Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Comparative Sequence Analysis Reveals The Origin And Evolution Of High Molecular Weight Glutenin Locus Regions In Wheat

Yong Qiang Gu¹ , Devin Coleman-Derr¹ , Xiuying Kong² , Olin Anderson¹

¹  Genomics and Gene Discovery Research Unit, USDA-ARS-WRRC, 800 Buchanan Street, Albany, CA 94710, USA

²  Institute of Crop Germplasm Resources, Chinese Academy of Agricultural Sciences, Beijing 100081, China

The high molecular weight (HMW) subunits of wheat glutenin are important determinants of the bread-making quality of wheat flour. The gene encoding this endosperm protein appears to be specific to Triticeae species. In the hexaploid wheat, each genome (A, B, and D) possesses two paralogous HMW-glutenin genes on the homoeologous group 1 chromosomes, while there is only one copy of the orthologous D-hordein gene in the barley genome. Previously, we sequenced and compared BAC contigs spanning orthologous HMW-glutenin locus regions from three wheat (A, B and D) genomes and the barley genome (Gu et al., Plant Physiol. 2004). Our results indicated that a globulin gene, also an endosperm specific gene, is immediately adjacent to the HMW-glutenin gene in a head-to-tail configuration. A 7.2-kb region containing both the globulin and HMW-glutenin genes was duplicated in the wheat lineage after wheat and barley diverged. To further understand the unique evolution of HMW-glutenin genes in the Triticeae lineage, we here report sequence analysis of the orthologous regions of rice and maize in comparison with the HMW-glutenin regions in wheat and barley genomes. Although the globulin gene is conserved, the HMW-glutenin sequence is not present in either rice or maize. Sequence alignment revealed that the globulin and HMW-glutenin genes share a considerable sequence similarity. Our data suggests that the globulin has undergone a duplication event in the Triticeae lineage and that the rapid diversification of the second copy resulted in the generation of the HMW-glutenin gene. Other diverse sequence rearrangements observed in these compared regions will also be discussed.