Molecular characterization and expression analysis of CSαβ defensin genes from the scorpion Mesobuthus martensii.

Yange Lang,Xiaohuan Pi,Huijuan Wang,Zhijian Cao,Xuan Li,Yao Yu,Yingliang Wu,Gaomin Liu,Zhiyong Di,Qian Zhang,Fangfang Li,Wenxin Li,Bingzheng Shen

doi:10.1042/bsr20171282

Abstract

Defensins are important components of innate host defence system against bacteria, fungi, parasites and viruses. Here, we predicted six potential defensin genes from the genome of the scorpion Mesobuthus martensii and then validated four genes from them via the combination of PCR and genomic sequence analysis. These four scorpion defensin genes share the same gene organization and structure of two exons and one phase-I intron with the GT-AG rule. Conserved motif and phylogenetic analysis showed that they belonged to the members of the invertebrate cysteine-stabilized α-helix/β-sheet motif defensin (CSαβ) defensin family. All these four CSαβ defensin genes have the expression feature of constitutive transcription (CON) by the whole scorpion infection model, promoter sequence analysis and dual luciferase assays. Further evolution and comparison analysis found that the invertebrate CSαβ defensin genes from most of arachnids and mollusks appear to share the expression pattern of CON, but those from insects and lower invertebrates (nematodes, annelids, cnidarians and sponges) seem to have identical inducible transcription (IND) after being challenged by microorganisms. Together, we identified four scorpion CSαβ defensin genes with the expression feature of CON, and characterized the diversified expression patterns of the invertebrate CSαβ defensin genes, which will shed insights into the evolution of the invertebrate CSαβ defensin genes and their expression patterns.

Highlights

Defensins are small cationic antimicrobial peptides containing three or four intramolecular disulphide bonds formed by six or eight cysteine residues in a complex folded arrangement of two or three antiparallel β-sheets with or without an α-helix structure [1-4]
The 3D structures display that six putative defensins from the scorpion M. martensii are composed of an α-helix linked to an antiparallel two-stranded β-sheet by three disulphide bridges (Figure 1b), suggesting that they all belong to the members of the invertebrate cysteine-stabilized α-helix/β-sheet motif defensin (CSαβ) defensin family
We developed an intact scorpion (M. martensii) challenge model using E. coli, S. aureus, LPS or lipoteichoic acid (LTA) to determine whether the four scorpion defensin genes (BmKDfsin2, BmKDfsin3, BmKDfsin4 and BmKDfsin6) undergo inducible or constitutive mRNA expression in vivo

Summary

Introduction

Defensins are small cationic antimicrobial peptides containing three or four intramolecular disulphide bonds formed by six or eight cysteine residues in a complex folded arrangement of two or three antiparallel β-sheets with or without an α-helix structure [1-4]. The spatial structures of defensins differ according to the arrangement of conserved cysteine residues [1-3,7]. The classification of invertebrate defensins differs based on the complex criteria [3]. One class is the invertebrate cysteine-stabilized α-helix/β-sheet motif defensin (CSαβ defensin), containing an α-helix linked c 2017 The Author(s).

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Results

Conclusion