Mapping and proteomic analysis of albumin and globulin proteins in hexaploid wheat kernels (Triticum aestivum L.)

Evaluation of flour protein for different bread wheat genotypes

Six different bread wheat genotypes; two Egyptian commercial varieties (control); Giza-168 and Gemmeiza-11, and four promising lines; L84 and L148, resulted via hybridization and M10 and M34 via radiation mutation program) were rheologically evaluated using extensograph and for protein, analysis using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The radiation mutant M10 and M34 had the highest maximum resistance which is a very good indicator of strong gluten. The amount of gluten content was higher in M10, L148, and M34 compared to the control samples Gz168 and Gm11. Sulfide amino acids (CYS and MET) are slightly higher in M10. The electrophoretic results and amino acid analyzers show that the best technological quality was exhibited by M10. Radiation mutants wheat genotypes have a protein with good characteristics, mainly gluten which is significantly higher compared to control samples. The rheological properties measured as extensograph and gel electrophoresis were much better in irradiated lines M10 and M34.

A proteomic analysis of grain yield-related traits in wheat

Grain yield, which is mainly contributed by tillering capacity as well as kernel number and weight, is the most important trait to plant breeders and agronomists. Label-free quantitative proteomics was used to analyse yield-contributing organs in wheat. These were leaf sample, tiller initiation, spike initiation, ovary and three successive kernel development stages at 5, 10 and 15 days after anthesis (DAA). We identified 3182 proteins across all samples. The largest number was obtained for spike initiation (1673), while the smallest was kernel sample at 15 DAA (709). Of the 3182 proteins, 296 of them were common to all seven organs. Organ-specific proteins ranged from 148 in ovary to 561 in spike initiation. When relative protein abundances were compared to that of leaf sample, 347 and 519 proteins were identified as differentially abundant in tiller initiation and spike initiation, respectively. When compared with ovary, 81, 35 and 96 proteins were identified as differentially abundant in kernels sampled at 5, 10 and 15 DAA, respectively. Our study indicated that two Argonaute proteins were solely expressed in spike initiation. Of the four expansin proteins detected, three of them were mainly expressed during the first 10 days of kernel development after anthesis. We also detected cell wall invertases and sucrose and starch synthases mainly during the kernel development period. The manipulation of these proteins could lead to increases in tillers, kernels per spike or final grain weight, and is worth exploring in future studies.

Effect of wheat grain protein composition on end-use quality

The quality of wheat products has been a new challenge next to wheat production which was achieved substantially during green revolution. The end-use quality of wheat is an essential factor for its commercial demand. The quality of wheat is largely based on the wheat storage proteins which extensively influences the dough properties. High molecular weight glutenin subunits (HMWGS), low molecular weight glutenin subunits (LMWGS) and gliadins significantly influence the end-use quality. Genomics and proteomics study of these gluten proteins of bread and durum wheat have explored new avenues for precise identification of the alleles and their role in end-use quality improvement. Secalin protein of Secale cereale encoded by Sec-1 loci and is associated with 1RS.1BL translocation has been known for deterioration of end-use quality. Chromosomal manipulations using various approaches have led to the development of new recombinant lines of wheat without secalin. Advanced techniques associated with assessment of end-use quality have integrated the knowledge of useful or deteriorating HMWGS/LMWGS alleles and their potential role in end-use quality. This review gives a comprehensive insight of different aspects of the end-use quality perspective for bread making in wheat along with some information on the immunological interference of gluten in celiac disease.

Gliadin protein antigenicity and health benefitting potential of Indian bread wheat (Triticum aestivum L.) varieties

Health benefitting potential of twenty leading wheat varieties was assessed for grain nutritional quality status in relation to antigenic reactivity level of gluten protein fractions. Among the nutritional parameters, macronutrients viz. starch, total sugar, total protein and gluten content were observed maximum in the varieties RAJ4120, RAJ4083, RAJ3077, and WH1021 respectively. Micronutrients- zinc and iron and phytochemicals- total phenolics and flavonoids were observed to be maximum in RAJ4083. Among the four protein fraction, albumin and globulin contents were the highest in RAJ3077, whereas gliadin and gluten content was maximum in GW322 and minimum in RAJ4120. The varieties were also characterized by SDS-PAGE and the results revealed significant polymorphism in all of the four protein fractions. The antigenic properties of flour gliadin proteins as evaluated by ELISA revealed that all the varieties possessed antigenicity with highest level in GW322 (0.217 OD). However, all the varieties possessed good baking qualities as studied by rheological measurements.

