Ribeiro Tiago, Marques André, Novák Petr, Schubert Veit, Vanzela André L L, Macas Jiri, Houben Andreas, Pedrosa-Harand Andrea
Laboratory of Plant Cytogenetics and Evolution, Federal University of Pernambuco (UFPE), Recife, PE, Brazil.
Laboratory of Genetic Resources, Campus Arapiraca, Federal University of Alagoas, Arapiraca, AL, Brazil.
Chromosoma. 2017 Mar;126(2):325-335. doi: 10.1007/s00412-016-0616-3. Epub 2016 Sep 19.
Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.
卫星DNA重复序列（或卫星DNA）是快速进化的序列，通常与浓缩的异染色质相关。为了测试在全着丝粒染色体物种中着丝粒和非着丝粒卫星DNA的染色体组织是否不同，我们鉴定并表征了全着丝粒莎草科物种纤毛刺子莞（2n = 10）、球形刺子莞（2n = 50）和细叶刺子莞（2n = 2x = 4和2n = 4x = 8）中的主要卫星DNA家族。虽然保守的着丝粒重复序列（存在于纤毛刺子莞和细叶刺子莞中）在两条染色单体上都显示出线性信号，但非着丝粒的物种特异性卫星DNA沿着染色体形成了不同的簇。两种重复类型的共定位在有丝分裂染色体上产生了梯状杂交模式。在间期，着丝粒卫星DNA分散，而非着丝粒卫星DNA聚集并部分共定位到染色中心。尽管聚集的卫星DNA呈现出带状杂交模式，但由于细叶刺子莞和纤毛刺子莞中同源物的杂交模式不规则，染色体对的识别受到了影响。这些差异可能是由细叶刺子莞中报道的减数分裂重组受限或受损引起的，或者是由复杂的染色体重排或同源中期染色体的不等凝聚引起的。因此，全着丝粒性影响染色体组织，导致着丝粒和非着丝粒卫星DNA的分布模式和凝聚动态存在差异。
