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Polymorphism and replication of heterochromatic repeats in the DNA of Arabidopsis.

机译：拟南芥DNA中异源重复序列的多态性和复制。

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摘要

The composition of the individual eukaryote's genome and its variation within a species remain poorly defined. Even for a sequenced genome such as that of the model plant Arabidopsis thaliana accession Col-0, the large arrays of heterochromatic repeats are incompletely sequenced. We defined by flow cytometry a set of A. thaliana accessions that differ in measured nuclear genome size. Using these geographically separate populations, we assayed variation in the heterochromatic repeat arrays using two independent methods and identified substantial polymorphism among them, with variation by as much as a factor of two in the centromeric 180 bp repeat, in the 45S rDNA arrays and in the Athila retroelements. In the accession with highest measured genome size, Loh-0, we measured more than a two-fold increase in 5S RNA gene copies relative to Col-0; results from fluorescence in situ hybridization with 5S probes were consistent with the existence of size polymorphism between Loh-0 and Col-0 at the 5S loci. Comparative genomic hybridization results of Loh-0 and Col-0 did not support contiguous variation in copy number of protein-coding genes on the scale needed to explain their observed genome size difference. We developed a computational data model to test whether the variation we measured in the repeat fractions could account for the different genome sizes determined with flow cytometry, and found that this proposed relationship could account for about 50% of the variance in genome size among the accessions. Our finding of a negative relationship between measured genome size and the copy number of centromeric repeats was unexpected, as centromeres may make up the single largest repeat class in the genome. Heterochromatic repeats have been demonstrated to be much less than fully replicated in the endoreplicated cells of some taxa. We investigated whether under-replication of repeated heterochromatic sequences in the higher ploidy nuclei of Arabidopsis distorts our genome size measurements or our assessment of the amounts of heterochromatin in the accessions. We found the under-replication amounts we observed with flow cytometry to be insufficient by a factor of five to account for the negative relationship between measured genome size and centromeric repeat amount.
机译：单个真核生物基因组的组成及其在一个物种内的变异仍然不清楚。即使对于诸如模型植物拟南芥（Arabidopsis thaliana）登录号Col-0之类的测序基因组，异色重复序列的大阵列也不完整。我们通过流式细胞仪定义了一组拟南芥的种，它们在测量的核基因组大小上不同。使用这些地理上不同的种群，我们使用两种独立的方法测定了异色重复序列的变异，并确定了它们之间的实质多态性，在着丝粒180 bp重复序列，45S rDNA序列和DNA中，变异高达2倍。 Athila改装元素。在测得的最大基因组大小为Loh-0的材料中，我们测得的5S RNA基因拷贝相对于Col-0的增加两倍以上；与5S探针进行荧光原位杂交的结果与在5S基因座处Loh-0和Col-0之间存在大小多态性是一致的。 Loh-0和Col-0的比较基因组杂交结果不支持蛋白质编码基因的拷贝数在解释其观察到的基因组大小差异所需的规模上连续变化。我们开发了计算数据模型来测试我们在重复级分中测得的变异是否可以解释通过流式细胞仪确定的不同基因组大小，并发现该提议的关系可以解释这些种质之间基因组大小变异的大约50％ 。我们发现测量的基因组大小与着丝粒重复序列的拷贝数之间存在负相关关系，这是出乎意料的，因为着丝粒可能构成了基因组中最大的单个重复序列。异色重复已被证明远小于在某些分类单元的内复制细胞中完全复制。我们调查了拟南芥较高倍性核中重复异色序列的重复复制是否扭曲了我们的基因组大小测量结果或我们对种质中异染色质含量的评估。我们发现我们用流式细胞仪观察到的重复不足量不足五分之一，以解释测量的基因组大小和着丝粒重复量之间的负相关关系。

著录项

  • 作者

    Davison, Jerry.;

  • 作者单位

    University of Washington.;

  • 授予单位 University of Washington.;
  • 学科 Biology Molecular.; Biology Botany.; Biology Cell.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 74 p.
  • 总页数 74
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 分子遗传学;植物学;细胞生物学;
  • 关键词

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