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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Acc homoeoloci and the evolution of wheat genomes
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Acc homoeoloci and the evolution of wheat genomes

机译：同源同源物与小麦基因组进化

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The DNA sequences of wheat Acc-1 and Acc-2 loci, encoding the piastid and cytosolic forms of the enzyme acetyl-CoA carboxylase, were analyzed with a view to understanding the evolution of these genes and the origin of the three genomes in modern hexaploid wheat. Acc-1 and Acc-2 loci from each of the wheats Triticum urartu (A genome), Aegilops tauschii (D genome), Triticum turgidum (AB genome), and Triticum aestivum (ABD genome), as well as two Acc-2-related pseudogenes from T. urartu were sequenced. The 2.3-2.4 Mya divergence time calculated here for the three homoeologous chromosomes, on the basis of coding and intron sequences of the Acc-1 genes, is at the low end of other estimates. Our clock was calibrated by using 60 Mya for the divergence between wheat and maize. On the same time scale, wheat and barley diverged 11.6 Mya, based on sequences of Acc and other genes. The regions flanking the Acc genes are not conserved among the A, B, and D genomes. They are conserved when comparing homoeologous genomes of diploid, tetraploid, and hexaploid wheats. Substitution rates in intergenic regions consisting primarily of repetitive sequences vary substantially along the loci and on average are 3.5-fold higher than the Acc intron substitution rates. The composition of the Acc homoeoloci suggests haplotype divergence exceeding in some cases 0.5 Mya. Such variation might result in a significant overestimate of the time sincerntetraploid wheat formation, which occurred no more than 0.5 Mya.
机译：分析小麦Acc-1和Acc-2基因座的DNA序列，编码乙酰辅酶A羧化酶的乳突形式和胞质形式，以了解这些基因的进化以及现代六倍体中这三个基因组的起源小麦。来自小麦小麦（A基因组），牛油草（Aegilops tauschii（D基因组），小麦小麦（AB基因组）和小麦（ABD基因组）以及两个Acc-2-小麦中的每个Acc-1和Acc-2基因座对来自乌拉尔木霉的相关假基因进行测序。根据Acc-1基因的编码和内含子序列，此处计算的三个同源染色体的2.3-2.4 Mya发散时间在其他估计值的低端。我们使用60 Mya校准了小麦和玉米之间的差异。在同一时间尺度上，基于Acc和其他基因的序列，小麦和大麦发散了11.6 Mya。在A，B和D基因组中，Acc基因侧翼的区域不保守。当比较二倍体，四倍体和六倍体小麦的同源基因组时，它们是保守的。在主要由重复序列组成的基因间区域中的取代率沿基因座变化很大，平均比Acc内含子取代率高3.5倍。 Acc同系物的组成表明单倍型差异在某些情况下超过0.5 Mya。这种差异可能导致自四倍体小麦形成以来的时间明显过高，发生时间不超过0.5 Mya。

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