Innan H, Tajima F, Terauchi R, Miyashita N T
Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Japan.
Genetics. 1996 Aug;143(4):1761-70. doi: 10.1093/genetics/143.4.1761.
Nucleotide variation in the Adh region of the wild plant Arabidopsis thaliana was analyzed in 17 ecotypes sampled worldwide to investigate DNA polymorphism in natural plant populations. The investigated 2.4-kb Adh region was divided into four blocks by intragenic recombinations between two parental sequence types that diverged 6.3 million years (Myr) ago, if the nucleotide mutation rate mu = 10(-9) is assumed. Within each block, dimorphism of segregating variations was observed with intermediate frequencies, which caused a substantial amount of nucleotide variation in A. thaliana at the species level. The first recombination introduced the divergent variation that resulted in dimorphism in this plant species approximately 3.3 Myr ago, and three subsequent intragenic combinations have occurred sporadically in approximately 1.1-Myr intervals. It was shown that there was only a limited number (six) of sequence types in this species and that no clear association was observed between sequence type and geographic origin. Taken together, these results suggest that A. thaliana has spread over the world only recently. It can be concluded that recombination played an important role in the evolutionary history of A. thaliana, especially through the generation of DNA polymorphism in the natural populations of this plant species.
对全球采集的17个生态型的野生植物拟南芥的乙醇脱氢酶（Adh）区域的核苷酸变异进行了分析，以研究天然植物种群中的DNA多态性。如果假设核苷酸突变率μ = 10^(-9)，那么所研究的2.4 kb的Adh区域通过630万年前分化的两种亲本序列类型之间的基因内重组被分为四个区段。在每个区段内，观察到分离变异的二态性，其频率处于中等水平，这在物种水平上导致了拟南芥中大量的核苷酸变异。第一次重组引入了导致该植物物种大约330万年前出现二态性的分歧变异，随后的三次基因内重组以大约110万年的间隔零星发生。结果表明，该物种中只有数量有限（六种）的序列类型，并且在序列类型和地理起源之间未观察到明显关联。综上所述，这些结果表明拟南芥只是在最近才遍布全球。可以得出结论，重组在拟南芥的进化历史中发挥了重要作用，特别是通过在该植物物种的自然种群中产生DNA多态性。
