Immature Wheat Grains Research Articles

Integrated transcriptomic and metabolomic analyses revealed the regulatory mechanism of sulfur application in grain yield and protein content in wheat (Triticum aestivum L.).

Sulfur fertilizers play an important role in increasing the yield and improving the dough quality of bread wheat, but their regulatory mechanism remains unclear. In this study, 0 kg·ha−1 (S0) and 60 kg·ha−1 (S60) of sulfur were applied on the anthesis date; subsequently, immature wheat grains at 8, 13, and 18 days post-anthesis (DPA) were subjected to integrated transcriptomic and metabolomic analyses to investigate the changes in the gene/metabolite activity in a typical strong-gluten wheat, Gaoyou2018 (GY2018). Our data show that the S60 treatment could significantly increase the grain yield and grain protein content by 13.2 and 3.6%, respectively. The transcriptomic analysis revealed that 10,694 differentially expressed genes (DEGs) were induced by S60 from 8 to 18 DPA when compared with their corresponding no-sulfur controls, and most DEGs were mainly involved in lipid metabolism and amino acid metabolism pathways. Ninety-seven MYB transcription factors (TFs) were identified as responsive to the S60 treatment; of these, 66 showed significantly differential expression at 13 DPA, and MYB118 might participate in the process of sulfur metabolism by regulating glucosinolate synthesis. In total, 542 significantly enriched differentially expressed (DE) metabolites (DEMs) were identified following the S60 treatment, which mainly included secondary metabolites, carbohydrates, and amino acids. Several metabolites (e.g., glutathione, sucrose, GDP-alpha-D-glucose, and amino acids) exhibited altered abundances following the S60 treatment. The combination of transcriptomic and metabolomic analyses highlighted the important role of amino acid metabolism (especially cysteine, methionine, and glutathione metabolism) and starch and sucrose metabolism pathways after S60 application. Our results provide valuable information enhancing our understanding of the molecular mechanism of the response to sulfur and provide useful clues for grain protein quality formation and yield improvement in bread wheat.

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

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 iron-57 (57 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. 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 transmission electron microscopy energy dispersive X-ray spectroscopy (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 57 Fe, was observed in aleurone cells and may represent iron being delivered to phytate globoids. Correlation of the 57 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.

Milky Stage Versus Dough Stage of Immature Wheat Grain: Effects on Phytic Acid and Fructan Contents, Antioxidant Activity, Textural Parameters, and Sensory Characteristics of Set-Type Yoghurts

HIGHLIGHTS Yoghurts were supplemented with milky and dough stage wheat grain flours. Total antioxidant capacity was improved by wheat grain flour supplementation. Milky stage wheat provided higher fructan content than that of dough stage wheat. Fermentation reduced phytic acid levels in yoghurts containing wheat grain flours.

Determination of aroma and volatile flavor compounds and sensory properties of set-type yoghurts enriched with immature wheat grain

Determination of aroma and volatile flavor compounds and sensory properties of set-type yoghurts enriched with immature wheat grain

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

SummaryWheat 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.

Immature wheat grain as a potential prebiotic ingredient in set-type yoghurts: impact on antioxidative, textural properties and survival of different probiotics.

The aim of this study was to investigate the effect of immature wheat grain (IWG) on the survival of Lactobacillus acidophilus NCFM (LNCFM), Lactobacillus casei 431 (L431) and Lactobacillus acidophilus 20079 (L20079) in yoghurts under cold storage. Furthermore, the impact of IWG on physicochemical, textural and antioxidative properties of yoghurts was evaluated. Fortification of yoghurt with IWG positively affected LNCFM and L20079 counts during cold storage whereas no statistical improvement was observed in the viability of L431. The addition of IWG clearly supported the antioxidative activity and total phenolic content in yoghurt. No statistical differences were discovered regarding syneresis and water holding capacity in all probiotic applications. Although, enrichment with IWG enhanced the firmness of probiotic yoghurts, it simultaneously reduced the cohesiveness and viscosity index. This study demonstrated that IWG may be used as a food additive for enhancing probiotic LNCFM and L20079 survival and providing functional aspects in yoghurt.

Metabolomic approach for characterization of phenolic compounds in different wheat genotypes during grain development.

