Publications by authors named "Peter Shewry"

185 Publications

Subcellular dynamics studies of iron reveal how tissue-specific distribution patterns are established in developing wheat grains.

New Phytol 2021 Apr 29. Epub 2021 Apr 29.

Department of Biological Chemistry, John Innes Centre, Norwich, NR4 7UH, UK.

Understanding the mechanisms of iron trafficking in plants is key to enhancing the nutritional quality of crops. Because it is difficult to image iron in transit, we currently have an incomplete picture of the route(s) of iron translocation in developing seeds and how the tissue-specific distribution is established. We have used a novel approach, combining Fe isotope labelling and Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS), to visualize iron translocation between tissues and within cells in immature wheat grain, Triticum aestivum L. This enabled us to track the main route of iron transport from maternal tissues to the embryo through the different cell types. Further evidence for this route was provided by genetically diverting iron into storage vacuoles, with confirmation provided by histological staining and TEM-EDS. Almost all iron in both control and transgenic grains was found in intracellular bodies, indicating symplastic rather than apoplastic transport. Furthermore, a new type of iron body, highly enriched in Fe, was observed in aleurone cells and may represent iron being delivered to phytate globoids. Correlation of the Fe enrichment profiles obtained by NanoSIMS with tissue-specific gene expression provides an updated model of iron homeostasis in cereal grains with relevance for future biofortification strategies.
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http://dx.doi.org/10.1111/nph.17440DOI Listing
April 2021

Accumulation and deposition of triacylglycerols in the starchy endosperm of wheat grain.

J Cereal Sci 2021 Mar;98:103167

Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.

A combination of lipidomics, transcriptomics and bioimaging has been used to study triacylglycerol synthesis and deposition in the developing starchy endosperm of wheat. The content of TAG increased between 14 and 34 days after anthesis, from 50 to 115 mg/100 g dry wt and from about 35 to 175 mg/100 g dry wt in two experiments. The major fatty acids were C16 (palmitic C16:0 and palmitoleic C16:1) and C18 (stearic C18:0, oleic C18:1, linoleic C18:2 and linolenic C18:3), with unsaturated fatty acids accounting for about 75-80% of the total throughout development. Linoleic acid (C18:2) was the major component at all stages and the proportion increased during development. Transcript profiling indicated that predominant route to TAG synthesis and oil accumulation is via the Kennedy pathway and diacylglycerol acyltransferase (DGAT) activity. Confocal microscopy of stained tissue sections showed that TAG accumulated in droplets which are associated with protein and concentrated in the starchy endosperm cells below the sub-aleurone cells. Transcripts encoding 16kd oleosins were also expressed, indicating that the oil droplets are in part stabilised by oleosin proteins.
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http://dx.doi.org/10.1016/j.jcs.2021.103167DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8047771PMC
March 2021

Wheat amino acid transporters highly expressed in grain cells regulate amino acid accumulation in grain.

PLoS One 2021 19;16(2):e0246763. Epub 2021 Feb 19.

Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom.

Amino acids are delivered into developing wheat grains to support the accumulation of storage proteins in the starchy endosperm, and transporters play important roles in regulating this process. RNA-seq, RT-qPCR, and promoter-GUS assays showed that three amino acid transporters are differentially expressed in the endosperm transfer cells (TaAAP2), starchy endosperm cells (TaAAP13), and aleurone cells and embryo of the developing grain (TaAAP21), respectively. Yeast complementation revealed that all three transporters can transport a broad spectrum of amino acids. RNAi-mediated suppression of TaAAP13 expression in the starchy endosperm did not reduce the total nitrogen content of the whole grain, but significantly altered the composition and distribution of metabolites in the starchy endosperm, with increasing concentrations of some amino acids (notably glutamine and glycine) from the outer to inner starchy endosperm cells compared with wild type. Overexpression of TaAAP13 under the endosperm-specific HMW-GS (high molecular weight glutenin subunit) promoter significantly increased grain size, grain nitrogen concentration, and thousand grain weight, indicating that the sink strength for nitrogen transport was increased by manipulation of amino acid transporters. However, the total grain number was reduced, suggesting that source nitrogen remobilized from leaves is a limiting factor for productivity. Therefore, simultaneously increasing loading of amino acids into the phloem and delivery to the spike would be required to increase protein content while maintaining grain yield.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0246763PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894817PMC
February 2021

The role of gene flow and chromosomal instability in shaping the bread wheat genome.

Nat Plants 2021 02 1;7(2):172-183. Epub 2021 Feb 1.

Life Sciences, University of Bristol, Bristol, UK.

Bread wheat (Triticum aestivum) is one of the world's most important crops; however, a low level of genetic diversity within commercial breeding accessions can significantly limit breeding potential. In contrast, wheat relatives exhibit considerable genetic variation and so potentially provide a valuable source of novel alleles for use in breeding new cultivars. Historically, gene flow between wheat and its relatives may have contributed novel alleles to the bread wheat pangenome. To assess the contribution made by wheat relatives to genetic diversity in bread wheat, we used markers based on single nucleotide polymorphisms to compare bread wheat accessions, created in the past 150 years, with 45 related species. We show that many bread wheat accessions share near-identical haplotype blocks with close relatives of wheat's diploid and tetraploid progenitors, while some show evidence of introgressions from more distant species and structural variation between accessions. Hence, introgressions and chromosomal rearrangements appear to have made a major contribution to genetic diversity in cultivar collections. As gene flow from relatives to bread wheat is an ongoing process, we assess the impact that introgressions might have on future breeding strategies.
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http://dx.doi.org/10.1038/s41477-020-00845-2DOI Listing
February 2021

Wheat Seed Proteins: Factors Influencing Their Content, Composition, and Technological Properties, and Strategies to Reduce Adverse Reactions.

