Department of Horticulture, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Institute of Food Crops, Provincial Key Laboratory of Agrobiology, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China.
New Phytol. 2018 Jun;218(4):1645-1657. doi: 10.1111/nph.15098. Epub 2018 Mar 25.
Centromeres in most higher eukaryotes are composed of long arrays of satellite repeats from a single satellite repeat family. Why centromeres are dominated by a single satellite repeat and how the satellite repeats originate and evolve are among the most intriguing and long-standing questions in centromere biology. We identified eight satellite repeats in the centromeres of tetraploid switchgrass (Panicum virgatum). Seven repeats showed characteristics associated with classical centromeric repeats with monomeric lengths ranging from 166 to 187 bp. Interestingly, these repeats share an 80-bp DNA motif. We demonstrate that this 80-bp motif may dictate translational and rotational phasing of the centromeric repeats with the cenH3 nucleosomes. The sequence of the last centromeric repeat, Pv156, is identical to the 5S ribosomal RNA genes. We demonstrate that a 5S ribosomal RNA gene array was recruited to be the functional centromere for one of the switchgrass chromosomes. Our findings reveal that certain types of satellite repeats, which are associated with unique sequence features and are composed of monomers in mono-nucleosomal length, are favorable for centromeres. Centromeric repeats may undergo dynamic amplification and adaptation before the centromeres in the same species become dominated by the best adapted satellite repeat.
在大多数高等真核生物中，着丝粒由单一卫星重复家族的长重复序列组成。为什么着丝粒主要由单一的卫星重复序列组成，以及卫星重复序列是如何起源和进化的，这些都是着丝粒生物学中最有趣和最长期的问题之一。我们在四倍体柳枝稷（Panicum virgatum）的着丝粒中鉴定出了 8 个卫星重复序列。7 个重复序列具有与经典着丝粒重复序列相关的特征，单体长度范围为 166-187bp。有趣的是，这些重复序列共享一个 80bp 的 DNA 基序。我们证明，这个 80bp 的基序可能决定了着丝粒重复序列与 cenH3 核小体的翻译和旋转相位。最后一个着丝粒重复序列 Pv156 的序列与 5S 核糖体 RNA 基因相同。我们证明，一个 5S 核糖体 RNA 基因簇被招募到柳枝稷的一条染色体上作为功能着丝粒。我们的研究结果表明，某些类型的卫星重复序列，它们与独特的序列特征相关，并且由单核小体长度的单体组成，有利于着丝粒。在同一物种的着丝粒被最佳适应的卫星重复序列主导之前，着丝粒重复序列可能会经历动态扩增和适应。
