Modeling grain nitrogen accumulation and protein composition to understand the sink/source regulations of nitrogen remobilization for wheat

A functional explanation for the regulation of grain nitrogen (N) accumulation in cereal by environmental and genetic factors remains elusive. Here, new mechanistic hypotheses of grain N accumulation are proposed and tested for wheat (Triticum aestivum). First, we tested experimentally the hypothesis that grain N accumulation is mostly source regulated. Four contrasting cultivars, in terms of their grain N concentrations and yield potentials, were grown with non-limiting N supply. Grain number per ear was reduced by removing the top part of the ear at anthesis. Reduction in grain number gave a significant increase in N content per grain for all cultivars, showing that grain N accumulation was source regulated. However, on a per ear basis, cultivars with a high grain number fully compensated their N accumulation for reduced grain number at anthesis. Cultivars with a lower grain number did not compensate completely, and grain N per ear was decreased by 16%. Second, new mechanistic hypotheses of the origins of grain N source regulation and its response to environment were tested by simulation. The hypotheses were: (a). The regulation by N sources of grain N accumulation applies only for the storage proteins (i.e. gliadin and glutenin fractions); (b). accumulation of structural and metabolic proteins (i.e. albumin-globulin and amphiphilic fractions) is sink-regulated; and (c). N partitioning between gliadins and glutenins is constant during grain development and unmodified by growing conditions. Comparison of experimental and simulation results of the accumulation of grain protein fractions under wide ranges of N fertilization, temperatures, and irrigation supported these hypotheses.     

A proteomic approach to verify in vivo expression of a novel gamma-gliadin containing an extra cysteine residue

Gliadins and glutenins are the main protein fractions present in wheat gluten. They are responsible for technological and nutritional quality of wheat based products. In particular, glutenins are mainly responsible for dough visco-elastic properties, whereas gliadins confer extensibility to dough and are the most important factor triggering celiac disease, the major human intolerance to gluten. Gliadins are monomeric proteins, whereas glutenins are polymers stabilized by disulfide bonds. Although they have distinctive structural characteristics, it is possible that some gliadins become part of the glutenin fraction because of mutations that affect cysteine number and distribution. Here, we provide evidence that a naturally mutated gamma-gliadin with an extra cysteine residue is incorporated into the polymeric fraction. This goal was achieved using an integrated approach involving heterologous expression, 2-DE, RP-HPLC and MS.     

高温下干旱和渍水对冬小麦花后旗叶光合特性和物质转运的影响

以蛋白质含量不同的两个冬小麦品种扬麦9号和豫麦34为材料,研究了不同温度和水分条件下小麦花后旗叶光合特性的变化、营养器官花前贮藏干物质和氮素转运特征及其与籽粒产量和品质形成的关系.结果表明,高温及干旱和渍水均明显降低了旗叶光合速率和叶绿素含量（SPAD值）,但高温下干旱和渍水对光合作用的影响加重.小麦营养器官花前贮藏干物质、氮素转运量和转运率在适温下表现为干旱>对照>渍水,高温下则表现为对照>干旱>渍水.适温下花后同化物积累量表现为对照>渍水>干旱,高温下则表现为对照>干旱>渍水.花后氮素积累量在适温和高温下均表现为对照>渍水>干旱.籽粒淀粉含量以适温适宜水分处理最高,高温渍水下最低;蛋白质含量以高温干旱下最高,适温渍水下最低.温度和水分逆境下小麦粒质量和淀粉含量的降低与花后较低的光合能力及干物质积累有关,而蛋白质含量则与花前贮藏氮素的转运量和转运率有关.     

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.     

Proteomic analysis of secretagogue-stimulated neutrophils implicates a role for actin and actin-interacting proteins in Rac2-mediated granule exocytosis

Background

Mineral nutrition during wheat grain development has large effects on wheat flour protein content and composition, which in turn affect flour quality and immunogenic potential for a commodity of great economic value. However, it has been difficult to define the precise effects of mineral nutrition on protein composition because of the complexity of the wheat flour proteome. Recent improvements in the identification of flour proteins by tandem mass spectrometry (MS/MS) and the availability of a comprehensive proteome map of flour from the US wheat Butte 86 now make it possible to document changes in the proportions of individual flour proteins that result from the application of mineral nutrition.

