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More tolerable durum wheat for non-celiac gluten sensitive subjects

by luciano

The aim of the study “In search of tetraploid wheat accessions reduced in celiac disease-related gluten epitopes” is the identification of accessions of durum wheat with the least amount of fractions (epitopes) that activate the adverse response of the human immune system in celiac disease and not only.
Durum wheat with a smaller amount of these fractions (epitopes) might help undiagnosed CD-patients (approximately 95% of all CD-patients) who are daily consuming CD-stimulating gluten proteins without realizing its effect on their health and well being.
Durnm wheat identified although not suitable for celiac subjects “may contribute to delay or even prevent the onset of CD and its symptom development in that part of the population that is genetically susceptible, especially in children 37 (van den Broeck et al. in press), because the quantity of consumed CD-epitopes is a major factor that may influence the clinical representation of CD, along with some other recognized factors such as the type of cow’s milk formulas, omission of breast feeding, and age at gluten introduction. “

The study analyzed the gluten of “103 tetraploid wheat accessions (obtained from the Dutch CGN genebank and from the French INRA collection) including landraces, old, modern, and domesticated accessions of various tetraploid species and subspecies from many geographic origins. Those accessions were typed for their level of T-cell stimulatory epitopes.” The study has highlighted the existence of “ 8 CGN and 6 INRA accessions with reduced epitope staining.”
…omissis “Tetraploid wheats contain less T-cell stimulatory a-gliadin epitopes than hexaploid bread wheat because of the absence of the D-genome. The highly immunodominant T-cell stimulating 33-mer is exclusively present in a-gliadins encoded by the D-genome (bread wheat). In addition, the levels of T-cell stimulatory epitopes have been shown to vary among varieties (van den Broeck et al. ). This opens possibilities to select for wheat varieties with significantly reduced a-gliadin epitope levels, aiming at direct use or to apply in breeding programs directed towards large-scale reduction or even total elimination of CD-stimulating gluten-elements from wheat.”

Note
From the study
“A landrace may be a mixture of genotypes, which evolved under the environmental conditions where they were grown because of natural selection and selection by the farmer. Tetraploid wheat can mix up with hexaploid bread wheat very easily under agricultural conditions and care should be taken if the tetraploid wheat should be maintained as a pure genotype. As a result, many commercial lots, currently sold as durum wheat, nearly always contain some hexaploid bread wheat.”

“Differences among wheat varieties in gluten proteins occur because of allelic variation (genotype) that determines the gluten protein composition. The approach we used in this study analyzes this genotypic variation by comparing the same amount of gluten protein per accession. Changes in gluten protein composition have been described, but are mainly expected if growth conditions are extreme (high or low temperature, dry or wet conditions). The varieties and accessions we have analyzed were grown under normal wheat growth conditions and therefore, their influence on the gluten protein composition is not expected.”

”The occurrence of different genotypes and even different ploidy levels in a single genebank accession is a complicating phenomenon for genebank managers to accurately characterize landraces. Many landraces often result from maintenance and selection practices by local farmers directed towards optimizations to local agronomic and food applications. As a consequence, genebank passport data turned out to be poor predictors of the real genetic composition of landrace accessions that may be mixtures of genotypes of tetraploid and even hexaploid wheat species.”

In search of tetraploid wheat accessions reduced in celiac disease-related gluten epitopes. Hetty van den Broeck et al.
www.rsc.org/molecularbiosystems. July 2010 DOI: 10.1039/c0mb00046a

Keywords:

durum wheat, less toxic wheat, immunogenicity of wheat, predisposition to celiac disease, more tolerable durum wheat varieties, gluten proteins

Genome of the ancestor of durum wheat

by luciano

Press release

“Svelato il genoma dell’antenato del frumento duro 07/07/2017

Un team internazionale di ricercatori ha ricostruito per la prima volta la sequenza del genoma del farro selvatico (Triticum turgidum ssp. dicoccoides). Il lavoro pubblicato sulla prestigiosa rivista Science, è stato guidato dall’Università di Tel Aviv ed ha coinvolto diverse decine di ricercatori provenienti da istituzioni di tutto il mondo. L’Italia ha contribuito a questo risultato attraverso la partecipazione di Crea (Centro di ricerca genomica e bioinformatica di Fiorenzuola d’Arda), del Cnr (Istituto di biologia e biotecnologia agraria e Progetto InterOmics) e dell’Università di Bologna (Dipartimento di scienze agrarie).

