title: Ribosomal DNAs: an exception to the conservation of gene order in rice genomes.
abstract: rDNA (18S-5.8S-25S rDNA) and 5S rDNA loci were visualized on the chromosomes of six species of the genus Oryza by fluorescence in situ hybridization (FISH) and the labeled rice chromosomes were identified based on their condensation patterns. As a result, the chromosomes harboring rDNA and/or 5S rDNA loci were determined in the complement for all the known rice genomes. Variation in the location of the rDNA loci indicated the transpositional nature of the rDNAs in the genus Oryza, as also suggested in Triticeae and Allium. Comparative analysis of the locations of rDNA loci among rice, maize and wheat revealed that variability in the physical location of the rDNA loci was characteristic of the genus Oryza and also of the genera of Gramineae. This variability in the location of the rDNA loci between evolutionarily related species is in sharp contrast to the conservation of the general order of genes in their genomes.
authors.affiliation: Department of Plant Science and Resources, College of Bioresource Sciences, Nihon University, Fujisawa, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Shishido
authors.forename: Y
authors.initials: Y
authors.lastname: Sano
authors.forename: K
authors.initials: K
authors.lastname: Fukui
mesh_terms: D002874:Chromosome Mapping; D015342:DNA Probes; D018744:DNA, Plant / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D018745:Genome, Plant; D017404:In Situ Hybridization, Fluorescence; D012275:Oryza / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012340:RNA, Ribosomal, 5.8S / Q000235:genetics; D014908:Triticum / Q000235:genetics; D003313:Zea mays / Q000235:genetics
chemical_list: D015342:DNA Probes; D018744:DNA, Plant; D004275:DNA, Ribosomal; D018749:RNA, Plant; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D012340:RNA, Ribosomal, 5.8S; C065039:RNA, ribosomal, 25S