Molecular and General Genetics MGG

, Volume 263, Issue 3, pp 388–394 | Cite as

Quantification of total genomic DNA and selected repetitive sequences reveals concurrent changes in different DNA families in indica and japonica rice

  • N. Ohmido
  • K. Kijima
  • Y. Akiyama
  • J. H. de Jong
  • K. Fukui
ORIGINAL PAPER

Abstract

This paper describes a fluorescence in situ hybridization (FISH) analysis of three different repetitive sequence families, which were mapped to mitotic metaphase chromosomes and extended DNA fibers (EDFs) of the two subspecies of rice (Oryza sativa), indica and japonica (2n=2x=24). The repeat families studied were (1) the tandem repeat sequence A (TrsA), a functionally non-significant repeat; (2) the [TTTAGGG]n telomere sequence, a non-transcribed, tandemly repeated but functionally significant repeat; and (3) the 5S ribosomal RNA (5S rDNA). FISH of the TrsA repeat to metaphase chromosomes of indica and japonica cultivars revealed clear signals at the distal ends of twelve and four chromosomes, respectively. As shown in a previous report, the 17S ribosomal RNA genes (17S rDNA) are located at the nucleolus organizers (NORs) on chromosomes 9 and 10 of the indica cultivar. However, the japonica rice lacked the rDNA signals on chromosome 10. The size of the 5S rDNA repeat block, which was mapped on the chromosome 11 of both cultivars, was 1.22 times larger in the indica than in the japonica genome. The telomeric repeat arrays at the distal ends of all chromosome arms were on average three times longer in the indica genome than in the japonica genome. Flow cytometric measurements revealed that the nuclear DNA content of indica rice is 9.7% higher than that of japonica rice. Our data suggest that different repetitive sequence families contribute significantly to the variation in genome size between indica and japonica rice, though to different extents. The increase or decrease in the copy number of several repetitive sequences examined here may indicate the existence of a directed change in genome size in rice. Possible reasons for this phenomenon of concurrent evolution of various repeat families are discussed.

Key words Repetitive sequences Oryza sativa L. indica rice japonica rice Genome size 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • N. Ohmido
    • 1
  • K. Kijima
    • 1
  • Y. Akiyama
    • 1
  • J. H. de Jong
    • 4
  • K. Fukui
    • 5
  1. 1.Hokuriku National Agricultural Experiment Station, Joetsu 943-0193, JapanJP
  2. 2.Graduate School of Science and Technology, Niigata University, Niigata 950-2181, JapanJP
  3. 3.Japan Science and Technology Corporation, Kawaguchi 332-0012, JapanJP
  4. 4.Laboratory of Genetics, Wageningen University, Dreijenlaan 2, 6703 HA, Wageningen, The NetherlandsNL
  5. 5.Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita 565-0871, Osaka, Japan E-mail: kfukui@cell.bio.eng.osaka-u.ac.jp Tel.: +81-6-68797440; Fax: +81-6-68797441JP

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