title: Rapid conversion of rDNA intergenic spacer of diploid mutants of rice derived from gamma-ray irradiated tetraploids.
abstract: The organization of tandemly repeated sequences of ribosomal DNA (rDNA) in rice mutants derived from gamma-irradiated tetraploids was analyzed. Southern hybridization analysis of nuclear DNA revealed that most of the intergenic spacers (IGSs) in mutant rDNA are replaced concertedly by new molecular species. The new IGSs are produced by the amplification of a subrepeat of about 250 bp. Results obtained from sequence analyses indicate that various intermediate molecular species of the subrepeat were formed during structuring of the IGS region and that many rearrangements occurred between them. These findings demonstrate the effectiveness of recurrent irradiation of tetraploids for inducing artificial genome rearrangement, and also indicate the extreme plasticity and variability of genome structure in plants.
authors.affiliation: Laboratory of Plant Breeding, Faculty of Agriculture, University of Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Fukuoka
authors.forename: Y
authors.initials: Y
authors.lastname: Kageyama
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: G
authors.initials: G
authors.lastname: Takeda
mesh_terms: D001483:Base Sequence; D015139:Blotting, Southern; D004252:DNA Mutational Analysis; D004275:DNA, Ribosomal / Q000235:genetics / Q000528:radiation effects*; D005720:Gamma Rays; D005784:Gene Amplification; D017343:Genes, Plant / Q000528:radiation effects*; D014644:Genetic Variation; D007438:Introns; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012275:Oryza / Q000235:genetics* / Q000528:radiation effects*; D012150:Polymorphism, Restriction Fragment Length; D011123:Polyploidy; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004275:DNA, Ribosomal