小麦高分子量麦谷蛋白亚基序列及其结构与加工品质的关系

高分子量麦谷蛋白亚基（high molecular weight glutenin subunit,HMW-GS）是小麦种子贮藏蛋白的主要成分,其组成、含量和结构直接影响小麦面粉面筋的弹展性,决定着小麦的加工品质。本文主要对小麦HMW-GS的序列、结构和亚基之间组合形式做了详细的综述,并较系统地讨论了HMW-GS的结构和组成、特点等与面粉的加工品质之间的关系以及如何从定性和定量两方面来影响面粉的加工品质。     

Evidence of physical interactions of puroindoline proteins using the yeast two-hybrid system

The puroindoline proteins PINA and PINB play key roles in determining wheat grain texture and also have potential antimicrobial roles. Many recent studies show that their roles in grain texture involve some interaction or interdependence, and their antimicrobial activity may also involve formation of protein complexes. The issue of whether any homo- and/or heteromeric associations occur amongst the PIN proteins is thus critical for understanding their biological functions and exploiting them for grain texture modifications or antimicrobial applications, but is as yet unresolved. This work has utilised the well-established yeast two-hybrid system to directly address this issue. The results confirm occurrence of in vivo interactions between the two PIN proteins for the first time, and show that PINB interacts with itself and also interacts, although somewhat weakly, with PINA, while PINA is a weaker interactor. The results explain the many reported observations suggesting a co-operative interaction between the two proteins and provide a rapid and efficient tool for testing the effects of various alleles/mutations on the interactions and lipid binding properties of these proteins, which are of functional significance to grain texture and antimicrobial defence functions.     

Proteomic analysis of the effect of heat stress on hexaploid wheat grain: Characterization of heat-responsive proteins from total endosperm

High temperatures during grain filling have been reported to be one of the factors that can affect the dough properties and quality characteristics of wheat. Responses to high temperature have been related to changes in protein composition at both quantitative and qualitative levels. The present study was conducted to determine the influence of high temperature during grain filling on the protein composition of bread wheat evaluated by proteomic tools. Plants were grown in the field and transferred to cabinets soon after flowering. They were subjected to two thermal regimes 18 degrees C/10 degrees C (day/night) and 34 degrees C/10 degrees C. Total proteins were extracted from control grains and treated plants at three different post-anthesis stages. The proteins were separated by two-dimensional gel electrophoresis and analysed by Melanie 3 software. Of the total number of mature wheat grain proteins, 37 were identified as significantly changed by heat treatment. Analysis by matrix-assisted laser desorption/ionization mass spectrometry and tandem mass spectrometry coupled with database searching allowed the characterization of 25 heat-induced proteins and only one heat-decreased protein spot. To learn more about the function of the identified proteins, we examined their expression during treatment.     

Opportunities for manipulating the seed protein composition of wheat and barley in order to improve quality

Wheat and barley are the major temperate cereals, being used for food, feed and industrial raw material. However, in all cases the quality may be limited by the amount, composition and properties of the grain storage proteins. We describe how a combination of biochemical and molecular studies has led to an understanding of the molecular basis for breadmaking quality in wheat and feed quality in barley, and also provided genes encoding key proteins that determine quality. The control of expression of these genes has been studied in transgenic tobacco plants and by transient expression in cereal protoplasts, providing the basis for the production of transgenic cereals with improved quality characteristics.     

Proteomes of hard and soft near-isogenic wheat lines reveal that kernel hardness is related to the amplification of a stress response during endosperm development

Wheat kernel texture, a major trait determining the end-use quality of wheat flour, is mainly influenced by puroindolines. These small basic proteins display in vitro lipid binding and antimicrobial properties, but their cellular functions during grain development remain unknown. To gain an insight into their biological function, a comparative proteome analysis of two near-isogenic lines (NILs) of bread wheat Triticum aestivum L. cv. Falcon differing in the presence or absence of the puroindoline-a gene (Pina) and kernel hardness, was performed. Proteomes of the two NILs were compared at four developmental stages of the grain for the metabolic albumin/globulin fraction and the Triton-extracted amphiphilic fraction. Proteome variations showed that, during grain development, folding proteins and stress-related proteins were more abundant in the hard line compared with the soft one. These results, taken together with ultrastructural observations showing that the formation of the protein matrix occurred earlier in the hard line, suggested that a stress response, possibly the unfolded protein response, is induced earlier in the hard NIL than in the soft one leading to earlier endosperm cell death. Quantification of the albumin/globulin fraction and amphiphilic proteins at each developmental stage strengthened this hypothesis as a plateau was revealed from the 500 °Cd stage in the hard NIL whereas synthesis continued in the soft one. These results open new avenues concerning the function of puroindolines which could be involved in the storage protein folding machinery, consequently affecting the development of wheat endosperm and the formation of the protein matrix.     

