Lin J Z, Brown A H, Clegg M T
Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.
Proc Natl Acad Sci U S A. 2001 Jan 16;98(2):531-6. doi: 10.1073/pnas.98.2.531. Epub 2001 Jan 9.
Patterns of nucleotide sequence diversity in the predominantly self-fertilizing species Hordeum vulgare subspecies spontaneum (wild barley) are compared between the putative alcohol dehydrogenase 3 locus (denoted "adh3") and alcohol dehydrogenase 1 (adh1), two related but unlinked loci. The data consist of a sequence sample of 1,873 bp of "adh3" drawn from 25 accessions that span the species range. There were 104 polymorphic sites in the sequenced region of "adh3." The data reveal a strong geographic pattern of diversity at "adh3" despite geographic uniformity at adh1. Moreover, levels of nucleotide sequence diversity differ by nearly an order of magnitude between the two loci. Genealogical analysis resolved two distinct clusters of "adh3" alleles (dimorphic sequence types) that coalesce roughly 3 million years ago. One type consists of accessions from the Middle East, and the other consists of accessions predominantly from the Near East. The two "adh3" sequence types are characterized by a high level of differentiation between clusters ( approximately 2.2%), which induces an overall excess of intermediate frequency variants in the pooled sample. Finally, there is evidence of intralocus recombination in the "adh3" data, despite the high level of self-fertilization characteristic of wild barley.
在主要进行自花授粉的物种——大麦野生亚种（野生大麦）中，对假定的乙醇脱氢酶3基因座（称为“adh3”）和乙醇脱氢酶1（adh1）这两个相关但不连锁的基因座之间的核苷酸序列多样性模式进行了比较。数据包括从跨越该物种分布范围的25个种质中提取的1873 bp的“adh3”序列样本。在“adh3”的测序区域中有104个多态性位点。数据显示，尽管adh1在地理上具有一致性，但“adh3”存在强烈的地理多样性模式。此外，两个基因座之间的核苷酸序列多样性水平相差近一个数量级。系统发育分析解析出“adh3”等位基因的两个不同聚类（二态序列类型），它们大约在300万年前合并。一种类型由来自中东的种质组成，另一种类型主要由来自近东的种质组成。两种“adh3”序列类型的特征是聚类之间的高度分化（约2.2%），这导致合并样本中中频变异总体过剩。最后，尽管野生大麦具有高度自花授粉的特征，但在“adh3”数据中仍有基因座内重组的证据。
