Mature Grains Research Articles

Localization of iron in rice grain using synchrotron X-ray fluorescence microscopy and high resolution secondary ion mass spectrometry

Cereal crops accumulate low levels of iron (Fe) of which only a small fraction (5–10%) is bioavailable in human diets. Extensive co-localization of Fe in outer grain tissues with phytic acid, a strong chelator of metal ions, results in the formation of insoluble complexes that cannot be digested by humans. Here we describe the use of synchrotron X-ray fluorescence microscopy (XFM) and high resolution secondary ion mass spectrometry (NanoSIMS) to map the distribution of Fe, zinc (Zn), phosphorus (P) and other elements in the aleurone and subaleurone layers of mature grain from wild-type and an Fe-enriched line of rice (Oryza sativa L.). The results obtained from both XFM and NanoSIMS indicated that most Fe was co-localized with P (indicative of phytic acid) in the aleurone layer but that a small amount of Fe, often present as “hotspots”, extended further into the subaleurone and outer endosperm in a pattern that was not co-localized with P. We hypothesize that Fe in subaleurone and outer endosperm layers of rice grain could be bound to low molecular weight chelators such as nicotianamine and/or deoxymugineic acid.

Effect of Subsoiling in Fallow Period and Nitrogen Application on Soil Moisture and Grain Protein Accumulation in Dryland Wheat

The objective of this study was to explore a technique to increase and maintain soil moisture of dryland through subsoiling during fallow period(SS) and the proper nitrogen(N) application in wheat production. In a two-year field experiment carried out in Wenxi County of Shanxi Province, China from autumn 2009 to summer 2011, we tested soil moistures in different soil layers, protein content and its components in grain, and activities of enzymes related to protein accumulation during grain filling after SS and non-tillage practice(CK) in combination with the applications of low(LN, 75 kg ha–1), medium(MN, 150 kg ha–1), or high(HN, 225 kg ha–1) N. Before sowing, the soil moistures in 0–300 cm soil layers under SS condition were higher than those under CK condition, especially in 60–160 cm soil layers, which were increased by 12%–34% in dry year and 10%–22% in humid year. Under SS condition, the activities of protein-related enzymes increased, such as glutamine synthetase(GS) in grain, glutamate synthase(GOGAT) in flag leaf, and GOGAT in grain in LN and MN treatments, and glutamic acid-pyruvate transaminase(GPT) in grain. In mature grains, the globulin content and protein yield in SS treatment were increased compared with CK, and Glutenin content and glutenin/gliadin ratio in humid year also increased in SS. The soil moisture in 20–200 cm soil layer at anthesis stage showed a decrease trend with the increase of nitrogen application level; however, the GS activity in grain, GOGAT activity in flag leaf at middle to late filling stage, GPT activity in grain at late filling stage were enhanced, and the contents of protein and its components in grain were increased. The glutenin/gliadin ratio in grain was the highest in MN treatment. Nitrogen application had obvious effects on soil moisture in the deep soil layer at anthesis, also on protein yield, GS and GPT activities in grainunder SS condition. Under SS plus N application condition, soil moisture at anthesis was closely correlated with grain albumin, glutenin, and protein content in humid year and with glutenin/gliadin ratio in dry year. In conclusion, subsoiling during fallow period is an effective method to maintain soil moisture in dryland; N application at 225 kg ha–1 has a positive effect on increasing contents of grain protein and its components, whereas N level of 150 kg ha–1 is favorable for high protein yield and glutenin/gliadin ratio in grain in dry year.

