Abstract
Venoms are complex mixtures of proteins that have evolved repeatedly in the animal kingdom. Cone snail venoms represent one of the best studied venom systems. In nature, this venom can be dynamically adjusted depending on its final purpose, whether to deter predators or hunt prey. Here, the transcriptome of the venom gland and the proteomes of the predation-evoked and defensive venoms of the molluscivorous cone snail Cylinder ammiralis were catalogued. A total of 242 venom-related transcripts were annotated. The conotoxin superfamilies presenting more different peptides were O1, O2, T, and M, which also showed high expression levels (except T). The three precursors of the J superfamily were also highly expressed. The predation-evoked and defensive venoms showed a markedly distinct profile. A total of 217 different peptides were identified, with half of them being unique to one venom. A total of 59 peptides ascribed to 23 different protein families were found to be exclusive to the predatory venom, including the cono-insulin, which was, for the first time, identified in an injected venom. A total of 43 peptides from 20 protein families were exclusive to the defensive venom. Finally, comparisons of the relative abundance (in terms of number of peptides) of the different conotoxin precursor superfamilies showed that most of them present similar abundance regardless of the diet.
Highlights
Venom systems are chemical weapons that confer a selective advantage and have evolved repeatedly in different animal lineages [1,2]
If comparisons are between venom gland transcriptomes of related species, it is possible to discriminate those toxins that are shared-derived from common ancestors from those that are exclusive of a given species, as well as uncover instances of convergence [11]
A combined transcriptomic and proteomic approach is currently the most efficient method to catalogue the peptides that are produced by an individual in the venom gland, as well as the fraction that is loaded into the harpoons to capture prey or deter predators [6,16]
Summary
Venom systems are chemical weapons that confer a selective advantage and have evolved repeatedly in different animal lineages [1,2]. The advent of RNA sequencing [9] opened the door to identify the complete set of transcripts that are expressed in the venom gland of a venomous animal. These transcripts encode for toxins, as well as for proteins involved in the folding and maturation of the toxins [10]. If comparisons involve other tissue transcriptomes, it is possible to uncover those genes that are essential for venom production, as well as variations in their expression in response to different stimuli [3]. Venom glands show regionalization of toxin production [6,15], which can be best characterized combining transcriptomics and proteomics approaches [16]
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