Unprocessed wheat γ-gliadin reduces gluten accumulation associated with the endoplasmic reticulum stress and elevated cell death

Type I MADS-box transcription factor TaMADS-GS regulates grain size by stabilizing cytokinin signalling during endosperm cellularization in wheat

Grain size is one of the important traits in wheat breeding programs aimed at improving yield, and cytokinins, mainly involved in cell division, have a positive impact on grain size. Here, we identified a novel wheat gene TaMADS-GS encoding type I MADS-box transcription factor, which regulates the cytokinins signalling pathway during early stages of grain development to modulate grain size and weight in wheat. TaMADS-GS is exclusively expressed in grains at early stage of seed development and its knockout leads to delayed endosperm cellularization, smaller grain size and lower grain weight. TaMADS-GS protein interacts with the Polycomb Repressive Complex 2 (PRC2) and leads to repression of genes encoding cytokinin oxidase/dehydrogenases (CKXs) stimulating cytokinins inactivation by mediating accumulation of the histone H3 trimethylation at lysine 27 (H3K27me3). Through the screening of a large wheat germplasm collection, an elite allele of the TaMADS-GS exhibits higher ability to repress expression of genes inactivating cytokinins and a positive correlation with grain size and weight, thus representing a novel marker for breeding programs in wheat. Overall, these findings support the relevance of TaMADS-GS as a key regulator of wheat grain size and weight.

An elite γ-gliadin allele improves end-use quality in wheat

Gluten is composed of glutenins and gliadins and determines the viscoelastic properties of dough and end-use quality in wheat (Triticum aestivum L.). Gliadins are important for wheat end-use traits, but the contribution of individual gliadin genes is unclear, since gliadins are encoded by a complex, multigenic family, including many pseudogenes. We used CRISPR/Cas9-mediated gene editing and map-based cloning to investigate the contribution of the γ-gliadin genes annotated in the wheat cultivar 'Fielder', showing that Gli-γ1-1D and Gli-γ2-1B account for most of the γ-gliadin accumulation. The impaired activity of only two γ-gliadin genes in knockout mutants improved end-use quality and reduced gluten epitopes associated with celiac disease (CD). Furthermore, we identified an elite haplotype of Gli-γ1-1D linked to higher end-use quality in a wheat germplasm collection and developed a molecular marker for this allele for marker-assisted selection. Our findings provide information and tools for biotechnology-based and classical breeding programs aimed at improving wheat end-use quality.

Effect of gliadin from Psathrostachys huashanica on dough rheological properties and biscuit quality

Psathrostachys huashanica (P. huashanica), a wild relative of common wheat, is widely used in wheat variety improvement because of its many beneficial properties. In this study, we carried out preliminary analysis on the grain and flour quality of wheat-P. huashanica addition line 7182-6Ns and its wheat parents 7182, and found that 7182-6Ns had a higher protein content and great dough rheological characteristics and investigated the reasons for the changes. The results indicated that 7182-6Ns contained exogenous gliadin, which changed the gliadin composition and increased the ratio of gliadin in total gluten proteins, rebuilt gluten microstructure and thus optimized dough extensibility. As the addition of 7182-6Ns gliadin gradually increased to wheat flour, the diameter, crispness and spread rate of biscuit increased, the thickness and hardness decreased, and the colour improved. The current research provides a basis for understanding the introduction of exogenic gliadin to improve biscuit wheat varieties.

Pinb-D1p is an elite allele for improving end-use quality in wheat (Triticum aestivum L.)

We identified ten QTLs controlling SDS-SV trait in a RIL population derived from ND3331 and Zang1817. Pinb-D1p is an elite allele from Tibetan semi‑wild wheat for good end-use quality. Gluten strength is an important factor for wheat processing and end-product quality and is commonly characterized using the sodium dodecyl sulfate-sedimentation volume (SDS-SV) test. The objective of this study was to identify quantitative trait loci (QTLs) associated with wheat SDS-SV traits using a recombinant inbred line (RIL) population derived from common wheat line NongDa3331 (ND3331) and Tibetan semi-wild wheat accession Zang1817. We detected 10 QTLs controlling SDS-SV on chromosomes 1A, 1B, 3A, 4A, 4B, 5A, 5D, 6B and 7A, with individual QTLs explaining 2.02% to 15.53% of the phenotypic variation. They included four major QTLs, Qsdss-1A, Qsdss-1B.1, Qsdss-1B.2, and Qsdss-5D, whose effects on SDS-SV were due to the Glu-A1 locus encoding the high-molecular-weight glutenin subunit 1Ax1, the 1B/1R translocation, 1Bx7 + 1By8 at the Glu-B1 locus, and the hardness-controlling loci Pina-D1 and Pinb-D1, respectively. We developed KASP markers for the Glu-A1, Glu-B1, and Pinb-D1 loci. Importantly, we showed for the first time that the hardness allele Pinb-D1p positively affects SDS-SV, making it a good candidate for wheat quality improvement. These results broaden our understanding of the genetic characterization of SDS-SV, and the QTLs identified are potential target regions for fine-mapping and marker-assisted selection in wheat breeding programs.