Evolution of ribosomal DNA unit on the X chromosome independent of autosomal units in the liverwort Marchantia polymorpha |
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| Authors: | Masaki Fujisawa Shigeki Nakayama Tomohisa Nishio Mariko Fujishita Kiwako Hayashi Kimitsune Ishizaki Masataka Kajikawa Katsuyuki T. Yamato Hideya Fukuzawa Kanji Ohyama |
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| Affiliation: | (1) Laboratory of Plant Molecular Biology, Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan;(2) Genetic Diversity Department, National Institute of Agrobiological Sciences, Kannondai, Tsukuba 305-8602, Japan;(3) Bio-oriented Technology Research Advancement Institution, Tokyo 105-0001, Japan;(4) Present address: Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8562, Japan;(5) Present address: Laboratory of Plant Molecular Genetics, Research Institute of Agricultural Resources, Ishikawa Agricultural College, 1-308, Suematsu, Nonoichi-machi, Ishikawa 921-8836, Japan |
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| Abstract: | In the haploid dioecious liverwort, Marchantia polymorpha, the X chromosome, but not the Y, carries a cluster of ribosomal RNA genes (rDNAs). Here we show that sequences of 5S, 17S, 5.8S and 26S rDNAs are highly conserved (>99% identity) between the X chromosomal and autosomal rDNA repeat units, but the intergenic spacer sequences differ considerably. The most prominent difference is the presence of a 615-bp DNA fragment in the intergenic spacer, X615, which has accumulated predominantly in the rDNA cluster of the X chromosome. These observations suggest that the rDNA repeat unit on the X chromosome evolved independently of that on autosomes, incorporating sex chromosome-specific sequences. This revised version was published online in July 2006 with corrections to the Cover Date. |
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| Keywords: | fluorescence in-situ hybridization intergenic spacer liverwort Marchantia ribosomal DNA X chromosome |
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