Identification of three wheat globulin genes by screening a Triticum aestivum BAC genomic library with cDNA from a diabetes-associated globulin

Beneficial effects of a T. monococcum wheat cultivar on diabetes incidence evaluated in non-obese diabetic mice and after in vitro simulated gastroduodenal digestion

Wheat consumption can represent one of the nutritional factors involved in the onset of diabetes. We specifically investigated the potential diabetogenic effects of Hammurabi, a T. monococcum wheat cultivar, in non-obese diabetic (NOD) mice and analysed the levels of resistant starch in pasta manufactured with Hammurabi after in vitro gastroduodenal digestion. NOD mice were fed with Hammurabi, bread wheat or rice flour to evaluate diabetes incidence and insulitis score. An enzymatic method was applied to compare the content of resistant starch in Hammurabi pasta and durum wheat pasta (control). In NOD mice, the Hammurabi-based diet significantly delayed diabetes onset (p = 0.0042) and reduced insulitis score compared to rice or wheat-based diet. Furthermore, the resistant starch value following in vitro digestion of Hammurabi pasta was significantly higher (4.08%) than that of durum wheat pasta (2.28%). Taken together, these results highlighted the potential positive effects of the Hammurabi-based diet on diabetes incidence.

The Impact of Diet Wheat Source on the Onset of Type 1 Diabetes Mellitus-Lessons Learned from the Non-Obese Diabetic (NOD) Mouse Model

Nutrition, especially wheat consumption, is a major factor involved in the onset of type 1 diabetes (T1D) and other autoimmune diseases such as celiac. While modern wheat cultivars possess similar gliadin proteins associated with the onset of celiac disease and T1D, alternative dietary wheat sources from Israeli landraces and native ancestral species may be lacking the epitopes linked with T1D, potentially reducing the incidence of T1D. The Non-Obese Diabetic (NOD) mouse model was used to monitor the effects of dietary wheat sources on the onset and development of T1D. The effects of modern wheat flour were compared with those from either T. aestivum, T. turgidum spp. dicoccoides, or T. turgidum spp. dicoccum landraces or a non-wheat diet. Animals which received wheat from local landraces or ancestral species such as emmer displayed a lower incidence of T1D and related complications compared to animals fed a modern wheat variety. This study is the first report of the diabetogenic properties of various dietary wheat sources and suggests that alternative dietary wheat sources may lack T1D linked epitopes, thus reducing the incidence of T1D.

Diagonal two-dimensional electrophoresis (D-2DE): a new approach to study the effect of osmotic stress induced by polyethylene glycol in durum wheat (Triticum durum Desf.)

Acclimatization to stress is associated with profound changes in proteome composition. The use of plant cell and tissue culture offers a means to investigate the physiological and biochemical processes involved in the adaptation to osmotic stress. We employed a new proteomic approach to further understand the response of calli to dehydration induced by polyethylene glycol (PEG6000). Calli of three durum wheat genotypes Djenah Khetifa, Oued Zenati and Waha were treated with two concentrations of polyethylene glycol to mimic osmotic stress. Changes in protein relative abundance were analyzed using a new electrophoretic approach named diagonal two-dimensional electrophoresis (D-2DE), combined with mass spectrometry. Total proteins were extracted from 30-day-old calli from three durum wheat genotypes that showed contrasting levels of drought stress tolerance in the field. The combination of one-dimensional electrophoresis and D-2DE gave a specific imprint of the protein extracts under osmotic stress, as well as characterizing and identifying individual target proteins. Of the variously expressed proteins, three were selected (globulin, GAPDH and peroxidase) and further analyzed using qRT-PCR at the transcriptome level in order to compare the results with the proteomic data. Western blot analysis was used to further validate the differences in relative abundance pattern. The proteins identified through this technique provide new insights as to how calli respond to osmotic stress. Our method of study provides an original and relevant approach of analyzing the osmotic-responsive mechanisms at the cellular level of durum wheat with agronomic perspectives.

Teff, an Orphan Cereal in the Chloridoideae, Provides Insights into the Evolution of Storage Proteins in Grasses

Seed storage proteins (SSP) in cereals provide essential nutrition for humans and animals. Genes encoding these proteins have undergone rapid evolution in different grass species. To better understand the degree of divergence, we analyzed this gene family in the subfamily Chloridoideae, where the genome of teff (Eragrostis tef) has been sequenced. We find gene duplications, deletions, and rapid mutations in protein-coding sequences. The main SSPs in teff, like other grasses, are prolamins, here called eragrostins. Teff has γ- and δ-prolamins, but has no β-prolamins. One δ-type prolamin (δ1) in teff has higher methionine (33%) levels than in maize (23–25%). The other δ-type prolamin (δ2) has reduced methionine residues (<10%) and is phylogenetically closer to α prolamins. Prolamin δ2 in teff represents an intermediate between δ and α types that appears to have been lost in maize and other Panicoideae, and was replaced by the expansion of α-prolamins. Teff also has considerably larger numbers of α-prolamin genes, which we further divide into five sub-groups, where α2 and α5 represent the most abundant α-prolamins both in number and in expression. In addition, indolines that determine kernel softness are present in teff and the panicoid cereal called foxtail millet (Setaria italica) but not in sorghum or maize, indicating that these genes were only recently lost in some members of the Panicoideae. Moreover, this study provides not only information on the evolution of SSPs in the grass family but also the importance of α-globulins in protein aggregation and germplasm divergence.

