteine-rich cationic C-terminal domain with three disulfide bonds between C1-C5, C2-C4, and C3-C6. Phylogenetic analysis showed that TgBD shared 76.80% similarity to its close relative ark shell (Scapharca broughtoni). In addition, TgBD expression was observed in all tissues investigated under normal conditions and was significantly induced by injection of Vibrio parahaemolyticus. Furthermore, synthetic N-terminal peptide of TgBD exhibited strong antimicrobial activity against Gram-positive bacteria tested. Our results indicated that TgBD is a constitutive and inducible acute phase AMP, which provides a universal and prompt protection for T. granosa.

Keywords: Antimicrobial peptide (AMP); Big defensin; Blood clam (Tegillarca granosa); Innate immunity; Vibrio parahaemolyticus.

MeSH terms

Animals
Anti-Infective Agents* / pharmacology
Arcidae*
Bivalvia* / genetics
Bivalvia* / metabolism
Defensins / chemistry
Defensins / genetics
Defensins / pharmacology
Phylogeny

Substances

Anti-Infective Agents
Defensins