Seed Biochemical Analysis Based Profiling of Diverse Wheat Genetic Resource from Pakistan

Wheat is the major nutrient source worldwide. In Pakistan, it has a crucial place in agriculture as well as in national economy. For seed biochemical compositional analysis, wheat germplasm (77 genotypes) was collected from different agro-climatic zones of Pakistan. Significant variation (p < 0.05) was observed for tested parameters among tested genotypes. Highest activity of ascorbate peroxidase (APX) was detected in Pavon (1,426.67 Units/g s. wt.), catalase (CAT) in Pasban-90 (633.33 Units/g s. wt.), peroxidase (POD) in IQBAL-2000 (42,579.6 Units/g s. wt.), and superoxide dismutase (SOD) in Manthar-2003 (278.93 Units/g s. wt.). Whereas, maximum activity of alpha amylase was found in SH-2002 (292.70 mg/g s. wt.), esterase in Dharabi 2011 (987.80 μM/min/g s. wt.), and protease in NR-234 (11,183.33 Units/g s. wt.) and highest total oxidant status (TOS) was detected in Faisalabad-2008 (390.0 μM/g s. wt.), malondialdehyde (MDA) content in Margalla-99 (679.23 μM/g s. wt.), total phenolic content (TPC) in Bhakkar-2000 (25,383.33 μM/g s. wt.), and ascorbic acid (AsA) content in SH-2002 (713.0 μg/g s. wt.). Maximum total soluble sugar was found in Saleem-2000 (29.86 mg/g s. wt.), reducing sugars in Punjab-96 (12.68 mg/g s. wt.), non-reducing sugars in Saleem-2000 (27.33 mg/g s. wt.). However, highest albumins was identified in TC-4928 (352.89 mg/g s. wt.) and globulins in MEXI PAK (252.67 mg/g s. wt.), salt soluble proteins in Faisalabad-2008 (162.44 mg/g s. wt.), and total soluble proteins in Punjab-96 (487.33 mg/g s. wt.) indicating good quality of wheat genotypes as well as good nutritional status. Genotypes which have been ranked high in respective parameter can be employed in breeding to enhance the nutritional quality of wheat.

Targeted Proteomics Approach for Precision Plant Breeding

Selected reaction monitoring (SRM) is a targeted mass spectrometry technique that enables precise quantitation of hundreds of peptides in a single run. This technique provides new opportunities for multiplexed protein biomarker measurements. For precision plant breeding, DNA-based markers have been used extensively, but the potential of protein biomarkers has not been exploited. In this work, we developed an SRM marker panel with assays for 104 potato (Solanum tuberosum) peptides selected using univariate and multivariate statistics. Thereafter, using random forest classification, the prediction markers were identified for Phytopthora infestans resistance in leaves, P. infestans resistance in tubers, and plant yield in potato leaf secretome samples. The results suggest that the marker panel has the predictive potential for three traits, two of which have no commercial DNA markers so far. Furthermore, the marker panel was also tested and found to be applicable to potato clones not used during the marker development. The proposed workflow is thus a proof-of-concept for targeted proteomics as an efficient readout in accelerated breeding for complex and agronomically important traits.

Wheat breadmaking properties in dependance on wheat enzymes status and climate conditions

The objective of this study was to evaluate albumins profile, proteolytic and amylolytic activity level and baking performance of wheat varieties grown in two production years with different climate conditions (2011 and 2012) in four locations. The results of ANOVA showed that variety, location, production year, and their interactions all had significant effects on all tested wheat quality parameters. The enzymatic activity and specific bread volume were mainly influenced by the variety. The samples from 2012 production year, had the lower values of albumin content, proteolytic and amylolytic activity, and bread specific volume. The correlation analysis, performed for 2011 production year, showed that albumin fraction (15-30 kDa) and proteolytic activity were negatively correlated with bread specific volume indicating the role of this fraction on lowering the crucial bread quality parameter. In 2012 production year, albumin fractions (5-15 kDa; 50-65 kDa) showed the most correlations, especially with parameters of bread quality.

