Matrix attachment regions and structural colinearity in the genomes of two grass species.

摘要

In order to gain insights into the relationship between spatial organization of the genome and genome function, the co-linear Sh2/A1-homologous regions of rice (30 kb) and sorghum (50 kb) were studied. The locations of matrix attachment regions (MARs) in these homologous chromosome segments have been identified, which could serve as anchors for individual structural units or loops. Despite the fact that the nucleotide sequences serving as MARs were not detectably conserved, the general organizational patterns of MARs relative to the neighbouring genes were preserved. All identified genes were placed in individual 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. The analysis demonstrated that the occurrence of various 'MAR motifs' is not indicative of MAR location. However, most of the MARs discovered in the two genomic regions were foundto co-localize with miniature inverted repeat transposable elements (MITEs), suggesting that MITEs preferentially insert near MARs and/or that they can serve as MARs.