Extreme diversity of scorpion venom peptides and proteins revealed by transcriptomic analysis: implication for proteome evolution of scorpion venom arsenal.

Venom is an important genetic development crucial to the survival of scorpions for over 400 million years. We studied the evolution of the scorpion venom arsenal by means of comparative transcriptome analysis of venom glands and phylogenetic analysis of shared types of venom peptides and proteins between buthids and euscorpiids. Fifteen types of venom peptides and proteins were sequenced during the venom gland transcriptome analyses of two Buthidae species (Lychas mucronatus and Isometrus maculatus) and one Euscorpiidae species (Scorpiops margerisonae). Great diversity has been observed in translated amino acid sequences of these transcripts for venom peptides and proteins. Seven types of venom peptides and proteins were shared between buthids and euscorpiids. Molecular phylogenetic analysis revealed that at least five of the seven common types of venom peptides and proteins were likely recruited into the scorpion venom proteome before the lineage split between Buthidae and Euscorpiidae with their corresponding genes undergoing individual or multiple gene duplication events. These are α-KTxs, βKSPNs (β-KTxs and scorpines), anionic peptides, La1-like peptides, and SPSVs (serine proteases from scorpion venom). Multiple types of venom peptides and proteins were demonstrated to be continuously recruited into the venom proteome during the evolution process of individual scorpion lineages. Our results provide an insight into the recruitment pattern of the scorpion venom arsenal for the first time.