Alternative mRNA Splicing in Three Venom Families Underlying a Possible Production of Divergent Venom Proteins of the Habu Snake, Protobothrops flavoviridis.

Ogawa Ogawa,Satoh Satoh,Nakamura Nakamura,Shibata Shibata,Yugeta Yugeta,Isomoto Isomoto,Yamasaki Yamasaki,Fukumaki Fukumaki,Oda-Ueda Oda-Ueda,Chijiwa Chijiwa,Hisata Hisata,Ohno Ohno,Hattori Hattori

doi:10.3390/toxins11100581

Abstract

Snake venoms are complex mixtures of toxic proteins encoded by various gene families that function synergistically to incapacitate prey. A huge repertoire of snake venom genes and proteins have been reported, and alternative splicing is suggested to be involved in the production of divergent gene transcripts. However, a genome-wide survey of the transcript repertoire and the extent of alternative splicing still remains to be determined. In this study, the comprehensive analysis of transcriptomes in the venom gland was achieved by using PacBio sequencing. Extensive alternative splicing was observed in three venom protein gene families, metalloproteinase (MP), serine protease (SP), and vascular endothelial growth factors (VEGF). Eleven MP and SP genes and a VEGF gene are expressed as a total of 81, 61, and 8 transcript variants, respectively. In the MP gene family, individual genes are transcribed into different classes of MPs by alternative splicing. We also observed trans-splicing among the clustered SP genes. No other venom genes as well as non-venom counterpart genes exhibited alternative splicing. Our results thus indicate a potential contribution of mRNA alternative and trans-splicing in the production of highly variable transcripts of venom genes in the habu snake.

Highlights

Many snakes have evolved the ability to produce venom, which is a complex mixture of toxic proteins
We obtained a total 97,405 reads of cDNA collected from the venom gland using PacBio RSII (Iso-Seq)
SvVEGF is a member of the group in which a single-copy gene is transcribed into one corresponding mRNA

Summary

Introduction

Many snakes have evolved the ability to produce venom, which is a complex mixture of toxic proteins. The toxic proteins contained in the venom are encoded by genes classified into more than ten gene families [1,2,3]. Protein components of venom are highly variable from species to species. These may vary from population to population and from individual to individual under different physiological and/or environmental conditions. This extensive diversity makes a full characterization of their repertoire difficult. Recent venomics studies, including high-throughput transcriptomics (RNA-seq), have demonstrated a highly divergent profile of mRNAs encoded by venom genes, and the involvement of alternative splicing is suggested to contribute to transcriptome variety [4,5,6]. In the era of genome science, the extent of alternative splicing can be examined on a genome-wide scale

Results

Discussion

Conclusion