Compr Rev Food Sci Food Saf 2019 Nov 9;18(6):1751-1769. Epub 2019 Sep 9.

Laboratory of Food Chemistry and Biochemistry, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Kasteelpark Arenberg 20, B-3001, Leuven, Belgium.

Wheat is the primary source of nutrition for many, especially those living in developing countries, and wheat proteins are among the most widely consumed dietary proteins in the world. However, concerns about disorders related to the consumption of wheat and/or wheat gluten proteins have increased sharply in the last 20 years. This review focuses on wheat gluten proteins and amylase trypsin inhibitors, which are considered to be responsible for eliciting most of the intestinal and extraintestinal symptoms experienced by susceptible individuals. Although several approaches have been proposed to reduce the exposure to gluten or immunogenic peptides resulting from its digestion, none have proven sufficiently effective for general use in coeliac-safe diets. Potential approaches to manipulate the content, composition, and technological properties of wheat proteins are therefore discussed, as well as the effects of using gluten isolates in various food systems. Finally, some aspects of the use of gluten-free commodities are discussed.
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http://dx.doi.org/10.1111/1541-4337.12493DOI Listing
November 2019

Increased bioavailability of phenolic acids and enhanced vascular function following intake of feruloyl esterase-processed high fibre bread: A randomized, controlled, single blind, crossover human intervention trial.

Clin Nutr 2021 Mar 8;40(3):788-795. Epub 2020 Aug 8.

Department of Food and Nutritional Sciences, School of Chemistry, Food and Pharmacy, University of Reading, Reading, UK (ALT, JPES).. Electronic address:

Background & Aims: Clinical trial data have indicated an association between wholegrain consumption and a reduction in surrogate markers of cardiovascular disease. Phenolics present in wholegrain bound to arabinoxylan fibre may contribute these effects, particularly when released enzymatically from the fiber prior to ingestion. The aim of the present study was therefore to determine whether the intake of high fibre bread containing higher free ferulic acid (FA) levels (enzymatically released during processing) enhances human endothelium-dependent vascular function.

Methods: A randomized, single masked, controlled, crossover, human intervention study was conducted on 19 healthy men. Individuals consumed either a high fibre flatbread with enzymatically released free FA (14.22 mg), an equivalent standard high fibre bread (2.34 mg), or a white bread control (0.48 mg) and markers of vascular function and plasma phenolic acid concentrations were measured at baseline, 2, 5 and 7 h post consumption.

Results: Significantly increased brachial arterial dilation was observed following consumption of the high free FA ('enzyme-treated') high fibre bread verses both a white bread (2 h: p < 0.05; 5 h: p < 0.01) and a standard high fibre bread (5 h: p < 0.05). Concurrently, significant increases in plasma FA levels were observed, at 2 h (p < 0.01) after consumption of the enzyme-treated bread, relative to control treatments. Blood pressure, heart rate, DVP-SI and DVP-RI were not significantly altered following intake of any of the breads (p > 0.05).

Conclusion: Dietary intake of bread, processed enzymatically to release FA from arabinoxylan fiber during production increases the bioavailability of FA, and induces acute endothelium-dependent vasodilation.

Clinical Trial Registry: NO: NCT03946293. WEBSITE: www.clinicaltrials.gov.
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http://dx.doi.org/10.1016/j.clnu.2020.07.026DOI Listing
March 2021

The contribution of fiber components to water absorption of wheat grown in the UK.

Cereal Chem 2020 Sep-Oct;97(5):940-948. Epub 2020 Jul 16.

Rothamsted Research Harpenden UK.

Background And Objectives: The water absorption (WA) of white wheat flour is a major factor affecting processing quality, and millers, therefore, process their wheat to achieve the required level. Although it is likely that WA is determined by the amounts and compositions of three major grain components, starch, protein, and arabinoxylan, the contribution of the latter is not agreed and not recognized in the widely used Farrand equation.

Findings: We have measured a range of parameters related to fiber amount and composition and tested the ability of these to improve the prediction of WA using a modified Farrand equation. The addition of a range of single fiber traits improved the prediction of WA from a baseline of 82.98% to a maximum of 86.78%, but inclusion of all fiber traits as PCs resulted in a further improvement to 90%. Inclusion of the PCs also accounted for variation in WA between harvest years. The greatest improvement from inclusion of a single trait was observed with β-glucan, the inclusion of arabinogalactan peptide (AGP) also resulted in improved prediction of WA.

Conclusions: The study shows that fiber components contribute to variation in WA, including differences between harvest years, but that β-glucan and AGP have similar or greater impacts than AX.

Significance And Novelty: The study dissects the contributions of AX amount and composition to WA and demonstrates a contribution of b-glucan for the first time.
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http://dx.doi.org/10.1002/cche.10316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540380PMC
July 2020

Genetic variation and heritability of grain protein deviation in European wheat genotypes.

Field Crops Res 2020 Sep;255:107896

Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.

