Towards reducing the immunogenic potential of wheat flour: omega gliadins encoded by the D genome of hexaploid wheat may also harbor epitopes for the serious food allergy WDEIA
2018
Omega-5
gliadinsare a group of highly repetitive gluten proteins in wheat flour encoded on the 1B chromosome of hexaploid wheat. These proteins are the major sensitizing allergens in a severe form of
food allergycalled wheat-dependent
exercise-induced anaphylaxis(WDEIA). The elimination of
omega-5
gliadinsfrom wheat flour through biotechnology or breeding approaches could reduce the immunogenic potential and adverse health effects of the flour. A mutant line missing low-molecular weight
gluteninsubunits encoded at the Glu-B3 locus was selected previously from a doubled haploid population generated from two Korean wheat cultivars. Analysis of flour from the mutant line by 2-dimensional gel electrophoresis coupled with tandem mass spectrometry revealed that the
omega-5
gliadinsand several gamma
gliadinsencoded by the closely linked Gli-B1 locus were also missing as a result of a deletion of at least 5.8 Mb of chromosome 1B. Two-dimensional immunoblot analysis of flour proteins using sera from WDEIA patients showed reduced IgE reactivity in the mutant relative to the parental lines due to the absence of the major
omega-5
gliadins. However, two minor proteins showed strong reactivity to patient sera in both the parental and the mutant lines and also reacted with a monoclonal antibody against
omega-5
gliadin. Analysis of the two minor reactive proteins by mass spectrometry revealed that both proteins correspond to
omega-5
gliadingenes encoded on chromosome 1D that were thought previously to be
pseudogenes. While breeding approaches can be used to reduce the levels of the highly immunogenic
omega-5
gliadinsin wheat flour, these approaches are complicated by the
genetic linkageof different classes of gluten protein genes and the finding that
omega-5
gliadinsmay be encoded on more than one chromosome. The work illustrates the importance of detailed knowledge about the genomic regions harboring the major gluten protein genes in individual wheat cultivars for future efforts aimed at reducing the immunogenic potential of wheat flour.
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