Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1392 USA
Relatively few studies have compared sequences of large segments of complex grass genomes. We have sequenced 225 kb around maize adh1-F gene and its orthologous region of 78 kb from sorghum. Comparative analysis of the regions allowed us to identify conserved and divergent sequences. 66.4 kb of the sorghum sequence covers 211.7 kb of the maize region, which is in good agreement with relative sizes of the maize and sorghum genomes. About 22% and 57% of the respective maize and sorghum sequences are conserved in the regions. Nine putative maize genes have homologs in the same orthologous position and predicted direction of transcription in sorghum. Three additional candidate genes were identified in two nonconserved regions in sorghum. Two adjacent Arabidopsis genes were found in orthologous positions to the sorghum genes, one of which is deleted in the maize region. Average gene density is 35 kb and 5.5 kb per gene for the maize and sorghum regions, respectively. However, a gene-dense maize region was found with 10 kb per gene. About 92% of nonconserved sequence in the maize region is composed of LTR retrotransposons, which is about 74% of the region. Six blocks, 14 kb to 70 kb in size, of 22 nested LTR retroelements were localized between genes. No retrotransposons were identified in the sorghum region. Numerous miniature transposon-like elements were uncovered in both regions, but none of them was detected within the 166 kb of LTR retroelements. To compare the putative chromatin structure of the regions, we mapped Matrix Attachment Regions (MARs). Structural colinearity of putative chromatin domains was observed.
Plant & Animal Genome VII Conference Plant & Animal Genome VII Conference