The contribution of different alpha-amylase isoenzymes of the commodity grain spring wheat in the formation of falling number values

The participation of various isoenzymes of alpha-amylase in the formation of falling number values of the commodity grain of wheat grown in the Republic of Kazakhstan was investigated. It was found that active isoenzymes alpha-AMY1 and alpha-AMY2 of the embryonic shield were present in the grain with an index over 200. A significant decrease in the falling number depended mainly on the synthesis of alpha-AMY1 and alpha-AMY2 isoenzymes in the aleurone layer. In the grain, isoenzymes with high isoelectric points (p1 > or = 7.3) were found; these isoenzymes belong to alpha-amylase or late maturing or alpha-amylase of practically mature grains. It was discovered that the exogenous hormone (gibberellic acid) induced synthesis of alpha-amylase isoenzymes of scutellum, whole caryopses, and aleurone. It was shown that the impact of exogenous gibberellic acid on the activity and structure of alpha-amylase is reduced in grain with a low falling number.

灌浆前期高温和干旱胁迫对小麦籽粒蛋白质含量和氮代谢关键酶活性的影响

To explore the physiological mechanisms of stresses on nitrogen metabolism and protein accumulation in wheat grains,a pot experiment was performed at the Scientific Educational Park of Henan Agricultural University from 2010 to2012. Zhengmai 366 and Yunong 949,wheat cultivars with different gluten-strengths,were grown in 24-cm pots with 10 kg loam soil for the experiment,which was performed using a completely randomized design in three replicates. Plants were initially grown in the field environment and were then transferred to a climate-controlled greenhouse for the high temperature( HT) treatment. HT began from the 8thday after anthesis( DAA) and ended at the 11 thDAA,with a high temperature of38°C for five hours from 11: 00 to 16: 00,after which the plants were returned to the field environment. The concentration of protein and its components,and the activities of glutamine synthetase( GS) and glutamic-pyruvic transaminase( GPT)in the grains were measured to evaluate the effects of the stresses. The results showed that HT,drought stress( DS) andtheir combination significantly increased protein and its components' concentrations,yet decreased the ratio of glutenin to gliadin. The protein accumulation was also reduced by stresses. For example,for Zhengmai 366,the protein yield significantly decreased by 20. 7% under HT,by 16. 2% under DS,and by 26. 1% under a combination of HT and DS. In Yunong 949,the protein yield decreased by 12. 4% under HT,by 11. 9% under DS and by 15. 8% under a combination of HT and DS. The grain weight significantly declined by 23. 2% under HT,by 18. 0% under DS and by 29. 9% under a combination of HT and DS,in Zhengmai 366,and decreased by 24. 0% under HT,by 16. 0% under DS,and by 29. 9%under a combination of HT and DS,in Yunong 949. However,the activities of GS and GPT were promoted under HT,DS and their combination. A correlation analysis showed that the activity of GS was positively correlated with the protein concentration in mature wheat grains at significant or extremely significant levels at 8,17,23,and 29 DAA. However,GS activity was negatively correlated with protein yield at extremely significant levels at 23 and 35 DAA,and it was negatively correlated with grain yield at significant or extremely significant levels at 8,17,23,29 and 35 DAA. The activity of GPT was positively correlated with protein concentration at extremely significant levels at 11 and 17 DAA. However,GPT activity was negatively correlated with protein yield at extremely significant levels at 8,17 and 23 DAA and negatively correlated with grain yield at significant or extremely significant levels at 8,11,17 and 23 DAA. The results also indicated that,under the present experimental conditions,the influence of the HT treatment was greater than that of the DS,and an overlap effect existed between HT and DS. In addition,Zhengmai 366,a high-gluten cultivar,showed more sensitivity to stresses than Yunong 949,a mid-gluten cultivar. These results may aid in understanding how HT and DS influence protein accumulation and may be useful in improving wheat quality.

Storage proteins in wheat (Triticum aestivum L.) and the ecological impacts affecting their quality and quantity, with a focus on nitrogen supply

Wheat (Triticum aestivum L.) is the most widely used basic staple for mankind. Wheat is also one of the most important cereals in Hungary with a high economic value. The aim of wheat production is twofold; to provide quantity and quality. Milling and baking quality of wheat is mainly determined by the genetic basis, however it can be influenced by management techniques. Storage proteins account for more than half of the total protein in mature cereal grains and have important impacts on their nutritional quality for humans and livestock and on their functional properties in food processing. Gluten proteins - gliadins and glutenins of wheat determine the quality of the grain for breadmaking and their amount and composition can be influenced by agronomic impacts leading to changes in dough properties and that of baking quality. The present review is dealing with the impact of various agronomic and environmental factors on the performance of storage proteins and within them gluten proteins.

