title: Elimination and rearrangement of parental rDNA in the allotetraploid Nicotiana tabacum.
abstract: Origin and rearrangement of ribosomal DNA repeats in natural allotetraploid Nicotiana tabacum are described. Comparative sequence analysis of the intergenic spacer (IGS) regions of Nicotiana tomentosiformis (the paternal diploid progenitor) and Nicotiana sylvestris (the maternal diploid progenitor) showed species-specific molecular features. These markers allowed us to trace the molecular evolution of parental rDNA in the allopolyploid genome of N. tabacum; at least the majority of tobacco rDNA repeats originated from N. tomentosiformis, which endured reconstruction of subrepeated regions in the IGS. We infer that after hybridization of the parental diploid species, rDNA with a longer IGS, donated by N. tomentosiformis, dominated over the rDNA with a shorter IGS from N. sylvestris; the latter was then eliminated from the allopolyploid genome. Thus, repeated sequences in allopolyploid genomes are targets for molecular rearrangement, demonstrating the dynamic nature of allopolyploid genomes.
authors.affiliation: Department of Cytology and Genetics, University of Vienna, Austria.
authors.forename: R A
authors.initials: RA
authors.lastname: Volkov
authors.forename: N V
authors.initials: NV
authors.lastname: Borisjuk
authors.forename: I I
authors.initials: II
authors.lastname: Panchuk
authors.forename: D
authors.initials: D
authors.lastname: Schweizer
authors.forename: V
authors.initials: V
authors.lastname: Hemleben
mesh_terms: D001483:Base Sequence; D018744:DNA, Plant / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D019143:Evolution, Molecular; D015321:Gene Rearrangement; D018745:Genome, Plant; D008969:Molecular Sequence Data; D010947:Plants, Toxic; D011110:Polymorphism, Genetic; D011123:Polyploidy; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014026:Nicotiana / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal