Evolution of Conus peptide genes: duplication and positive selection in the A-superfamily.
A remarkable diversity of venom peptides is expressed in the genus Conus (known as "conotoxins" or "conopeptides"). Between 50 and 200 different venom peptides can be found in a single Conus species, each having its own complement of peptides. Conopeptides are encoded by a few gene superfamilies; here we analyze the evolution of the A-superfamily in a fish-hunting species clade, Pionoconus. More than 90 conopeptide sequences from 11 different Conus species were used to build a phylogenetic tree. Comparison with a species tree based on standard genes reveals multiple gene duplication events, some of which took place before the Pionoconus radiation. By analysing several A-conopeptides from other Conus species recorded in GenBank, we date the major duplication events after the divergence between fish-hunting and non-fish-hunting species. Furthermore, likelihood approaches revealed strong positive selection; the magnitude depends on which A-conopeptide lineage and amino-acid locus is analyzed. The four major A-conopeptide clades defined are consistent with the current division of the superfamily into families and subfamilies based on the Cys pattern. The function of three of these clades (the κA-family, the α4/7-subfamily, and α3/5-subfamily) has previously been characterized. The function of the remaining clade, corresponding to the α4/4-subfamily, has not been elucidated. This subfamily is also found in several other fish-hunting species clades within Conus. The analysis revealed a surprisingly diverse origin of α4/4 conopeptides from a single species, Conus bullatus. This phylogenetic approach that defines different genetic lineages of Conus venom peptides provides a guidepost for identifying conopeptides with potentially novel functions.
Puillandre
Nicolas
N
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA. puillandre@biology.utah.edu
Watkins
Maren
M
Olivera
Baldomero M
BM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D020916:Conotoxins / Q000235:genetics*; D052078:Conus Snail / Q000235:genetics*; D030541:Databases, Genetic; D019143:Evolution, Molecular; D020440:Gene Duplication; D008969:Molecular Sequence Data; D010802:Phylogeny; D012641:Selection, Genetic; D016415:Sequence Alignment
D020916:Conotoxins