Metz E C, Robles-Sikisaka R, Vacquier V D
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202, USA.
Proc Natl Acad Sci U S A. 1998 Sep 1;95(18):10676-81. doi: 10.1073/pnas.95.18.10676.
Strong positive Darwinian selection acts on two sperm fertilization proteins, lysin and 18-kDa protein, from abalone (Haliotis). To understand the phylogenetic context for this dramatic molecular evolution, we obtained sequences of mitochondrial cytochrome c oxidase subunit I (mtCOI), and genomic sequences of lysin, 18-kDa, and a G protein subunit. Based on mtDNA differentiation, four north Pacific abalone species diverged within the past 2 million years (Myr), and remaining north Pacific species diverged over a period of 4-20 Myr. Between-species nonsynonymous differences in lysin and 18-kDa exons exceed nucleotide differences in introns by 3.5- to 24-fold. Remarkably, in some comparisons nonsynonymous substitutions in lysin and 18-kDa genes exceed synonymous substitutions in mtCOI. Lysin and 18-kDa intron/exon segments were sequenced from multiple red abalone individuals collected over a 1,200-km range. Only two nucleotide changes and two sites of slippage variation were detected in a total of >29,000 nucleotides surveyed. However, polymorphism in mtCOI and a G protein intron was found in this species. This finding suggests that positive selection swept one lysin allele and one 18-kDa allele to fixation. Similarities between mtCOI and lysin gene trees indicate that rapid adaptive evolution of lysin has occurred consistently through the history of the group. Comparisons with mtCOI molecular clock calibrations suggest that nonsynonymous substitutions accumulate 2-50 times faster in lysin and 18-kDa genes than in rapidly evolving mammalian genes.
强烈的正向达尔文选择作用于鲍鱼（鲍属）的两种精子受精蛋白，即溶解素和18 kDa蛋白。为了理解这种显著分子进化的系统发育背景，我们获得了线粒体细胞色素c氧化酶亚基I（mtCOI）的序列，以及溶解素、18 kDa蛋白和一种G蛋白亚基的基因组序列。基于线粒体DNA的分化，北太平洋的四种鲍鱼物种在过去200万年（Myr）内分化，其余北太平洋物种在4 - 20 Myr的时间段内分化。溶解素和18 kDa外显子的种间非同义差异比内含子中的核苷酸差异高出3.5至24倍。值得注意的是，在一些比较中，溶解素和18 kDa基因中的非同义替换超过了mtCOI中的同义替换。我们对在1200公里范围内采集的多个红鲍个体的溶解素和18 kDa内含子/外显子片段进行了测序。在总共超过29000个核苷酸的检测中，仅检测到两个核苷酸变化和两个滑动变异位点。然而，在该物种中发现了mtCOI和一个G蛋白内含子的多态性。这一发现表明正向选择使一个溶解素等位基因和一个18 kDa等位基因固定下来。mtCOI和溶解素基因树之间的相似性表明，溶解素的快速适应性进化在该类群的历史中一直持续发生。与mtCOI分子钟校准的比较表明，溶解素和18 kDa基因中非同义替换的积累速度比快速进化的哺乳动物基因快2至50倍。
