Kawabe A, Yamane K, Miyashita N T
Laboratory of Plant Genetics, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Genetics. 2000 Nov;156(3):1339-47. doi: 10.1093/genetics/156.3.1339.
DNA variation in a 4.7-kb region of the cytosolic phosphoglucose isomerase (PgiC) locus was investigated for 21 ecotypes of Arabidopsis thaliana. The estimated nucleotide diversity was 0.0038, which was one-third of those in previously investigated loci. Since most of the nucleotide variations (93%) were singleton and doubleton, Tajima's test statistic was significantly negative. About 50% of nucleotide polymorphisms in exons were replacement, which caused significance in McDonald and Kreitman's test when compared with Arabis gemmifera and Cardaminopsis petraea. These results indicated that DNA polymorphism at the PgiC locus was not under neutrality. There were two divergent sequence types in the PgiC region, which were associated with allozyme variation. The Fast allozyme was shown to have originated from the Slow allozyme, since two outgroup species had the Slow form. A phylogenetic tree of ecotypes with the Fast allozyme had the shape of a star phylogeny. Mismatch distribution of the Fast allozyme ecotypes resembled that expected under an expanding population model. These results suggest positive selection for the Fast allozyme of the PGIC in A. thaliana.
对21种拟南芥生态型的胞质磷酸葡萄糖异构酶（PgiC）基因座4.7kb区域的DNA变异进行了研究。估计的核苷酸多样性为0.0038，是先前研究基因座的三分之一。由于大多数核苷酸变异（93%）为单态和双态，Tajima检验统计量显著为负。外显子中约50%的核苷酸多态性为替换型，与高山南芥和岩生碎米荠相比，在McDonald和Kreitman检验中具有显著性。这些结果表明，PgiC基因座的DNA多态性并非处于中性。PgiC区域存在两种不同的序列类型，它们与等位酶变异相关。快速等位酶被证明起源于慢速等位酶，因为两个外类群物种具有慢速形式。具有快速等位酶的生态型的系统发育树呈星状系统发育形状。快速等位酶生态型的错配分布类似于在种群扩张模型下预期的分布。这些结果表明拟南芥中PGIC的快速等位酶受到正选择。
