BAC REPRESENTATION OF 2 LOW-COPY REGIONS OF THE GENOME OF ARABIDOPSIS-THALIANA

Two regions of Arabidopsis chromosome 4, totalling 4.7 Mb, were assaye d for representation in the TAMU and IGF BAC libraries. A directed app roach to BAC identification was developed. Gel-purified DNA samples of YACs selected from the YAC-based physical map of chromosome 4 were us ed to probe high-density colony arrays of the BAC libraries. Strategie s were developed that allowed the efficient construction of restrictio n maps and BAC contigs. Four hundred and sixty-four BACs were mapped, assembled into two complete contigs and used to analyse genomic repres entation. These BACs provided a mean of 9.4-fold redundant coverage, w ith a range of 2- to 22-fold. The representation provided by the two l ibraries showed almost coincident peaks and troughs, with a periodicit y of approximately 200 kb. These results demonstrate that, provided bo th TAMU and IGF libraries are used in their entirety, BACs should prov ide an excellent resource for both physical mapping and sequencing of the Arabidopsis genome.