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Wheat genotypes containing minimally harmful gluten sequences

by luciano

“Previous studies have documented that landraces and older wheat varieties contain more diverse gene combinations for prolamins (wheat proteins) in comparison to modern varieties (10, 11). Literature shows variations for specific gene sequences mainly in the epitopic regions of Glia-α9, Glia-α2, Glia-α20, and Glia-α in older landraces (9). In the last decade in the context of CD, the immunogenicity of T-cell specific epitopes has been bought to the forefront (9, 12). The immunogenic potential amongst different hexaploid wheat varieties is variable; hence it is possible that there are breeding-induced differences in the presence and expression of T-cell stimulatory epitopes in modern varieties of wheat (13, 14). This raises the question of, whether there is any specific variety of wheat which is less immunogenic and can be used in breeding programs for developing a wheat genotype completely safe for consumption by patients suffering from CD”.

Highlights:
• The identification of less/non-immunogenic wheat species is an important milestone that could help patients or even prevent CD.
• With the use of gluten-specific T-cells and PBMCs, wheat genotypes containing minimally harmful gluten sequences can be selected.

Genetic Diversity of wheat

by luciano

A-B-D Genomes

Wheat occurs in a range of diploid, tetraploid and hexaploid forms (summarised in Table 1). The earliest cultivated forms were the A genome diploid einkorn (T. monococcum var monococcum) and tetraploid emmer (T. turgidum var. dicoccum) with the A and B genomes. These are closely related to wild forms: diploid T. monococcum var. monococcum and T. ururtu and tetraploid T. turgidum var. dicoccoides, respectively. Modern tetraploid durum (pasta) wheat (T. turgidum var. durum) probably arose from mutations in cultivated emmer.
Hexaploid wheat (Triticum aestivum) (genomes ABD)
Hexaploid wheat (Triticum aestivum) (genomes ABD) has never existed as a wild species and no wild hexaploid wheats are known. It probably arose by hybridization of cultivated emmer with the related wild grass T. tauschii (goat grass, also called Aegilops tauschii and Ae. squarossa). This hybridization probably occurred in south-eastern Turkey about 9000 years ago (Feldman, 1995, Dubcovsky and Dvorak, 2007) and contributed the D genome. All cultivated hexaploid wheats, including spelt, are forms of T. aestivum.
A major difference between “ancient” cultivated wheats (einkorn, emmer, spelt) and their wild relatives and modern durum and bread wheats is whether the grain are hulled or free threshing. In hulled wheats the glumes and palea adhere to the grain and the threshed material consists of intact spikelets.
α-gliadins
As the most coeliac-active T-cell epitopes are present on the α-gliadins, emphasis has been placed on exploring differences in the amounts and sequences of proteins of this class. Kasarda
et al. (1976)
33mer fragment of α-gliadin
The studies of van Herpen et al. (2006) showed that T-cell stimulatory epitopes were more abundant in α-gliadins encoded by the D genome, and Molberg et al. (2005) who demonstrated that the immunodominant 33mer fragment of α-gliadin was encoded by chromosome 6D (and hence absent from diploid einkorn and tetraploid wheats).
The absence of the D genome from durum wheat
The absence of the D genome from durum wheat could result in lower coeliac activity due to the absence of the T-cell stimulatory epitopes at the Gli-D2 locus. van den Broeck et al. (2010a) therefore screened 103 accessions of tetraploid wheat by immunoblotting of gluten protein extracts with monoclonal antibodies against the Glia-α9 and Glia-α20 epitopes. This identified three accessions with significantly reduced levels of both epitopes. Further analysis of 61 durum wheat accessions by high throughput transcript sequencing similarly identified some accessions with lower abundances of transcripts containing coeliac disease epitopes (Salentjin et al., 2013).
Other gluten proteins
Although impressive progress has been made with identifying variation in the abundances of coeliac disease epitopes in α-gliadins, it must be borne in mind that other groups of gluten protein also contain coeliac active sequences. This was demonstrated in the survey of gluten protein sequences in the Uniprot protein sequence database by Spaenij-Dekking et al. (2005) which is referred to above. They showed that T-cell stimulatory epitopes were present in all γ-gliadin sequences (17/17), in 95.5% (21/22) of HMW subunit sequences and in 5% of LMW subunit sequences (3/57), in addition to 66% (19/29) of α-gliadin sequences. (Improving wheat to remove coeliac epitopes but retain functionality. Peter R. Shewry and Arthur S. Tatham 2016).
 

Preliminary operations the grinding of wheat : Grain conditioning

by luciano

Phase in which the grain is wet with a sufficient quantity of water, to facilitate the detachment of the external parts (integuments) from the floury almond and the breaking of the same. The purpose of this phase is to soften the casing to prevent its fragmentation and promote its detachment, to reduce the hardness of the albumen to facilitate its transformation into flour and to obtain a degree of damage to the starch that is optimal for the various uses. . Conditioning is influenced by the amount of water added, the temperature of the treatment and the duration of the rest of the grain.

Organic cultivation and ancient grains

by luciano

Organic cultivation is particularly suitable for ancient grains: why?
• The varieties of ancient wheat are particularly rustic, that is, adapted to survive in hostile, nutrients and water-poor conditions because selected during a period when agriculture was not yet intensive and supported by the unbridled use of chemical fertilizers, pesticides and irrigation systems. This characteristic allows them to cultivate areas defined as “marginal”, where modern varieties would struggle or require high economic effort.
• Given the strength of ancient grains, these varieties are particularly suitable for cultivation under organic conditions, where the use of non-natural chemical fertilizers is absolutely forbidden, thus protecting the environment. Fertilizers, among other things, not even necessary because they extract micronutrients from the soil by very deep roots.
• We all know that the diversity of the diet is of fundamental importance for human health. On average 60% of our calories come from wheat, rice and maize; for this reason it is important to alternate the use of the varieties of these three plant species and therefore get used to buying flours and products derived from the use of ancient grains that guarantee a real variety in the diet.
• Protect biodiversity.
The term “organic farming” refers to a method of cultivation that only allows the use of natural substances, ie present in nature, excluding the use of chemical synthesis substances (fertilizers, herbicides, insecticides). Organic farming means developing a production model that avoids the over-exploitation of natural resources, especially soil, water and air, using these resources instead within a development model that can last over time.
Deepening:
How to grow organic