GENOMICS AND MOLECULAR APPROACHES TO WHEAT TRAITS
Location: Genomics and Gene Discovery
Title: Structure of the omega-gliadin gene family
Submitted to: Functional and Integrative Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 2009
Publication Date: April 15, 2009
Citation: Anderson, O.D., Gu, Y.Q., Kong, K., Lazo, G.R., Wu, J. 2009. Structure of the omega-gliadin gene family. Functional and Integrative Genomics. 9: 397-410.
Interpretive Summary: The omega gliadins are one of the classes of proteins found in the wheat seed. As with the other gliadin and glutenin proteins, the omega gliadin contribute to the unique physical-chemical properties of wheat doughs - water/flour mixtures that possess visco-elastic properties that allow a wide range of food products including leavened and unleavened breads, biscuits, cookies, cakes, pasta, and as a common ingredient in many processed foods. This study characterizes the family of genes that encode the omega gliadins and gives, for the first time, a reliable picture of the structure of the complement of omega gliadin proteins found in the wheat seed.
The '-gliadins are one of the classes of wheat seed storage proteins, but are the least characterized. In this report, an analysis is made of all available '-gliadin DNA sequences including '-gliadins genes within a large genomic clone, previously reported gene sequences, and ESTs identified from the large wheat EST collection. A contiguous portion of the Gli-B3 locus is shown to contain two apparently active '-gliadin genes, two pseudogenes, and four fragments of the 3' portion of '-gliadin sequences. Results show three groupings of '-gliadin active gene sequences assigned to each of the three hexaploid wheat genomes, and a fourth group thus far consisting of pseudogenes assigned to the A-genome. Analysis of '-gliadin ESTs allows reconstruction of two full-length model sequences encoding the AREL- and ARQL-type proteins from the Gli-A3 and Gli-D3 loci, respectively, and there is no DNA evidence of multiple active genes from these two loci. In contrast, ESTs allow identification of at least 3-4 distinct active genes at the Gli-B3 locus of some cultivars. Additional results from EST and gene analysis include more information on the position of cysteines in some '-gliadin genes and a C-terminal frameshift in one active '-gliadin gene. Problems in studying the '-gliadin gene family are discussed and include high rates of chimeric, frame-shifted, and deleted clones, and cautions interpreting sequences dependent on sequence replications, particularly isolated through PCR.