Plant Genome IV Conference Plant Genome IV Conference
Recent studies in our laboratory have indicated that most intergenic regions of the maize genome are methylated 5-200 kb blocks composed of intermixed repetitive DNAs. We have found that many of these repetitive sequences are expressed retroelements, making it difficult to identify the standard genes in a region by a cDNA approach. The conservation of gene composition and segments of conserved gene order observed in the grasses suggested that we could use these properties to identify all of the genes in a cloned chromosomal continuum. In comparisons of the maize, rice and sorghum genomes near homologues of the maize adh1 and a1-sh2 loci,we have found that both gene content and orientation are highly conserved. This allows an efficient process of genomic cross-referencing to identify genes and to perform chromosome walks.