Integration of transcriptomic and proteomic data from a single wheat cultivar provides new tools for understanding the roles of individual alpha gliadin proteins in flour quality and celiac disease

The complement of alpha gliadins expressed in a single wheat cultivar was examined by assembling expressed sequence tags (ESTs) from Triticum aestivum cv. Butte 86. Twelve of 19 resulting contigs encoded complete proteins, but only two were identical to proteins reported previously. Eight contained various combinations of epitopes important in celiac disease (CD), while four lacked typical CD epitopes. One alpha gliadin contained an additional cysteine residue that could allow incorporation of the protein into glutenin polymers. In addition, two new types of alpha gliadins ending in GFFGTN and GIMSTN were identified. Based on the number of ESTs, genes encoding proteins that contained the greatest numbers of CD epitopes were expressed at the highest levels. Proteins corresponding to 12 contigs were distinguished in Butte 86 flour by tandem mass spectrometry (MS/MS). Unique peptide tags for individual alpha gliadins, including some that lack CD epitopes and the protein containing the extra cysteine, are reported. The ability to distinguish closely related alpha gliadins by MS/MS makes it possible to explore the roles of individual proteins in flour quality, better define relationships between specific proteins and celiac disease, and devise strategies to reduce the immunogenic potential of wheat flour for patients with CD.