Evolution of ribosomal DNA unit on the X chromosome independent of autosomal units in the liverwort Marchantia polymorpha.
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.
Fujisawa
Masaki
M
Laboratory of Plant Molecular Biology, Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Nakayama
Shigeki
S
Nishio
Tomohisa
T
Fujishita
Mariko
M
Hayashi
Kiwako
K
Ishizaki
Kimitsune
K
Kajikawa
Masataka
M
Yamato
Katsuyuki T
KT
Fukuzawa
Hideya
H
Ohyama
Kanji
K
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
D004275:DNA, Ribosomal