Spawn By Irradiation of Grains and Mushroom Production

Sterilization of grains for spawn preparation is a means of contamination control in and around the media. To avoid the tedious procedure of steam sterilization, 60 Co ɣ- irradiation was used to sterilize the mature and uniform quality wheat grains var. sharbati. The irradiation dose was standardized in order to destroy all the spores inside the grains and any glassware or polypacks contaminants. The effects of irradiation on the spawn shelf life and the yield of button mushroom (Agaricus bisporus) were studied. Total food reserves to sustain the mycelium for longer periods were also compared. Standard spawn as per Stoller-1962 was used as control. Samples were prepared in half-liter glass jars and 1-litre polypacks and were incubated for 14 and 21 days, respectively. An irradiation dose of 3.8 mega rads was found to be most effective for best quality (shelf life), maximum food reserves of spawn and yield of button mushroom. Constraints of steam sterilization like overcooking, shaking of autoclaved bottles, altitude of spawn laboratory, wetting of cotton plugs, and loss of food reserves were also checked.

Effects of nitrogen nutrition on the synthesis and deposition of the ω-gliadins of wheat

Background and AimsThe ω-gliadin storage proteins of wheat are of interest in relation to their impact on grain processing properties and their role in food allergy, particularly the ω-5 sub-group and wheat-dependent exercise-induced anaphylaxis. The ω-gliadins are also known to be responsive to nitrogen application. This study therefore compares the effects of cultivar and nitrogen availability on the synthesis and deposition of ω-gliadins in wheat grown under field conditions in the UK, including temporal and spatial analyses at the protein and transcript levels.MethodsSDS–PAGE, western blotting and N-terminal amino acid sequencing were used to compare the patterns of ω-gliadin components in mature grain of six British wheat (Triticum aestivum) cultivars and their accumulation during the development of grain grown in field plots with varying nitrogen supply. Changes in gene expression during development were determined using real-time reverse transcription–PCR (RT–PCR). Spatial patterns of gene expression and protein accumulation were determined by in situ hybridization and immunofluorescence microscopy, respectively.Key ResultsTwo patterns of ω-gliadins were identified in the six cultivars, including both monomeric ‘gliadin’ proteins and subunits present in polymeric ‘glutenin’ fractions. Increasing the level of nitrogen fertilizer in field plots resulted in increased expression of ω-gliadin transcripts and increased proportions of ω-5 gliadins. Nitrogen supply also affected the spatial patterns of ω-gliadin synthesis and deposition, which were differentially increased in the outer layers of the starchy endosperm with high levels of nitrogen.ConclusionsWheat ω-gliadins vary in amount and composition between cultivars, and in their response to nitrogen supply. Their spatial distribution is also affected by nitrogen supply, being most highly concentrated in the sub-aleurone cells of the starchy endosperm under higher nitrogen availability.

Exportação de macronutrientes do solo em área cultivada com milho para alimentação de bovinos confinados

