糯性和非糯性小麦灌浆期胚乳直/支链淀粉积累及其相关酶活性研究

选用3份糯性和2份非糯性小麦材料,通过田间试验在灌浆过程中分别检测了各材料的籽粒直链和支链淀粉积累量、淀粉积累速率及淀粉合成关键酶活性的动态变化过程,探讨籽粒淀粉累积与相关酶活性的关系.结果表明:(1)非糯小麦在花后7 d前均未检测到直链淀粉存在,而此时已经检测到支链淀粉含量,并且糯小麦仅含有支链淀粉,支链淀粉早于直链淀粉合成.(2)糯性和非糯性小麦灌浆期籽粒的直、支链淀粉积累速率均呈先增加后降低的趋势,且直、支链淀粉最终积累量取决于最大积累速率和平均积累速率的大小,而积累活跃期的调节作用较小;糯性和非糯性小麦在淀粉合成过程中的腺苷二磷酸葡萄糖焦磷酸化酶(AGPP)、可溶性淀粉合成酶(SSS)、颗粒结合型淀粉合成酶(GBSS)和淀粉分支酶(SEB)活性均呈单峰曲线变化,活性峰值基本上都出现在花后20～25 d左右.(3)直链淀粉积累速率与AGPP、SSS、GBSS和SBE活性变化显著或极显著正相关,而支链淀粉积累速率仅与SSS活性变化极显著正相关,总淀粉积累速率与AGPP和SSS活性变化显著或极显著正相关.     

氮素水平对冬小麦籽粒灌浆过程中淀粉合成关键酶活性的影响

小麦籽粒灌浆过程中,淀粉合成关键酶腺苷二磷酸葡萄糖焦磷酸化酶(ADPG-PPase)、可溶性淀粉合成酶(SSS)、淀粉分支酶(SBE)和束缚态淀粉合成酶(GBSS)均随着灌浆进程呈单峰曲线变化,峰值出现在花后25d;不同氮肥施用量对灌浆前期酶活性的影响较小,而在花后20d之后影响较大;随着氮肥施用量的增加,4种酶活性均呈增加趋势,但氮肥过量时酶活性下降,表明适当增加施氮量有利于淀粉合成关键酶活性的提高。     

施氮量和花后土壤含水量对优质强筋小麦产量和品质的影响

在防雨池栽条件下,研究了施氮量和花后土壤含水量对优质强筋小麦产量和品质的影响.结果表明,在同一施氮量条件下,表现为花后土壤含水量过高(80%～90%)或过低(40%～50%)导致穗粒数减少,千粒重降低,最终使产量降低.在同一土壤含水量下,表现为增加施氮量有利于提高穗数,但过多(300kg/hm2)或过少(150kg/hm2)施氮均不利于穗粒数和千粒重的提高,而导致减产.在同一土壤含水量下,总蛋白质、醇溶蛋白、麦谷蛋白含量及谷/醇比随着施氮量的增加而增加.在同一施氮量条件下,总蛋白质及各组分均随着土壤含水量的增加而降低,同时谷/醇比也降低.在同一施氮量下,花后土壤含水量过高(80%～90%)或过低(40%～50%)均不利于淀粉及其组分含量的提高.在同一土壤含水量下,过高(300kg/hm2)或过低(150kg/hm2)施用氮肥均不利于淀粉及其组分含量的提高.只有保持适宜的花后土壤含水量和施适宜的氮肥才有利于支/直比的提高.适量增施氮肥或花后土壤含水量适宜可提高小麦的加工品质.这说明在小麦生产中可以通过施用氮肥和控制花后土壤水分含量技术,调控小麦品质和产量的形成,从而实现优质高产.     

