Lin Jing-Zhong, Morrell Peter L, Clegg Michael T
Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
Genetics. 2002 Dec;162(4):2007-15. doi: 10.1093/genetics/162.4.2007.
Patterns of nucleotide sequence diversity are analyzed for three duplicate alcohol dehydrogenase loci (adh1-adh3) within a species-wide sample of 25 accessions of wild barley (Hordeum vulgare ssp. spontaneum). The adh1 and adh2 loci are tightly linked (recombination fraction <0.01) while the adh3 locus is inherited independently. Wild barley is predominantly self-fertilizing (approximately 98%), and as a consequence, effective recombination is restricted by the extreme reduction in heterozygosity. Large reductions in effective recombination, in turn, widen the conditions for linkage to influence nucleotide sequence diversity through the action of selective sweeps or background selection. These considerations would appear to predict (1) homogeneity in patterns of nucleotide sequence diversity, especially between closely linked loci, and (2) extensive linkage disequilibrium relative to random-mating species. In contrast to these expectations, the wild barley data reveal heterogeneity in patterns of nucleotide sequence diversity and levels of linkage disequilibrium that are indistinguishable from those observed at adh1 in maize, an outbreeding grass species.
对野生大麦（Hordeum vulgare ssp. spontaneum）25个种内样本中的三个重复乙醇脱氢酶基因座（adh1 - adh3）的核苷酸序列多样性模式进行了分析。adh1和adh2基因座紧密连锁（重组率<0.01），而adh3基因座独立遗传。野生大麦主要是自花授粉（约98%），因此，有效重组受到杂合性极度降低的限制。有效重组的大幅减少反过来又拓宽了连锁通过选择清除或背景选择作用影响核苷酸序列多样性的条件。这些考虑似乎预示着（1）核苷酸序列多样性模式的同质性，尤其是紧密连锁基因座之间的同质性，以及（2）相对于随机交配物种而言广泛的连锁不平衡。与这些预期相反，野生大麦的数据揭示了核苷酸序列多样性模式和连锁不平衡水平的异质性，这与在异交禾本科物种玉米的adh1中观察到的情况无法区分。
