Lee Y H, Ota T, Vacquier V D
Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, LaJolla 92093-0202.
Mol Biol Evol. 1995 Mar;12(2):231-8. doi: 10.1093/oxfordjournals.molbev.a040200.
Lysin is a 16kDa acrosomal protein used by abalone sperm to create a hole in the egg vitelline envelope (VE). The interaction of lysin with the VE is species-selective and is one step in the multistep fertilization process that restricts heterospecific (cross-species) fertilization. For this reason, the evolution of lysin could play a role in establishing prezygotic reproductive isolation between species. Previously, we sequenced sperm lysin cDNAs from seven California abalone species and showed that positive Darwinian selection promotes their divergence. In this paper an additional 13 lysin sequences are presented representing species from Japan, Taiwan, Australia, New Zealand, South Africa, and Europe. The total of 20 sequences represents the most extensive analysis of a fertilization protein to date. The phylogenetic analysis divides the sequences into two major clades, one composed of species from the northern Pacific (California and Japan) and the other composed of species from other parts of the world. Analysis of nucleotide substitution demonstrates that positive selection is a general process in the evolution of this fertilization protein. Analysis of nucleotide and codon usage bias shows that neither parameter can account for the robust data supporting positive selection. The selection pressure responsible for the positive selection on lysin remains unknown.
溶素是一种16千道尔顿的顶体蛋白，鲍鱼精子利用它在卵黄膜（VE）上制造一个孔。溶素与卵黄膜的相互作用具有物种选择性，是多步骤受精过程中的一个步骤，该过程限制了异种（跨物种）受精。因此，溶素的进化可能在建立物种之间的合子前生殖隔离中发挥作用。此前，我们对来自七种加利福尼亚鲍鱼物种的精子溶素cDNA进行了测序，并表明正达尔文选择促进了它们的分化。在本文中，我们展示了另外13个溶素序列，代表来自日本、台湾、澳大利亚、新西兰、南非和欧洲的物种。这20个序列的总数代表了迄今为止对一种受精蛋白最广泛的分析。系统发育分析将这些序列分为两个主要分支，一个由北太平洋（加利福尼亚和日本）的物种组成，另一个由世界其他地区的物种组成。核苷酸取代分析表明，正选择是这种受精蛋白进化中的一个普遍过程。核苷酸和密码子使用偏好分析表明，这两个参数都无法解释支持正选择的有力数据。导致溶素正选择的选择压力仍然未知。