不同类型土壤上种植的小麦籽粒中与淀粉合成相关的酶活性变化

测定池栽条件下灰潮土、水稻土、砂姜黑土上种植的强筋小麦‘郑麦9023’籽粒灌浆过程中腺苷二磷酸葡萄糖焦磷酸化酶（AGPP）、尿苷二磷酸葡萄糖焦磷酸化酶（UGPP）、可溶性淀粉合成酶（SSS）、淀粉粒结合淀粉合成酶（GBSS）、淀粉分支酶（SBE）5个与淀粉合成有关的酶活性变化的结果表明,不同类型土壤上种植的小麦籽粒中AGPP、UGPP、SSS、GBSS、SBE活性均呈单峰曲线变化,花后18d,AGPP、UGPP、SSS和SBE活性达到峰值,而GBSS则在花后24d达到峰值。AGPP、SSS、SBE活性峰值表现为灰潮土〉水稻土〉砂姜黑土,UGPP峰值表现为灰潮土〉砂姜黑土〉水稻土,GBSS峰值则表现为水稻土〉灰潮土〉砂姜黑土。     

氮、硫配施对弱筋小麦籽粒淀粉特性的影响

在大田条件下研究了不同氮、硫配施对弱筋小麦品种豫麦50籽粒淀粉特性的影响.结果表明:氮、硫及其互作对籽粒淀粉组分含量和直支比的影响均达到了极显著水平,氮肥对峰值粘度、低谷粘度、最终粘度和稀懈值的影响也达到了极显著水平,硫肥仅对稀懈值和糊化温度的影响达到了显著和极显著水平.每公顷施纯氮240 kg(N240)和纯硫20~60 kg(S20和S60)可提高总淀粉和支链淀粉含量,降低直链淀粉含量和直支比.每公顷施纯氮150 kg(N150)和纯硫20 kg(S20)可以提高峰值粘度、低谷粘度和最终粘度,改善淀粉品质.     

硫营养对小麦籽粒淀粉合成及相关酶活性的影响

在田间条件下,研究了施硫对小麦籽粒淀粉合成及相关酶活性的影响.结果表明:在0～20 cm土层土壤有效硫含量为5.84 mg/kg的地块上施硫不仅提高了小麦籽粒中蔗糖的含量,而且催化蔗糖降解代谢的蔗糖合成酶(SS)活性提高,利于籽粒蔗糖的降解.施硫显著提高了灌浆期间籽粒可溶性淀粉合成酶(SSS)活性,并使腺苷二磷酸葡萄糖焦磷酸化酶(ADPGPPase)和束缚态淀粉合成酶(GBSS)活性在灌浆中、后期维持在较高水平,对直链和支链淀粉的合成都起促进作用, 使总淀粉积累增加,千粒重提高,产量增加.     

秸秆还田对旱作马铃薯块茎淀粉合成关键酶活性及基因表达的影响

为探讨秸秆还田下旱作马铃薯块茎形成过程中淀粉合成关键酶活性及基因表达特性,以马铃薯栽培品种"青薯9号"为材料,以露地栽培为对照,设置秸秆还田处理,研究了马铃薯块茎形成过程中淀粉合成关键酶活性、基因表达、淀粉糊化及累积指标。结果表明:秸秆还田显著提高了旱作马铃薯SSS酶活性,降低了AGPP、GBSS酶活性,而对SBE酶活性没有显著影响;显著提高了SSⅡ、SSⅢ基因表达量,降低了AGPase、GBSSⅠ、SBEⅠ、SBEⅡ基因表达量;显著增加了淀粉崩解值,减少了淀粉各阶段粘度、回生值,而对淀粉糊化温度没有显著影响;显著增加了直链淀粉含量及直/支链淀粉比,减少了总淀粉含量;GBSS酶活性与AGPase、SBEⅠ基因表达量呈显著正相关,与直链淀粉含量、直/支链淀粉比呈显著负相关;SBE酶活性与SSⅡ基因表达量、峰值粘度、低谷粘度、最终粘度、总淀粉含量呈显著正相关,与崩解值、糊化温度呈显著负相关;AGPase基因表达量与直链淀粉含量呈显著负相关;GBSSⅠ基因表达量与最终粘度、回生值呈显著正相关,与糊化温度呈显著负相关;淀粉糊化与累积无显著相关性。     

