Abstract

The venom of various Conus species is composed of a rich variety of unique bioactive peptides, commonly referred to as conotoxins (conopeptides). Most conopeptides have specific receptors or ion channels as physiologically relevant targets. In this paper, high-throughput transcriptome sequencing was performed to analyze putative conotoxin transcripts from the venom duct of a vermivorous cone snail species, Conus litteratus native to the South China Sea. A total of 128 putative conotoxins were identified, most of them belonging to 22 known superfamilies, with 43 conotoxins being regarded as belonging to new superfamilies. Notably, the M superfamily was the most abundant in conotoxins among the known superfamilies. A total of 15 known cysteine frameworks were also described. The largest proportion of cysteine frameworks were VI/VII (C-C-CC-C-C), IX (C-C-C-C-C-C) and XIV (C-C-C-C). In addition, five novel cysteine patterns were also discovered. Simple sequence repeat detection results showed that di-nucleotide was the major type of repetition, and the codon usage bias results indicated that the codon usage bias of the conotoxin genes was weak, but the M, O1, O2 superfamilies differed in codon preference. Gene cloning indicated that there was no intron in conotoxins of the B1- or J superfamily, one intron with 1273–1339 bp existed in a mature region of the F superfamily, which is different from the previously reported gene structure of conotoxins from other superfamilies. This study will enhance our understanding of conotoxin diversity, and the new conotoxins discovered in this paper will provide more potential candidates for the development of pharmacological probes and marine peptide drugs.

Highlights

  • IntroductionThere are about 800 species of Conus worldwide, which are distributed in tropical seas [1,2]

  • The genus Conus is a large family of gastropods belonging to mollusks

  • Raw reads of the transcriptome sequencing were deposited in the NCBI Sequence Read Archive (SRA) database with a project ID PRJNA586870 including SRX7667250–SRX7667252

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Summary

Introduction

There are about 800 species of Conus worldwide, which are distributed in tropical seas [1,2] According to their diet habits, cone snails can be divided into three groups, vermivorous (V), molluscivorous (M), and piscivorous (P). Species [3,4,5] They move slowly, cone snails can prey on creatures with quick movement by skillfully injecting a small amount of a complex cocktail containing potent venom peptides. Cone snails can prey on creatures with quick movement by skillfully injecting a small amount of a complex cocktail containing potent venom peptides These venom peptides are commonly named conotoxins or conopeptides, and are a mixture of different bioactive compounds for defense and preying. These peptides, with different pharmacological activities, are composed of a small number of amino-acid residues that are especially rich in cysteines, and have become one of the main sources of peptide medicine [6,7,8]

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