The molecular evolution of sperm bindin in six species of sea urchins (Echinoida: Strongylocentrotidae) |
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Authors: | Biermann CH |
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Institution: | Department of Ecology and Evolution, State University of New York at Stony Brook, USA. c.h.biermann@biosci.hull.ac.uk |
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Abstract: | The acrosomal protein bindin attaches sperm to eggs during sea urchin
fertilization. Complementary to ongoing functional biochemical studies, I
take a comparative approach to explore the molecular evolution of bindin in
a group of closely related free-spawning echinoid species. Two alleles of
the mature bindin gene were sequenced for each of six species in the sea
urchin family Strongylocentrotidae. The nucleotide sequences diverged by at
least 1% per Myr at both silent and replacement sites. Two short sections
flanking the conserved block show an excess of nonsynonymous substitutions.
Each is homologous to a region that had been identified as a target of
selection in other sea urchin comparisons. A large proportion of the
bindin-coding sequence consists of a highly variable repeat region. Bindin
sequences, even including the large intron, could not resolve the branching
order among five of the species.
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