Results

Plants of Triticum aestivum 'Butte 86' were grown with or without post-anthesis fertilization (PAF) and quantitative 2-dimensional gel electrophoresis (2-DE) was used to analyze protein composition of the resulting flour. Significant changes in the proportions of 54 unique proteins were observed as a result of the treatment. Most omega-gliadins, high molecular weight glutenin subunits (HMW-GS) and serpins as well as some alpha-gliadins increased in proportion with PAF. In contrast, alpha-amylase/protease inhibitors, farinins, purinins and puroindolines decreased in proportion. Decreases were also observed in several low molecular weight glutenin subunits (LMW-GS), globulins, defense proteins and enzymes. The ratio of HMW-GS to LMW-GS in the flour increased from 0.61 to 0.95 and the ratio of gliadins to glutenins increased from 1.02 to 1.30 with PAF. Because flour protein content doubled with PAF from 7 to 14%, most protein types actually increased in absolute amount (μg/mg flour protein). Data further suggest that flour proteins change with PAF according to their content of sulfur-containing amino acids Cys + Met.

Conclusions

A 2-DE approach revealed changes in the wheat flour proteome due to PAF that are important for flour quality and immunogenic potential. The work forms a baseline for further studies of the effects of environmental variables on flour protein composition and provides clues about the regulation of specific flour protein genes. The study also is important for identifying targets for breeding programs and biotechnology efforts aimed at improving flour quality.     

Suppression of gliadins results in altered protein body morphology in wheat

Wheat gluten proteins, gliadins and glutenins, are of great importance in determining the unique biomechanical properties of wheat. Studies have therefore been carried out to determine their pathways and mechanisms of synthesis, folding, and deposition in protein bodies. In the present work, a set of transgenic wheat lines has been studied with strongly suppressed levels of γ-gliadins and/or all groups of gliadins, using light and fluorescence microscopy combined with immunodetection using specific antibodies for γ-gliadins and HMW glutenin subunits. These lines represent a unique material to study the formation and fusion of protein bodies in developing seeds of wheat. Higher amounts of HMW subunits were present in most of the transgenic lines but only the lines with suppression of all gliadins showed differences in the formation and fusion of the protein bodies. Large rounded protein bodies were found in the wild-type lines and the transgenic lines with reduced levels of γ-gliadins, while the lines with all gliadins down-regulated had protein bodies of irregular shape and irregular formation. The size and number of inclusions, which have been reported to contain triticins, were also higher in the protein bodies in the lines with all the gliadins down-regulated. Changes in the protein composition and PB morphology reported in the transgenic lines with all gliadins down-regulated did not result in marked changes in the total protein content or instability of the different fractions.     

Implications of high-temperature events and water deficits on protein profiles in wheat (Triticum aestivum L. cv. Vinjett) grain

Increased climatic variability is resulting in an increase of both the frequency and the magnitude of extreme climate events. Therefore, cereals may be exposed to more than one stress event in the growing season, which may ultimately affect crop yield and quality. Here, effects are reported of interaction of water deficits and/or a high-temperature event (32°C) during vegetative growth (terminal spikelet) with either of these stress events applied during generative growth (anthesis) in wheat. Influence of combinations of stress on protein fractions (albumins, globulins, gliadins and glutenins) in grains and stress-induced changes on the albumin and gliadin proteomes were investigated by 2-DE and MS. The synthesis of individual protein fractions was shown to be affected by both the type and time of the applied stresses. Identified drought or high-temperature-responsive proteins included proteins involved in primary metabolism, storage and stress response such as late embryogenesis abundant proteins, peroxiredoxins and α-amylase/trypsin inhibitors. Several proteins, e.g. heat shock protein and 14-3-3 protein changed in abundance only under multiple high temperatures.     

