title: The widespread crucifer species Cardamine flexuosa is an allotetraploid with a conserved subgenomic structure.
abstract: The origin of Cardamine flexuosa (Wavy Bittercress) has been a conundrum for more than six decades. Here we identify its parental species, analyse its genome structure in comparison to parental genomes and describe intergenomic structural variations in C. flexuosa. Genomic in situ hybridization (GISH) and comparative chromosome painting (CCP) uncovered the parental genomes and the chromosome composition of C. flexuosa and its presumed diploid progenitors. Cardamine flexuosa is an allotetraploid (2n = 4x = 32), originating from two diploid species, Cardamine amara and Cardamine hirsuta (2n = 2x = 16). The two parental species display almost perfectly conserved chromosomal collinearity for seven out of the eight chromosomes. A 13 Mb pericentric inversion distinguishes chromosome CA1 from CH1. A comparative cytomolecular map was established for C. flexuosa by CCP/GISH. Whereas conserved chromosome collinearity between the C. amara and C. hirsuta subgenomes might have promoted intergenomic rearrangements through homeologous recombination, only one reciprocal translocation between two homeologues has occurred since the origin of C. flexuosa. The genome of C. flexuosa demonstrates that allopolyploids can maintain remarkably stable subgenomes over 10(4) -10(5)  yr throughout a wide distribution range. By contrast, the rRNA genes underwent genome-specific elimination towards a diploid-like number of loci.
authors.affiliation: Plant Cytogenomics research group, Central European Institute of Technology (CEITEC), Masaryk University, CZ-62500, Brno, Czech Republic.
authors.forename: Terezie
authors.initials: T
authors.lastname: Mandáková
authors.affiliation: Institute of Botany, Slovak Academy of Sciences, SK-84523, Bratislava, Slovakia.|Department of Botany, Faculty of Science, Charles University, CZ-12801, Prague, Czech Republic.
authors.forename: Karol
authors.initials: K
authors.lastname: Marhold
authors.affiliation: Plant Cytogenomics research group, Central European Institute of Technology (CEITEC), Masaryk University, CZ-62500, Brno, Czech Republic.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Lysak
mesh_terms: D031217:Cardamine / Q000235:genetics*; D020223:Chromosome Painting; D032461:Chromosomes, Plant / Q000235:genetics; D017124:Conserved Sequence; D004275:DNA, Ribosomal / Q000235:genetics; D004171:Diploidy; D056426:Genetic Loci / Q000235:genetics; D059646:Genome Size / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D017403:In Situ Hybridization; D007621:Karyotyping; D011123:Polyploidy; D013045:Species Specificity; D014178:Translocation, Genetic
chemical_list: D004275:DNA, Ribosomal
keywords: Brassicaceae; Cardamine flexuosa (Wavy Bittercress); GISH (genomic in situ hybridization); chromosome painting; genome collinearity; intergenome translocation; polyploidy