Allopolyploidy-Induced Rapid Genome Evolution in the Wheat (Aegilops–Triticum) Group
Allopolyploidy-Induced Rapid Genome Evolution in the Wheat (Aegilops–Triticum) Group
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DOI：
10.1105/tpc.010082
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发表时间：
2001-08
期刊：
影响因子：
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通讯作者：
H. Ozkan;A. Levy;M. Feldman
中科院分区：
文献类型：
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作者：
H. Ozkan;A. Levy;M. Feldman
为了更好地了解伴随异源多倍体形成的遗传事件，我们研究了山羊草和小麦的F1代和新形成的异源多倍体的8个DNA序列的消除速度和时间。总共分析了35个种间和属间杂种和22个衍生的异源多倍体，并与它们的直系亲本进行了比较。所研究的序列存在于小麦科所有二倍体物种中，但只存在于一个基因组中，在多倍体小麦中，要么存在于一对同源序列(染色体特异序列[CSSs])中，要么存在于同一基因组的几对(基因组特有序列[GSSS])中。研究发现，在新合成的异源多倍体中，CSS和GSSS的快速消除是一种普遍现象。GSSS的消除在F1植株中已经开始，并在第二代或第三代异源多倍体完成，而CSSs的消除从第一代异源多倍体开始，在第二代或第三代完成。与自然界中不存在的异源多倍体相比，基因组结构与自然多倍体相似的异源多倍体的序列消除开始得更早。消除是一个非随机和可重复的事件，其方向由杂交种或异源多倍体的基因组组合决定。它不受亲本的基因型、细胞质或倍性水平的影响，也不是基因组间重组的结果。异源多倍体诱导的序列消除发生在相当大一部分基因组和明显非编码的序列中。这一发现表明在多倍体水平上增强同源染色体的分化，从而为新形成的异源多倍体的类似二倍体的减数分裂行为提供了物理基础。在我们看来，这种快速的基因组调整可能有助于成功地建立新形成的异源多倍体作为新物种。
To better understand genetic events that accompany allopolyploid formation, we studied the rate and time of elimination of eight DNA sequences in F1 hybrids and newly formed allopolyploids of Aegilops and Triticum. In total, 35 interspecific and intergeneric F1 hybrids and 22 derived allopolyploids were analyzed and compared with their direct parental plants. The studied sequences exist in all the diploid species of the Triticeae but occur in only one genome, either in one homologous pair (chromosome-specific sequences [CSSs]) or in several pairs of the same genome (genome-specific sequences [GSSs]), in the polyploid wheats. It was found that rapid elimination of CSSs and GSSs is a general phenomenon in newly synthesized allopolyploids. Elimination of GSSs was already initiated in F1 plants and was completed in the second or third allopolyploid generation, whereas elimination of CSSs started in the first allopolyploid generation and was completed in the second or third generation. Sequence elimination started earlier in allopolyploids whose genome constitution was analogous to natural polyploids compared with allopolyploids that do not occur in nature. Elimination is a nonrandom and reproducible event whose direction was determined by the genomic combination of the hybrid or the allopolyploid. It was not affected by the genotype of the parental plants, by their cytoplasm, or by the ploidy level, and it did not result from intergenomic recombination. Allopolyploidy-induced sequence elimination occurred in a sizable fraction of the genome and in sequences that were apparently noncoding. This finding suggests a role in augmenting the differentiation of homoeologous chromosomes at the polyploid level, thereby providing the physical basis for the diploid-like meiotic behavior of newly formed allopolyploids. In our view, this rapid genome adjustment may have contributed to the successful establishment of newly formed allopolyploids as new species.