水氮互作对小麦籽粒蛋白质、淀粉含量及其组分的影响

以两个不同品质类型的小麦品种（强筋品种豫麦34、弱筋品种豫麦50）为材料,在大田条件下,研究了3个灌水处理（W₁：拔节水;W₂：拔节水+花后15 d灌浆水;W₃：拔节水+灌浆水+花后28 d麦黄水）和3个氮肥水平（0、150、270 kg·hm^-2）对籽粒蛋白质、淀粉含量及其组分的影响.结果表明：270 kg·hm^-2的施氮量有利于提高强筋小麦（豫麦34）籽粒蛋白质含量,籽粒清蛋白、醇溶蛋白和谷蛋白含量明显提高,谷/醇增大;支链淀粉和总淀粉含量提高,直/支下降;籽粒产量增加.弱筋小麦（豫麦50）在150 kg·hm^-2 的施氮量下,清蛋白和醇溶蛋白含量增加,球蛋白和谷蛋白含量下降,谷/醇降低;支链淀粉和总淀粉含量提高;不施氮肥或氮肥施用过多（270 kg·hm^-2）均影响籽粒蛋白质和淀粉的积累,使产量下降.W₂处理促进了籽粒蛋白质和淀粉积累,W₁或W₃处理均不利于籽粒蛋白质和淀粉积累,且导致籽粒产量下降.水、氮互作效应中,强筋和弱筋小麦分别以全生育期270 kg·hm^-2和150 kg·hm^-2施氮量配合拔节水+灌浆水（W₂）为比较理想的水氮运筹方式.     

Genetic analysis of dry matter and nitrogen accumulation and protein composition in wheat kernels

The maximum rate and duration for grain dry matter (DM) and nitrogen (N) accumulation were evaluated in 194 recombinant inbred lines (RILs) from a cross between the two French wheat cultivars Récital and Renan. These cultivars were previously identified as having contrasting kinetics of grain DM and N accumulation. Grain protein composition was analysed by capillary electrophoresis (CE), which enabled quantification of the different storage protein fractions (-gliadins, -gliadins, LMW glutenins, HMW glutenins, and each of their subunits). Correlation analyses revealed that DM and N accumulation rates were closely correlated and repeatable over several years, which was not the case for DM and N accumulation durations, and that protein composition was primarily influenced by the N accumulation rate. This was particularly true for the LMW-glutenins and the -gliadins, the most abundant protein fractions. A genetic map of 254 molecular markers covering nearly 80% of the wheat genome was used for quantitative trait loci (QTL) analysis. A total of seven QTLs were found. Five QTLs were significantly associated with the kinetics of DM and N accumulation, and two of them also influenced protein composition. Two QTLs affected only the protein composition. One major QTL explained more than 70% of the total variation in HMW-GS Glu1B-x content.     

A proteomics view on the role of drought-induced senescence and oxidative stress defense in enhanced stem reserves remobilization in wheat

Drought is one of the major factors limiting the yield of wheat (Triticum aestivum L.) particularly during grain filling. Under terminal drought condition, remobilization of pre-stored carbohydrates in wheat stem to grain has a major contribution in yield. To determine the molecular mechanism of stem reserve utilization under drought condition, we compared stem proteome patterns of two contrasting wheat landraces (N49 and N14) under a progressive post-anthesis drought stress, during which period N49 peduncle showed remarkably higher stem reserves remobilization efficiency compared to N14. Out of 830 protein spots reproducibly detected and analyzed on two-dimensional electrophoresis gels, 135 spots showed significant changes in at least one landrace. The highest number of differentially expressed proteins was observed in landrace N49 at 20days after anthesis when active remobilization of dry matter was observed, suggesting a possible involvement of these proteins in effective stem reserve remobilization of N49. The identification of 82 of differentially expressed proteins using mass spectrometry revealed a coordinated expression of proteins involved in leaf senescence, oxidative stress defense, signal transduction, metabolisms and photosynthesis which might enable N49 to efficiently remobilized its stem reserves compared to N14. The up-regulation of several senescence-associated proteins and breakdown of photosynthetic proteins in N49 might reflect the fact that N49 increased carbon remobilization from the stem to the grains by enhancing senescence. Furthermore, the up-regulation of several oxidative stress defense proteins in N49 might suggest a more effective protection against oxidative stress during senescence in order to protect stem cells from premature cell death. Our results suggest that wheat plant might response to soil drying by efficiently remobilize assimilates from stem to grain through coordinated gene expression.     