Expression of wild-type pinB sequence in transgenic wheat complements a hard phenotype

Wheat grain hardness is a major factor in the wheat end-product quality. Grain hardness in wheat affects such parameters as milling yield, starch damage and baking properties. A single locus determines whether wheat is hard or soft textured. This locus, termed Hardness ( Ha), resides on the short arm of chromosome 5D. Sequence alterations in the tryptophan-rich proteins puroindoline a and b (PINA and PINB) are inseparably linked to hard textured grain, but their role in endosperm texture has been controversial. Here, we show that the pinB-D1b alteration, common in hard textured wheats, can be complemented by the expression of wild-type pinB-D1a in transformed plants. Transgenic wheat seeds expressing wild-type pinB were soft in phenotype, having greatly increased friabilin levels, and greatly decreased kernel hardness and damaged starch. These results indicate that the pinB-D1b alteration is most likely the causative Ha mutation in the majority of hard wheats.     

Effects of starch synthase IIa gene dosage on grain, protein and starch in endosperm of wheat

Starch synthases (SS) are responsible for elongating the alpha-1,4 glucan chains of starch. A doubled haploid population was generated by crossing a line of wheat, which lacks functional ssIIa genes on each genome (abd), and an Australian wheat cultivar, Sunco, with wild type ssIIa alleles on each genome (ABD). Evidence has been presented previously indicating that the SGP-1 (starch granule protein-1) proteins present in the starch granule in wheat are products of the ssIIa genes. Analysis of 100 progeny lines demonstrated co-segregation of the ssIIa alleles from the three genomes with the SGP-1 proteins, providing further evidence that the SGP-1 proteins are the products of the ssIIa genes. From the progeny lines, 40 doubled haploid lines representing the eight possible genotypes for SSIIa (ABD, aBD, AbD, ABd, abD, aBd, Abd, abd) were characterized for their grain weight, protein content, total starch content and starch properties. For some properties (chain length distribution, pasting properties, swelling power, and gelatinization properties), a progressive change was observed across the four classes of genotypes (wild type, single nulls, double nulls and triple nulls). However, for other grain properties (seed weight and protein content) and starch properties (total starch content, granule morphology and crystallinity, granule size distribution, amylose content, amylose-lipid dissociation properties), a statistically significant change only occurred for the triple nulls, indicating that all three genes had to be missing or inactive for a change to occur. These results illustrate the importance of SSIIa in controlling grain and starch properties and the importance of amylopectin fine structure in controlling starch granule properties in wheat.     

Wheat quality related differential expressions of albumins and globulins revealed by two-dimensional difference gel electrophoresis (2-D DIGE)

Comparative proteomics analysis offers a new approach to identify differential proteins among different wheat genotypes and developmental stages. In this study, the non-prolamin expression profiles during grain development of two common or bread wheat cultivars (Triticum aestivum L.), Jing 411 and Sunstate, with different quality properties were analyzed using two-dimensional difference gel electrophoresis (2-D DIGE). Five grain developmental stages during the post-anthesis period were sampled corresponding to the cumulative averages of daily temperatures (°C: 156 °C, 250 °C, 354 °C, 447 °C and 749.5 °C). More than 400 differential protein spots detected at one or more of the developmental stages of the two cultivars were monitored, among which 230 proteins were identified by MS. Of the identified proteins, more than 85% were enzymes possessing different physiological functions. A total of 36 differential proteins were characterized between the two varieties, which are likely to be related to wheat quality attributes. About one quarter of the proteins identified expressed in multiple spots with different pIs and molecular masses, implying certain post-translational modifications (PTMs) of proteins such as phosphorylations and glycosylations. The results provide new insights into biochemical mechanisms for grain development and quality.     

