ABSTRACT
Venomous reptiles produce their toxins in specialized venom glands, creating a library of toxin transcripts within these tissues. Venom profiles can be inferred from venom gland transcriptomes, and these transcripts provide complete coding sequences (translatable into amino acids) for each toxin. A venom gland transcriptome can be useful as a custom database for proteomic identifications, especially for venoms that contain unknown or hypervariable components not present in public databases. From these transcriptomes, potential novel toxins can be discovered, and the knowledge of their complete sequence makes it possible to recombinantly express and functionally characterize new toxins. Transcripts of venom protein genes also provide crucial information about venom variation and evolution. Given the large amount of information obtained from a venom gland transcriptome, combined with the increasing affordability of next-generation sequencing (NGS) technologies, these studies have become very appealing, and published venom gland transcriptomes have substantially increased in number. The sensitivity of NGS has also made these approaches feasible even for reptiles with small venom glands and low venom yields, which were previously difficult to characterize. Advances in NGS technologies have been paralleled by advances in bioinformatics, essential for the interpretation of these large data sets. Unlike the past wet lab–based generation of venom gland transcriptomes using expressed sequenced tags, NGS transcriptomics is computationally intensive, and skills in bioinformatics are required. This chapter will provide discussions on NGS venom gland transcriptome assembly and toxin annotation as well as an overview of toxin gene expression and the evolutionary insights these studies have provided. Venom gland transcriptomics, especially the assembly of venom gland transcriptomes de novo, will surely be a fundamental component of venom research for many years to come.