Grain subproteome responses to nitrogen and sulfur supply in diploid wheat Triticum monococcum ssp. monococcum

Wheat grain storage proteins (GSPs) make up most of the protein content of grain and determine flour end‐use value. The synthesis and accumulation of GSPs depend highly on nitrogen (N) and sulfur (S) availability and it is important to understand the underlying control mechanisms. Here we studied how the einkorn (Triticum monococcum ssp. monococcum) grain proteome responds to different amounts of N and S supply during grain development. GSP composition at grain maturity was clearly impacted by nutrition treatments, due to early changes in the rate of GSP accumulation during grain filling. Large‐scale analysis of the nuclear and albumin‐globulin subproteomes during this key developmental phase revealed that the abundance of 203 proteins was significantly modified by the nutrition treatments. Our results showed that the grain proteome was highly affected by perturbation in the N:S balance. S supply strongly increased the rate of accumulation of S‐rich α/β‐gliadin and γ‐gliadin, and the abundance of several other proteins involved in glutathione metabolism. Post‐anthesis N supply resulted in the activation of amino acid metabolism at the expense of carbohydrate metabolism and the activation of transport processes including nucleocytoplasmic transit. Protein accumulation networks were analyzed. Several central actors in the response were identified whose variation in abundance was related to variation in the amounts of many other proteins and are thus potentially important for GSP accumulation. This detailed analysis of grain subproteomes provides information on how wheat GSP composition can possibly be controlled in low‐level fertilization condition.     

水稻籽粒灌浆过程中蛋白质表达特性及其对氮肥运筹的响应

采用大田栽培的方式,研究了大穗型水稻金辉809籽粒灌浆过程中蛋白质的差异表达变化模式以及同一施氮量下不同的氮肥施用比例(总施氮量225 kg/hm2,基蘖肥:穗粒肥分别为7∶3和6∶4)对强弱势粒灌浆影响的分子机制。获得了水稻不同灌浆时段籽粒总蛋白的表达图谱,共发现32个在灌浆过程中发生显著差异表达的蛋白点,涉及籽粒的淀粉合成,能量代谢,激素信号转导,基因表达调节和抗逆响应等。在此基础上,进一步构建了不同灌浆发育时段水稻强弱势籽粒响应不同氮肥比例调控的蛋白表达图谱,结果发现强势籽粒响应氮肥调控出现差异表达的蛋白点有8个,而弱势籽粒有26个,可见强势籽粒灌浆具有更强的环境稳定性,相对地,弱势籽粒灌浆则易被环境所调节。在总施氮量不变的情况下,适当增加生育后期氮肥的施用量,有利于增强弱势籽粒中信号转导,促进相关基因的表达,提高物质调运与能量代谢速率,增强抗逆性,增强弱势籽粒的代谢水平,延长其灌浆时期,提升弱势籽粒活性和灌浆强度,增加结实率和千粒重,最终实现高产高效。研究结果对于进一步明确氮素调控水稻强弱势粒灌浆的分子生态特性具有重要的理论与实际意义。     

Nitrogen fertiliser rate and post-anthesis waterlogging effects on carbohydrate and nitrogen dynamics in wheat

Waterlogging is predicted to increase in both magnitude and frequency along with global warming, and will become one of the most severe adversities for crop production in many regions. Nitrogen is considered to be an effective up-regulatory nutrient for crops grown under stress and non-stress conditions. In this study, we try to evaluate N fertiliser effects on contents of carbohydrate and N dynamics, dry matter accumulation in shoot, yield under post-anthesis waterlogging. Waterlogging after anthesis significantly reduced grain yield due to decrease in thousand-kernel-weight and in grain number per spike. High N fertiliser application aggravated grain yield loss due to post-anthesis waterlogging. These yield losses were related to the decreases in dry matter accumulation, redistribution of stored photosynthate to the grain, and the conversion capacity from carbohydrate to starch in grain. The decrease in dry matter accumulation could be attributed to the reduced activities of Pn (photosynthesis) and SPS (sucrose phosphate synthase) in the flag leaf, while the low capacity in starch synthesis could be explained by the reduced activities of sucrose synthase (SS) and soluble starch synthase (SSS) in grain. Total N uptake in shoot was also reduced, which could contribute to the losses in biomass and yield by waterlogging. The decrease in Pn was inconsistent with the increase in N content in the flag leaf at high N fertiliser application under post-anthesis waterlogging.     

