Exploiting the reference genome sequence of hexaploid wheat: a proteomic study of flour proteins from the cultivar Chinese Spring

Authors: Altenbach, Susan; Chang, Han-Chang; Simon-Buss, Annamaria; Mohr, Toni; HUO, NAXIN - University Of California, Davis; Gu, Yong

Submitted to: Functional and Integrative Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2019
Publication Date: 6/27/2019
Citation: Altenbach, S.B., Chang, H., Simon-Buss, A., Mohr, T.J., Huo, N., Gu, Y.Q. 2019. Exploiting the reference genome sequence of hexaploid wheat: a proteomic study of flour proteins from the cultivar Chinese Spring. Functional and Integrative Genomics. 1-16. https://doi.org/10.1007/s10142-019-00694-z.
DOI: https://doi.org/10.1007/s10142-019-00694-z

Interpretive Summary: The gluten proteins are a complex group of abundant proteins in wheat flour that make it possible to produce a wide range of food products, including different types of breads, tortillas, noodles, and baked goods. The composition of these proteins and the amounts of individual proteins in the flour determine the suitability of the flour for different products. In the past, it has been difficult to study the wheat gluten proteins because of the large numbers of very similar proteins in individual cultivars as well as the tremendous variation of protein sequences among different cultivars. Recently, as a result of international efforts to sequence the genome of the reference wheat Chinese Spring, the sequences for a complete set of 56 gluten protein genes were obtained from a single cultivar. In this paper, we used quantitative two-dimensional gel electrophoresis combined with tandem mass spectrometry to associate 40 of 56 gluten protein gene sequences from Chinese Spring with flour proteins from the same cultivar. We also determined the amounts of the different proteins in the flour. The extension of this work to commercial cultivars grown throughout the world should provide new information on the molecular basis of wheat flour quality.

Technical Abstract: Although the economic value of wheat flour is determined by the complement of gluten proteins, these proteins have been challenging to study because of the complexity of the major protein groups and the tremendous sequence diversity among wheat cultivars. The completion of a high-quality wheat genome sequence from the reference wheat Chinese Spring recently facilitated the assembly and annotation of a complete set of gluten protein genes from a single cultivar, making it possible to link individual proteins in the flour to specific gene sequences. In a proteomic analysis of total wheat flour protein from Chinese Spring using quantitative two-dimensional gel electrophoresis combined with tandem mass spectrometry, gliadins or low-molecular-weight glutenin subunits were identified as the predominant proteins in 72 protein spots. Individual spots were associated with 40 of 56 Chinese Spring gene sequences, including 16 of 26 alpha gliadins, 10 of 11 gamma gliadins, six of seven omega gliadins, one of two delta gliadins and nine of ten LMW-GS. Genes that were not associated with protein spots were either expressed at low levels in endosperm or encoded proteins with high similarity to other proteins. A wide range of protein accumulation levels were observed and discrepancies between transcript levels and protein levels were noted. This work and similar studies using other commercial cultivars should provide new insight into the molecular basis of wheat flour quality and allergenic potential.