Guyot Romain, Yahiaoui Nabila, Feuillet Catherine, Keller Beat
Institute of Plant Biology, Zollikerstrasse 107, 8008 Zurich, Switzerland.
Funct Integr Genomics. 2004 Mar;4(1):47-58. doi: 10.1007/s10142-004-0103-4. Epub 2004 Feb 6.
Comparative RFLP mapping has revealed extensive conservation of marker order in different grass genomes. However, microcolinearity studies at the sequence level have shown rapid genome evolution and many exceptions to colinearity. Most of these studies have focused on a limited size of genomic fragment and the extent of microcolinearity over large distances or across entire genomes remains poorly characterized in grasses. Here, we have investigated the microcolinearity between the rice genome and a total of 1,500 kb from physical BAC contigs on wheat chromosome 1AS. Using ESTs mapped in wheat chromosome bins as an additional source of physical data, we have identified 27 conserved orthologous sequences between wheat chromosome 1AS and a region of 1,210 kb located on rice chromosome 5S. Our results extend the orthology described earlier between wheat chromosome group 1S and rice chromosome 5S. Microcolinearity was found to be frequently disrupted by rearrangements which must have occurred after the divergence of wheat and rice. At the Lr10 orthologous loci, microrearrangements were due to the insertion of mobile elements, but also originated from gene movement, amplification, deletion and inversion. These mechanisms of genome evolution are at the origin of the mosaic conservation observed between the orthologous regions. Finally, in silico mapping of wheat genes identified an intragenomic colinearity between fragments from rice chromosome 1L and 5S, suggesting an ancestral segmental duplication in rice.
比较性限制性片段长度多态性（RFLP）图谱分析揭示了不同禾本科植物基因组中标记顺序的广泛保守性。然而，序列水平上的微共线性研究表明基因组进化迅速，且共线性存在许多例外情况。这些研究大多集中在有限大小的基因组片段上，而禾本科植物中远距离或整个基因组范围内的微共线性程度仍未得到充分表征。在此，我们研究了水稻基因组与小麦1AS染色体上物理BAC重叠群共1500 kb区域之间的微共线性。利用定位在小麦染色体 bins 中的 ESTs 作为物理数据的额外来源，我们在小麦1AS染色体与水稻5S染色体上一个1210 kb的区域之间鉴定出27个保守的直系同源序列。我们的结果扩展了先前描述的小麦第1S染色体组与水稻5S染色体之间的直系同源关系。发现微共线性经常因重排而中断，这些重排肯定发生在小麦和水稻分化之后。在Lr10直系同源位点，微重排是由于移动元件的插入，但也源于基因移动、扩增、缺失和倒位。这些基因组进化机制是直系同源区域间镶嵌式保守现象的根源。最后，小麦基因的电子定位确定了水稻1L染色体和5S染色体片段之间的基因组内共线性，表明水稻中存在祖先片段重复。