Grain quality characteristics of spring wheat (Triticum aestivum) as affected by free-air CO2 enrichment

Spring wheat (Triticum aestivum L. cv. Triso) was grown in a free-air carbon dioxide (CO₂) enrichment (FACE) system at Stuttgart–Hohenheim (Germany) in 2008 to examine effects on crop yield and grain quality. Elevated CO₂ had no significant impacts on aboveground biomass and grain yield components except for an increase in thousand grain weight by 5.4% with size distribution shifted towards larger grains. Total grain protein concentration decreased by 7.9% under CO₂ enrichment, and protein composition was altered. Total gliadins and their single types (ω5-gliadins, ω1,2-gliadins, α-gliadins, and γ-gliadins) were reduced, while albumins/globulins, total glutenins and their subunits were not influenced. The gluten proteins (gliadins plus glutenins) were lowered by 11.3% in the high-CO₂ treatment, whereas proportions of gluten protein types were slightly affected as only ω1,2-gliadins decreased. Accordingly, all proteinogenic amino acids were decreased by 4.2 to 7.9% in concentrations per unit flour mass, although partly below the level of statistical significance. In contrast, the composition of amino acids on a per protein basis remained unaffected except for a decline in serine. Among the minerals, the concentrations of calcium, magnesium, iron and cobalt decreased, while an increase was observed for boron. The concentrations of total non-structural carbohydrates and starch decreased, whereas fructose, raffinose and fructan increased. Total lipid concentration remained unaffected by the CO₂ enrichment, whereas the grain carbon/nitrogen relation was increased by 8.5%. Implications may occur for consumer nutrition and health, and for industrial processing, thus breeding of new wheat cultivars that exploit CO₂ fertilisation and maintain grain quality properties is regarded as one potential option to assure the supply chain for the future.     

The use of comparative quantitative proteomics analysis in rice grain-filling in determining response to moderate soil drying stress

Moderate soil drying (MSD) stress at the grain filling stage can improve grain filling efficiently and thus increase grain yield. To elucidate the molecular response of grain filling to MSD stress, a labeling LC-based quantitative proteomics approach using tandem mass tags was applied to determine the changes in leaf and grain protein abundance level at 15 days after flowering. A total of 2109 leaf proteins and 3220 grain proteins were detected, and 251 leaf proteins and 220 grain proteins were differentially expressed under MSD stress. Based on MapMan ontology, differentially expressed proteins in leaf and grain were categorized within 22 and 18 functional categories, respectively. The patterns observed were interesting in that in some categories such as photosynthesis-related protein in leaf and cell division related proteins in grain showed higher expression abundant under MSD stress, which facilities increasing the source supply and sink size. In other categories, such as carbohydrate metabolism and mitochondrial electron transport, surprisingly showed a completely different expression pattern between leaf and grain under MSD stress, which led to faster and better remobilization of carbon from leaf to grain. Additionally, the complicated functional network including the small GTP-binding proteins, calmodulin, and 14-3-3 proteins play an important role in regulation carbon remobilization mediated by the stressful signals from soil after rice plants were treated with MSD at grain-filling stage. The findings provide theoretical evidence for better quality control and scientific improvement of rice in practice.     

谷物籽粒淀粉研究进展

谷物籽粒是人类最基本的粮食,其胚乳淀粉与品质有密切的关系.本文就谷物胚乳淀粉的合成积累过程、谷物淀粉合成酶的作用与特性、淀粉特性与品质的关系以及基因工程在改良作物淀粉品质方面的研究进展进行了综述,并对谷物籽粒淀粉进一步的研究提出了展望,为谷物淀粉品质育种提供参考.     

Proteomic analysis of the expression of proteins related to rice quality during caryopsis development and the effect of high temperature on expression

Proteins are essential to rice caryopsis development and quality formation. High temperature is an important environmental factor, which may decrease grain quality. In the present study rice caryopsis proteins were profiled by two-dimensional polyacrylamide gel electrophoresis, and differentially expressed proteins were analyzed by liquid chromatography/tandem mass spectrometry. Expressions of more than 400 polypeptide spots during caryopsis development, in response to temperature treatments or between varieties were monitored. Among them, more than 70 differentially expressed polypeptides were analyzed by liquid chromatography/tandem mass spectrometry. We identified 54 proteins with known functions. Of these, 21 were involved with carbohydrate metabolism, 14 with protein synthesis and sorting, and 9 with stress responses. Waxy (Wx) proteins and glutelins were the most significant spots, which increased significantly during development. Allergen-like proteins, PPDK and NADH-SDH, also were expressed during development, implying their physiological roles in caryopsis. Expression of large isoforms of Wx proteins was correlated with the amylose content of rice caryopses. One protein with high GC content in its DNA sequence was correlated with the chalky trait of kernels. High temperature (35/30 degrees C) decreased the expression of Wx proteins, allergen-like proteins, and elongation factor 1beta, but increased the expression of small heat shock proteins (sHSP), glyceraldehyde-3-phosphate dehydrogenase, and prolamin. sHSP was positively correlated with the appearance of chalky kernels. During development, glutelins were phosphorylated and glycosylated, indicating that these molecules were post-translationally modified. Possible functions of the expression of candidate proteins on the grain quality are discussed.     

