Assortative Mating Drives Linkage Disequilibrium between Sperm and Egg Recognition Protein Loci in the Sea Urchin Strongylocentrotus purpuratus
Assortative Mating Drives Linkage Disequilibrium between Sperm and Egg Recognition Protein Loci in the Sea Urchin Strongylocentrotus purpuratus
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DOI：
10.1093/molbev/msv010
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发表时间：
2015-04-01
影响因子：
10.7
通讯作者：
Levitan, Don R.
中科院分区：
文献类型：
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作者：
Stapper, Andres Plata;Beerli, Peter;Levitan, Don R.
精子和卵子的表面有相互作用的蛋白质，在受精过程中影响它们的相容性。这些蛋白质在物种内通常是多态的，产生配子亲和的变异。我们首先证明了各种精子结合蛋白（bindin）变异在紫癜斑海胆中的适应性后果，以及基于精子结合蛋白基因型的雄性和雌性之间的分类交配。这种基于精子结合蛋白基因型的选择性交配的实证发现可能是由相互作用的精子和卵子识别位点之间的连锁不平衡（LD）引起的。然后，我们研究了海胆卵子精子结合蛋白受体（EBR1）的8个外显子的序列变异。我们发现EBR1的8个外显子之间几乎没有LD的证据，但精子结合蛋白与EBR1之间总体存在LD的有力证据，并且精子结合蛋白在8个外显子之间存在不同程度的LD。我们拒绝了由共同的进化史、群体结构或基因组上这些相互作用位点之间的密切物理联系驱动的LD的其他假设。对这种遗传模式最简洁的解释是，它代表了基于这些精子和卵子位点之间相互作用的分类交配驱动的选择。这些发现表明了持续的性选择在维持蛋白质多态性和LD中的重要性，并且更普遍地强调了LD如何被用作当前配偶选择的指示，而不是历史选择。
Sperm and eggs have interacting proteins on their surfaces that influence their compatibility during fertilization. These proteins are often polymorphic within species, producing variation in gamete affinities. We first demonstrate the fitness consequences of various sperm bindin protein (Bindin) variants in the sea urchin Strongylocentrotus purpuratus, and assortative mating between males and females based on their sperm Bindin genotype. This empirical finding of assortative mating based on sperm Bindin genotype could arise by linkage disequilibrium (LD) between interacting sperm and egg recognition loci. We then examine sequence variation in eight exons of the sea urchin egg receptor for sperm Bindin (EBR1). We find little evidence of LD among the eight exons of EBR1, yet strong evidence for LD between sperm Bindin and EBR1 overall, and varying degrees of LD between sperm Bindin among the eight exons. We reject the alternate hypotheses of LD driven by shared evolutionary histories, population structure, or close physical linkage between these interacting loci on the genome. The most parsimonious explanation for this pattern of LD is that it represents selection driven by assortative mating based on interactions among these sperm and egg loci. These findings indicate the importance of ongoing sexual selection in the maintenance of protein polymorphisms and LD, and more generally highlight how LD can be used as an indication of current mate choice, as opposed to historic selection.