Cytological characterization of the tandem repetitive sequences and their methylation status in the Antirrhinum majus genome.
Cytological characterization of the tandem repetitive sequences and their methylation status in the Antirrhinum majus genome.
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DOI：
10.1016/j.ygeno.2008.04.008
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发表时间：
2008-08
期刊：
影响因子：
4.4
通讯作者：
Dongfen Zhang;Qiuying Yang;Yongtao Ding;Xiaofeng Cao;Yongbiao Xue;Zhukuan Cheng
中科院分区：
文献类型：
--
作者：
Dongfen Zhang;Qiuying Yang;Yongtao Ding;Xiaofeng Cao;Yongbiao Xue;Zhukuan Cheng
串联重复序列是真核生物基因组中常见的DNA基序，通常嵌入异染色质区域。在大多数真核生物中，核糖体基因以及着丝粒和端粒或亚端粒与大量重复序列的串联阵列相关，并且通常代表完成全基因组测序的最终障碍。这些重复序列的性质使得很难估计它们的实际大小。本研究结合DNA fiber-FISH和粗线期染色体FISH两种细胞学技术，对金鱼草全基因组范围内的串联重复序列进行了分析，鉴定出4种类型的串联重复序列，即45 S rDNA、5S rDNA、CentA 1和CentA 2，它们代表了金鱼草的主要串联重复序列，总长度为18.50 Mb，占A. majus基因组。FISH检测发现，所有的串联重复序列都对应于粗线期染色体上的异染色质球沿着。此外，在体细胞和花粉母细胞从花药组织中的串联重复序列的甲基化状态进行了研究，使用针对5-甲基胞嘧啶的抗体结合顺序FISH分析。结果表明，这些重复序列在花药组织中，尤其是在粗线期的花粉母细胞中低甲基化。
Tandem repetitive sequences are DNA motifs common in the genomes of eukaryotic species and are often embedded in heterochromatic regions. In most eukaryotes, ribosomal genes, as well as centromeres and telomeres or subtelomeres, are associated with abundant tandem arrays of repetitive sequences and typically represent the final barriers to completion of whole-genome sequencing. The nature of these repeats makes it difficult to estimate their actual sizes. In this study, combining the two cytological techniques DNA fiber-FISH and pachytene chromosome FISH allowed us to characterize the tandem repeats distributed genome wide in Antirrhinum majus and identify four types of tandem repeats, 45S rDNA, 5S rDNA, CentA1, and CentA2, representing the major tandem repetitive components, which were estimated to have a total length of 18.50 Mb and account for 3.59% of the A. majus genome. FISH examination revealed that all the tandem repeats correspond to heterochromatic knobs along the pachytene chromosomes. Moreover, the methylation status of the tandem repeats was investigated in both somatic cells and pollen mother cells from anther tissues using an antibody against 5-methylcytosine combined with sequential FISH analyses. Our results showed that these repeats were hypomethylated in anther tissues, especially in the pollen mother cells at pachytene stage.