The phenolic-profiling of seven different wheat (Triticum aestivum) genotypes was investigated for the first time during different stages of grain development (milky, softy, physiological maturity and mature). Free and bound phenolic compounds were extracted separately and analyzed by UPLC-QTOF-MSE. Total phenolic content significantly decreased, up to 50% depending on the genotype, towards the maturation of grain. The highest content (free and bound) was observed in the most immature grains, while the lowest level was found in mature grains (408.0 and 165.0 GAE mg/100 g, respectively). Globally, 237 phenolic compounds were identified, divided into 5 classes: flavonoids (85), phenolic acids (77), other polyphenols (51), lignans (16) and stilbenes (8). UPLC-MS results showed a progressively decrease of the number of phenolic identification (ID) all along grain development, milky (213), softy (192), physiological maturity (169) and mature (144). The proportion bound to free phenolic progressively increased, reaching the maximum at physiological maturity, indicating a possible enzymatic reactions and complexation during grain growth. Ferulic acid, diphyllin, 4-hydroxybenzoic acid, ferulic acid isomer, apigenin 7-O-apiosyl-glucoside isomer and myricetin isomer were the most abundant compounds. Chemometric tools showed a clear separation between immature and mature grain for all genotypes. Phenolic profile varied significantly among genotypes, this result can help the selection of varieties towards a higher retention of bioactive compounds. Noteworthy, immature wheat grains can be considered a rich source of phenolic compounds and as an attractive ingredient to incorporate to functional foods.

Chemical Composition and Microbiological Properties of Tarhana Enriched with Immature Wheat Grain

In this study, the effect of immature wheat grain (IWG) supplementation on the tarhana formulation was investigated by determining color values and some chemical and microbiological properties. Flours obtained from IWG, harvested at 26 (IWG-1) and 36 days (IWG-2) after anthesis, were used in the tarhana formulation as a replacement of white wheat flour in concentrations of 10, 30 and 50%. Ash, Ca, Mg, K, P and Zn contents of tarhana samples increased by IWG-1 addition. IWG-2 addition resulted in an increase in moisture and protein contents. IWG-1 addition into the tarhana provided an increase in the antioxidant activity and total phenolic contents of the samples. The total counts of mesophilic aerobic bacteria and lactic acid bacteria of tarhana with IWG-1 were higher than those of other tarhana samples. Practical Applications Some changes occur in the physical properties and chemical composition of wheat during maturation period. These changes have an effect on the nutritional components and health benefits of wheat grain. In this study, two different immature wheat grains were used in tarhana production. Some chemical and microbiological properties of enriched tarhanas were assessed. Using immature wheat flour increased the mineral content of tarhana samples. The antioxidant activity of samples increased with immature wheat flour addition. Counts of lactic acid bacteria of enriched tarhanas was higher than the control.

Prebiotic Content of Bread Prepared with Flour from Immature Wheat Grain and Selected Dextran-Producing Lactic Acid Bacteria

In the last few years the need to produce food with added value has fueled the search for new ingredients and health-promoting compounds. In particular, to improve the quality of bakery products with distinct nutritional properties, the identification of new raw materials, appropriate technologies, and specific microbial strains is necessary. In this study, different doughs were prepared, with 10% and 20% flour from immature wheat grain blended with type "0 America" wheat flour. Immature flour was obtained from durum wheat grains harvested 1 to 2 weeks after anthesis. Doughs were obtained by both the straight-dough and sourdough processes. Two selected exopolysaccharide-producing strains of lactic acid bacteria (LAB), Leuconostoc lactis A95 and Lactobacillus curvatus 69B2, were used as starters. Immature flour contained 2.21 g/100 g (dry weight) of fructo-oligosaccharides. Twenty percent immature flour in dough resulted in a shorter leavening time (4.23 ± 0.03 h) than with the control and dough with 10% immature flour. The total titratable acidity of sourdough with 20% immature flour was higher (12.75 ± 0.15 ml 0.1 N NaOH) than in the control and sourdough with 10% immature wheat flour (9.20 ml 0.1 N NaOH). Molecular analysis showed that all samples contained three LAB species identified as L. lactis, L. curvatus, and Pediococcus acidilactici. A larger amount of exopolysaccharide was found in sourdough obtained with 20% immature flour (5.33 ± 0.032 g/kg), positively influencing the exopolysaccharide content of the bread prepared by the sourdough process (1.70 ± 0.03 g/kg). The addition of 20% immature flour also led to a greater presence of fructo-oligosaccharides in the bread (900 mg/100 g dry weight), which improved its nutritional characteristics. While bread volume decreased as the concentration of immature wheat flour increased, its mechanical characteristics (stress at a strain of 30%) were the same in all samples obtained with different percentages of fructo-oligosaccharides. These data support the use of immature wheat grain flour, and exopolysaccaride-producing lactic acid bacteria in formulating functional prebiotic baked goods whose nutritional value can be suitably improved.

