Shaked H, Kashkush K, Ozkan H, Feldman M, Levy A A
Department of Plant Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel.
Plant Cell. 2001 Aug;13(8):1749-59. doi: 10.1105/tpc.010083.
Interspecific or intergeneric hybridization, followed by chromosome doubling, can lead to the formation of new allopolyploid species. Recent studies indicate that allopolyploid formation is associated with genetic and epigenetic changes, although little is known about the type of changes that occur, how rapidly they occur, and the type of sequences involved. To address these matters, we have surveyed F1 hybrids between diploid species from the wheat (Aegilops and Triticum) group and their derived allotetraploids by screening a large number of loci using amplified fragment length polymorphism and DNA gel blot analysis and by assaying the extent of cytosine methylation. We found that sequence elimination is one of the major and immediate responses of the wheat genome to wide hybridization or allopolyploidy, that it affects a large fraction of the genome, and that it is reproducible. In one cross between AE: sharonensis x AE: umbellulata, 14% of the loci from AE: sharonensis were eliminated compared with only 0.5% from AE: umbellulata, with most changes occurring in the F1 hybrid. In contrast, crosses between AE: longissima x T. urartu showed that sequence elimination was more frequent after chromosome doubling. Alterations in cytosine methylation occurred in approximately 13% of the loci, either in the F1 hybrid or in the allopolyploid. For eight of nine bands that were isolated, the sequences that underwent elimination corresponded to low-copy DNA, whereas alterations in methylation patterns affected both repetitive DNA sequences, such as retrotransposons, and low-copy DNA in approximately equal proportions.
种间或属间杂交，随后进行染色体加倍，可导致新的异源多倍体物种形成。最近的研究表明，异源多倍体的形成与遗传和表观遗传变化有关，尽管对于所发生变化的类型、变化的速度以及所涉及的序列类型知之甚少。为了解决这些问题，我们通过使用扩增片段长度多态性和DNA凝胶印迹分析筛选大量位点，并检测胞嘧啶甲基化程度，对小麦（山羊草属和小麦属）组二倍体物种及其衍生的异源四倍体之间的F1杂种进行了调查。我们发现，序列消除是小麦基因组对远缘杂交或异源多倍体的主要且即时的反应之一，它影响基因组的很大一部分，并且具有可重复性。在AE: sharonensis × AE: umbellulata的一次杂交中，与AE: umbellulata仅0.5%的位点相比，AE: sharonensis有14%的位点被消除，大多数变化发生在F1杂种中。相比之下，AE: longissima × 乌拉尔图小麦的杂交表明，染色体加倍后序列消除更为频繁。胞嘧啶甲基化的改变发生在约13%的位点，无论是在F1杂种还是异源多倍体中。对于分离出的九条带中的八条，发生消除的序列对应于低拷贝DNA，而甲基化模式的改变对重复DNA序列（如反转录转座子）和低拷贝DNA的影响比例大致相等。
