DNA sequence evidence for the segmental allotetraploid origin of maize
DNA sequence evidence for the segmental allotetraploid origin of maize
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DOI：
10.1073/pnas.94.13.6809
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发表时间：
1997-06-24
影响因子：
11.1
通讯作者：
Doebley, JF
中科院分区：
文献类型：
--
作者：
Gaut, BS;Doebley, JF
长期以来人们一直怀疑玉米是一次历史性的四倍体事件的产物。一些观察结果支持这种可能性，包括玉米基因组包含具有共线基因排列的重复染色体片段这一事实。这些重复片段中的一些基因已被测序。在这项研究中，我们检测了14对重复基因之间的序列差异模式。我们将差异模式与玉米基因组进化的四种模型——同源四倍体、基因组异源四倍体、部分异源四倍体和多次部分重复所预测的模式进行了比较。我们的分析表明，重复序列的合并时间分为两个不同的组，大致对应于2050万年和1140万年。这一观察结果有力地否定了玉米基因组是基因组异源四倍体事件产物的可能性，并且也难以与同源四倍体或多次独立的部分重复相协调。然而，部分异源四倍体模型预测存在两个（且仅有两个）合并时间。如果如这些数据所表明的那样，玉米基因组是一次部分异源四倍体事件的产物，那么它的两个二倍体祖先大约在2050万年前分化，而这次异源四倍体事件可能发生在大约1140万年前。玉米和高粱序列的比较表明，两个祖先二倍体中的一个与高粱共享的共同祖先比它与另一个祖先二倍体更近。
It has long been suspected that maize is the product of an historical tetraploid event, Several observations support this possibility, including the fact that the maize genome contains duplicated chromosomal segments with colinear gene arrangements, Some of the genes from these duplicated segments have been sequenced, In this study, we examine the pattern of sequence divergence among 14 pairs of duplicated genes, We compare the pattern of divergence to patterns predicted by four models of the evolution of the maize genome-autotetraploidy, genomic allotetraploidy, segmental allotetraploidy, and multiple segmental duplications, Our analyses indicate that coalescent times for duplicated sequences fall into two distinct groups, corresponding to roughly 20.5 and 11.4 million years, This observation strongly discounts the possibility that the maize genome is the product of a genomic allotetraploid event, and it is also difficult to reconcile with either autotetraploidy or multiple independent segmental duplications, However, the presence of two (and only two) coalescent times is predicted by the segmental allotetraploid model, If the maize genome is the product of a segmental allotetraploid event, as these data suggest, then its two diploid progenitors diverged roughly 20.5 million years ago (Mya), and the allotetraploid event probably occurred approximately 11.4 Mya, Comparison of maize and sorghum sequences suggests that one of the two ancestral diploids shares a more recent common ancestor with sorghum than it does with the other ancestral diploid.