There is a well-established negative relationship between the yield and the concentration of protein in the mature wheat grain. However, some wheat genotypes consistently deviate from this relationship, a phenomenon known as Grain Protein Deviation (GPD). Positive GPD is therefore of considerable interest in relation to reducing the requirement for nitrogen fertilization for producing wheat for breadmaking. We have carried out two sets of field experiments on multiple sites in South East England. The first set comprised 11 field trials of 6 cultivars grown over three years (2008-2011) and the second comprised 9 field trials of 40 genotypes grown over two years (2015-2017) and 5 field trials of 30 genotypes grown in a single year (2017-2018). All trials comprised three replicate randomized plots of each genotype and nutrient regime. These studies showed strong genetic variation in GPD, which also differed in stability between genotypes, with cultivars bred in the UK generally having higher GPD and higher stability than those bred in other European countries. The heritability of GPD was estimated as 0.44, based on data from the field trials of 30 and 40 genotypes. The largest component contributing to the genetic variance was genotype (0.30), with a smaller contribution of the interaction between genotype and year/site (0.11) and a small (but statistically significant) contribution of nitrogen level. These studies suggest that selection for GPD is a viable target for breeders.
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http://dx.doi.org/10.1016/j.fcr.2020.107896DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397848PMC
September 2020

Mapping Coeliac Toxic Motifs in the Prolamin Seed Storage Proteins of Barley, Rye, and Oats Using a Curated Sequence Database.

Front Nutr 2020 17;7:87. Epub 2020 Jul 17.

Division of Infection, Immunity and Respiratory Medicine, Faculty of Biology, Medicine and Health, Manchester Institute of Biotechnology, University of Manchester, Manchester, United Kingdom.

Wheat gluten, and related prolamin proteins in rye, barley and oats cause the immune-mediated gluten intolerance syndrome, coeliac disease. Foods labelled as gluten-free which can be safely consumed by coeliac patients, must not contain gluten above a level of 20 mg/Kg. Current immunoassay methods for detection of gluten can give conflicting results and may underestimate levels of gluten in foods. Mass spectrometry methods have great potential as an orthogonal method, but require curated protein sequence databases to support method development. The GluPro database has been updated to include avenin-like sequences from bread wheat ( = 685; GluPro v1.1) and genes from the sequenced wheat genome ( = 699; GluPro v 1.2) and ssp durum ( = 210; GluPro v 2.1). Companion databases have been developed for prolamin sequences from barley ( = 64; GluPro v 3.0), rye ( = 41; GluPro v 4.0), and oats ( = 27; GluPro v 5.0) and combined to provide a complete cereal prolamin database, GluPro v 6.1 comprising 1,041 sequences. Analysis of the coeliac toxic motifs in the curated sequences showed that they were absent from the minor avenin-like proteins in bread and durum wheat and barley, unlike the related avenin proteins from oats. A comparison of prolamin proteins from the different cereal species also showed α- and γ-gliadins in bread and durum wheat, and the sulphur poor prolamins in all cereals had the highest density of coeliac toxic motifs. Analysis of ion-mobility mass spectrometry data for bread wheat (cvs Chinese Spring and Hereward) showed an increased number of identifications when using the GluPro v1.0, 1.1 and 1.2 databases compared to the limited number of verified sequences bread wheat sequences in reviewed UniProt. This family of databases will provide a basis for proteomic profiling of gluten proteins from all the gluten containing cereals and support identification of specific peptide markers for use in development of new methods for gluten quantitation based on coeliac toxic motifs found in all relevant cereal species.
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http://dx.doi.org/10.3389/fnut.2020.00087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7379453PMC
July 2020

Editorial: : Promising Genesources to Improve Agronomical and Quality Traits of Wheat.

Front Plant Sci 2020 14;11:1060. Epub 2020 Jul 14.

Department of Plant Science, Rothamsted Research, Harpenden, United Kingdom.

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http://dx.doi.org/10.3389/fpls.2020.01060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7371959PMC
July 2020

Genetic variation in wheat grain quality is associated with differences in the galactolipid content of flour and the gas bubble properties of dough liquor.

Food Chem X 2020 Jun 2;6:100093. Epub 2020 Jun 2.

Department of Plant Science, Rothamsted Research, West Common, Harpenden, Hertfordshire AL5 2JQ, UK.

Lipids affect the quality of wheat flour for breadmaking. One possible mechanism is stabilization of the gas cells which are formed during dough mixing and expanded during fermentation, leading to a greater loaf volume and evenness of texture. We therefore compared the lipidomic profiles of flour and dough liquor fractions (which contain surface-active components present at the gas bubble interface) from two sets of wheat lines differing in allelic variation at a QTL for loaf volume. Analyses of fractions from three field trials showed consistent increases in the contents of galactolipids (monogalactosyl diglyceride and digalactosyl diglyceride) in flour and dough liquor of the lines with the increasing (good quality) allele. Biophysical analysis showed that this was associated with greater elasticity of the dough liquor fraction. This is consistent with published studies reporting a relationship between galactolipids and breadmaking quality and suggests a mechanism of action for the QTL.
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http://dx.doi.org/10.1016/j.fochx.2020.100093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7292906PMC
June 2020

Transitions in wheat endosperm metabolism upon transcriptional induction of oil accumulation by oat endosperm WRINKLED1.

BMC Plant Biol 2020 May 25;20(1):235. Epub 2020 May 25.

Department of Plant Breeding, Swedish University of Agricultural Sciences, SE-23053, Alnarp, Sweden.

Background: Cereal grains, including wheat (Triticum aestivum L.), are major sources of food and feed, with wheat being dominant in temperate zones. These end uses exploit the storage reserves in the starchy endosperm of the grain, with starch being the major storage component in most cereal species. However, oats (Avena sativa L.) differs in that the starchy endosperm stores significant amounts of oil. Understanding the control of carbon allocation between groups of storage compounds, such as starch and oil, is therefore important for understanding the composition and hence end use quality of cereals. WRINKLED1 is a transcription factor known to induce triacylglycerol (TAG; oil) accumulation in several plant storage tissues.

