MATRIX ATTACHMENT REGIONS AND STRUCTURAL COLINEARITY IN THE GENOMES OF 2 GRASS SPECIES

In order to gain insights into the relationship between spatial organi zation of the genome and genome function we have initiated studies of the co-linear Sh2/A1-homologous regions of rice (30 kb) and sorghum (5 0 kb). We have identified the locations of matrix attachment regions ( MARs) in these homologous chromosome segments, which could serve as an chors for individual structural units or loops. Despite the fact that the nucleotide sequences sewing as MARs were not detectably conserved, the general organizational patterns of MARs relative to the neighbori ng genes were preserved. All identified genes were placed in individua l loops that were of comparable size for homologous genes. Hence, gene composition, gene orientation, gene order and the placement of genes into structural units has been evolutionarily conserved in this region . Our analysis demonstrated that the occurrence of various 'MAR motifs ' is not indicative of MAR location. However, most of the MARs discove red in the two genomic regions were found to co-localize with miniatur e inverted repeat transposable elements (MITEs), suggesting that MITEs preferentially insert near MARs and/or that they can serve as MARs.