Plant Genome III Conference Plant Genome III Conference
There is a considerable effort internationally to map and sequence the Arabidopsis genome. Efforts at the John Innes Centre, Norwich are directed at the physical mapping of chromosomes 4 and 5. Chromosome 4 is currently covered by 13 YAC contigs, ranging in size up to 4.5Mb. Chromosome 5 is covered by 40 contigs.
The integration of the genetic and cytogenetic maps in Arabidopsis has been poor. The centromere and one of the nucleolus organizer regions have now been placed on the physical map of chromosome 4. A complex arrangement of repeated sequence families is located in the centromeric region. In situ hybridization analysis has been used to analyse the distribution of these repeated sequences in the genome.
The availability of the physical map of chromosome 4 has allowed the organization of the chromosome to be analysed. The distribution of repeated sequences relative to low copy sequences is being determined and the relationship of genetic distance to physical distance over large genomic regions has been investigated. In order to begin the process of identification of all the genes encoded on chromosome 4, a 1.5Mb region is being sequenced as part of the European Communities Arabidopsis sequencing programme (ESSA). Currently, 700kb has been covered in restriction mapped cosmid contigs and 250kb of genomic sequence has been completed (coordinated by M. Bevan, JIC).