Results: An oat endosperm homolog of WRI1 (AsWRI1) expressed from the endosperm-specific HMW1Dx5 promoter resulted in drastic changes in carbon allocation in wheat grains, with reduced seed weight and a wrinkled seed phenotype. The starch content of mature grain endosperms of AsWRI1-wheat was reduced compared to controls (from 62 to 22% by dry weight (dw)), TAG was increased by up to nine-fold (from 0.7 to 6.4% oil by dw) and sucrose from 1.5 to 10% by dw. Expression of AsWRI1 in wheat grains also resulted in multiple layers of elongated peripheral aleurone cells. RNA-sequencing, lipid analyses, and pulse-chase experiments using C-sucrose indicated that futile cycling of fatty acids could be a limitation for oil accumulation.

Conclusions: Our data show that expression of oat endosperm WRI1 in the wheat endosperm results in changes in metabolism which could underpin the application of biotechnology to manipulate grain composition. In particular, the striking effect on starch synthesis in the wheat endosperm indicates that an important indirect role of WRI1 is to divert carbon allocation away from starch biosynthesis in plant storage tissues that accumulate oil.
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http://dx.doi.org/10.1186/s12870-020-02438-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7249431PMC
May 2020

Stability analysis of wheat lines with increased level of arabinoxylan.

PLoS One 2020 8;15(5):e0232892. Epub 2020 May 8.

Agricultural Institute, Centre for Agricultural Research, Martonvásár, Hungary.

Plant breeders have long sought to develop lines that combine outstanding performance with high and stable quality in different environments. The high-arabinoxylan (AX) Chinese variety Yumai-34 was crossed with three Central European wheat varieties (Lupus, Mv-Mambo, Ukrainka) and 31 selected high-AX lines were compared for physical (hectolitre weight, thousand grain weight, flour yield), compositional (protein content, gluten content, pentosan) and processing quality traits (gluten index, Zeleny sedimentation, Farinograph parameters) in a three-year experiment (2013-2015) in the F7-F9 generations. The stability and heritability of different traits, including the relative effects of the genotype (G) and environment (E), were determined focusing on grain composition. The contents of total and water-soluble pentosans were significantly affected by G, E and G × E interactions, but the heritability of total (TOT)-pentosan was significantly lower (0.341) than that of water-extractable (WE)-pentosan (0.825). The main component of the pentosans, the amount and composition (arabinose:xylose ratio) of the arabinoxylan (AX), was primarily determined by the environment and, accordingly, the broader heritability of these parameters were 0.516 and 0.772. However, genotype significantly affected the amount of water-soluble arabinoxylan and its composition and thus the heritability of these traits was also significant (0.840 and 0.721). The genotypes exhibiting higher stability of content of TOT-pentosan also showed more stable contents of WE-pentosan. There was a positive correlation between the stability of contents of WE-pentosan and WE-AX, while the stability of the WE-AX content and AX composition were also strongly correlated. Water absorption was strongly genetically determined with a heritability of 0.829 with the genotype determining 38.67% of the total variance. Many lines were grouped in the GGE biplot, indicating that they did not significantly differ stability.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0232892PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7209258PMC
August 2020

Loss of TaIRX9b gene function in wheat decreases chain length and amount of arabinoxylan in grain but increases cross-linking.

Plant Biotechnol J 2020 11 17;18(11):2316-2327. Epub 2020 May 17.

Plant Sciences, Rothamsted Research, Harpenden, UK.

Wheat contains abundant xylan in cell walls of all tissues, but in endosperm, there is an unusual form of xylan substituted only by arabinose (arabinoxylan; AX) that has long chains and low levels of feruloylation, a fraction of which is extractable in water (WE-AX). WE-AX acts as soluble dietary fibre but also gives rise to viscous extracts from grain, a detrimental trait for some non-food uses of wheat. Here, we show that a glycosyl transferase family 43 wheat gene abundantly expressed in endosperm complements the Arabidopsis irx9 mutant and so name the three homoeologous genes TaIRX9b. We generated wheat lines with a constitutive knockout of TaIRX9b by stacking loss-of-function alleles for these homeologues from a mutagenized hexaploid wheat population resulting in decreases in grain extract viscosity of 50%-80%. The amount and chain length of WE-AX molecules from grain of these triple-stack lines was decreased accounting for the changes in extract viscosity. Imaging of immature wheat grain sections of triple-stacks showed abolition of immunolabelling in endosperm with LM11 antibody that recognizes epitopes in AX, but also showed apparently normal cell size and shape in all cell types, including endosperm. We identified differentially expressed genes from endosperm of triple-stacks suggesting that compensatory changes occur to maintain this endosperm cell wall integrity. Consistent with this, we observed increased ferulate dimerization and increased cross-linking of WE-AX molecules in triple-stacks. These novel wheat lines lacking functional TaIRX9b therefore provide insight into control of wheat endosperm cell walls.
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http://dx.doi.org/10.1111/pbi.13393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589350PMC
November 2020

Historical changes in the contents and compositions of fibre components and polar metabolites in white wheat flour.

Sci Rep 2020 04 3;10(1):5920. Epub 2020 Apr 3.

Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.

Thirty-nine UK adapted wheat cultivars dating from between 1790 and 2012 were grown in replicated randomised field trials for three years, milled, and white flour analysed for the contents of dietary fibre components (arabinoxylan and β-glucan) and polar metabolites (sugars, amino acids, organic acids, choline and betaine) to determine whether the composition had changed due to the effects of intensive breeding. The concentrations of components varied between study years, indicating strong effects of environment. Nevertheless, some trends were observed, with the concentrations of arabinoxylan fibre and soluble sugars (notably sucrose, maltose and fructose) increasing and most amino acids (including asparagine which is the precursor of acrylamide formed during processing) decreasing between the older and newer types. The concentration of betaine, which is beneficial for cardio-vascular health, also increased. The study therefore provided no evidence for adverse effects of intensive breeding on the contents of beneficial components in wheat flour.
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http://dx.doi.org/10.1038/s41598-020-62777-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7125105PMC
April 2020

Novel sources of variation in grain Zinc (Zn) concentration in bread wheat germplasm derived from Watkins landraces.