The maize cultivated for forage requires special care with soil management. The nutrients exportation by silage might cause reducing of soil fertility, with consequent decrease of yield and nutritional quality of posterior crops. The aim of this work was assess levels of macronutrients in maize plant fragments (stem, leaves, bracts plus cob and grains), at stage of ensilage, in entire plant (silage forage) and in the mature grains; measure the nutrients exportation from soil by forage or grains. After, two diets were used in feedlot cattle, first was based on silage and other based in grains, to appraise the potential of nutrients to return into soil by manure and the final account of nutrients balance. The levels of N, P, K, Ca and Mg from forage were, respectively: 1,37; 0,24; 0,81; 0,2 and 0,22%; and in grains: 1,8; 0,28; 0,34; 0,12; and 0,11%. The fertilization performed was enough to supply extracted nutrients when was harvested only grains, promoting deficits in soil of 93 kg ha-1 of N and 84 kg ha-1 of K when was harvested forage. The manure of animals feed with silage+concentrated, compared to diet without roughage (80% grains and 20% protein core), cycled different amounts of N (276,28 vs 59,37), P (128,12 vs 33,37), K (58,32 vs 5,38), Ca (177,7 vs 78,89) and Mg (43,64 vs 11,81) in the cultivated area. The evaluated production systems presented capacity to maintain the levels of nutrients at soil through replacement via manure, and might contribute to the enrichment of fertility and reduce costs with mineral fertilizers in successive crops. The system which forage was used presented deficit of 25 kg ha-1 de K, probably due to insufficient amount of K applied, which recommendation is frequently made to grain production.

Increase in transcript accumulation of Psy1 and e-Lcy genes in grain development is associated with differences in seed carotenoid content between durum wheat and tritordeum

Carotenoid rich diets have been associated with lower risk of certain diseases. The great importance of cereals in human diet has directed breeding programs towards carotenoid enhancement to alleviate these deficiencies in developing countries and to offer new functional foods in the developed ones. The new cereal tritordeum (×Tritordeum Ascherson et Graebener) derived from durum wheat (Triticum turgidum ssp. durum) and the wild barley Hordeum chilense, naturally presents carotenoid levels 5-8 times higher than those of durum wheat. The improvement of tritordeum properties as a new functional food requires the elucidation of biosynthetic steps for carotenoid accumulation in seeds that differ from durum wheat. In this work expression patterns of nine genes from the isoprenoid and carotenoid biosynthetic pathways were monitored during grain development in durum wheat and tritordeum. Additionally, a fine identification and quantification of pigments (chlorophylls and carotenoids) during grain development and in mature seeds has been addressed. Transcript levels of Psy1, Psy2, Zds, e-Lcy and b-Lcy were found to correlate to carotenoid content in mature grains. The specific activation of the homeologous genes Psy1, e-Lcy from H. chilense and the high lutein esterification found in tritordeum may serve to explain the differences with durum wheat in carotenoid accumulation.

Dissipation of pendimethalin in the soil of field pea (Pisum sativum L.) and detection of terminal residues in plants

Dissipation of pendimethalin in the soil of field peas (Pisum sativum L.) at 0 to 110 days, and terminal residues in green and mature pea were studied under field conditions. Pendimethalin was applied as pre-emergence herbicide at 750, to 185 g a.i. ha−1 in winter, in field peas. Dissipation of pendimethalin in the soil at 0 to 110 days followed first-order kinetics showing a half-life of 19.83 days averaged over all doses. Low pendimethalin residues were found in mature pea grain (0.004, 0.003, <0.001 μg g−1), and straw (0.007, 0.002, <0.001 μg g−1) at 750, 350 and 185 g a.i. ha−1 treatments, respectively. The study indicated that residues of pendimethalin in green and mature pea were within the prescribed MRL limits.

Feeding preference of Nezara viridula (Hemiptera: Pentatomidae) and attractiveness of soybean genotypes

Nezara viridula (L.) (Hemiptera: Pentatomidae) is a cosmopolitan insect that causes economic damages to several cultures, in particular soybeans ( Glycine max [L.] Merr.) Among the techniques that involve Integrated Pest Management, the resistance of plants is pointed as a tool of great value and can contribute to the reduction of populations of insects. The feeding preferences of adults of southern green stink bug (N. viridula), and the attractiveness of soybean genotypes were evaluated under laboratory conditions to detect the most resistant material against attack from this insect. A choice test, using mature grains and green pods of the genotypes was carried out, in which the number of individuals attracted in different periods was counted. Feeding preference was evaluated in the choice tests using green pods and the number of pricks and the average time spent feeding by pricks were evaluated. In addition, texture and trichome density in the green pods were evaluated. The mature grains of ‘TMG 117RR’ and ‘TMG 121RR’ were less attractive to the adults of N. viridula. Regarding the green pods, ‘IAC 17’ and PI 227687 were less attractive; ‘IAC 17’ and ‘IAC PL1’ were less consumed, indicating the feeding non-preference as a resistance mechanism. ‘IAC 17’, ‘TMG-117RR’ and PI 227687 presented high levels of trichome density, and in ‘IAC 17’ this morphological characteristic was considered to be the main resistance factor against N. viridula. These results may be useful for breeding programs that focus on the resistance of soybeans to insects.

