Silencing of omega-5 gliadins in transgenic wheat eliminates a major source of environmental variability and improves dough mixing properties of flour

Authors: Altenbach, Susan; Tanaka, Charlene; Seabourn, Bradford

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2014
Publication Date: 12/24/2014
Citation: Altenbach, S.B., Tanaka, C.K., Seabourn, B.W. 2014. Silencing of omega-5 gliadins in transgenic wheat eliminates a major source of environmental variability and improves dough mixing properties of flour. Biomed Central (BMC) Plant Biology. 14:393 doi: 10.1186/s12870-014-0393-1.

Interpretive Summary: The end-use quality of wheat flour varies as a result of the growth conditions of the plant. Among the wheat gluten proteins, the omega-5 gliadins have been identified as a major source of environmental variability. These proteins also are involved in human food allergies. Recently, gene silencing was used to produce transgenic wheat plants in which the omega-5 gliadins were significantly reduced or eliminated in the flour. In the current study, two of the transgenic lines and a control line were grown in greenhouses with different levels of fertilizer and the effects of the fertilizer treatment on the accumulation of individual proteins in the flour were evaluated. Changes in flour proteins other than the omega gliadins in response to the fertilizer treatment were similar in the control and transgenic lines. The functional properties of the flour from the same samples were also assessed. Flour from transgenic lines showed improved mixing properties, demonstrating that it is possible to eliminate a group of proteins that are a major source of environmental variability as well as an important food allergen from wheat flour without compromising flour functionality. The data suggest that changes in quality with the growth environment may be due in part to alterations in the levels of the omega gliadins. By eliminating an important food allergen and one of the major sources of environmentally-induced variation in wheat flour protein composition, the transgenic lines may yield flour with both improved end-use quality and more consistent functionality when grown in different locations.

Technical Abstract: Background The end-use quality of wheat flour varies as a result of the growth conditions of the plant. Among the wheat gluten proteins, the omega-5 gliadins have been identified as a major source of environmental variability, increasing in proportion in grain from plants that receive fertilizer or are subjected to high temperatures during grain development. The omega-5 gliadins also are the cause of the food allergy wheat-dependent exercise-induced anaphylaxis (WDEIA). Recently, transgenic lines with reduced levels of omega-5 gliadins were developed using RNA interference (RNAi). These lines make it possible to determine whether changes in the levels of omega-5 gliadins in response to environmental conditions and agronomic inputs may be responsible for changes in flour end-use quality. Results Two transgenic wheat lines and a non-transgenic control were grown under a controlled temperature regimen with or without post-anthesis fertilizer and the protein composition of the resulting flour was analyzed by quantitative two-dimensional gel electrophoresis (2-DE). In one transgenic line, all 2-DE spots identified as omega-5 gliadins were substantially reduced without effects on other proteins. In the other transgenic line, the omega-5 gliadins were absent and there was a partial reduction in the levels of the omega-1,2 gliadins and the omega-1,2 chain-terminating gliadins as well as small changes in several other proteins. With the exception of the omega gliadins, the non-transgenic control and the transgenic plants showed similar responses to the fertilizer treatment. Protein contents of flour were determined by the fertilizer regimen and were similar in control and transgenic samples produced under each regimen while both mixing time and mixing tolerance were improved in flour from transgenic lines when plants received post-anthesis fertilizer. Conclusions The data indicate that omega-5 gliadins have a negative effect on flour quality and suggest that changes in quality with the growth environment may be due in part to alterations in the levels of the omega gliadins. By eliminating an important food allergen and one of the major sources of environmentally-induced variation in wheat flour protein composition, the transgenic lines may yield flour with both improved end-use quality and more consistent functionality when grown in different locations.