Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Flowering Time Divergence And Genomic Rearrangements In Resynthesized Brassica Polyploids (Brassicaceae)

J. Chris Pires¹ , Robert T. Gaeta¹ , Enrique J. Leon¹ , Jianwei Zhao^{1, 2} , M. Eric Schranz^1,3 , Pablo A. Quijada¹ , Lewis N. Lukens^{1, 4} , Thomas C. Osborn¹

¹  Department of Agronomy, 1575 Linden Drive, University of Wisconsin, Madison, Wisconsin 53706-1597, USA

²  Agronomy Department, Huazhong Agricultural University, Wuhan, 43007, China.

³  Hans-Knöll-Straße 8, Max Planck Institute of Chemical Ecology, 07745 Jena, Germany

⁴  Department of Plant Agriculture, University of Guelph, Guelph, Ontario, N1G 2W1, Canada

Novel phenotypes often arise immediately following polyploidization. Separate lineages derived from a single resynthesized Brassica napus allopolyploid show rapidly evolved heritable differences in flowering time. We assessed the early- and late-flowering B. napus lineages for changes in genome structure, and for changes in transcript levels of four homoeologous FLOWERING LOCUS C (FLC) loci. The two lines had different chromosomal rearrangements and changes in transcript level for two FLC genes, while a third FLC gene was epigenetically silenced in all polyploids. A key question that emerges from this study is to what degrees are evolutionary changes directed as opposed to random? Results from an ongoing investigation of 50 identical B. napus allopolyploids are beginning to reveal the dynamics of changes in phenotype, genotype, and transcriptome at the early stages in polyploid evolution. To date, it appears that epigenetic changes occur immediately after polyploid formation, and that chromosomal rearrangements soon follow. The effect of these changes on gene expression and phenotype are under investigation.