Il farro selvatico è il progenitore da cui sono stati selezionati quasi tutti i frumenti coltivati, tra cui il grano duro ed il grano tenero utilizzati per produrre, rispettivamente, pasta e pane. Il farro selvatico non è coltivato a causa della bassissima produzione e dei caratteri selvatici che lo caratterizzano. Ad esempio, i semi maturi del farro selvatico cadono spontaneamente a terra rendendo difficile la loro raccolta da parte dell’uomo, mentre nel farro coltivato i semi rimangono sulla spiga. La decodifica del genoma del farro selvatico rappresenta un contributo fondamentale per lo studio dei caratteri genetici utili per il miglioramento dei frumenti coltivati (in relazione alla resistenza agli stress biotici ed abiotici, in particolare la siccità) e per la ricostruzione della storia evolutiva del frumento nella fase antecedente la nascita dell’agricoltura. La disponibilità del genoma del farro selvatico ed il confronto con il patrimonio genetico dei frumenti coltivati ha infatti consentito di identificare i geni responsabili dell’addomesticamento. In particolare sono stati caratterizzati due geni la cui mutazione spontanea impedisce la dispersione dei semi dalle spighe mature, una modifica che, rendendo possibile lo sviluppo dell’agricoltura nel neolitico, è stata determinante nell’indirizzare la storia dell’umanità.

Il genoma del farro selvatico è circa il triplo del genoma umano, caratteristica che rende la sua ‘lettura’ particolarmente difficile. Il Centro di ricerca genomica e bioinformatica ha partecipato con le proprie competenze bioinformatiche all’annotazione funzionale del genoma, ovvero all’identificazione della funzione dei geni, occupandosi in particolare di una porzione del genoma tanto misteriosa quanto affascinante poiché coinvolta nell’attività di regolazione genica in quanto sede di produzione dei cosiddetti RNA non codificanti. Ed è proprio questa parte del genoma ad essere la più interessante per la genomica del futuro permettendo di svelare i meccanismi di accensione e spegnimento coordinati degli oltre 65.000 geni presenti nel genoma del farro selvatico.

Cnr e Università di Bologna hanno contribuito allo studio dell’addomesticamento e della diversità genetica presente nelle popolazioni di farro selvatico e domestico, fonti importanti di variabilità ed una riserva fondamentale di varianti genetiche naturali tuttora scarsamente esplorata ed utilizzata per il miglioramento del frumento moderno. Da questo lavoro sono attese ricadute importanti sulle attività di miglioramento genetico per incrementare la sostenibilità, la resistenza alla siccità, la tolleranza alle patologie e gli aspetti nutrizionali e salutistici dei frumenti del futuro.

“L’approccio di sequenziamento ed analisi bioinformatica utilizzato per il farro selvatico è senza precedenti e ha aperto la strada al sequenziamento del frumento duro, la forma addomesticata del farro selvatico. Ora possiamo capire meglio come l’uomo ha trasformato questa pianta selvatica in un grano duro moderno ad alto rendimento”, ha detto il Luigi Cattivelli, direttore del Centro di ricerca Crea di genomica e bioinformatica e coordinatore del Consorzio internazionale di sequenziamento del frumento duro.

“La disponibilità della sequenza del farro selvatico è un vero e proprio filo di Arianna che ci consentirà di individuare più facilmente i geni per selezionare frumenti di qualità migliore ed a minor impatto ambientale. Conoscere questi geni è la premessa indispensabile per utilizzare le nuove metodiche di selezione come l’editing dei geni, la cui applicazione potrà assicurare la competitività della granicoltura nazionale”, ha detto Roberto Tuberosa, responsabile del Laboratorio di genomica dei cereali presso il Dipartimento di scienze agrarie dell’Università di Bologna.

Aldo Ceriotti, direttore dell’Istituto di biologia e biotecnologia agraria del Cnr, sottolinea come “Il confronto fra la sequenza del farro selvatico e quella del frumento duro ci permetterà di evidenziare come la selezione fatta dall’uomo abbia favorito l’accumulo di specifiche modificazioni nella sequenza del genoma di una delle principali specie coltivate nell’area del Mediterraneo, e costituirà una solida base per lo studio della variabilità genetica e lo sviluppo di nuove varietà di frumento duro”.”

La scheda: Chi: Cnr (Istituto di biologia e biotecnologia agraria e Progetto InterOmics); Università di Tel Aviv; Crea; Università di Bologna.

Che cosa: Studio sul genoma del farro selvatico, pubblicato su Science

Per informazioni: Aldo Ceriotti, direttore Ibba-Cnr, tel. 02/23699444, e-mail: ceriotti@ibba.cnr.it

Capo ufficio stampa:
Marco Ferrazzoli
marco.ferrazzoli@cnr.it
ufficiostampa@cnr.it

 

Quantitation of the immunodominant 33-mer peptide from α-gliadin in wheat flours

by luciano

In wheat there are multiple fractions able to activate the adverse response of the human immune system. Among these fractions the most active is that called 33-mer because it is the most resistant to human digestion and because it contains six copies of the three toxic epitopes and its intermolecular bonds are very strong. It is therefore important to know the quantity of this fraction in the grains. The study of which some parts are reported, examined 57 different types of wheat, ancient and modern, noting that the difference, in all soft wheat and spelt flour, of 33-mer is wide: from 90.9 to 602.6 μg / g made with flour. On the other hand, its presence in monococcum wheat and durum wheat was not detected. These results take on great importance because they allow grains to be chosen with limited or no presence of this important toxic fraction for products that are more suitable for non-celiac gluten sensitive people or those suffering from gluten disorders.