‘Billings’ Wheat Combines Early Maturity, Disease Resistance, and Desirable Grain Quality for the Southern Great Plains, USA

‘Billings’ Wheat Combines Early Maturity, Disease Resistance, and Desirable Grain Quality for the Southern Great Plains, USA

Structural and functional properties of alkali-treated high-amylose rice starch

Native starches were isolated from mature grains of high-amylose transgenic rice TRS and its wild-type rice TQ and treated with 0.1% and 0.4% NaOH for 7 and 14days at 35°C. Alkali-treated starches were characterised for structural and functional properties using various physical methods. The 0.1% NaOH treatment had no significant effect on structural and functional properties of starches except that it markedly increased the hydrolysis of starch by amylolytic enzymes. The 0.4% NaOH treatment resulted in some changes in structural and functional properties of starches. The alkali treatment affected granule morphology and decreased the electron density between crystalline and amorphous lamellae of starch. The effect of alkali on the crystalline structure including long- and short-range ordered structure was not pronounced. Compared with control starch, alkali-treated TRS starches had lower amylose content, higher onset and peak gelatinisation temperatures, and faster hydrolysis of starch by HCl and amylolytic enzymes.

Individual and combined effects of pre- and post-anthesis temperature on protein composition of two malting barley cultivars

The present study has investigated the individual and combined influence of pre- and post-anthesis temperatures and cultivars on the protein composition in barley grains. Two barley cultivars were grown in soil and hydroponic systems in daylight chambers with different pre- and post-anthesis temperatures. Size exclusion (SE)-HPLC was used to evaluate the protein composition in mature barley grains. The results showed that individual and interactive effects of pre- and post-anthesis temperatures and cultivar variations influenced protein composition in the barley grains. Pre-anthesis temperature greatly affected the amounts of total sodium dodecyl sulphate (SDS) extractable proteins (TOTE) and explained 30% of the variation in TOTE. The barley cultivars accounted for 20% of the variation in TOTE. Variation in malting barley cultivars was found to influence the SDS extractable small monomers (41% of the variation). Percentage of SDS un-extractable polymeric proteins in total amount of polymeric proteins (%UPP) was governed by post-anthesis temperature, accounting for 11% of the variation and cultivar differences accounted for 7% of the variation. Thus, the climatic conditions during the specific growing period and a choice of cultivars played a major role in determining the protein composition and ultimately the malting quality of spring barley.

Nutritional evaluation of immature grains in two Korean rice cultivars during maturation

The amounts of selected nutrient components of Korean rice cv. Chuchungbyeo and cv. Samkwangbyeo were compared depending on their harvest time. Rice grains harvested at the 15th and 25th day after heading (DAH) were considered as immature grains while the one at the 40th DAH was considered as mature grains. The results showed that the contents of protein (7.46–7.92 g/100 g) and reducing sugar (230.85–533.49 mg/100 g) in the immature grains were significantly higher than those in the mature grains. Phosphorus and potassium were the dominant minerals in both of cultivars during maturation. Vitamin C and provitamin A (i.e., β-carotene) were found only in immature rice grains of 2 rice cultivars. And immature rice grains contained higher level of vitamin B2, B3, and B6 compared with mature grains. γ-Tocochromanols content in immature grains was higher than that in mature grains.