二氧化碳浓度增高对稻、麦品质影响研究进展

作物品质的形成是品种遗传特性和环境条件综合作用的结果.一般认为大气中CO₂浓度增高将对作物品质产生重要影响.本文分别从蛋白质与氮含量、微量元素以及其他品质性状等3个方面综述了国内外关于CO₂浓度增高对水稻、小麦品质影响的研究进展,强调了该领域研究的必要性和紧迫性,并提出了研究的重点内容及主要方向.主要包括：大气中CO₂浓度增高对水稻、小麦品质的直接影响及品种间的差异;大气中CO₂浓度增高及其与其它气候因子协同作用对水稻、小麦品质的综合影响及其指标量化;大气中CO₂浓度增高及气候变化对水稻、小麦品质形成过程的影响机理;适应CO₂浓度增高的水稻、小麦品质改良育种的方向与策略;适应CO₂浓度增高的水稻、小麦品质改良的综合生产技术体系和分子标记及转基因技术在水稻、小麦品质改良育种方面的应用.     

Processing‐Performance Evolution of Perovskite Solar Cells: From Large Grain Polycrystalline Films to Single Crystals

Solution‐processable halide perovskites have emerged as strong contenders for next‐generation solar cells owing to their favorable optoelectronic properties. To maintain the efficiency momentum of perovskite solar cells (PSCs), development of advanced processing techniques, particularly for the perovskite layer, is imperative. There is a close correlation between the quality of the perovskite layer and its photophysical properties: Highly crystalline large grains with uniform morphology of the perovskite layer and their interface with charge transporters are crucial for achieving high performance. Significant efforts have been dedicated to achieve perovskite films with large grains reaching the millimeter‐scale for high‐efficiency PSCs. Recent work showcases a transition from large grain polycrystalline to single‐crystalline (SC) PSCs made possible by the facile growth of perovskite single crystals. In this review, the recent progress of the large grain polycrystalline PSCs and grain boundary‐free SC‐PSCs is reported, particularly focusing on the recent approach of depositing large‐grained perovskite layers and single crystal growth technique, that have been adopted for fabrication of efficient PSCs. In addition, prospects of SC‐PSCs and their further development in terms of efficiency, device design, scalability, and stability are discussed.     

Assessment of allelic variation in serpin gene (Srp5B) in Indian wheats

Serpins (Serine proteinase inhibitors) are the family of proteins involved in the inhibition of proteinases from endogenous and other sources and thus have role in disease and pest resistance. In addition, serpins have the properties influencing grain quality traits. The genes coding for serpin proteins are present on the long arm of the 5B chromosome. In the present investigation, allelic variations in the serpin genes encoded by Srp5Bb were assessed using CAP-PCR among the 300 wheat varieties developed in India during the last 100?years. Eighty percent of the varieties exhibited wild type (Srp5Ba) and 20% mutated (Srp5Bb) form of the allele. Moreover, the frequency of Srp5Bb allele decreased among the recently released varieties as compared to older varieties. Only six out of 50 varieties used as checks in national trials showed the presence of Srp5Bb allele. There was no relationship between Srp5B allelic types and grain hardness. The information is useful to further investigate the role of Srp5B alleles in disease resistance and imparting grain quality.     

