Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2003
Publication Date: 1/28/2004
Citation: Dupont, F.M., Encarnacao, T.M., Chan, R., Vensel, W.H., Kasarda, D.D. 2004. Identification and characterization of omega gliadins from t. urartu and those encoded on chromosome 1a of hexaploid wheat. Theoretical and Applied Genetics. 108:1299-1308. Interpretive Summary: In order to understand wheat flour quality it is important to understand the proteins that provide the unique viscoelastic properties of flour dough. The omega-gliadins represent 10% or less of total wheat flour proteins, but they vary in amount more than other gluten proteins, and are unusual in terms of their repetitive sequences rich in glutamine and proline, lack of cysteine and lack of alpha-helical structure. The relative amount of w-gliadins has been reported to change in response to nitrogen and sulfur availability, as well as in response to other environmental factors. It is possible that changes in w-gliadin amounts or proportions contribute to variability in flour quality. It has been difficult to clone the genes for the w-gliadins. In this paper, we identified, purified and characterized the omega gliadins that are encoded on wheat chromosome 1A. We discovered evidence that the w-gliadins are sometimes modified by an enzyme that cleaves the proteins next to an asparagine residue. The experiments are part of a broader research effort to understand the molecular basis for the effects of environment on flour quality.
Technical Abstract: The w-gliadins encoded on chromosome 1 of the A genome were purified from hexaploid bread wheat, Triticum aestivum L. (2n=6x=42; AABBDD) cv Butte86 and nullisomic 1D-tetrasomic 1A of cv Chinese Spring (CS N1DT1A) and from T. urartu (2n=2x=14; AA), the A genome donor. The proteins were characterized with respect to molecular mass and N-terminal sequences. RP-HPLC combined with SDS-PAGE of gliadin extracts from CS nullisomic-tetrasomic (NT) lines confirmed the assignment to chromosome 1A. The 1A encoded w-gliadins had apparent molecular masses of 45,000 to 59,000 in SDS PAGE but true molecular masses of only 34,523 to 43,363 determined by mass spectrometry. They were generally smaller than the chromosome 1B or 1D encoded w-gliadins. The N-terminal amino acid sequences for the 1A w-gliadin mature peptides were similar to those for the 1D w-gliadins, barley C-hordeins, and rye w-secalins and unlike the N-terminal sequences for the 1B w-gliadins. The data suggest that post-translational cleavage by an asparaginyl endoprotease may produce those 1A and 1D w-gliadins with N-terminal sequences beginning with KEL.