Comparison of leaf proteomes of cassava (Manihot esculenta Crantz) cultivar NZ199 diploid and autotetraploid genotypes

Cassava polyploid breeding has drastically improved our knowledge on increasing root yield and its significant tolerance to stresses. In polyploid cassava plants, increases in DNA content highly affect cell volumes and anatomical structures. However, the mechanism of this effect is poorly understood. The purpose of the present study was to compare and validate the changes between cassava cultivar NZ199 diploid and autotetraploid at proteomic levels. The results showed that leaf proteome of cassava cultivar NZ199 diploid was clearly differentiated from its autotetraploid genotype using 2-DE combined MS technique. Sixty-five differential protein spots were seen in 2-DE image of autotetraploid genotype in comparison with that of diploid. Fifty-two proteins were identified by MALDI-TOF-MS/MS, of which 47 were up-regulated and 5 were down-regulated in autotetraploid genotype compared with diploid genotype. The classified functions of 32 up-regulated proteins were associated with photosynthesis, defense system, hydrocyanic acid (HCN) metabolism, protein biosynthesis, chaperones, amino acid metabolism and signal transduction. The remarkable variation in photosynthetic activity, HCN content and resistance to salt stress between diploid and autotetraploid genotypes is closely linked with expression levels of proteomic profiles. The analysis of protein interaction networks indicated there are direct interactions between the 15 up-regulation proteins involved in the pathways described above. This work provides an insight into understanding the protein regulation mechanism of cassava polyploid genotype, and gives a clue to improve cassava polyploidy breeding in increasing photosynthesis and resistance efficiencies.

Role of non-prolamin proteins and low molecular weight redox agents in protein folding and polymerization in wheat grains and influence on baking quality parameters

The various enzyme systems and low molecular weight (LMW) redox agents are related to the folding and polymerization of prolamins in the ripening wheat grains and the formation of baking quality. Protein disulfide isomerases (PDIs) and cyclophylins accelerate "correct" folding of prolamins, which is most likely necessary for the subsequent formation of the macromolecular structure of the gluten protein matrix. PDIs are also involved in the polymerization of prolamins, catalyzing the oxidation of protein sulfhydryl groups. Molecular chaperone binding BiP protein facilitates folding of prolamins, with its role increasing in the stressful conditions. Reducing systems of thioredoxin and glutaredoxin, LMW redox pairs GSH/GSSG and Asc/DHAsc, thiol oxidases, and lipoxygenases (LOXs) regulate redox balance and the rate of polymerization of prolamins at the different stages of grain ripening. Additionally, LOX is probably involved in the protein-starch-lipid interactions between the starch granule and the protein matrix, mediated by puroindolines, determining the formation of grain texture. It is assumed that the high variability of baking quality in different environmental conditions is due to the interaction of labile enzyme systems with the storage proteins in the developing wheat caryopsis.

Proteomic and genetic analysis of wheat endosperm albumins and globulins using deletion lines of cultivar Chinese Spring

Albumins and globulins from the endosperm of Triticum aestivum L. cv Chinese Spring (CS) were analysed to establish a proteome reference map for this standard wheat cultivar. Approximately, 1,145 Coomassie-stained spots were detected by two-dimensional gel electrophoresis (2DE), 410 of which were identified using mass spectrometry and data mining. Salt-soluble endosperm proteins from 67 CS deletion lines were also separated by 2DE (four gels per line). Image analysis of the 268 2DE gels as compared to the CS reference proteome allowed the detection of qualitative and quantitative variations in endosperm proteins due to chromosomal deletions. This differential analysis of spots allowed structural or regulatory genes, encoding 211 proteins, to be located on segments of the 21 wheat chromosomes. In addition, variance analysis of quantitative variations in spot volume showed that the expression of 391 proteins is controlled by one or more chromosome bins with 262 significant increases and 196 significant decreases in spot volume. The spot volume of several proteins was increased or decreased by numerous chromosomal regions and homoeologous-like regulation was revealed for some proteins. Quantitative or qualitative variation in a total of 386 proteins was influenced by genes assigned to at least one chromosomal region, while 66 % of all stained proteins were not found to be influenced by chromosome bins. Proteomics of deletion lines can, therefore, be used to simultaneously analyse the composition and genetics of a complex tissue, such as the wheat endosperm.