PLoS One 2020 28;15(2):e0229107. Epub 2020 Feb 28.

School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom.

A diverse panel of 245 wheat genotypes, derived from crosses between landraces from the Watkins collection representing global diversity in the early 20th century and the modern wheat cultivar Paragon, was grown at two field sites in the UK in 2015-16 and the concentrations of zinc and iron determined in wholegrain using inductively coupled plasma-mass spectrometry (ICP-MS). Zinc concentrations in wholegrain varied from 24-49 mg kg-1 and were correlated with iron concentration (r = 0.64) and grain protein content (r = 0.14). However, the correlation with yield was low (r = -0.16) indicating little yield dilution. A sub-set of 24 wheat lines were selected from 245 wheat genotypes and characterised for Zn and Fe concentrations in wholegrain and white flour over two sites and years. White flours from 24 selected lines contained 8-15 mg kg-1 of zinc, which was positively correlated with the wholegrain Zn concentration (r = 0.79, averaged across sites and years). This demonstrates the potential to exploit the diversity in landraces to increase the concentration of Zn in wholegrain and flour of modern high yielding bread wheat cultivars.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0229107PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7048275PMC
May 2020

Spatial distribution of functional components in the starchy endosperm of wheat grains.

J Cereal Sci 2020 Jan;91:102869

School of Agriculture, Policy and Development, University of Reading, Whiteknights Campus, Early Gate, RG6 6AR, Reading, UK.

The starchy endosperm of the mature wheat grain comprises three major cell types, namely sub-aleurone cells, prismatic cells and central cells, which differ in their contents of functional components: gluten proteins, starch, cell wall polysaccharides (dietary fibre) and lipids. Gradients are established during grain development but may be modified during grain maturation and are affected by plant nutrition, particularly nitrogen application, and environmental factors. Although the molecular controls of their formation are unknown, the high content of protein and low content of starch of sub-aleurone cells, compared to the other starchy endosperm cells types, may result from differences in developmental programming related to the cells having a separate origin (from anticlinal division of the aleurone cells). The gradients within the grain may be reflected in differences in the compositions of mill streams, particularly those streams enriched in the central and outer cells of the starchy endosperm, respectively, allowing the production of specialist flours for specific end uses.
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http://dx.doi.org/10.1016/j.jcs.2019.102869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7015275PMC
January 2020

Identification of a major QTL and associated molecular marker for high arabinoxylan fibre in white wheat flour.

PLoS One 2020 5;15(2):e0227826. Epub 2020 Feb 5.

John Innes Centre, Norwich Research Park, Colney Lane, Norwich, United Kingdom.

Dietary fibre (DF) has multiple health benefits and wheat grains are major sources of DF for human health. However, DF is depleted in white wheat flour which is more widely consumed than wholegrain. The major DF component in white flour is the cell wall polysaccharide arabinoxylan (AX). We have identified the Chinese wheat cultivar Yumai 34 as having unusually high contents of AX in both water-soluble and insoluble forms. We have therefore used populations generated from crosses between Yumai 34 and four other wheat cultivars, three with average contents of AX (Ukrainka, Altigo and Claire) and one also having unusually high AX (Valoris), in order to map QTLs for soluble AX (determined as relative viscosity of aqueous extracts of wholemeal flours) and total AX (determined by enzyme fingerprinting of white flour). A number of QTL were mapped, but most were only detected in one or two crosses. However, all four crosses showed strong QTLs for high RV/total AX on chromosome 1B, with Yumai 34 being the increasing parent, and a KASP marker for the Yumai 34 high AX allele was validated by analysis of high AX lines derived from Yumai 34 but selected by biochemical analysis. A QTL for RV was also mapped on chromosome 6B in Yumai 34 x Valoris, with Valoris being the increasing allele, which is consistent with the observation of transgressive segregation for this population. Association studies in an independent germplasm panel identified marker trait associations for relative viscosity in these same locations while direct selection for fibre content in breeding resulted in high levels of enrichment for the Yumai 34 1B allele. The data therefore indicate that marker-assisted breeding can be used to develop wheat with high AX fibre in white flour.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0227826PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7001892PMC
April 2020

Comparative prebiotic activity of mixtures of cereal grain polysaccharides.

AMB Express 2019 Dec 21;9(1):203. Epub 2019 Dec 21.

Department of Plant Science, Rothamsted Research, Harpenden, AL5 2JQ, Hertfordshire, UK.

The main components of the non-starch polysaccharide (NSP) fraction of wheat flour are arabinoxylan (AX) and β-glucan. These are also present in other cereal grains, but their proportions vary with AX being the major component in wheat and rye and β-glucan in barley and oats. Therefore, it was hypothesised that these NSPs could act synergistically when fermented in vitro at the ratios present in the major foods consumed, resulting in increased prebiotic activity. AX and β-glucan were therefore tested in in vitro fermentation studies to assess their prebiotic activity when used individually and/or in different ratios. Short-chain fatty-acids (SCFAs) produced from in vitro fermentation were measured using HPLC and bacterial populations were measured using flow cytometry with fluorescence in situ hybridisation (Flow-FISH). Fermentation of AX alone resulted in a significant bifidogenic activity and increased concentrations of SCFAs, mainly acetate, after 8-24 h of fermentation, however β-glucan alone did not show prebiotic activity. The greatest prebiotic activity, based on concentration of total SCFAs and increases in total bacteria as well as beneficial Bifidobacterium and Clostridium coccoides/Eubacterium groups, was observed when AX and β-glucan were combined at a 3:1 ratio, which corresponds to their ratios in wheat flour which is major source of cereal fibre in the diet. This indicates that the population of bacteria in the human GI tract may be modulated by the composition of the fibre in the diet, to maximise the prebiotic potential.
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http://dx.doi.org/10.1186/s13568-019-0925-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6925609PMC
December 2019

Large increase in yield is predicted by wheat ideotypes for Europe under future climate.

