PAG-IV Plant Genome IV Conference

Town & Country Conference Center, San Diego, CA, January, 1995.

W20
Physical Mapping of Arabidopsis Chromosomes 4 and 5

RENATE SCHMIDT(2), Joanne West(1), Karina Love(1), Zoe Lenehan(1), Melanie Stammers(1), Clare Lister(1), Helen Thompson(1) and Caroline Dean(1)
1. Department of Molecular Genetics, John Innes Centre, UK
2. Present address: Max-Delbrueck-Laboratory in the MPG, Carl-von-Linne-Weg 10, 50829 Cologne, Germany

A physical map of Arabidopsis thaliana chromosome 4 was constructed in yeast artificial chromosome clones. Four YAC contigs made up of 563 clones, covering >90% of the chromosome and ca. 17 Mb, have been produced using a total of 263 probes. The use of 140 genetically mapped markers as probes guarantees that the YAC contig map is of direct use for map-based cloning experiments. The availability of duplicate cover over most genomic intervals means that the map is very reliable despite the fact that more than 18% of the clones forming the map are chimaeric. The availability of the physical map for this chromosome has allowed a first insight into the organization of this chromosome. Mapping of the nucleolar organizing region and the centromere integrated the physical and cytogenetic maps. Across the centromeric region, but nowhere else on chromosome 4, 8 repeated DNA sequence families were found in a complex arrangement. A first comparison of physical with genetic distances revealed that the frequency of recombination varied substantially with hot and cold spots along the whole chromosome. Our current effort is concentrated on a YAC contig map for chromosome 5. Use of 158 markers has resulted in 35 contigs containing an estimated 21 Mb. Our efforts to reduce this number of contigs will be presented.

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