不同耕作方式对旱作冬小麦旗叶衰老和籽粒产量的影响

在旱作条件下研究了一次深翻、免耕、深松和传统耕作4种耕作方式对冬小麦花后旗叶衰老、小麦籽粒产量及土壤水分和养分状况的影响.结果表明：免耕和深松提高了小麦旗叶SOD和POD活性及可溶性蛋白和叶绿素含量,降低了MDA和O₂^-·含量,延缓了小麦叶片的衰老进程;同时,免耕、深松在开花期和灌浆期0～40 cm土层土壤水分含量分别比传统耕作提高了4.13％、6.23％和5.50％、9.27％,土壤碱解氮、速效磷和速效钾含量均显著高于传统耕作.一次深翻0～40 cm土层土壤水分含量低于传统耕作,土壤养分含量高于传统耕作,但两处理间差异不显著.与传统耕作相比,免耕和深松花后干物质生产量分别提高4.34％和4.76％,花后干物质转运率分别提高15.56％和13.51％,产量分别提高10.22％和9.26%.免耕和深松为冬小麦花后生长发育提供了良好的环境,延缓了小麦叶片衰老,促进了花后干物质积累及干物质向籽粒的转运,从而使籽粒产量显著提高,是旱作麦区适宜的耕作方式.     

Evidence for the presence of two different types of protein bodies in wheat endosperm

Storage proteins of wheat grains (Triticum L. em Thell) are deposited in protein bodies inside vacuoles. However, the subcellular sites and mechanisms of their aggregation into protein bodies are not clear. In the present report, we provide evidence for two different types of protein bodies, low- and high-density types that accumulate concurrently and independently in developing wheat endosperm cells. Gliadins were present in both types of protein bodies, whereas the high molecular weight glutenins were localized mainly in the dense ones. Pulse-chase experiments verified that the dense protein bodies were not formed by a gradual increase in density but, presumably, by a distinct, quick process of storage protein aggregation. Subcellular fractionation and electron microscopy studies revealed that the wheat homolog of immunoglobulin heavy-chain-binding protein, an endoplasmic reticulum-resident protein, was present within the dense protein bodies, implying that these were formed by aggregation of storage proteins within the endoplasmic reticulum. The present results suggest that a large part of wheat storage proteins aggregate into protein bodies within the rough endoplasmic reticulum. Because these protein bodies are too large to enter the Golgi, they are likely to be transported directly to vacuoles. This route may operate in concert with the known Golgi-mediated transport to vacuoles in which the storage proteins apparently condense into protein bodies at a postendoplasmic reticulum location. Our results further suggest that although gliadins are transported by either one of these routes, the high molecular weight glutenins use only the Golgi bypass route.     

Post-anthesis alternate wetting and moderate soil drying enhances activities of key enzymes in sucrose-to-starch conversion in inferior spikelets of rice

This study tested the hypothesis that a post-anthesis moderate soil drying can improve grain filling through regulating the key enzymes in the sucrose-to-starch pathway in the grains of rice (Oryza sativa L.). Two rice cultivars were field grown and two irrigation regimes, alternate wetting and moderate soil drying (WMD) and conventional irrigation (CI, continuously flooded), were imposed during the grain-filling period. The grain-filling rate and activities of four key enzymes in sucrose-to-starch conversion, sucrose synthase (SuSase), adenosine diphosphate-glucose pyrophosphorylase (AGPase), starch synthase (StSase), and starch branching enzyme (SBE), showed no significant difference between WMD and CI regimes for the earlier flowering superior spikelets. However, they were significantly enhanced by the WMD for the later flowering inferior spikelets. The activities of both soluble and insoluble acid invertase in the grains were little affected by the WMD. The two cultivars showed the same tendencies. The activities of SuSase, AGPase, StSase, and SBE in grains were very significantly correlated with the grain-filling rate. The abscisic acid (ABA) concentration in inferior spikelets was remarkably increased in the WMD and very significantly correlated with activities of SuSase, AGPase, StSase, and SBE. Application of ABA on plants under CI produced similar results to those seen in plants receiving WMD. Applying fluridone, an indirect inhibitor of ABA synthesis, produced the opposite effect. The results suggest that post-anthesis WMD could enhance sink strength by regulating the key enzymes involved, and consequently, increase the grain-filling rate and grain weight of inferior spikelets. ABA plays an important role in this process.     