“All gluten protein fractions, namely the alcohol-soluble prolamins and the insoluble glutelins, contain CD-active epitopes3. The prolamin fraction is particularly rich in proline and glutamine and the numerous proline residues lead to a high resistance to complete proteolytic digestion by human gastric, pancreatic, and brushborder enzymes. Studies by Shan et al. (2002) showed that a large 33-mer peptide (LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF) from α2-gliadin (position in the amino acid sequence of α2-gliadin: 56–88) is resistant to cleavage by intestinal peptidases4,5. The 33-mer is widely called the most immunodominant gluten peptide4,6,7, because it contains three overlapping T-cell epitopes, namely PFPQPQLPY (DQ2.5-glia-α1a, one copy), PYPQPQLPY (DQ2.5-glia-α1b, two copies) and PQPQLPYPQ (DQ2.5-glia-α2, three copies)3, which result in the initiation of a strong immune response.

Einkorn, emmer and durum wheat

by luciano

Einkorn, emmer and durum wheat: they do not have the “33mer” fraction considered the most active in activating the adverse response of the immune system in celiac subjects. Also for this reason they are the most suitable genotypes for the researches whose aim is to “detoxify” the flours or to intervene with particular enzymes to hydrolyse the “toxic peptides”, however present; they are also more suitable for non-celiac gluten sensitive subjects.

“Quantitation of the immunodominant 33-mer peptide from α-gliadin in wheat flours by liquid chromatography tandem mass spectrometry.

Kathrin Schalk , Christina Lang , Herbert Wieser , Peter Koehler  & Katharina Anne Scherf. Scientific Reports volume 7, Article number: 45092 (2017)

Abstract

Coeliac disease (CD) is triggered by the ingestion of gluten proteins from wheat, rye, and barley. The 33-mer peptide from α2-gliadin has frequently been described as the most important CD-immunogenic sequence within gluten. However, from more than 890 published amino acid sequences of α-gliadins, only 19 sequences contain the 33-mer. In order to make a precise assessment of the importance of the 33-mer, it is necessary to elucidate which wheat species and cultivars contain the peptide and at which concentrations. This paper presents the development of a stable isotope dilution assay followed by liquid chromatography tandem mass spectrometry to quantitate the 33-mer in flours of 23 hexaploid modern and 15 old common (bread) wheat as well as two spelt cultivars. All flours contained the 33-mer peptide at levels ranging from 91–603 μg/g flour. In contrast, the 33-mer was absent (<limit of detection) from tetra- and diploid species (durum wheat, emmer, einkorn), most likely because of the absence of the D-genome, which encodes α2-gliadins. Due to the presence of the 33-mer in all common wheat and spelt flours analysed here, the special focus in the literature on this most immunodominant peptide seems to be justified……Omissis…..

Analysis of durum wheat, emmer and einkorn

The 33-mer peptide was also analysed in two durum wheat and two emmer cultivars (genome AABB) as well as two diploid einkorn cultivars (genome AA) (Table 1). In each of these wheat species, the 33-mer was not detected (<LOD). In comparison to hexaploid common wheat, durum wheat, emmer, and einkorn do not contain the D-genome, which originated from hybridisation of T. turgidum dicoccum (genome AABB) with Aegilops tauschii (genome DD)36. The absence of the 33-mer peptide can be explained by the fact that this peptide is encoded by genes located in the Gli-2 locus on chromosome 6D, which is missing in durum wheat, emmer, and einkorn. Studies by Molberg et al. showed clear variations in intestinal T-cell responses between common wheat and tetra- or diploid species due to different degrees of T-cell immunoreactivity between the gluten proteins encoded on the A-, B-, and D-genome. Einkorn cultivars were only recognized by DQ2.5-glia-α1a-specific T-cell clones, but not by DQ2.5-glia-α1b- and DQ2.5-glia-α2-specific T-cell clones. Emmer and durum wheat cultivars were all recognized by DQ2.5-glia-α1a-specific T-cell clones, but only two out of four emmer cultivars and three out of ten durum wheat cultivars activated DQ2.5-glia-α1b- and DQ2.5-glia-α2-specific T-cell clones37. Consistent with our results, Prandi et al.38 found that the 33-mer was not present in durum wheat. As a consequence, this peptide was used as a marker peptide to identify the presence of common wheat in durum wheat flours. One durum wheat cultivar was also analysed by van den Broeck et al.33 and the 33-mer peptide was not detected either”. https://creativecommons.org/licenses/by/4.0/deed.it