title: Evolution of ribosomal DNA unit on the X chromosome independent of autosomal units in the liverwort Marchantia polymorpha.
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.
authors: Laboratory of Plant Molecular Biology, Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors: Masaki
authors: M
authors: Fujisawa
authors: Shigeki
authors: S
authors: Nakayama
authors: Tomohisa
authors: T
authors: Nishio
authors: Mariko
authors: M
authors: Fujishita
authors: Kiwako
authors: K
authors: Hayashi
authors: Kimitsune
authors: K
authors: Ishizaki
authors: Masataka
authors: M
authors: Kajikawa
authors: Katsuyuki T
authors: KT
authors: Yamato
authors: Hideya
authors: H
authors: Fukuzawa
authors: Kanji
authors: K
authors: Ohyama
mesh_terms: D015139:Blotting, Southern; D002875:Chromosomes / Q000648:ultrastructure*; D017124:Conserved Sequence; D004275:DNA, Ribosomal / Q000235:genetics* / Q000648:ultrastructure*; D015723:Gene Library; D016678:Genome; D035926:Hepatophyta / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008957:Models, Genetic; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D014960:X Chromosome
chemical_list: D004275:DNA, Ribosomal