Abstract
Ingestion of gluten proteins (gliadins and glutenins) from wheat, barley and rye can cause coeliac disease (CD) in genetically predisposed individuals. The only remedy is a strict and lifelong gluten-free diet. There is a growing desire for coeliac-safe, whole-grain wheat-based products, as consumption of whole-grain foods reduces the risk of chronic diseases. However, due to the large number of gluten genes and the complexity of the wheat genome, wheat that is coeliac-safe but retains baking quality cannot be produced by conventional breeding alone. CD is triggered by immunogenic epitopes, notably those present in α-, γ-, and ω-gliadins. RNA interference (RNAi) silencing has been used to down-regulate gliadin families. Recently, targeted gene editing using CRISPR/Cas9 has been applied to gliadins. These methods produce offspring with silenced, deleted, and/or edited gliadins, that overall may reduce the exposure of patients to CD epitopes. Here we review methods to efficiently screen and select the lines from gliadin gene editing programs for CD epitopes at the DNA and protein level, for baking quality, and ultimately in clinical trials. The application of gene editing for the production of coeliac-safe wheat is further considered within the context of food production and in view of current national and international regulatory frameworks.
Highlights
Increased consumption of cereal grains has gone hand-in-hand with human development
Analysis of T1 seeds revealed that of about 50 different highly presented α-gliadin sequences in bread wheat and durum wheat, 25–78% were mutated by CRISPR/Cas9 as determined by Illumina sequencing [21], while Acid-PAGE analysis of CRISPR/Cas9 derived germplasm has found up to 30%
Gene editing using CRISPR/Cas9 offers the prospect of producing hypoimmunogenic wheat
Summary
Increased consumption of cereal grains has gone hand-in-hand with human development. Some 6 million years ago, as humans moved from the African forests into savannah areas, grass species with small, hard seeds became part of the human diet [1, 2]. With the onset of agriculture during the Neolithic period, cereal grain consumption increased further, and has continued to do so right up to the present day. Flour milled from wheat (Triticum aestivum L., an allohexaploid wheat species with an AABBDD genome) became renown in Roman times for its fine viscoelastic doughs and flavorful white breads [3]. 220 million ha of bread wheat are cultivated annually, producing 700–750 million tons of grain annually [4], and used in a huge variety of food products [5]
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