High mature grain phytase activity in the Triticeae has evolved by duplication followed by neofunctionalization of the purple acid phosphatase phytase (PAPhy) gene.

The phytase activity in food and feedstuffs is an important nutritional parameter. Members of the Triticeae tribe accumulate purple acid phosphatase phytases (PAPhy) during grain filling. This accumulation elevates mature grain phytase activities (MGPA) up to levels between ~650 FTU/kg for barley and 6000 FTU/kg for rye. This is notably more than other cereals. For instance, rice, maize, and oat have MGPAs below 100 FTU/kg. The cloning and characterization of the PAPhy gene complement from wheat, barley, rye, einkorn, and Aegilops tauschii is reported here. The Triticeae PAPhy genes generally consist of a set of paralogues, PAPhy_a and PAPhy_b, and have been mapped to Triticeae chromosomes 5 and 3, respectively. The promoters share a conserved core but the PAPhy_a promoter have acquired a novel cis-acting regulatory element for expression during grain filling while the PAPhy_b promoter has maintained the archaic function and drives expression during germination. Brachypodium is the only sequenced Poaceae sharing the PAPhy duplication. As for the Triticeae, the duplication is reflected in a high MGPA of ~4200 FTU/kg in Brachypodium. The sequence conservation of the paralogous loci on Brachypodium chromosomes 1 and 2 does not extend beyond the PAPhy gene. The results indicate that a single-gene segmental duplication may have enabled the evolution of high MGPA by creating functional redundancy of the parent PAPhy gene. This implies that similar MGPA levels may be out of reach in breeding programs for some Poaceae, e.g. maize and rice, whereas Triticeae breeders should focus on PAPhy_a.

Partial Purification and Characterization of Peroxidase from Pearl Millet (Pennisetum Glaucum [L.] R. Br.) Grains

Peroxidase from pearl millet hybrid HHB 94 was purified stepwise by (NH4)2SO4 fractionation, gel filtration and ion exchange chromatography using Sephadex G-100 and DEAE-cellulose to near homogeneity. The protocol yielded 41% of peroxidase with 33.2-fold purification. The purified enzyme preparation has molecular masses of 31 kDa, as determined by gel filtration through Sephadex G-100, and 30.4 kDa, as determined by SDS-PAGE, suggesting that the enzyme is a monomer. The enzyme exhibited maximum activity at pH 5.6 and 30C. It was significantly more stable in the pH range of 6.0–6.8 and at temperature below 35C. Peroxidase showed Km values of 0.10 and 11 mM for o-dianisidine and H2O2, respectively. The activity of peroxidase was highly inhibited by DTT, β-mercaptoethanol and hydrazine, and moderately by sodium azide, sodium borohydride, oxalic acid, EDTA, DTNB, Mn2+, Na+ and K+. The enzyme activity was enhanced by Ca2+ and Fe3+. Practical Applications Peroxidase is considered to have an empirical relationship to off-flavors and odors in foods. Earlier we have shown that peroxidase activity varied in different genotypes, i.e., HHB 94 (high) and 94222A × 78/711 (low), which appeared to be responsible for odor generation in stored pearl millet meal. In 94222A × 78/711, less off-odor was observed. The enzyme purified from mature pearl millet grains is strongly inhibited by DTT. This new information has been used to assay the enzyme in situ. We have found that in comparison to extractable activity, in situ activity of the enzyme is more strongly correlated with the development of off-odor in stored flour. Thus, in situ assay is being used to screen germplasm for selecting contrasting genotypes (with respect to off-odor) that will be used to develop pearl millet hybrids with improved shelf life of flour.