施氮量和花后土壤含水量对小麦旗叶衰老及粒重的影响

在防雨池栽培条件下,研究了施氮量和花后土壤含水量对小麦旗叶衰老和粒重的影响.结果表明：各氮肥处理下,小麦旗叶SPAD值、可溶性蛋白质含量、超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性和光合速率（P_n）均表现为：花后土壤含水量60%～70%处理>80%～90%处理>40%～50%处理,小麦旗叶丙二醛（MDA）含量表现为：花后土壤含水量40%～50%处理>80%～90%处理>60%～70%处理,表明花后土壤含水量过高或过低均可导致小麦旗叶早衰,影响籽粒灌浆,降低粒重.在花后相同土壤含水量条件下,旗叶SPAD值、可溶性蛋白质含量、SOD活性、CAT活性和P_n均随施氮量的增加而升高,MDA含量随施氮量的增加而降低,表明增施氮肥可以延缓小麦旗叶衰老,但过量施用氮肥则不利于小麦粒重的提高,尤其是在花后土壤缺水的情况下,施用过多氮肥可导致小麦粒重下降.在小麦生产中可以将施用氮肥和控制花后土壤水分含量相结合,延缓小麦植株衰老,提高粒重.     

花后干旱或渍水逆境下氮素对小麦籽粒产量和品质的影响

 池栽试验条件下,设置渍水、干旱和对照3个水分处理,每个水分处理下设置两个施氮水平 ,研究了花后渍水或干旱逆境下氮素营养对两个不同类型小麦（Triticum aestivum） 品种籽粒产量和品质性状的影响。结果表明,与对照相比,花后渍水或干旱处理显著降低了小麦的千粒重、穗粒数和籽粒产量。在适宜水分和干旱条件下,增施氮肥增加了小麦籽粒产量,而在渍水条件下,增施氮肥降低了产量。干旱处理提高了蛋白质含量,干、湿面 筋含量,沉降值和降落值;而渍水处理则降低了小麦籽粒蛋白质含量和干、湿面筋含量。同 一水分处理下,增施氮肥提高了蛋白质含量,谷蛋白/醇溶蛋白比,支链淀粉含量和支/直链淀粉比。在小麦籽粒主要品质性状上存在显著的水氮互作效应,且水分、氮肥及水氮互作效 应对小麦籽粒产量和品质的影响因品种的不同而异。     

花后干旱或渍水下氮素供应对小麦光合和籽粒淀粉积累的影响

防雨池栽条件下,设置渍水、干旱和对照3个土壤水分处理,每水分处理下再设置两个施氮水平,研究了花后渍水和干旱逆境下氮素水平对两个蛋白质含量不同的小麦品种光合特性和籽粒淀粉积累的影响.结果表明,与对照相比,花后渍水和干旱处理显著降低小麦旗叶净光合速率和SPAD值,干物质积累量下降.干旱处理下,增施氮肥提高旗叶光合速率和SPAD值,渍水处理下则相反.水分逆境明显降低籽粒可溶性总糖含量,且渍水处理下增施氮肥降低小麦叶片和籽粒可溶性总糖含量,干旱状态下规律相反.渍水处理下增施氮肥降低淀粉积累速率.水分逆境明显降低小麦粒重、产量和淀粉产量,且干旱处理下增施氮肥有利于籽粒重、产量和淀粉产量的提高,而渍水下增施氮肥使粒重和产量进一步降低.试验结果表明,花后渍水和干旱逆境下施用氮肥对小麦旗叶光合速率和籽粒淀粉积累有明显的调节效应.     