Quality and nutritional properties of pasta products enriched with immature wheat grain

In this study, nutritional and sensory properties of pasta enriched with 30% immature wheat grain (IWG), a natural source of fructo-oligosaccharides (FOS), are evaluated. Colour and cooking quality, nutritional value and glycaemic index (GI) of pasta were assessed in comparison with commercially enriched inulin and 100% wholewheat pastas. IWG integration induced deep changes in colour, without negatively affecting the cooking quality of pasta, and promoted nutritional quality by increasing the fibre content; IWG pasta presented a remarkable leaching of FOS in cooking water, thus providing only 1 g of FOS per serving. IWG pastas showed a GI of 67 (dried) and 79 (fresh), not significantly different from commercial pasta products. IWG can be considered an interesting ingredient to obtain functional products ‘naturally enriched’ in FOS and fibre. Results about FOS leaching suggest that, in dealing with functional effects, the actual prebiotic content should be carefully considered on food ‘as eaten’.

Localisation of iron in wheat grain using high resolution secondary ion mass spectrometry

Insufficient iron (Fe) is one of the most prevalent micronutrient deficiencies in humans, with billions of people affected. Cereal grains are an important source of Fe for humans but the bioavailability of Fe in cereals is generally low. Information regarding the cellular and sub-cellular localisation of Fe in wheat grain will aid optimising nutrient delivery for human health. In this study high resolution secondary ion mass spectrometry (NanoSIMS) was used to map the distribution of Fe in the aleurone layer and in the endosperm of immature wheat grain. Iron was shown to be localised strongly in the phytin globoids in the aleurone cells and to a lesser extent in the cytoplasm around the starch granules in the endosperm.

Prebiotic potential and gastrointestinal effects of immature wheat grain (IWG) biscuits

In this study the effects of immature wheat grains (IWG), a natural source of fructo-oligosaccharides (FOS), on intestinal microbiota and gastrointestinal function were evaluated. Ileal effluents from three ileostomates were collected for 8h after IWG-enriched or Control biscuit administration, and then fermented in vitro with human faecal inoculum. On fermentation broths, microbial counts and SCFA were measured. Moreover, we investigated the effect of IWG biscuits on gastric emptying. Twelve healthy volunteers underwent ultrasound measurement of gastric emptying of a standard meal consumed 5h after a breakfast composed by lactose-free milk and IWG or Control biscuits; hunger and satiety sensations were also evaluated in this period. Bifidobacteria and lactic acid bacteria counts were higher (P<0.05) in IWG than in Control cultures, supporting the prebiotic effects of IWG, probably linked to its FOS content; moreover IWG fermentation produced more acetate. In vivo IWG biscuits delayed gastric emptying of the next meal (P<0.05), decreased hunger (P<0.001) and increased satiety (P<0.005). Therefore in vitro results substantiate the potential of IWG as a prebiotic ingredient and in vivo data suggest an effect of IWG on gastric emptying and on persistent satiety. These preliminary data tend to support the use of IWG in formulating functional prebiotic products suitable to promote satiety.

Variation in two PPO genes associated with polyphenol oxidase activity in seeds of common wheat

Polyphenol oxidase (PPO) is often regarded as a major factor resulting in time-dependent darkening and discoloration of Asian noodles and other wheat end products. To understand the relationship between variation of PPO genes and PPO activity of seed, the three PPO genes, which express in immature wheat grain, were investigated in 216 common wheat cultivars. The results indicated that only TaPPO-A1 and TaPPO-D1 showed high polymorphisms related to PPO activity. Two alleles in both TaPPO-A1 (TaPPO-A1a and TaPPO-A1b) and TaPPO-D1 (TaPPO-D1a and TaPPO-D1b) were detected using denaturing polyacrylamide gel electrophoresis. Wheat cultivars with TaPPO-A1b usually showed higher PPO activity than those with TaPPO-A1a. The TaPPO-D1a allele was often found in lower-PPO-activity cultivars, compared with TaPPO-D1b. The sequencing results of DNA fragments confirmed that two introns existed in TaPPO-D1 like TaPPO-A1. Some variation of introns was detected in the two alleles of TaPPO-D1. During seed development, the high-PPO-activity cultivar, Yangmai 158 (TaPPO-A1b/TaPPO-D1b) showed higher transcription of the two PPO genes, in comparison to low-activity cultivar, Yongchuanbaimai (TaPPO-A1a/TaPPO-D1a). These results suggested that variation in introns may influence the transcription of TaPPO-A1 and TaPPO-D1 in immature seeds of wheat.

