Poster: Comparative Genomics

Abs # 920: Comparative Sequence Analysis of Barley D-hordein Region and Wheat HMW-glutenin Locus Complex

Presenter:	Gu, Yong Qiang , ygu@pw.usda.gov
Authors	Gu, Yong Qiang  (A)   Kong, Xiuying  (A)   Coleman-Derr, Devin  (A)   Londeoer, Cindy F (A)   Chibbar, Ravindra N (B)   Anderson, Olin D (A)
Affiliations:	(A): USDA-ARS, Western Regional Research Center (B): Plant Biotechnology Institute, National Research Council Canada

Bread wheat is a hexaploid species comprised of three different but highly related genomes (A, B, D). These genomes are derived from a cross between its ancestral tetraploid wheat, Triticum turgidum, (A and B) and diploid wheat, Aegilops tauschii,(D). To understand the wheat genome organization and evolution, we sequenced large-insert BAC clones containing High Molecular Weight glutenin genes of ancestral wheat genomes. The sequence of a barley BAC clone containing D-Hordein that is highly homologous to the HMW-Glutenin is included in this study. Comparative sequence analysis among these orthologous regions reveals that gene content and order are generally conserved. Genes included in these regions are leucine-rich repeat receptor kinases, globulins, HMW-glutenins, and serine/threonine protein kinases. However, in wheat genomes, a region containing globulin and HMW-glutenin genes was duplicated, resulting in paralogous x-type and y-type HMW-glutenin genes. In addition, the distance between genes in the different genomes is quite different. While the two paralogous HMW-glutenin genes are 50-kb apart in the D genome, they are 185-kb apart in the A genome. The DNA sequences separating the two paralogous HMW-glutenin genes are mainly clusters of retrotransposable elements. Only limited collinear transposable element sequences were shared among different wheat genomes, suggesting most retroelements were inserted after the divergence of wheat genomes.