不同氮肥基追比例对高温胁迫下小麦籽粒产量和品质的影响

选用强筋小麦品种济麦20、烟农19、藁麦8901做试验材料,设置不同氮肥基追比例和籽粒灌浆中后期高温胁迫处理,研究了不同氮肥基追比例对高温胁迫条件下小麦籽粒产量和品质的影响.研究结果表明,追氮比例由50%增加到70%,3个品种的千粒重、籽粒产量、粗蛋白含量、湿面筋含量、醇溶蛋白含量、谷蛋白含量、HMW-GS含量、LMW-GS含量、HMW-GS/LMW-GS比值显著提高.济麦20和烟农19的谷蛋白大聚合体含量、谷蛋白大聚合体体积加权平均粒径和表面积加权平均粒径因追氮比例提高而升高, 藁麦8901则无显著变化.济麦20和烟农19的面团形成时间、面团稳定时间因追氮比例提高而延长, 藁麦8901基本不受影响.追氮比例由50%增加到70%,3个品种的籽粒支链淀粉/直链淀粉比值显著降低,淀粉糊化高峰黏度、低谷黏度、稀懈值、最终黏度和反弹值相应降低.总之,提高氮肥追施比例可在一定程度上缓解灌浆期高温胁迫对小麦粒重和蛋白质质量的不利影响,但对淀粉质量产生负面效应,且品种间存在差异.     

Effects of exogenous ABA and cytokinin on leaf photosynthesis and grain protein accumulation in wheat ears cultured <Emphasis Type="Italic">in vitro</Emphasis>

A detached culture system and steady-state ¹⁵N labeling technique were used to study the effects of exogenous ABA and ZR on photosynthetic characteristics, nitrogen remobilization and the activities of key enzymes for nitrogen metabolism in detached wheat parts during grain protein accumulation. The differences in net photosynthetic rate, chlorophyll content (SPAD value) and soluble protein content in the flag leaves of detached culture system between the treatments of ABA and ZR showed that ABA facilitates the post-anthesis senescence course compared to the ZR treatment. The differences in the changes of ¹⁵N amount in different organs in the detached culture system between the ABA and ZR treatments showed that nitrogen remobilization from vegetative organs to the grain is accelerated by the ABA treatment but is delayed by ZR. The activities of GS and GPT in grains treated with ABA were significantly higher than those with the control treatment at 5 DAC, but reduced significantly compared with control at 11 DAC. The two enzyme activities in grains were reduced significantly by ZR at 5 DAC and increased significantly at 11 DAC, compared with those treated with ABA. The above changes of enzyme activity showed that the ABA treatment hastens amino acid conversion into grains and protein accumulation in grains, whereas the ZR treatment delays these processes. A significant reduction in grain weight with ABA treatment is associated with the reduction of net photosynthesis, chlorophyll content, and soluble protein content in flag leaves. Compared with the control and ZR treatments, a significant increase in grain protein content with the ABA treatment may result from the accelerating effects of ABA on N remobilization, amino acid conversion into grains and protein accumulation in grains.     

花后土壤水分状况对小麦籽粒淀粉和蛋白质积累关键调控酶活性的影响

在温室盆栽条件下,以2个不同蛋白质含量的冬小麦(Triticum aestivum L．)品种皖麦38和扬麦9为材料,研究了花后第4天开始的土壤干旱(SRWC=45％～50％)和渍水对籽粒蛋白质和淀粉积累关键调控酶活性的影响。小麦叶片和籽粒的测定结果均表明,小麦源库器官中籽粒蛋白质和淀粉积累的关键调控酶活性变化趋势在2个品种间基本一致。与对照(SRWC=75％～80％)相比,干旱和渍水均明显降低了花后旗叶中蔗糖含量和磷酸蔗糖合成酶(SPS)活性,而氨基酸含量和谷氨酰胺合成酶(GS)活性略有下降。干旱和渍水均降低了籽粒库蔗糖合成酶(SS)和结合态淀粉合成酶(GBSS)活性,可溶性淀粉合成酶(SSS)活性降低尤甚。其中干旱处理下SS的下降比渍水更为明显。与对照相比,渍水明显降低了籽粒谷丙转氨酶(GPT)和GS活性,而干旱的影响较小。相关性分析结果表明籽粒淀粉产量和含量与SPS,SSS和GBSS活性的关系比与SS活性的关系更为密切,籽粒蛋白质产量和含量与叶中GS和籽粒中GPT活性的关系比与籽粒中GS关系活性更为密切。这些结果表明小麦源库器官中调控籽粒蛋白质和淀粉积累的关键酶活性变化是花后不同水分状况影响籽粒淀粉和蛋白质特性的重要因素。