Changes in Carbohydrate Content during Wheat Maturation—What is Measured by near Infrared Spectroscopy?

The role of bread, pasta and related products produced from milled wheat seeds is important to the human diet, so monitoring changes of starch content in developing grain is essential. Immature wheat grains are also used as a functional food, particularly as a source of water-soluble carbohydrates. The amount and variation in content of different carbohydrates changes considerably during maturation and these changes were non-destructively monitored in developing grain using near infrared (NIR) spectroscopy. Characteristic changes in three carbohydrate absorption bands [1585–1595 nm (Carbohydrate I), 2270–2280 nm (Carbohydrate II) and 2325–2335 nm (Carbohydrate III)] were identified and it was concluded that the different dynamics of carbohydrates (starch accumulation as well as synthesis/decomposition of water-soluble carbohydrates) could be followed sensitively by monitoring these three different regions of NIR spectra. Carbohydrate I represents the effect of starch accumulation during maturation based on the vibrations of intermolecular hydrogen bonded O–H groups in polysaccharides. Carbohydrate II is the manifestation of O–H stretching and C–C stretching vibrations existing unengaged in water-soluble carbohydrates while Carbohydrate III describes the changes in C–H stretching and deformation band of poly- and mono-oligosaccharides. NIR spectroscopic techniques are shown to be effective in monitoring plant physiological processes and the spectra have hidden information for predicting the stage of growth in wheat seed.

Effects of desiccation and a change in temperature on germination of immature grains of wheat (Triticum aestivum L.)

A study was made of the effects of desiccation and a change in temperature on the germination of wheat grains harvested 20 days after anthesis. When the germination test was performed immediately after harvesting, germination percentages ranged from 5.2% to 10.7%. Germination percentages increased to 48.2% to 90.3% after grain had been desiccated at 20 °C and then hydrated at 10 °C. This increase occurred even if grains had been desiccated in an atmosphere of high relative humidity. The germination percentage of non-desiccated grains depended on the germination temperature. When the pericarp and testa were removed from embryos, the germination percentage of grains incubated at 20 °C and then at 10 °C was higher than that of grains incubated at 10 °C. In general, a low germination temperature is believed to be effective in breaking dormancy of wheat grains. However, a change in temperature stimulated germination to a greater extent than a constant low temperature. The germination percentage of 5-day cycle alternating temperature was greater than that with 1-day, 2-day and 10-day cycles. Although the germination of immature wheat grains was stimulated by both high and low germination temperatures, it is likely that cycles shorter and, also, longer than a critical period induce limited germination. Loss of dormancy commonly occurs when development of wheat grains proceeds at a high temperature, with imbibition at a low temperature. However, germination ability of non-desiccated immature wheat grain was enhanced by a change in temperature during germination.

Wheat Cultivar Susceptibility to Grain Damage by the New Zealand Wheat Bug,Nysius huttoni, and Cultivar Susceptibility to the Effects of Bug Proteinase on Baking Quality

Immature wheat grain in New Zealand is attacked sporadically by the native insect (bug),Nysius huttoni.This ‘bug-damaged wheat’ contains a bug salivary proteinase, and bread made from this wheat has a characteristically poor loaf volume and texture. Historical baking data suggest variations in wheat cultivar susceptibility to bug damage. This suggestion was tested in two trials (1992/1993 and 1993/1994) on immature wheat using nine or seven New Zealand cultivars and breeding lines enclosed together in nylon mesh cages with and withoutN. huttoni.Visible damage, bug-proteinase levels, electrophoretic protein patterns, and baking properties of the grain were analysed. Both trials showed that susceptibility to bug damage was significantly different amongst cultivars and breeding lines. The ranking of cultivar susceptibility was the same for the two trials, except for cv. Arawa, which was one of the most susceptible cultivars in the first trial, but one of the least susceptible in the second trial. Cultivars Domino and Oroua consistently showed less susceptibility to bug attack. The breeding line WW378 and the cultivar Otane were the most susceptible to bug attack. The high quality bread wheats (Otane, Oroua, Domino and Batten) were less susceptible to the effects of bug proteinase in baking than the poor baking quality wheats (Karamu, WW378, ASPS9927 and ASPS9928). Batten was significantly less susceptible than any other cultivar in test baking. There was no relationship between bug-damage susceptibility and grain characters such as colour, hardness and texture, or head characters such as shape, awns and waxiness.

