Predicting allergenicity of wheat genotypes

Research output: ThesisDoctoral Thesis

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Abstract

Wheat is probably the most important crop in the world and has been grown and consumed by humans for about 12,000 years. Wheat grain contains unique proteins that give flour the ability to make numerous nutritious products, from simple bread that can be cooked under stone age conditions, to end products resulting from sophisticated baking. Wheat therefore played and continues to play a significant role in human civilisation and it is gown by most cultures of the world.
A considerable number of people in primarily western populations, chose to follow gluten free diets and wheat flour products have gained the reputation of being a controversial food. Prevalence of gluten related food disorders, e.g. Coeliac Disease, Wheat Allergy, Gluten Intolerance etc. have increased in the last 20 years and modern wheat varieties are often blamed. It is claimed that intensive wheat breeding during and since the green revolution has changed wheat from a safe nutritious food to one that has become immunogenic. Gliadins are the principal immunoreactive fraction of gluten, due to the high content of specific immune reactive peptide sequences (epitopes) in their primary sequences. One hundred and twelve Australian wheat cultivars released over the last 160 years (1860 to 2015), grown in the same environment, were assessed to determine their immunogenicity. We used three replicates and analysed the results obtained with Matrix Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry, Liquid Chromatography MS MS, Reverse Phase and Size Exclusion High Performance Liquid Chromatography, using Data Explorer, Genomic WorkBench, Excel, UniProt and ProPepper software. We analysed and quantified the gliadin content and
composition of these cultivars and determined their immunoreactive epitope content. xv
During this process we discovered a small, highly toxic ω-gliadin group, and mapped the immunoreactive epitopes of its members. The allergenicity of each of these Australian wheat cultivars was estimated, based on their gliadin abundance and immunoreactive epitope content. We used similar methodologies to carry out experiments using 10 cultivars from the selection, to determine what effects different environments may have on the expression of protein content and composition of these immunoreactive proteins. In addition, we analysed 5 deletion lines with Gli-1 null alleles, to determine their levels of immunoreactive epitopes and their potential to be used in wheat breading programmes.
We identified considerable variation in the gliadin content, composition and immunoreactive epitope content, of varieties tested, regardless of their date of release, and significant responses to heat and drought conditions. We observed that historic wheat varieties are potentially as immunogenic as the more recently released cultivars dispelling the claim that recent intensive breeding techniques are responsible for the immunogenicity of modern cultivars. Australian wheat breeding companies are now able to select varieties with low immunogenicity to use in their breeding programmes, in their endeavour to develop cultivars whose flour products will be more suitable for people at the lower end of gluten intolerance.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Blanchard, Christopher, Principal Supervisor
  • Vanniasinkam, Thiru, Co-Supervisor
Award date13 Nov 2019
Place of PublicationAustralia
Publisher
Publication statusPublished - 2019

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