Molecules and Cells

Korean Society for Molecular and Cellular Biology (한국분자세포생물학회)
권호 표지

Characterization of rDNAs and Tandem Repeats in the Heterochromatin of Brassica rapa

  • Lim, Ki-Byung (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • de Jong, Hans (Laboratory of Genetics, Wageningen University) ;
  • Yang, Tae-Jin (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Park, Jee-Young (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Kwon, Soo-Jin (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Kim, Jung Sun (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Lim, Myung-Ho (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Kim, Jin A (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Jin, Mina (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Jin, Yong-Moon (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Kim, Seog Hyung (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Lim, Yong Pyo (Department of Horticulture, Chungnam National University) ;
  • Bang, Jae-Wook (Department of Horticulture, Chungnam National University) ;
  • Kim, Ho-Il (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration) ;
  • Park, Beom-Seok (Brassica Genomics Team, National Institute of Agricultural Biotechnology, Rural Development Administration)
  • Received : 2005.02.07
  • Accepted : 2005.03.11
  • Published : 2005.06.30
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Abstract

We describe the morphology and molecular organization of heterochromatin domains in the interphase nuclei, and mitotic and meiotic chromosomes, of Brassica rapa, using DAPI staining and fluorescence in situ hybridization (FISH) of rDNA and pericentromere tandem repeats. We have developed a simple method to distinguish the centromeric regions of mitotic metaphase chromosomes by prolonged irradiation with UV light at the DAPI excitation wavelength. Application of this bleached DAPI band (BDB) karyotyping method to the 45S and 5S rDNAs and 176 bp centromere satellite repeats distinguished the 10 B. rapa chromosomes. We further characterized the centromeric repeat sequences in BAC end sequences. These fell into two classes, CentBr1 and CentBr2, occupying the centromeres of eight and two chromosomes, respectively. The centromere satellites encompassed about 30% of the total chromosomes, particularly in the core centromere blocks of all the chromosomes. Interestingly, centromere length was inversely correlated with chromosome length. The morphology and molecular organization of heterochromatin domains in interphase nuclei, and in mitotic and meiotic chromosomes, were further characterized by DAPI staining and FISH of rDNA and CentBr. The DAPI fluorescence of interphase nuclei revealed ten to twenty conspicuous chromocenters, each composed of the heterochromatin of up to four chromosomes and/or nucleolar organizing regions.

Keywords

Acknowledgement

Supported by : Rural Development Administration

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