Schmuths H, Hoffmann M H, Bachmann K
Department of Taxonomy, Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany.
Plant Biol (Stuttg). 2004 Mar-Apr;6(2):128-39. doi: 10.1055/s-2004-817837.
Range expansion from Pleistocene refugia and anthropogenic influences contribute to the present distribution pattern of Arabidopsis thaliana. We scored a genome-wide set of CAPSs and found two markers with an east-west geographic distribution across the Eurasian range of the species. Regions around the two SNPs were sequenced in 98 accessions, including newly collected plants from Middle Asia and Western Siberia. These regions correspond to a gene ( approximately 1500 bp) and a non-coding region ( approximately 500 bp) 300 kbp apart on chromosome 2. Nucleotide diversities, pi, of the two sequenced fragments were 0.0032 and 0.0130. The haplotypes of both sequences belonged to one of two groups: a rather uniform "Asian" and a more variable "European" haplotype group, on the basis of non-disjunct clusters of SNPs. Recombination between "Asian" and "European" haplotypes occurs where they meet. Especially in the "European" haplotype, many rare SNP variants representing independent mutations are scattered among the shared haplotype-specific SNPs. This agrees with previous suggestions of two large haplotype groups in A. thaliana and the post-glacial colonization of central Europe from the east and the west. A clear correlation between climatic factors and the haplotype distribution may reflect the dispersal history rather than local climate adaptation. The pattern of SNP variation within the contiguous sequences explains why only a minority of SNPs selected across the genome show evidence of this geographic pattern.
更新世避难所的范围扩张和人为影响促成了拟南芥目前的分布格局。我们对全基因组的一组CAPS标记进行了评分，发现有两个标记在该物种的欧亚分布范围内呈东西向地理分布。在98份材料中对这两个单核苷酸多态性（SNP）周围的区域进行了测序，其中包括从中亚和西西伯利亚新采集的植株。这些区域分别对应于2号染色体上相隔300千碱基对（kbp）的一个基因（约1500碱基对）和一个非编码区（约500碱基对）。两个测序片段的核苷酸多样性π分别为0.0032和0.0130。基于SNP的非间断聚类，这两个序列的单倍型都属于两个组中的一个：一个相当一致的“亚洲”单倍型组和一个更具变异性的“欧洲”单倍型组。“亚洲”和“欧洲”单倍型在相遇处发生重组。特别是在“欧洲”单倍型中，许多代表独立突变的罕见SNP变体散布在共享的单倍型特异性SNP之间。这与之前关于拟南芥存在两个大单倍型组以及中欧在冰期后从东部和西部殖民的观点一致。气候因素与单倍型分布之间的明显相关性可能反映的是扩散历史而非局部气候适应性。连续序列内SNP变异的模式解释了为什么在全基因组中选择的SNP中只有少数显示出这种地理模式的证据。