Impact of Eurygaster maura (Heteroptera: Scutelleridae) feeding on quality of bread wheat in relation to attack period

Sunn pest (or cereal bug) (Heteroptera: Pentatomidae and Scutelleridae) infestations of wheat, Triticum aestivum L., in the grain filling stage have the potential to adversely affect the quality of harvested grain for bread making. In the absence of resistant wheat cultivars, producers must rely on chemical control to protect their crop from sunn pest infestations. To implement an efficient environment friendly control strategy, there is a need to pinpoint the relationships between the timing of the bug attack and gluten degradation. Recent outbreaks of Eurygaster maura (L.) in northwestern Italy have increased the local concern toward this problem. A 3-yr study was carried out by caging plants of two bread wheat cultivars, characterized by different seed texture and bread-making quality, and introducing adults of E. maura in four periods corresponding to different grain filling stages: heading, early milk-ripe, milk-ripe, and late milk-ripe. The degree of bread-making quality depletion was assessed by analytical and biochemical methods and related to the attack period. Using analysis of variance, significant differences were found in the quality traits of kernels attacked by E. maura in different grain filling stages, the maximum damage occurring with bug feeding at the late milk-ripe stage. Biochemical investigations on gluten confirmed analytical results; in grain samples infested at the late milk-ripe stage, SDS gel electrophoresis revealed the degradation of some components of the high-molecular-weight glutenins, and high-performance liquid chromatography analyses showed a breakdown of the first peak of the insoluble fraction, mainly containing polymeric proteins highly related to dough strength.     

Proteomic analysis of positive influence of alternate wetting and moderate soil drying on the process of rice grain filling

Rice (Oryza sativa L.) is one of the most important crops in the world to feed ever increasing world population. An increase in output of rice crop per unit is imminent. Alternate wetting and moderate soil drying (AWD) irrigation technology has been recommended as a good practice method to improve grain filling of rice crop at late growing stages. Physiological, molecular and agronomic parameters were adopted to elucidate the role of rice stem and sheath under AWD treatment as compared to the conventional irrigation during the grain filling stage. AWD treatment significantly increased stem and sheath dry weight, carbohydrate reserves and their remobilization to the grain, especially inferior spikelet grains. The results showed that the transport and conversion rate of the stem and sheath photoassimilates increased by 9.87 and 8.37%, respectively. Furthermore, protein expression profiles of the stem and sheath at 10, 20 and 30 days after flowering were analyzed. We examined 220 differentially expressed proteins, and successfully identified 166 proteins, including 71 proteins in the stem and 95 proteins in the sheath involved in thirteen important functional groups. Our results suggest that the AWD treatment at the rice grain filling stage is highly conducive to trigger the mobilization of the N assimilates from leave and root to the stem and sheath, and then promotes to remobilize the reserves to the grain through coordinately expressed proteins involved in photosynthesis, systematic senescence, oxidative stress defense, signal transduction and other metabolisms. This study reveals the metabolic mechanism of the stem and sheath in response to AWD at grain filling stage, and provides theoretical evidence for better quality control and scientific improvement of rice in practice.     

Coexpression of the High Molecular Weight Glutenin Subunit 1Ax1 and Puroindoline Improves Dough Mixing Properties in Durum Wheat (Triticum turgidum L. ssp. durum)

Wheat end-use quality mainly derives from two interrelated characteristics: the compositions of gluten proteins and grain hardness. The composition of gluten proteins determines dough rheological properties and thus confers the unique viscoelastic property on dough. One group of gluten proteins, high molecular weight glutenin subunits (HMW-GS), plays an important role in dough functional properties. On the other hand, grain hardness, which influences the milling process of flour, is controlled by Puroindoline a (Pina) and Puroindoline b (Pinb) genes. However, little is known about the combined effects of HMW-GS and PINs on dough functional properties. In this study, we crossed a Pina-expressing transgenic line with a 1Ax1-expressing line of durum wheat and screened out lines coexpressing 1Ax1 and Pina or lines expressing either 1Ax1 or Pina. Dough mixing analysis of these lines demonstrated that expression of 1Ax1 improved both dough strength and over-mixing tolerance, while expression of PINA detrimentally affected the dough resistance to extension. In lines coexpressing 1Ax1 and Pina, faster hydration of flour during mixing was observed possibly due to the lower water absorption and damaged starch caused by PINA expression. In addition, expression of 1Ax1 appeared to compensate the detrimental effect of PINA on dough resistance to extension. Consequently, coexpression of 1Ax1 and PINA in durum wheat had combined effects on dough mixing behaviors with a better dough strength and resistance to extension than those from lines expressing either 1Ax1 or Pina. The results in our study suggest that simultaneous modulation of dough strength and grain hardness in durum wheat could significantly improve its breadmaking quality and may not even impair its pastamaking potential. Therefore, coexpression of 1Ax1 and PINA in durum wheat has useful implications for breeding durum wheat with dual functionality (for pasta and bread) and may improve the economic values of durum wheat.