Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Plateau Institute of Biology, Chinese Academy of Sciences, Xining 810001, China.
Theor Appl Genet. 2013 Jul;126(7):1885-96. doi: 10.1007/s00122-013-2103-z. Epub 2013 May 1.
Eleven tandemly repetitive sequences were identified from a Cot-1 library by FISH and sequence analysis of alfalfa (Medicago sativa). Five repetitive sequences (MsCR-1, MsCR-2, MsCR-3, MsCR-4, and MsCR-5) were centromeric or pericentromeric, of which three were satellite DNAs and two were minisatellite DNAs. Monomers of 144, 148, and 168 bp were identified in MsCR-1, MsCR-2, and MsCR-3, respectively, while 15 and 39 bp monomers were identified in MsCR-4 and MsCR-5, respectively. Three repetitive sequences were characterized as subtelomeric; one repetitive sequence, MsTR-1, had a 184 bp monomer, and two repetitive sequences had fragments of 204 and 327 bp. Sequence analysis revealed homology (70-80 %) between MsTR-1 and a highly repeated sequence (C300) isolated from M. ssp. caerulea. Three identified repetitive sequences produced hybridization signals at multiple sites in a few of the chromosomes; one repetitive sequence was identified as the E180 satellite DNA previously isolated from M. sativa, while the other 163 and 227 bp fragments had distinct sequences. Physical mapping of the repetitive sequences with double-target FISH revealed different patterns. Thus, nine novel tandemly repetitive sequences that can be adopted as distinct chromosome markers in alfalfa were identified in this study. Furthermore, the chromosome distribution of each sequence was well described. Though significant chromosome variations were detected within and between cultivars, a molecular karyotype of alfalfa was suggested with the chromosome markers we identified. Therefore, these novel chromosome markers will still be a powerful tool for genome composition analysis, phylogenetic studies, and breeding applications.
从紫花苜蓿（Medicago sativa）的 Cot-1 文库中通过 FISH 和序列分析鉴定了 11 个串联重复序列。其中 5 个重复序列（MsCR-1、MsCR-2、MsCR-3、MsCR-4 和 MsCR-5）位于着丝粒或着丝粒周围，其中 3 个是卫星 DNA，2 个是微卫星 DNA。在 MsCR-1、MsCR-2 和 MsCR-3 中分别鉴定出 144、148 和 168 bp 的单体，而在 MsCR-4 和 MsCR-5 中分别鉴定出 15 和 39 bp 的单体。3 个重复序列被表征为端粒序列；一个重复序列 MsTR-1 具有 184 bp 的单体，另外两个重复序列具有 204 和 327 bp 的片段。序列分析显示 MsTR-1 与从 M. ssp. caerulea 分离出的高度重复序列（C300）具有同源性（70-80%）。鉴定出的 3 个重复序列在少数染色体的多个位点产生杂交信号；一个重复序列被鉴定为先前从紫花苜蓿中分离出的 E180 卫星 DNA，而其他 163 和 227 bp 片段具有独特的序列。用双靶标 FISH 对重复序列进行物理作图显示出不同的模式。因此，本研究在紫花苜蓿中鉴定出 9 个新的串联重复序列，可作为其独特的染色体标记。此外，还很好地描述了每个序列的染色体分布。尽管在品种内和品种间检测到显著的染色体变异，但我们鉴定的染色体标记提出了紫花苜蓿的分子核型。因此，这些新的染色体标记仍然是基因组组成分析、系统发育研究和育种应用的有力工具。
