Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Workshop: Comparative Genomics
            

COMPARATIVE SEQUENCE ANALYSIS OF ORTHOLOGOUS HMW-GLUTENIN REGIONS OF WHEAT AND BARLEY GENOMES

Genomics and Gene Discovery Unit, USDA-ARS, WRRC, 800 Buchanan Street, Albany, CA 94710, USA

Comparative mapping with anchored probes have indicated a syntenic relationship among the grass genomes. However, detailed sequence analyses have revealed dynamic change within the genomes, which are mainly due to the contribution of large number of retrotransposon elements. To understand genome evolution of more closely related species, we have sequenced orthologous high-molecular-weight (HMW) glutenin regions from the A and B genomes of Triticum turgidum, a tetraploid wheat, Am genome of Triticum monococcum, D genome of Aegilops tauschii, and an orthologous D-hordein region from barley. Comparative sequence analysis revealed that the gene content and order are generally conserved. Genes included in these orthologous regions are arranged in the following order: Xa21-like receptor kinase, HMW-glutenin, globulin, and serine/threonine protein kinase. However, in all the wheat genomes, but not the barley, a region spanning the HMW-glutenin and globulin genes was duplicated, indicating that this duplication event occurred after the separation of wheat and barley genomes. The intergenic regions are largely divergent with regard to the sequence and structure organization. In the D genome of Aegilops tauschii, the two HMW-glutenin genes are 50-kb apart, as compared to over 170-kb apart in the A and B genomes of the tetraploid wheat. It was found that different types of retroelements are responsible for the intergenic structure divergence in the wheat and barley genomes.