Comparative analysis of gluten proteins in three durum wheat cultivars by a proteomic approach

The gluten protein composition and expression level influence dough properties and are cultivar and environment dependent. To broaden the knowledge of the durum wheat gluten proteome, three cultivars were compared in two different growing seasons by a proteomic approach. Cultivar-specific and differentially expressed spots in the two years were identified by mass spectrometry. Significant differences were observed among the cultivars: Ofanto showed the lowest protein spot volumes in the high molecular weight (HMW) and low molecular weight (LMW) <35,000 regions and the highest in the LMW 48,000-35,000 region, Latino the lowest in the LMW 48,000-35,000 region, and Simeto an intermediate expression level in both LMW regions. In the warmer year the up-regulation of HMW glutenins, α-gliadins, and a globulin 3 protein and the down-expression of LMW glutenins and γ-gliadins were observed. Among the cultivars, Simeto showed the highest stability across the environments.

Proteomic analysis of albumins and globulins from wheat variety Chinese Spring and its fine deletion line 3BS-8

The relationship between chromosome deletion in wheat and protein expression were investigated using Chinese Spring and fine deletion line 3BS-8. Through 2-DE (2-D electrophoresis) analysis, no differentially expressed proteins (DEPs) were found in leaf samples; however, 47 DEPs showed at least two-fold abundance variation (p < 0.05) in matured wheat grains and 21 spots were identified by tandem MALDI-TOF/TOF-MS. Among the identified spots, four were cultivar-specific, including three (spots B15, B16, and B21) in Chinese Spring and one in 3BS-8 (spot B10). Among variety-different DEPs between Chinese Spring and 3BS-8, most spots showed a higher express profile in CS; only four spots showed up-regulated expression tendency in 3BS-8. An interesting observation was that more than half of the identified protein spots were involved in storage proteins, of which 11 spots were identified as globulins. According to these results, we can presume that the encoded genes of protein spots B15, B16, and B21 were located on the chromosome segment deleted in 3BS-8.

Seed storage proteins of the globulin family are cleaved post-translationally in wheat embryos

Background

The 7S globulins are plant seed storage proteins that have been associated with the development of a number of human diseases, including peanut allergy. Immune reactivity to the wheat seed storage protein globulin-3 (Glo-3) has been associated with the development of the autoimmune disease type 1 diabetes in diabetes-prone rats and mice, as well as in a subset of human patients.

Findings

The present study characterized native wheat Glo-3 in salt-soluble wheat seed protein extracts. Glo-3-like peptides were observed primarily in the wheat embryo. Glo-3-like proteins varied significantly in their molecular masses and isoelectric points, as determined by two dimensional electrophoresis and immunoblotting with anti-Glo-3A antibodies. Five major polypeptide spots were identified by mass spectrometry and N-terminal sequencing as belonging to the Glo-3 family.

Conclusions

These results in combination with our previous findings have allowed for the development of a hypothetical model of the post-translational events contributing to the wheat 7S globulin profile in mature wheat kernels.

Animal models to study gluten sensitivity

The initial development and maintenance of tolerance to dietary antigens is a complex process that, when prevented or interrupted, can lead to human disease. Understanding the mechanisms by which tolerance to specific dietary antigens is attained and maintained is crucial to our understanding of the pathogenesis of diseases related to intolerance of specific dietary antigens. Two diseases that are the result of intolerance to a dietary antigen are celiac disease (CD) and dermatitis herpetiformis (DH). Both of these diseases are dependent upon the ingestion of gluten (the protein fraction of wheat, rye, and barley) and manifest in the gastrointestinal tract and skin, respectively. These gluten-sensitive diseases are two examples of how devastating abnormal immune responses to a ubiquitous food can be. The well-recognized risk genotype for both is conferred by either of the HLA class II molecules DQ2 or DQ8. However, only a minority of individuals who carry these molecules will develop either disease. Also of interest is that the age at diagnosis can range from infancy to 70-80 years of age. This would indicate that intolerance to gluten may potentially be the result of two different phenomena. The first would be that, for various reasons, tolerance to gluten never developed in certain individuals, but that for other individuals, prior tolerance to gluten was lost at some point after childhood. Of recent interest is the concept of non-celiac gluten sensitivity, which manifests as chronic digestive or neurologic symptoms due to gluten, but through mechanisms that remain to be elucidated. This review will address how animal models of gluten-sensitive disorders have substantially contributed to a better understanding of how gluten intolerance can arise and cause disease.