Bug damage in New Zealand wheat grain: The role of various heteropterous insects

Abstract Certain heteropterousinsects (true bugs) in New Zealand deposit salivary enzymes into immature wheat grain while feeding. These enzymes survive in harvested wheat, destroy gluten structure in dough, and cause poor quality bread. This study investigates what insect is responsible for bug-damaged wheat The following field-collected insect species were caged on wheat at the watery ripe growth stage: Nysius huttoni, Rhypodes sp., Stenotus binotatus, Calocoris norvegicus, Sidnia kinbergi, and Dictyotus caenosus. All the insects produced visible signs of damage on kernels and reduced kernel weight, but only wheat damaged by N. huttoni and S. binotatus had sufficiently high levels of pH 9 active, gluten-degrading enzyme to cause poor quality bread. However, the electrophoretic patterns of protein subunits from degraded glutenand the characteristics of bug damage in bread were different for these two insects. Also, the appearances of the damaged kernels and levels of α-amylase were clearly different in t...

Endogenous abscisic acid and wheat germ agglutinin content in wheat grains during development

Abscisic acid (ABA) and wheat germ agglutinin content of immature wheat grains and embryos was determined by immunoassay throughout the development of a field‐grown wheat crop (Triticum aestivum cv. Timmo). Wheat germ agglutinin accumulation in the embryo was not preceded by an increase in endogenous abscisic acid amount or concentration in either embryos or grains. At a later stage in development the endogenous concentration of abscisic acid in both embryos and grains was found to be two orders of magnitude lower than the endogenous levels required to inhibit precocious germination and promote wheat germ agglutinin accumulation in excised embryos cultured in vitro. These findings are discussed in the context of the control of embryo development in vivo by both ABA and the water status of the grain and embryo.

Expression of ?-amylase and other gibberellin-regulated genes in aleurone tissue of developing wheat grains

Aleurone tissue from freshly harvested immature wheat grains (Triticum aestivum L. cv. Sappo) which is normally unresponsive to gibberellic acid can be made responsive by subjecting the tissue to a pre-incubation treatment in a simple buffered medium prior to the addition of the growth substance. The effectiveness of this treatment is dependent on grain age, with grains less than 15-20 days post anthesis failing to become converted to a responsive state whilst tissue from grains older than this become increasingly susceptible. Tissue from grains of a certain age (approx. 25-28 days post anthesis) produce small amounts of α-amylase following this treatment even in the absence of exogenously applied growth substance. Using different (32)-labelled complementary-DNA probes for α-amylase in wheat it was demonstrated that the failure of freshly harvested tissue to produce α-amylase was correlated with the absence of the appropriate mRNA species. Inability to accumulate α-amylase mRNA in response to gibberellic acid was removed by the pre-iccubation treatment and also by enforced drying. The gibberellin-regulated expression of other unidentified genes also responds to pre-incubation or drying. Induction of gibberellin-responsiveness in immature aleurone cells did not extend to the secretion of acid phosphatase, protease and ribonuclease.

MECHANISM OF INTERCELLULAR MOVEMENT OF PROTOPLASM IN WHEAT NUCELLUS

The outermost layer of the nucellus, immediately after it is carefully taken off from an immature wheat grain (reaching 1/2—2/3 its full size), can exhibit intercellular movement of protoplasm in vivo as has been recorded previously by us in cinemicrographs. The present investigation on its underlying mechanism with electron microscope and by physiological treatment substantiate the visual observation that the intercellular movement is carried out through the enlarged and open channels of the modified plasmodesmata by alternate vigorous contraction and expansion of the protoplasm. Acid phosphatase, presumably released from the lysosome nearby, can be detected in the vicinity of the channel and might be involved in the dissolution of its internal structure and enlargement of its aperture (200—300 mm or even larger). Low temperature (5—6℃), KCN (0.05M) and cytochalasin B (20μg/ml) can withhold the movement reversibly. The energy required for such movement is directly derived from ATP, as is evidenced by the high ATPase activity of the moving units, and the moving apparatus is closely connected with microfilament.