Reducing the immunogenic potential of wheat flour: silencing of alpha gliadin genes in a U.S. wheat cultivar

Authors: Altenbach, Susan; Chang, Han-Chang; ROWE, MATTHEW - Clontech; YU, XUECHEN - Columbia University - New York; SIMON-BUSS, ANNAMARIA - University Of Hamburg; Seabourn, Bradford; GREEN, PETER - Columbia University - New York; ALAEDINI, A. - Columbia University - New York

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2020
Publication Date: 2/25/2020
Citation: Altenbach, S.B., Chang, H., Rowe, M., Yu, X.B., Simon-Buss, A., Seabourn, B.W., Green, P.H., Alaedini, A. 2020. Reducing the immunogenic potential of wheat flour: silencing of alpha gliadin genes in a U.S. wheat cultivar. Frontiers in Plant Science. 11:20. https://doi.org/10.3389/fpls.2020.00020.
DOI: https://doi.org/10.3389/fpls.2020.00020

Interpretive Summary: The gluten proteins are a complex group of proteins that are responsible for the unique viscoelastic properties of wheat flour that make it possible to produce a wide range of different food products. Some gluten proteins also trigger a chronic autoimmune condition called celiac disease in genetically susceptible individuals. The current work describes a biotechnology approach that was used to create transgenic plants in which harmful proteins within one group of gluten proteins, the alpha gliadins, were eliminated from wheat flour. In the study, flour protein compositions from two of the resulting lines were analyzed in detail. Although only genes encoding alpha gliadins known to contain sequences that trigger celiac disease were targeted, all alpha gliadins were eliminated from the flour. The reactivity of flour proteins from the new lines with sera from patients with celiac disease was tested and showed reduced reactivity relative to the control. In addition, tests that are routinely used to assess the performance of flour in producing wheat-based products demonstrated that the mixing properties of the flour were not altered substantially in the transgenic lines although there was a decrease in dough strength. This work contributes to efforts to reduce the immunogenic potential of wheat flour.

Technical Abstract: The alpha gliadins are a group of more than 20 proteins with very similar sequences that comprise about 15-20% of the total flour protein and contribute to the functional properties of wheat flour dough. Some alpha gliadins also contain immunodominant epitopes that trigger celiac disease, a chronic autoimmune disease that affects approximately 1% of the worldwide population. In an attempt to reduce the immunogenic potential of wheat flour from the U.S. spring wheat cultivar Butte 86, RNA interference was used to silence a subset of alpha gliadin genes encoding proteins containing celiac disease epitopes. Two of the resulting transgenic lines were analyzed in detail by quantitative two-dimensional gel electrophoresis combined with tandem mass spectrometry. Although only some genes were targeted by the RNA interference construct, all alpha gliadins were effectively silenced in the transgenic plants. In addition, some off-target silencing of high molecular weight glutenin subunits was detected in both transgenic lines despite a lack of homology between the gene sequences and the targeting construct. Compensatory effects were not observed within other gluten protein classes. Reactivities of IgG and IgA antibodies from a cohort of patients with celiac disease toward proteins from the two transgenic lines were reduced significantly relative to the non-transgenic line. Despite the elimination of a major class of gluten proteins, mixing properties of the flour were not altered substantially. However, SDS sedimentation analysis of flour suggested that there was a decrease in dough strength in the transgenic lines. The data suggest that it will be very difficult to selectively silence specific genes within families as complex as the wheat alpha gliadins. Nonetheless, it may be possible to reduce the immunogenic potential of the flour and still retain many of the functional properties essential for the utilization of wheat.