Glob Chang Biol 2019 Dec 4. Epub 2019 Dec 4.

Department of Plant Sciences, Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom.

A substantial increase in food production is needed for future global food security. Raising upper limits in crop yield potential is the key for increasing food production under future climates. Europe is the largest wheat producer delivering about 35% wheat globally, but its genetic yield potential under future climate is yet unknown. Using the Sirius wheat model, we estimated genetic yield potential of wheat in Europe under 2050-climate (HadGEM2, RCP8.5) by designing in silico wheat ideotypes, based on state-of-the-art knowledge in crop physiology and availability of genetic variation in wheat germplasm. Wheat ideotypes were optimised for yield in rainfed condition by using an evolutionary algorithm with self-adaptation and utilizing the full parameter ranges in a multidimensional space of cultivar traits. To evaluate importance of heat and drought stresses around flowering, a critical stage in wheat development, sensitive and tolerant ideotypes were designed. Grain yields of wheat ideotypes under 2050-climate ranged from 9-17 t/ha across major wheat growing regions in Europe. Yield potential of wheat ideotypes were highest in north-western Europe, followed by central-western and central-eastern Europe, whereas yield was lowest in north-eastern and south-western Europe. Both ideotypes showed a substantially greater yield of 66%-89% compared to current local cultivars under optimal managements. Advantages of a tolerant ideotype over sensitive were region specific reaching up to 44% greater yields for tolerant ideotypes in south-western Europe. Optimal canopy structure, phenology and root water uptake, and tolerance to heat and drought stresses around flowering were identified as key traits for improvements to achieve maximum genetic yield potentials. Ideotype design is a powerful methodology with the potential to accelerate crop improvement, genetic adaptation and breeding by providing selection targets and their optimal combination for increased yield under global climate change.
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http://dx.doi.org/10.1111/gcb.14943DOI Listing
December 2019

Development of a reproducible method of analysis of iron, zinc and phosphorus in vegetables digests by SEC-ICP-MS.

Food Chem 2020 Mar 15;308:125652. Epub 2019 Oct 15.

Rothamsted Research, West Common, Harpenden, Hertfordshire AL5 2JQ, UK.

Vegetables contain iron, zinc and phosphorus as complexes with phytates limiting their availability from a vegetarian diet, meaning non-haem iron deficiency anaemia and zinc deficiency immune malfunction are a risk. Although these elements have been analysed previously in biological fluids and cereal using LC-ICP-MS, there is no method suitable for analysing iron, zinc and phosphorus simultaneously in vegetables because of their complex matrix. In this study, we analysed iron, zinc and phosphorus in cabbage, broccoli, pepper, spinach, kale and rocket after a simulated gastrointestinal digestion using a newly optimised SEC-ICP-MS method. Ammonium nitrate, as the mobile phase, and a suitable rinsing regime, allowed good reproducibility and maintenance of the equipment. The method showed good reproducibility and can be easily adapted to other vegetables, as required.
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http://dx.doi.org/10.1016/j.foodchem.2019.125652DOI Listing
March 2020

Improving Rice Dietary Fibre Content and Composition for Human Health.

J Nutr Sci Vitaminol (Tokyo) 2019 ;65(Supplement):S48-S50

Department of Plant Sciences, Rothamsted Research.

Soft textured rice is the major source of calories in the diet of most South East (SE) Asian countries. However, it is most often consumed after polishing which removes the bran and embryo and hence most of the vitamins, minerals and dietary fibre (DF) are lost. Consequently, white rice comprises over 90% starch with only trace amounts of DF and is rapidly digested in the human gastrointestinal tract, resulting in a high glycaemic index (GI). The excessive consumption of high GI foods is associated with increased risks of a range of chronic diseases including type-2 diabetes, cardiovascular disease (CVD) and some types of cancer. Furthermore, the incidence of these conditions is dramatically increasing in areas where white rice is the staple food, notably Asia, with the prevalence of diabetes in SE Asia alone predicted to reach 120 million by 2030. It is therefore necessary to develop rice lines in which high energy content is combined with low GI. This may be achieved by combining acceptable levels of resistant starch (RS) with an increased content of the cell wall derived-dietary fibre components.
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http://dx.doi.org/10.3177/jnsv.65.S48DOI Listing
March 2020

Adverse Reactions to Wheat or Wheat Components.

Compr Rev Food Sci Food Saf 2019 Sep 17;18(5):1437-1452. Epub 2019 Jul 17.

Div. of Gastroenterology-Hepatology, Dept. of Internal Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht Univ. Medical Center, Maastricht, The Netherlands.

