Paux Etienne, Roger Delphine, Badaeva Ekatherina, Gay Georges, Bernard Michel, Sourdille Pierre, Feuillet Catherine
UMR ASP 1095, INRA, Université Blaise Pascal, 63100 Clermont-Ferrand, France.
Plant J. 2006 Nov;48(3):463-74. doi: 10.1111/j.1365-313X.2006.02891.x. Epub 2006 Sep 29.
Bread wheat (Triticum aestivum) is one of the most important crops worldwide. However, because of its large, hexaploid, highly repetitive genome it is a challenge to develop efficient means for molecular analysis and genetic improvement in wheat. To better understand the composition and molecular evolution of the hexaploid wheat homoeologous genomes and to evaluate the potential of BAC-end sequences (BES) for marker development, we have followed a chromosome-specific strategy and generated 11 Mb of random BES from chromosome 3B, the largest chromosome of bread wheat. The sequence consisted of about 86% of repetitive elements, 1.2% of coding regions, and 13% remained unknown. With 1.2% of the sequence length corresponding to coding sequences, 6000 genes were estimated for chromosome 3B. New repetitive sequences were identified, including a Triticineae-specific tandem repeat (Fat) that represents 0.6% of the B-genome and has been differentially amplified in the homoeologous genomes before polyploidization. About 10% of the BES contained junctions between nested transposable elements that were used to develop chromosome-specific markers for physical and genetic mapping. Finally, sequence comparison with 2.9 Mb of random sequences from the D-genome of Aegilops tauschii suggested that the larger size of the B-genome is due to a higher content in repetitive elements. It also indicated which families of transposable elements are mostly responsible for differential expansion of the homoeologous wheat genomes during evolution. Our data demonstrate that BAC-end sequencing from flow-sorted chromosomes is a powerful tool for analysing the structure and evolution of polyploid and highly repetitive genomes.
普通小麦（Triticum aestivum）是全球最重要的作物之一。然而，由于其庞大的六倍体、高度重复的基因组，开发小麦分子分析和遗传改良的有效方法具有挑战性。为了更好地理解六倍体小麦同源基因组的组成和分子进化，并评估BAC末端序列（BES）用于标记开发的潜力，我们采用了染色体特异性策略，从普通小麦最大的染色体3B上生成了11 Mb的随机BES。该序列约86%由重复元件组成，1.2%为编码区，13%仍未知。由于1.2%的序列长度对应于编码序列，估计3B染色体上有6000个基因。鉴定出了新的重复序列，包括一个小麦族特异性串联重复序列（Fat），它占B基因组的0.6%，并且在多倍体化之前在同源基因组中差异扩增。约10%的BES包含嵌套转座元件之间的连接，这些连接被用于开发物理和遗传作图的染色体特异性标记。最后，与节节麦D基因组的2.9 Mb随机序列进行序列比较表明，B基因组较大是由于重复元件含量较高。这也表明了哪些转座元件家族在进化过程中主要导致同源小麦基因组的差异扩增。我们的数据表明，从流式分选染色体进行BAC末端测序是分析多倍体和高度重复基因组结构和进化的有力工具。
