Diversity and evolution of conotoxins in Conus virgo, Conus eburneus, Conus imperialis and Conus marmoreus from the South China Sea

The venom peptides of cone snails are encoded by a large gene family, and can selectively bind to voltage-gated ion channels (Na+ K+ and Ca2+ channels) and to membrane receptors (nAChR, 5-HT3R, NMDAR). To identify novel conotoxin genes and analyze the evolution of typical conotoxin superfamily genes from different Conus species, we have constructed cDNA libraries derived from the venom ducts of Conus virgo, Conus eburneus, Conus imperialis and Conus marmoreus, which were collected from the South China Sea. 1312 transcripts from four Conus venom duct cDNA libraries were analyzed and 38.7-49.6% of the transcripts encoded conotoxin sequences. In addition to known conotoxins, 34 novel conotoxins have been identified and can be classified into eleven superfamilies, some of which showed unique patterns of cysteines or different signal peptide sequences. The evolutionary trees of T- and A-superfamily conotoxins were analyzed. Likelihood approaches revealed that T-superfamily conotoxins from the four Conus species undergo positive selection, mostly located in the mature toxin region. These findings contribute to a better understanding of the diversity and evolution of conotoxins from the South China Sea, and some novel conotoxins are valuable for further functional investigations. (c) 2012 Elsevier Ltd. All rights reserved.