Submitted to: Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/29/2006
Publication Date: 11/15/2006
Citation: Gu, Y., Salse, J., Coleman-Derr, D., Dupin, A., Crossman, C., Lazo, G., Huo, N., Belcram, H., Ravel, C., Charmet, G., Charles, M., Anderson, O., Chalhoub, B. 2006. Types and Rates of Sequence Evolution at the HMW-Glutenin Locus in Hexaploid Wheat and Its Ancestral Genomes. Genetics. 174:1493-1504. Interpretive Summary: In wheat, the Glu-1 locus is one of the most important single genetic loci because it encodes the HMW-glutenin protein subunits, which are the major determinants of bread-making quality for wheat flour. Since bread wheat is hexaploid species with three subgenomes designated A, B and D. It, therefore, has three Glu-1 loci, named Glu-1A, Glu-1B, and Glu-1D. In this manuscript, we sequenced all three regions from a single cultivated wheat species and compared the sequences with the corresponding regions from diploid and tetraploid wheats, the ancestral species of bread wheat. Our results reveal the gene content and organization in these regions and sequence evolution occurred in the evolutionary history of wheat genome. The knowledge gained from this study can help us not only understand the genome evolution and wheat domestication, but also provide potential strategies to genetic improvement of wheat quality.
Technical Abstract: The Glu-1 locus, encoding the High Molecular Weight-glutenin protein subunits, controls bread-making quality in hexaploid wheat (Triticum aestivum) and represents a recently evolved region unique to Triticeae genomes. To understand the molecular evolution of this locus region, three orthologous Glu-1 regions from the three subgenomes of a single hexaploid wheat species were sequenced, totaling 729 kb of sequence. Comparing each Glu-1 region with its corresponding homologous region from the D genome of diploid wheat, Aegilop tauschii, and A and B genomes of tetraploid wheat, Triticum turgidum, revealed that in addition to the conservation of microsynteny in the genic regions, sequences in the intergenic regions, composed of blocks of nested retroelements, are also generally conserved, although a few non-shared retroelements that differentiate the homologous Glu-1 regions were detected in each pair of the A and D genomes. Analysis of the indel frequency and the rate of nucleotide substitution, which represent the most frequent types of sequence changes in the Glu-1 regions, demonstrated that the two A genomes are significantly more divergent than the two B genomes, further supporting the hypothesis that hexaploid wheat may have more than one tetraploid ancestor.