Physicochemical properties of endosperm and pericarp starches during maize development

Endosperm starch and pericarp starch were isolated from maize (B73) kernels at different developmental stages. Starch granules, with small size (2–4 μm diameter), were first observed in the endosperm on 5 days after pollination (DAP). The size of endosperm-starch granules remained similar until 12DAP, but the number increased extensively. A substantial increase in granule size was observed from 14DAP (diameter 4–7 μm) to 30DAP (diameter10–23 μm). The size of starch granules on 30DAP is similar to that of the mature and dried endosperm-starch granules harvested on 45DAP. The starch content of the endosperm was little before 12DAP (less than 2%) and increased rapidly from 10.7% on 14DAP to 88.9% on 30DAP. The amylose content of the endosperm starch increased from 9.2% on 14DAP to 24.2% on 30DAP and 24.4% on 45DAP (mature and dried). The average amylopectin branch chain-length of the endosperm amylopectin increased from DP23.6 on 10DAP to DP26.9 on14DAP and then decreased to DP25.4 on 30DAP and DP24.9 on 45DAP. The onset gelatinization temperature of the endosperm starch increased from 61.3 °C on 8DAP to 69.0 °C on 14DAP and then decreased to 62.8 °C on 45DAP. The results indicated that the structure of endosperm starch was not synthesized consistently through the maturation of kernel. The pericarp starch, however, showed similar granule size, starch content, amylose content, amylopectin structure and thermal properties at different developmental stages of the kernel.     

Effects of protein on crosslinking of normal maize, waxy maize, and potato starches

Channels of maize starch granules are lined with proteins and phospholipids. Therefore, when they are treated with reagents that react at or near the surfaces of channels, three types of crosslinks could be produced: protein–protein, protein–starch, starch–starch. To determine which of these may be occurring and the effect(s) of channel proteins (and their removal) on crosslinking, normal and waxy maize starches were treated with a proteinase (thermolysin, which is known to remove protein from channels) before and after crosslinking, and the properties of the products were compared to those of a control (crosslinking without proteinase treatment). After establishing that treatment of starch with thermolysin alone had no effect on the RVA trace, three reaction sequences were used: crosslinking alone (CL), proteinase treatment before crosslinking (Enz-CL), proteinase treatment after crosslinking (CL-Enz). Two crosslinking reagents were used: phosphoryl chloride (POCl₃), which is known to react at or near channel surfaces; STMP, which is believed to react throughout the granule matrix. Three concentrations of POCl₃ (based on the weight of starch) were used. For both normal maize starch (NMS) and waxy maize starch (WMS) reacted with POCl₃, the trends were generally the same, with apparent relative degrees of crosslinking indicated to be CL-Enz = CL > Enz-CL, but the effects were greater with NMS and there were differences when different concentrations of reagent were used. The basic trends were the same when potato starch was used in the same experiments. Crosslinking with STMP was done both in the presence and the absence of sodium sulfate (SS). Both with and without SS and with both NMS and WMS, the order of indicated crosslinking was generally the same as found after reaction with POCl₃, with the indicated swelling inhibition being greater when SS was present in the reaction mixture. Examination of the maize starches with a protein stain indicated that channel protein was removed by treatment with thermolysin when the proteinase treatment occurred before crosslinking with either POCl₃ or STMP, but only incompletely or not at all if the treatment with the proteinase occurred after crosslinking. Because the crosslinking reactions were less effective when the protein was removed, the results are tentatively interpreted as indicating that they involved protein molecules, although there may not be a direct relationship.     

RVA analysis of mixtures of wheat flour and potato, sweet potato, yam, and cassava starches

Rapid visco analysis (RVA) was performed to study the pasting properties of mixtures of wheat flour and tuber starches, i.e., potato starch (PS), sweet potato starch (SPS), yam starch (YS), and cassava starch (CS), at 10–50% starch in the mixtures. Lower phosphorus and higher amylose contents were observed in CS, followed by YS, SPS, and PS. The peak, breakdown, final, and setback viscosities of the control wheat flour were lower than those of the control PS, SPS, YS, and CS. The peak viscosity of wheat–PS mixtures was higher than those of the wheat–SPS, wheat–YS, and wheat–CS because of the higher phosphorus and lower amylose content of PS, which resulted in higher swelling of PS than that of SPS, YS, and CS. The breakdown viscosities increased as the starch content of the PS, SPS, and CS in the mixtures increased to up to the 50%, and the values tended to decrease in the wheat–YS mixture. The setback viscosities of wheat–SPS, wheat–YS, and wheat–CS increased significantly as the starch content increased from 10% to 50%, and that of wheat–PS dropped dramatically at 50%. The findings in this work provide evidence that tuber starches could be used as a partial substitute for wheat flour in some wheat-based products.     