Mass spectrometry in the proteome analysis of mature cereal kernels

In the last decade, the improved performance and versatility of the mass spectrometers together with the increasing availability of gene and genomic sequence database, led the mass spectrometry to become an indispensable tool for either protein and proteome analyses in cereals. Mass spectrometric works on prolamins have rapidly evolved from the determination of the molecular masses of proteins to the proteomic approaches aimed to a large-scale protein identification and study of functional and regulatory aspects of proteins. Mass spectrometry coupled with electrophoresis, chromatographic methods, and bioinformatics tools is currently making significant contributions to a better knowledge of the composition and structure of the cereal proteins and their structure-function relationships. Results obtained using mass spectrometry, including characterization of prolamins, investigation of the gluten toxicity for coeliac patients, identification of proteins responsible of cereal allergies, determination of the protein pattern and its modification under environmental or stress effects, investigation of genetically modified varieties by proteomic approaches, are summarized here, to illustrate current trends, analytical troubles and challenges, and suggest possible future perspectives.

Characterization of proteins from grain of different bread and durum wheat genotypes

The classical Osborne wheat protein fractions (albumins, globulins, gliadins, and glutenins), as well as several proteins from each of the four subunits of gliadin using SDS-PAGE analyses, were determined in the grain of five bread (T. aestivum L.) and five durum wheat (T. durum Desf.) genotypes. In addition, content of tryptophan and wet gluten were analyzed. Gliadins and glutenins comprise from 58.17% to 65.27% and 56.25% to 64.48% of total proteins and as such account for both quantity and quality of the bread and durum wheat grain proteins, respectively. The ratio of gliadin/total glutenin varied from 0.49 to 1.01 and 0.57 to 1.06 among the bread and durum genotypes, respectively. According to SDS-PAGE analysis, bread wheat genotypes had a higher concentration of α + β + γ-subunits of gliadin (on average 61.54% of extractable proteins) than durum wheat (on average 55.32% of extractable proteins). However, low concentration of ω-subunit was found in both bread (0.50% to 2.53% of extractable proteins) and durum (3.65% to 6.99% of extractable proteins) wheat genotypes. On average, durum wheat contained significantly higher amounts of tryptophan and wet gluten (0.163% dry weight (d.w.) and 26.96% d.w., respectively) than bread wheat (0.147% d.w. and 24.18% d.w., respectively).

Assessment of allergenicity of diploid and hexaploid wheat genotypes: identification of allergens in the albumin/globulin fraction

Wheat is an important part of the daily diet of millions of people. However, this staple food is also responsible for food allergies. Ancient cultivars of wheat are gaining interest today but nothing is known about their allergenicity. Many wheat proteins have been reported as causative food allergens, including some prolamin-type gluten proteins, and salt soluble proteins of the albumin/globulin (A/G) type. The objective of this work is to obtain information about the allergenicity of the salt soluble A/G fraction of an ancient diploid cultivar compared with a standard hexaploid bread wheat cultivar using 20 sera from patients with wheat allergy. Differences in the IgE reactivity of sera towards the two genotypes were quantified by ELISA. Qualitative differences in IgE-binding proteins were searched after 1D or 2D electrophoresis. For most of the sera, the concentration in A/G specific IgE was higher for the hexaploid T. aestivum (cv Récital) than for the diploid T. monococcum (cv Engrain). The analysis of 2D spots revealed by immunoblotting leads to the identification by mass spectrometry of 39 IgE-binding proteins, some of them unknown until now as wheat allergens. Numerous allergens were identified, differences observed between Engrain and Récital will be discussed.

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.