Wheat is an important staple food globally, providing a significant contribution to daily energy, fiber, and micronutrient intake. Observational evidence for health impacts of consuming more whole grains, among which wheat is a major contributor, points to significant risk reduction for diabetes, cardiovascular disease, and colon cancer. However, specific wheat components may also elicit adverse physical reactions in susceptible individuals such as celiac disease (CD) and wheat allergy (WA). Recently, broad coverage in the popular and social media has suggested that wheat consumption leads to a wide range of adverse health effects. This has motivated many consumers to avoid or reduce their consumption of foods that contain wheat/gluten, despite the absence of diagnosed CD or WA, raising questions about underlying mechanisms and possible nocebo effects. However, recent studies did show that some individuals may suffer from adverse reactions in absence of CD and WA. This condition is called non-celiac gluten sensitivity (NCGS) or non-celiac wheat sensitivity (NCWS). In addition to gluten, wheat and derived products contain many other components which may trigger symptoms, including inhibitors of α-amylase and trypsin (ATIs), lectins, and rapidly fermentable carbohydrates (FODMAPs). Furthermore, the way in which foods are being processed, such as the use of yeast or sourdough fermentation, fermentation time and baking conditions, may also affect the presence and bioactivity of these components. The present review systematically describes the characteristics of wheat-related intolerances, including their etiology, prevalence, the components responsible, diagnosis, and strategies to reduce adverse reactions.
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http://dx.doi.org/10.1111/1541-4337.12475DOI Listing
September 2019

Composition and content of phenolic acids and avenanthramides in commercial oat products: Are oats an important polyphenol source for consumers?

Food Chem X 2019 Sep 4;3:100047. Epub 2019 Jul 4.

Department of Food and Nutritional Sciences, School of Chemistry and Pharmacy, University of Reading, UK.

Oats contain a range of phenolic acids and avenanthramides which may have health benefits. Analysis of 22 commercial oat products (oat bran concentrate, oat bran, flaked oats, rolled oats and oatcakes) using HPLC-DAD detected eleven bound and thirteen free + conjugated phenolic acids and avenanthramides. The oat products (excluding concentrate) provided between 15.79 and 25.05 mg total phenolic acids (9.9-19.33 mg bound, 4.96-5.72 mg free + conjugated) and between 1.1 and 2 mg of avenanthramides in a 40 g portion while an 11 g portion of oat concentrate provided 16.7 mg of total phenolic acids (15.17 mg bound, 1.53 mg free + conjugated) and 1.2 mg of avenanthramides. The compositions and concentrations of the components in the different products were broadly similar, with the major component being ferulic acid (58-78.1%). The results show that commercial oat products are a source of phenolic acids and avenanthramides for consumers.
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http://dx.doi.org/10.1016/j.fochx.2019.100047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6694861PMC
September 2019

What Is Gluten-Why Is It Special?

Authors:
Peter Shewry

Front Nutr 2019 5;6:101. Epub 2019 Jul 5.

Rothamsted Research, Harpenden, Hertfordshire, United Kingdom.

Wheat gluten has an immense impact on human nutrition as it largely determines the processing properties of wheat flour, and in particular the ability to make leavened breads, other baked products, pasta and noodles. However, there has been increasing interest in wheat gluten over the past two decades because of its well-established role in triggering coeliac disease, and its perceived role in other adverse reactions to wheat. The literature on wheat gluten is vast and extends back over two centuries, with most studies focusing on the structures of gluten proteins and their role in determining the functional properties of wheat flour and dough. This article provides a concise account of wheat gluten, focusing on properties, and features which are relevant to its role in triggering coeliac disease and, to a lesser extent, other gluten-related disorders. It includes descriptions of the biological role of the gluten proteins, the structures and relationships of gluten protein families, and the presence of related types of protein which may also contribute to functional properties and impacts on health. It therefore provides an understanding of the gluten protein system at the level required by those focusing on its impact on human health.
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http://dx.doi.org/10.3389/fnut.2019.00101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6625226PMC
July 2019

Gradients of Gluten Proteins and Free Amino Acids along the Longitudinal Axis of the Developing Caryopsis of Bread Wheat.

J Agric Food Chem 2019 Aug 25;67(31):8706-8714. Epub 2019 Jul 25.

Plant Sciences Department , Rothamsted Research , Harpenden , Hertfordshire AL5 2JQ , U.K.

Gradients in the contents and compositions of gluten proteins and free amino acids and the expression levels of gluten protein genes in developing wheat caryopses were determined by dividing the caryopsis into three longitudinal sections, namely, proximal (En1), middle (En2), and distal (En3) to embryo. The total gluten protein content was lower in En1 than in En2 and En3, with decreasing proportions of HMW-GS, LMW GS, and α/β- and γ-gliadins and increasing proportions of ω-gliadins. These differences were associated with the abundances of gluten protein transcripts. Gradients in the proportions of the gluten protein polymers which affect dough processing quality also occurred, but not in total free amino acids. Microscopy showed that the lower gluten protein content in En1 may have resulted, at least in part, from the presence of modified cells in the dorsal part of En1, but the reasons for the differences in composition are not known.
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http://dx.doi.org/10.1021/acs.jafc.9b02728DOI Listing
August 2019

Determination of the prebiotic activity of wheat arabinogalactan peptide (AGP) using batch culture fermentation.

Eur J Nutr 2020 Feb 6;59(1):297-307. Epub 2019 Feb 6.

Department of Food and Nutritional Sciences, University of Reading, Whiteknights, PO Box 226, Reading, RG6 6AP, UK.

Purpose: To test the prebiotic activity of wheat arabinogalactan-peptide (AGP), which is a soluble dietary fibre composed of arabinogalactan polysaccharide linked to a 15-residue peptide, which accounts for up to 0.4% of the dry weight of wheat flour.

Methods: The prebiotic activity of AGP prepared from white wheat flour was tested using in vitro fermentation by colonic bacteria in automated pH-controlled anaerobic stirred batch cultures and compared to fructooligosaccharide (FOS) and wheat flour arabinoxylan (AX). Bacterial populations were measured using fluorescence in situ hybridisation (flow-FISH) and short chain fatty acid (SCFA) concentrations were measured using HPLC.