Mechanisms Regulating Grain Contamination with Trichothecenes Translocated from the Stem Base of Wheat (Triticum aestivum) Infected withFusarium culmorum

Factors limiting trichothecene contamination of mature wheat grains after Fusarium infection are of major interest in crop production. In addition to ear infection, systemic translocation of deoxynivalenol (DON) may contribute to mycotoxin levels in grains after stem base infection with toxigenic Fusarium spp. However, the exact and potential mechanisms regulating DON translocation into wheat grains from the plant base are still unknown. We analyzed two wheat cultivars differing in susceptibility to Fusarium head blight (FHB), which were infected at the stem base with Fusarium culmorum in climate chamber experiments. Fungal DNA was found only in the infected stem base tissue, whereas DON and its derivative, DON-3-glucoside (D3G), were detected in upper plant parts. Although infected stem bases contained more than 10,000 μg kg⁻¹ dry weight (DW) of DON and mean levels of DON after translocation in the ear and husks reached 1,900 μg kg⁻¹ DW, no DON or D3G was detectable in mature grains. D3G quantification revealed that DON detoxification took mainly place in the stem basis, where ≤ 50% of DON was metabolized into D3G. Enhanced expression of a gene putatively encoding a uridine diphosphate-glycosyltransferase (GenBank accession number FG985273) was observed in the stem base after infection with F. culmorum. Resistance to F. culmorum stem base infection, DON glycosylation in the stem base, and mycotoxin translocation were unrelated to cultivar resistance to FHB. Histological studies demonstrated that the vascular transport of DON labeled with fluorescein as a tracer from the peduncle to the grain was interrupted by a barrier zone at the interface between grain and rachilla, formerly described as "xylem discontinuity". This is the first study to demonstrate the effective control of influx of systemically translocated fungal mycotoxins into grains at the rachilla-seed interface by the xylem discontinuity tissue in wheat ears.

Wheat Gluten Polymer Structures: The Impact of Genotype, Environment, and Processing on Their Functionality in Various Applications

ABSTRACTFor a number of applications, gluten protein polymer structures are of the highest importance in determining end‐use properties. The present article focuses on gluten protein structures in the wheat grain, genotype‐ and environment‐related changes, protein structures in various applications, and their impact on quality. Protein structures in mature wheat grain or flour are strongly related to end‐use properties, although influenced by genetic and environment interactions. Nitrogen availability during wheat development and genetically determined plant development rhythm are the most important parameters determining the gluten protein polymer structure, although temperature during plant development interacts with the impact of the mentioned parameters. Glutenin subunits are the main proteins incorporated in the gluten protein polymer in extracted wheat flour. During dough mixing, gliadins are also incorporated through disulfide‐sulfhydryl exchange reactions. Gluten protein polymer size and complexity in the mature grain and changes during dough formation are important for breadmaking quality. When using the gluten proteins to produce plastics, additional proteins are incorporated in the polymer through disulfide‐sulfhydryl exchange, sulfhydryl oxidation, β‐eliminations with lanthionine formation, and isopeptide formation. In promising materials, the protein polymer structure is changed toward β‐sheet structures of both intermolecular and extended type and a hexagonal close‐packed structure is found. Increased understanding of gluten protein polymer structures is extremely important to improve functionality and end‐use quality of wheat‐ and gluten‐based products.

Spatial Patterns of Gluten Protein and Polymer Distribution in Wheat Grain

The starchy endosperm is the major storage tissue in the mature wheat grain and exhibits quantitative and qualitative gradients in composition, with the outermost cell layers being rich in protein, mainly gliadins, and the inner cells being low in protein but enriched in high-molecular-weight (HMW) subunits of glutenin. We have used sequential pearling to produce flour fractions enriched in particular cell layers to determine the protein gradients in four different cultivars grown at two nitrogen levels. The results show that the steepness of the protein gradient is determined by both genetic and nutritional factors, with three high-protein breadmaking cultivars being more responsive to the N treatment than a low-protein cultivar suitable for livestock feed. Nitrogen also affected the relative abundances of the three main classes of wheat prolamins: the sulfur-poor ω-gliadins showed the greatest response to nitrogen and increased evenly across the grain; the HMW subunits also increased in response to nitrogen but proportionally more in the outer layers of the starchy endosperm than near the core, while the sulfur-rich prolamins showed the opposite trend.