Antibodies from a patient with type 1 diabetes and celiac disease bind to macrophages that express the scavenger receptor CD163

Antibodies against the wheat storage globulin Glo-3A from a patient with both type 1 diabetes (T1D) and celiac disease were enriched to identify potential molecular mimicry between wheat antigens and T1D target tissues. Recombinant Glo-3A was used to enrich anti-Glo-3A immunoglobulin G antibodies from plasma by batch affinity chromatography. Rat jejunum and pancreas, as well as human duodenum and monocytes were probed, and binding was evaluated by immunohistochemistry and confocal microscopy. Glo-3A-enriched antibodies bound to a specific subset of cells in the lamina propria of rat jejunum that co-localized mostly with a marker of resident, alternatively activated CD163-positive (CD163⁺) macrophages. Blood monocytes and macrophage-like cells in human duodenum were also labelled with the enriched antibodies. Blocking studies revealed that binding to CD163⁺ macrophages was not due to cross-reactivity with anti-Glo-3A antibodies, but rather to non-Glo-3A antibodies co-purified during antibody enrichment. The novel finding of putative autoantibodies against tolerogenic intestinal CD163⁺ macrophages suggests that regulatory macrophages were targeted in this patient with celiac disease and T1D.

Deciphering the complexities of the wheat flour proteome using quantitative two-dimensional electrophoresis, three proteases and tandem mass spectrometry

BACKGROUND

Wheat flour is one of the world's major food ingredients, in part because of the unique end-use qualities conferred by the abundant glutamine- and proline-rich gluten proteins. Many wheat flour proteins also present dietary problems for consumers with celiac disease or wheat allergies. Despite the importance of these proteins it has been particularly challenging to use MS/MS to distinguish the many proteins in a flour sample and relate them to gene sequences.

RESULTS

Grain from the extensively characterized spring wheat cultivar Triticum aestivum 'Butte 86' was milled to white flour from which proteins were extracted, then separated and quantified by 2-DE. Protein spots were identified by separate digestions with three proteases, followed by tandem mass spectrometry analysis of the peptides. The spectra were used to interrogate an improved protein sequence database and results were integrated using the Scaffold program. Inclusion of cultivar specific sequences in the database greatly improved the results, and 233 spots were identified, accounting for 93.1% of normalized spot volume. Identified proteins were assigned to 157 wheat sequences, many for proteins unique to wheat and nearly 40% from Butte 86. Alpha-gliadins accounted for 20.4% of flour protein, low molecular weight glutenin subunits 18.0%, high molecular weight glutenin subunits 17.1%, gamma-gliadins 12.2%, omega-gliadins 10.5%, amylase/protease inhibitors 4.1%, triticins 1.6%, serpins 1.6%, purinins 0.9%, farinins 0.8%, beta-amylase 0.5%, globulins 0.4%, other enzymes and factors 1.9%, and all other 3%.

CONCLUSIONS

This is the first successful effort to identify the majority of abundant flour proteins for a single wheat cultivar, relate them to individual gene sequences and estimate their relative levels. Many genes for wheat flour proteins are not expressed, so this study represents further progress in describing the expressed wheat genome. Use of cultivar-specific contigs helped to overcome the difficulties of matching peptides to gene sequences for members of highly similar, rapidly evolving storage protein families. Prospects for simplifying this process for routine analyses are discussed. The ability to measure expression levels for individual flour protein genes complements information gained from efforts to sequence the wheat genome and is essential for studies of effects of environment on gene expression.

Proteomic analysis of peripheral layers during wheat (Triticum aestivum L.) grain development

Grains of hexaploid wheat, Triticum aestivum (cv. Récital), were collected at 15 stages of development, from anthesis to physiological maturity, 0-700°C days (degree days after anthesis). Two hundred and seven proteins of grain peripheral layers (inner pericarp, hyaline, testa and aleurone layer) were identified by 2-DE, MALDI-TOF MS and data mining, then were classified in 16 different functional categories. Study of the protein expression over time allowed identification of five main profiles and four distinct phases of development. Composite expression curves indicated that there was a shift from metabolic processes, translation, transcription and ATP interconversion towards storage and defence processes. Protein synthesis, protein turnover, signal transduction, membrane transport and biosynthesis of secondary metabolites were the mediating functions of this shift. A picture of the dynamic processes taking place in peripheral layers during grain development was obtained in this study. It should further help in the construction of proteome reference maps for the developing peripheral layers.

