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Speciation of Cone Snails and Interspecific Hyperdivergence of Their Venom Peptides: Potential Evolutionary Significance of Introns a
Author(s) -
OLIVERA BALDOMERO M.,
WALKER CRAIG,
CARTIER G. EDWARD,
HOOPER DAVID,
SANTOS AMEURFINA D.,
SCHOENFELD ROBERT,
SHETTY RESHMA,
WATKINS MAREN,
BANDYOPADHYAY PRADIP,
HILLYARD DAVID R.
Publication year - 1999
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1999.tb08883.x
Subject(s) - biology , venom , conus , evolutionary biology , nonsynonymous substitution , intron , molecular evolution , genetics , interspecific competition , phylogenetic tree , gene , ecology , genome
All 500 species of cone snails ( Conus ) are venomous predators. From a biochemical/genetic perspective, differences among Conus species may be based on the 50‐200 different peptides in the venom of each species. Venom is used for prey capture as well as for interactions with predators and competitors. The venom of every species has its own distinct complement of peptides. Some of the interspecific divergence observed in venom peptides can be explained by differential expression of venom peptide superfamilies in different species and of peptide superfamily branching in various Conus lineages into pharmacologic groups with different targeting specificity. However, the striking interspecific divergence of peptide sequences is the dominant factor in the differences observed between venoms. The small venom peptides (typically 10‐35 amino acids in length) are processed from larger prepropeptide precursors (ca. 100 amino acids). If interspecific comparisons are made between homologous prepropeptides, the three different regions of a Conus peptide precursor (signal sequence, pro‐region, mature peptide) are found to have diverged at remarkably different rates. Analysis of synonymous and nonsynonymous substitution rates for the different segments of a prepropeptide suggests that mutation frequency varies by over an order of magnitude across the segments, with the mature toxin region undergoing the highest rate. The three sections of the prepropeptide which exhibit apparently different mutation rates are separated by introns. This striking segment‐specific rate of divergence of Conus prepropeptides suggests a role for introns in evolution: exons separated by introns have the potential to evolve very different mutation rates. Plausible mechanisms that could underlie differing mutational frequency in the different exons of a gene are discussed.