Hanson R, Zhao X P, Islam-Faridi M N, Paterson A, Zwick M, Crane C, McKnight T, Stelly D, Price H J
Department of Soil and Crop Sciences, TexasA&M University, College Station, Texas 77843-2474;
Am J Bot. 1998 Oct;85(10):1364-8.
Very little is known regarding how repetitive elements evolve inpolyploid organisms. Here we address this subject by fluorescent insitu hybridization (FISH) of 20 interspersed repetitive elements tometaphase chromosomes of the cotton AD-genome tetraploid Gossypiumhirsutum and its putative A- and D-genome diploid ancestors. Theseelements collectively represent an estimated 18% of the G.hirsutum genome, and constitute the majority of high-copyinterspersed repetitive elements in G. hirsutum. Seventeen ofthe elements yielded FISH signals on chromosomes of both G.hirsutum subgenomes, while three were A-subgenome specific. Hybridization of eight selected elements, two of which were A-subgenomespecific, to the A(2) genome of G. arboreum yielded asignal distribution that was similar to that of the G. hirsutumA-subgenome. However, when hybridized to the D(5) genome ofG. raimondii, the putative diploid ancestor of the G.hirsutum D-subgenome, none of the probes, including elements thatstrongly hybridized to both G. hirsutum subgenomes, yieldeddetectable signal. The results suggest that the majority, although notall, G. hirsutum interspersed repetitive elements haveundergone intergenomic concerted evolution following polyploidizationand that this has involved colonization of the D-subgenome byA-subgenome elements and/or replacement of D-subgenome elements byelements of the A-subgenometype.
关于重复元件在多倍体生物中如何进化，人们了解得非常少。在这里，我们通过对棉花AD基因组四倍体陆地棉及其假定的A基因组和D基因组二倍体祖先的中期染色体进行20个散在重复元件的荧光原位杂交（FISH）来解决这个问题。这些元件总共约占陆地棉基因组的18%，并且构成了陆地棉中高拷贝散在重复元件的大部分。其中17个元件在陆地棉两个亚基因组的染色体上产生了FISH信号，而另外3个是A亚基因组特异的。8个选定元件（其中2个是A亚基因组特异的）与亚洲棉的A(2)基因组杂交，产生的信号分布与陆地棉A亚基因组相似。然而，当与雷蒙德氏棉的D(5)基因组（陆地棉D亚基因组的假定二倍体祖先）杂交时，包括那些能与陆地棉两个亚基因组强烈杂交的元件在内，没有一个探针产生可检测到的信号。结果表明，虽然不是全部，但大多数陆地棉散在重复元件在多倍体化后经历了基因组间的协同进化，这涉及A亚基因组元件对D亚基因组的定殖和/或A亚基因组类型的元件对D亚基因组元件的替代。
