Conotoxin Diversity in Chelyconus ermineus (Born, 1778) and the Convergent Origin of Piscivory in the Atlantic and Indo-Pacific Cones

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2018-10Department
Ciencia de los Materiales e Ingeniería Metalúrgica y Química InorgánicaSource
Genome Biology and Evolution, Volume 10, Issue 10, October 2018, Pages 2643–2662Abstract
The transcriptome of the venom duct of the Atlantic piscivorous cone species Chelyconus ermineus (Born, 1778) was
determined. The venom repertoire of this species includes at least 378 conotoxin precursors, which could be ascribed to
33 known and 22 new (unassigned) protein superfamilies, respectively.Most abundant superfamilies were T,W, O1, M, O2,
and Z, accounting for 57% of all detected diversity. A total of three individuals were sequenced showing considerable
intraspecific variation: each individual had many exclusive conotoxin precursors, and only 20% of all inferred mature
peptides were common to all individuals. Three different regions (distal, medium, and proximal with respect to the venom
bulb) of the venom duct were analyzed independently. Diversity (in terms of number of distinct members) of conotoxin
precursor superfamilies increased toward the distal region whereas transcripts detected toward the proximal region showed
higher expression levels. Only the superfamilies A and I3 showed statistically significant differential expression across regions
of the venom duct. Sequences belonging to the alpha (motor cabal) and kappa (lightning-strike cabal) subfamilies of the
superfamily A were mainly detected in the proximal region of the venom duct. The mature peptides of the alpha subfamily
had the a4/4 cysteine spacing pattern, which has been shown to selectively target muscle nicotinic-acetylcholine receptors,
ultimately producing paralysis. This function is performed by mature peptides having a a3/5 cysteine spacing pattern in
piscivorous cone species from the Indo-Pacific region, thereby supporting a convergent evolution of piscivory in cones.
Subjects
conotoxin; conopeptide; convergence; transcriptome; Conidae; expressionCollections
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