Kulikova Olga, Geurts René, Lamine Monique, Kim Dong-Jin, Cook Douglas R, Leunissen Jack, de Jong Hans, Roe Bruce A, Bisseling Ton
Laboratory of Molecular Biology, Department of Plant Sciences, Wageningen University, Wageningen, The Netherlands.
Chromosoma. 2004 Dec;113(6):276-83. doi: 10.1007/s00412-004-0315-3. Epub 2004 Oct 6.
Most eukaryotic centromeres contain long arrays of tandem repeats, with unit lengths of 150-300 bp. We searched for such repeats in the functional centromeres of the model legume Medicago truncatula (Medicago) accession Jemalong A17. To this end three repeats, MtR1, MtR2 and MtR3, were identified in 20 Mb of a low-pass, whole genome sequencing data set generated by a random shotgun approach. The nucleotide sequence composition, genomic organization and abundance of these repeats were characterized. Fluorescent in situ hybridization of these repeats on chromosomes at meiosis I showed that only the MtR3 repeat, encompassing stretches of 450 kb to more than 1.0 Mb, is located in the functional portion of all eight centromeres. MtR1 and MtR2 occupy distinct regions in pericentromeric heterochromatin. We also studied the presence and distribution of MtRs in Medicago accession R108-1, a genotype with a genome that is 20% smaller than that of Jemalong A17. We determined that while MtR3 is also centromeric on all pachytene bivalents in R108-1, MtR1 and MtR2 are not present in the R108 genome.
大多数真核生物的着丝粒包含长串联重复序列阵列，其单位长度为150 - 300 bp。我们在模式豆科植物蒺藜苜蓿（Medicago truncatula，简称Medicago）品种Jemalong A17的功能着丝粒中搜索此类重复序列。为此，在通过随机鸟枪法生成的低覆盖度全基因组测序数据集中的20 Mb区域内，鉴定出了三个重复序列，即MtR1、MtR2和MtR3。对这些重复序列的核苷酸序列组成、基因组组织和丰度进行了表征。在减数分裂I期对这些重复序列进行染色体荧光原位杂交显示，只有包含450 kb至超过1.0 Mb片段的MtR3重复序列位于所有八个着丝粒的功能部分。MtR1和MtR2占据着近着丝粒异染色质中的不同区域。我们还研究了MtRs在蒺藜苜蓿品种R108 - 1中的存在情况和分布，该基因型的基因组比Jemalong A17小20%。我们确定，虽然MtR3在R108 - 1的所有粗线期二价体上也是着丝粒的，但R108基因组中不存在MtR1和MtR2。
