Dissecting Toxicity: The Venom Gland Transcriptome and the Venom Proteome of the Highly Venomous Scorpion Centruroides limpidus (Karsch, 1879)

Abstract

Venom glands and soluble venom from the Mexican scorpion Centruroides limpidus (Karsch, 1879) were used for transcriptomic and proteomic analyses, respectively. An RNA-seq was performed by high-throughput sequencing with the Illumina platform. Approximately 80 million reads were obtained and assembled into 198,662 putative transcripts, of which 11,058 were annotated by similarity to sequences from available databases. A total of 192 venom-related sequences were identified, including Na⁺ and K⁺ channel-acting toxins, enzymes, host defense peptides, and other venom components. The most diverse transcripts were those potentially coding for ion channel-acting toxins, mainly those active on Na⁺ channels (NaScTx). Sequences corresponding to β- scorpion toxins active of K⁺ channels (KScTx) and λ-KScTx are here reported for the first time for a scorpion of the genus Centruroides. Mass fingerprint corroborated that NaScTx are the most abundant components in this venom. Liquid chromatography coupled to mass spectometry (LC-MS/MS) allowed the identification of 46 peptides matching sequences encoded in the transcriptome, confirming their expression in the venom. This study corroborates that, in the venom of toxic buthid scorpions, the more abundant and diverse components are ion channel-acting toxins, mainly NaScTx, while they lack the HDP diversity previously demonstrated for the non-buthid scorpions. The highly abundant and diverse antareases explain the pancreatitis observed after envenomation by this species.

Keywords: Centruroides limpidus Karch; proteome; scorpion; transcriptome; venom toxicity.

Figure 1

Habitus and distribution of Centruroides limpidus. (A) The morphology of C. limpidus, male (left) and female (right). (B) Geographical distribution of C. limpidus in 10 Mexican States (red dots indicate the places of sampling). (B) Reproduced with permission from [14] Copyright 2009, Universidad Nacional Autónoma de México.

Figure 2

Relative diversity of transcripts related to venom components. For the graphic, only the number of different transcripts identified for each category.

Figure 3

Examples of Na⁺ channel-specific toxins. (A) Putative α-NaScTx and (B) Putative β-NaScTx. The transcript-derived peptides are aligned to their reference sequences. The percentage of identity was calculated considering only the mature sequences. Accession numbers and species’ names of the references were taken from UniProt or GenBank. Conserved cysteine residues are highlighted in blue. Dots indicate identical residues, and dashes indicate gaps.

Figure 4

Examples of K⁺ channel-specific toxins. (A–E) show the alignments of the transcript-derived sequences of members of the α, β, γ, δ, and λ-KScTx families, respectively, with the reference sequences. The percentage of identity was calculated considering only the mature sequences. Accession numbers and species’ names of the references were taken from UniProt or GenBank. Conserved cysteine residues are highlighted in blue. Dots indicate identical residues, and dashes indicate gaps.

Figure 5

Examples of host defense peptides (HDPs). The translated sequences from representative transcripts coding for HDPs found in the C. limpidus transcriptome are shown aligned to matching sequences from databases. The complete precursor sequences are shown and the complete precursor was considered in the calculation of the percentage of identity. (A) Defensins. (B) The unique NDBP-2 precursor found. (C) Two putative NDBP-4 precursors. (D) The unique precursor for the putative anionic peptide. Accession numbers and species’ names of the references were taken from UniProt or GenBank. Conserved cysteine residues are highlighted in blue. The predicted mature sequences are indicated in bold typeface, the predicted signal peptides are underlined and the propeptides are indicated in italics. Dots indicate identical residues and dashes indicate gaps.

Figure 6

Distribution of the C. limpidus venom components detected by mass fingerprint with respect to their molecular masses.

Figure 7

Comparative diversity of the transcripts coding for toxins (A), HDPs (B), and enzymes (C) found in C. limpidus versus those from non-buthid species reported in other transcriptomic analyses.