Functional properties of pregelatinized and cross-linked cassava starch obtained by extrusion with sodium trimetaphosphate

Cassava starch was cross-linked with sodium trimetaphosphate (STMP) on a Cerealtec single-screw extruder at different extrusion temperatures and concentrations of STMP and NaOH. The effect of variables on functional properties of the products was analysed by the response–surface methodology. The degree of substitution (DS) was influenced by NaOH and phosphorus level, and increased when their concentration increased. Extrusion temperature affected water absorption, cold viscosity and gel characteristics. The introduction of phosphate groups by cross-linking, with maximum DS of 1.5×10⁻⁴, increased the gel strength, water absorption index, resistance to high temperature and shear, and decreased gel cohesiveness, starch clarity and water solubility index. The products had different DS and degree of gelatinization and thus can be applied in several kinds of foods.     

Improved cold starch hydrolysis with urea addition and heat treatment at subgelatinization temperature

We explore how the presence of urea can influence the kinetics of amylolysis, with a long-term objective of developing practical and energy efficient bioconversion protocols. In this study, triticale and corn starches were hydrolyzed by a granular starch hydrolyzing enzyme with or without addition of urea and a pre-heating treatment at subgelatinization temperature. Differential scanning calorimetry showed that the gelatinization parameters of triticale and corn starches were negatively correlated with the urea concentration in the starch suspension. Addition of urea did not significantly affect starch amylolysis by the granular starch hydrolyzing enzyme at 30 °C. However when pre-heating at a higher yet sub-gelatinization temperature (50 °C for triticale and 61 °C for corn, 5 °C below the onset of starch gelatinization) for 30 min, the presence of urea greatly facilitated the amylolysis of both tricticale and corn starches. Scanning electron microcopy revealed starch granule mophological changes to a porous structure in residual starch granules/fragments rich in resistant starch. This means that the amylolysis pattern in the presence of urea was fundamentally changed, and urea disrupts starch hydrogen bonds effectively with heating treatment at a sub-gelatinization temperature. This treatment combination increased both starch hydrolysis rate and extent. Since extra energy was not necessary to gelatinize starch, this method may benefit starch and bio-enthanol industries to reduce the costs of starch hydrolysis.     

Influence of incubation temperature and time on resistant starch type III formation from autoclaved and acid-hydrolysed cassava starch

Raw cassava starch, having 74.94 and 0.44 g/100 g resistant starch type II and III (RS II and RS III), respectively, was autoclaved at 121 °C in water, 1, 10 or 100 mmol/L lactic acid. The formation of RS III was evaluated in relation to variable incubation temperature (−20 to 100 °C), incubation time (6–48 h) and autoclaving time (15–90 min). Negligible to low quantities of RS III (0.59–2.42 g/100 g) were formed from autoclaved starch suspended in 100 mmol/L lactic acid, whereas intermediate to high quantities (2.68–9.97 g/100 g) were formed from autoclaved starch suspended in water, 1 or 10 mmol/L lactic acid, except for treatments with water or 10 mmol/L lactic acid incubated at 100 °C for 6 h (1.74 g/100 g). Autoclaving times corresponding to maximum RS III contents were 15 and 45 min for water and 10 mmol/L lactic acid, respectively. Whereas, the RS III fractions from cassava starch suspended in water had melt transitions between 158 and 175 °C with low endothermic enthalpies (0.2–1.6 J/g), the thermal transitions of the acid treated samples were indistinct.     

禾谷类作物淀粉合酶

淀粉合酶是禾谷类作物淀粉合成所必需的一类酶.根据淀粉合酶家族成员的氨基酸序列的相似性,分别介绍了一个颗粒性淀粉合酶亚家族和四个可溶淀粉合酶亚家族的组成、基因结构和表达特点,并从转录、转录后和翻译后水平上对这些基因的表达调控做了概述.     

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.