Antibodies to the wheat storage globulin Glo-3A in children before and at diagnosis of celiac disease

OBJECTIVE

Celiac disease (CD) is an autoimmune disease triggered by exposure to gluten-containing foods. IgA autoantibodies to tissue transglutaminase (TTG) are elevated in CD, but little is known about the gastrointestinal state before the appearance of TTG. Antibodies to wheat storage globulin Glo-3A have been studied in type 1 diabetes, and may be a marker of altered mucosal barrier and/or immune function. In the present study, we investigated antibody responses to Glo-3A in CD.

PATIENTS AND METHODS

In the Diabetes Autoimmunity Study in the Young, children were studied prospectively from birth for the appearance of TTG and CD. Fifty cases of CD were frequency matched with 50 controls on age (of TTG seroconversion in the case), sex, ethnicity, presence of a first-degree relative with type 1 diabetes mellitus, and human leukocyte antigen -DR3 genotype. In cases and controls, IgG antibodies to Glo-3A were analyzed in a blinded manner in the sample collected at the time of seroconversion to TTG positivity (or the matched sample in controls) and in all of the previous samples since birth (mean 4.5 samples). The association between Glo-3A antibody levels and CD case status was explored using t tests at the TTG-positive visit and when Glo-3A levels were highest, and mixed modeling to describe Glo-3A over time.

RESULTS

At the time of first elevated TTG (mean 4.9 years), patients with CD had higher Glo-3A antibody levels than controls (13.3 ± 17.2 vs 7.6 ± 11.7, P = 0.005). In both cases and controls, Glo-3A antibodies appear to peak at a mean age of 2.9 years, before mean age of initial TTG seroconversion. The peak Glo-3A antibody levels were higher in cases than controls (25.5 ± 21.8 vs 14.9 ± 18.3 P = 0.0007). Using mixed modeling to account for multiple visits per person, cases had higher levels of Glo-3A antibodies than controls at all ages from birth to TTG seroconversion (β = 0.53, P = 0.002).

CONCLUSIONS

Compared with controls, CD cases have higher Glo-3A antibody responses in the beginning years, before initial detection of TTG.

Brachypodium distachyon grain: identification and subcellular localization of storage proteins

Seed storage proteins are of great importance in nutrition and in industrial transformation because of their functional properties. Brachypodium distachyon has been proposed as a new model plant to study temperate cereals. The protein composition of Brachypodium grain was investigated by separating the proteins on the basis of their solubility combined with a proteomic approach. Salt-soluble proteins as well as salt-insoluble proteins separated by two-dimensional gel electrophoresis revealed 284 and 120 spots, respectively. Proteins from the major spots were sequenced by mass spectrometry and identified by searching against a Brachypodium putative protein database. Our analysis detected globulins and prolamins but no albumins. Globulins were represented mainly by the 11S type and their solubility properties corresponded to the glutelin found in rice. An in silico search for storage proteins returned more translated genes than expressed products identified by mass spectrometry, particularly in the case of prolamin type proteins, reflecting a strong expression of globulins at the expense of prolamins. Microscopic examination of endosperm cells revealed scarce small-size starch granules surrounded by protein bodies containing 11S globulins. The presence of protein bodies containing glutelins makes B. distachyon closer to rice or oat than to wheat endosperm.

Peripherin-reactive antibodies in mouse, rabbit, and human blood

Type 1 diabetes (T1D) is an autoimmune disorder that results from the destruction of insulin-producing beta-cells in the islets of Langerhans. To date, autoimmune T-cell response and antibody reactivity to more than 20 autoantigens have been linked to this disease. Some studies have described the intermediate filament protein peripherin (PRPH) as an autoantigen associated with T1D in non-obese diabetic (NOD) mice. We evaluated immune reactivity of mouse and rabbit sera and human plasma to a 58 kDa protein expressed in RIN-m5F rat insulinoma cells. The protein was isolated using 2-DE and identified by mass spectrometry as PRPH. Antibodies from healthy humans and T1D patients, CD-1 mice, C57BL/6 mice, NOR (non-obese diabetes resistant) mice, and NOD mice reacted with PRPH on Western blots. However, antibody response to PRPH was stronger in NOD than non-autoimmune prone C57BL/6 mice. We conclude that immune reactivity to PRPH is not exclusively associated with NOD mice or human patients with T1D. Furthermore, the frequent occurrence of PRPH-reactive antibodies in mouse and human blood suggests that binding may be non-specific or could reflect the presence of natural autoantibodies against PRPH. These findings point to the need for a re-evaluation of PRPH as a T1D autoantigen in NOD mice and raise the question of the physiological relevance of such widespread immune reactivity against this peripheral nervous system protein.