Identification and analysis of homoeologous segments of the genomes of rice and Arabidopsis thaliana

Using contiguous genomic DNA sequences of Arabidopsis thaliana, we were abl e to identify a region of conserved structure in the genome of rice. The co nserved, and presumptive homoeologous segments, are 194 kb and 219-300 kb i n size in Arabidopsis and rice, respectively. They contain five homologous genes, distinguished in order by a single inversion. These represent the fi rst homoeologous segments identified in the genomes of a dicot and a monoco t, demonstrating that fine-scale conservation of genome structure exists an d is detectable across this major divide in the angiosperms. The conserved framework of genes identified is interspersed with non-conserved genes, ind icating that mechanisms beyond segmental inversions and translocations need to be invoked to fully explain plant genome evolution, and that the benefi ts of comparative genomics over such large taxonomic distances may be limit ed.