Kuittinen H, Aguadé M
Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Spain.
Genetics. 2000 Jun;155(2):863-72. doi: 10.1093/genetics/155.2.863.
An approximately 1.9-kb region encompassing the CHI gene, which encodes chalcone isomerase, was sequenced in 24 worldwide ecotypes of Arabidopsis thaliana (L.) Heynh. and in 1 ecotype of A. lyrata ssp. petraea. There was no evidence for dimorphism at the CHI region. A minimum of three recombination events was inferred in the history of the sampled ecotypes of the highly selfing A. thaliana. The estimated nucleotide diversity theta(TOTAL) = 0.004, theta(SIL) = 0. 005 was on the lower part of the range of the corresponding estimates for other gene regions. The skewness of the frequency spectrum toward an excess of low-frequency polymorphisms, together with the bell-shaped distribution of pairwise nucleotide differences at CHI, suggests that A. thaliana has recently experienced a rapid population growth. Although this pattern could also be explained by a recent selective sweep at the studied region, results from the other studied loci and from an AFLP survey seem to support the expansion hypothesis. Comparison of silent polymorphism and divergence at the CHI region and at the Adh1 and ChiA revealed in some cases a significant deviation of the direct relationship predicted by the neutral theory, which would be compatible with balancing selection acting at the latter regions.
对包含编码查尔酮异构酶的CHI基因的约1.9kb区域，在24个全球范围内的拟南芥生态型以及1个琴叶拟南芥岩生亚种生态型中进行了测序。在CHI区域没有发现二态性的证据。在高度自交的拟南芥抽样生态型的历史中推断至少发生了三次重组事件。估计的核苷酸多样性θ（总计）=0.004，θ（同义）=0.005，处于其他基因区域相应估计值范围的较低部分。频率谱向低频多态性过量倾斜，以及CHI处成对核苷酸差异的钟形分布，表明拟南芥最近经历了快速的种群增长。尽管这种模式也可以用研究区域最近的选择性清除来解释，但其他研究位点和AFLP调查的结果似乎支持扩张假说。CHI区域以及Adh1和ChiA处同义多态性与分歧的比较在某些情况下揭示了中性理论预测的直接关系的显著偏差，这与在后者区域起作用的平衡选择是一致的。
