title: Molecular evidence for transcription of genes on a B chromosome in Crepis capillaris.
abstract: Dispensable, supernumerary (B) chromosomes are found in diverse eukaryotic species. The origin and genetic consequences of B chromosomes have been the subjects of speculation for more than a century. Until now, there has been no molecular evidence that B chromosome DNA is transcribed and there is no unequivocal evidence as to their origin. B chromosomes are considered to be genetically inert although they appear to cause a variety of phenotypic effects. We report that members of one of two ribosomal RNA gene families that are confined to the B chromosomes of a plant, Crepis capillaris, are transcribed--thus providing the first molecular evidence of gene activity on B chromosomes. Sequence analysis of part of the A and B chromosome rRNA genes, together with comparisons with related species, indicates that the B chromosome rRNA genes originate from the A chromosome.
authors.affiliation: School of Molecular and Biomedical Science (Genetics), The University of Adelaide, South Australia, Australia.
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Leach
authors.forename: Andreas
authors.initials: A
authors.lastname: Houben
authors.forename: Bruce
authors.initials: B
authors.lastname: Field
authors.forename: Klaus
authors.initials: K
authors.lastname: Pistrick
authors.forename: Dmitri
authors.initials: D
authors.lastname: Demidov
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Timmis
mesh_terms: D001483:Base Sequence; D002869:Chromosome Aberrations; D032461:Chromosomes, Plant / Q000235:genetics*; D027468:Crepis / Q000235:genetics*; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D035264:Flowers / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D012340:RNA, Ribosomal, 5.8S / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012335:RNA, Ribosomal; D012340:RNA, Ribosomal, 5.8S