Pires, J. Chris , Xiong , Zhiyong .
Homoeologous chromosome pairing and rearrangements identified in allopolyploid Brassica napus by an integrated BAC-FISH karyotype of diploid Brassica.
Study of the chromosomes of Brassica rapa (2n = 20, A genome), Brassica oleracea (2n = 18, C genome), and Brassica napus (2n = 38, AC genome) has been difficult due to small chromosome size and lack of distinct karyological features. To identify all 10 pairs of B. rapa chromosomes and integrate the karyotype with genetic and physical maps, a multicolor fluorescence in situ hybridization (FISH) procedure was developed. We used16 bacterial artificial chromosomes (BACs) that have been genetically and physically mapped and sequenced as part of the Multinational Brassica Genome Project (MBGP). Given the close phylogenentic relationship and synteny of the A and C genomes, we were able to perform reciprocal FISH experiments: B. rapa and B. oleracea BAC clones were both co-hybridized to B. rapa chromosomes, and then to B. oleracea chromosomes. When this same BAC-FISH karyotype cocktail is applied to allopolyploid B. napus followed by a second sequential genomic in situ hybridization (GISH), we are able to identify all the chromosomes of B. napus. Our procedure was then simplified by developing a set of repetitive DNA probes that collectively identify all of the Brassica chromosomes. To our knowledge, this is the first homoeologous chromosome painting toolkit developed for allopolyploid plants. This molecular cytogenetic approach can be used to precisely identify pairing and chromosomal rearrangements that until now have only been inferred by molecular markers. More generally, our robust karotype toolkit should facilitate the study of the chromosomal relationships among diploid and allopolyploid species in the genus Brassica.
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1 - University of Missouri, Biological Sciences, 311 Bond Life Sciences Center, 1201 Rollins Street , Columbia, MO, 65211-7310, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood C/Snowbird Center
Date: Monday, July 27th, 2009
Time: 11:15 AM