COMPARATIVE PHYSICAL MAPPING OF SEGMENTS OF THE GENOME OF Brassica oleracea VAR. alboglabra THAT ARE HOMOEOLOGOUS TO SEQUENCED REGIONS OF CHROMOSOMES 4 AND 5 OF Arabidopsis thaliana

John Innes Centre Norwich Research Park Norwich NR4 7UH UK

The Brassicas include the group of crops most closely related to the key model plant Arabidopsis thaliana. They therefore represent an obvious first target for the application of the genome sequence and functional genomics data being generated from Arabidopsis. The Brassicas also provide an excellent opportunity to study the mechanisms effecting genome evolution in plants. To support work in these areas, we have constructed and characterized a new BAC library (the JBO library) using genomic DNA from Brassica oleracea var. alboglabra and the transformation-competent vector pBIBAC2. We have used the library to analyze the extent of conservation of triplicated (paralogous) segments of the B. oleracea genome relative to their homoeologous regions in the genome of Arabidopsis. The relatively large size of the inserts in the JBO BACs (average 145kb) was crucial to our near-complete representation in BAC contigs of 6 regions of the genome of B. oleracea. Details will be presented of the extensive divergence we have observed in gene content, gene order and gene spacing between the 2 regions of the genome of Arabidopsis and their corresponding 6 regions in the genome of B. oleracea.