Results: Fermentation of AGP resulted in a significant bifidogenic activity and increased concentrations of SCFAs, mainly acetate after 24 h of fermentation.

Conclusions: These results were comparable to those obtained with AX and confirm the prebiotic potential of AGP. Furthermore, fermentation of a mixture of AGP and AX was faster compared to the single substrates and more similar to FOS, indicating that combinations of fermentable carbohydrates with different structures are potentially more effective as prebiotics than single substrates.
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http://dx.doi.org/10.1007/s00394-019-01908-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7000537PMC
February 2020

Drought stress affects the protein and dietary fiber content of wholemeal wheat flour in wheat/Aegilops addition lines.

PLoS One 2019 5;14(2):e0211892. Epub 2019 Feb 5.

Department of Plant Science, Rothamsted Research, Harpenden, United Kingdom.

Wild relatives of wheat, such as Aegilops spp. are potential sources of genes conferring tolerance to drought stress. As drought stress affects seed composition, the main goal of the present study was to determine the effects of drought stress on the content and composition of the grain storage protein (gliadin (Gli), glutenin (Glu), unextractable polymeric proteins (UPP%) and dietary fiber (arabinoxylan, β-glucan) components of hexaploid bread wheat (T. aestivum) lines containing added chromosomes from Ae. biuncialis or Ae. geniculata. Both Aegilops parents have higher contents of protein and β-glucan and higher proportions of water-soluble arabinoxylans (determined as pentosans) than wheat when grown under both well-watered and drought stress conditions. In general, drought stress resulted in increased contents of protein and total pentosans in the addition lines, while the β-glucan content decreased in many of the addition lines. The differences found between the wheat/Aegilops addition lines and wheat parents under well-watered conditions were also manifested under drought stress conditions: Namely, elevated β-glucan content was found in addition lines containing chromosomes 5Ug, 7Ug and 7Mb, while chromosomes 1Ub and 1Mg affected the proportion of polymeric proteins (determined as Glu/Gli and UPP%, respectively) under both well-watered and drought stress conditions. Furthermore, the addition of chromosome 6Mg decreased the WE-pentosan content under both conditions. The grain composition of the Aegilops accessions was more stable under drought stress than that of wheat, and wheat lines with the added Aegilops chromosomes 2Mg and 5Mg also had more stable grain protein and pentosan contents. The negative effects of drought stress on both the physical and compositional properties of wheat were also reduced by the addition of these. These results suggest that the stability of the grain composition could be improved under drought stress conditions by the intraspecific hybridization of wheat with its wild relatives.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0211892PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6363227PMC
November 2019

Gradients in compositions in the starchy endosperm of wheat have implications for milling and processing.

Trends Food Sci Technol 2018 Dec;82:1-7

Plant Science Department, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK.

Background: Wheat is the major food grain consumed in temperate countries. Most wheat is consumed after milling to produce white flour, which corresponds to the endosperm storage tissue of the grain. Because the starchy endosperm accounts for about 80% of the grain dry weight, the miller aims to achieve flour yields approaching this value.

Scope And Approach: Bioimaging can be combined with biochemical analysis of fractions produced by sequential pearling of whole grains to determine the distributions of components within the endosperm tissue.

Key Findings And Conclusions: This reveals that endosperm is not homogeneous, but exhibits gradients in composition from the outer to the inner part. These include gradients in both amount and composition. For example, the content of gluten proteins decreases but the proportion of glutenin polymers increases from the outside to the centre of the tissue. However, the content of starch increases with changes in the granule size distribution, the proportions of amylose and amylopectin, and their thermal properties. Hence these parts of the endosperm differ in the functional properties for food processing. Gradients also exist in minor components which may affect health and processing, such as dietary fibre and lipids. The gradients in grain composition are reflected in differences in the compositions of the mill streams which are combined to give white flour (which may number over 20). These differences could therefore be exploited by millers and food processors to develop flours with compositions and properties for specific end uses.
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http://dx.doi.org/10.1016/j.tifs.2018.09.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267945PMC
December 2018

Evaluation of the prebiotic potential of arabinoxylans extracted from wheat distillers' dried grains with solubles (DDGS) and in-process samples.

Appl Microbiol Biotechnol 2018 Sep 28;102(17):7577-7587. Epub 2018 Jun 28.

Department of Food and Nutritional Sciences, University of Reading, Whiteknights, PO Box 226, Reading, RG6 6AP, UK.

Distillers' dried grains with solubles (DDGS) is a low-value agro-industrial by-product, rich in arabinoxylans (AX), which is produced by commercial distillery and bioethanol plants. In a first approach, we investigated the prebiotic potential of four fractions comprising arabinoxylan oligosaccharides (AXOS) and xylooligosaccharides (XOS) obtained by enzymatic hydrolysis of AX fractions derived from DDGS and wet solids (in-process sample of DDGS production process). Anaerobic batch cultures in controlled pH conditions were used to test the prebiotic activity of the samples. Results did not show significant differences between the enzymatic treatments used, and all AXOS/XOS were extensively fermented after 24 h. In addition, significant increases (P < 0.05) in Bifidobacterium and total short-chain fatty acids (SCFAs) were observed after 24 h of fermentation. Finally, DDGS-derived hydrolysates were separated on an anionic semi-preparative column to prepare AXOS/XOS fractions with degree of polymerisation (DP) greater than 3. Bifidogenic activity and an increase of SCFAs were again observed after 24 h of fermentation, although this time, the selectivity was higher and the fermentation slower, suggesting that the fermentation of this substrate could take place (at least partially) in the distal part of the colon with highly desirable beneficial effects.
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http://dx.doi.org/10.1007/s00253-018-9171-6DOI Listing
September 2018