Construction of physical maps of the Hor1 locus of two barley cultivars by pulsed field gel electrophoresis.

In order to construct a physical map of the Hor1 locus of barley (Hordeum vulgare) high molecular weight DNA was prepared from leaf mesophyll protoplasts. Seventeen different restriction endonucleases containing CpG or CpXpG motifs in their recognition sequences were tested and ten proved useful for the generation of high molecular weight DNA fragments. Physical maps of the Hor1 region of the barley cultivars IGRI and FRANKA spanning a distance of 370 and 430 kb respectively were constructed. The maps include sites of nine restriction endonucleases in IGRI and of eight in FRANKA. The maximal extent of the Hor1 locus could be limited to a 135 kb DNA fragment occurring in both cultivars. The differences in arrangement of restriction sites and in fragment lengths reveal major differences in the Hor1 flanking region in the two cultivars. The location of a CpG island, however, is highly conserved in both cultivars and reflects similarities to the organization of mammalian genomes.