不同类型玉米发育籽粒中淀粉合成及相关酶活性比较

以普通玉米、爆裂玉米、甜玉米和糯玉米为试材,分析和比较不同类型的玉米品种之间籽粒发育过程中淀粉合成及相关酶活性的变化。结果表明,淀粉合成速率和蔗糖合成酶(SS)、可溶性淀粉合成酶(SSS)、束缚态淀粉合成酶(GBSS)、淀粉分支酶(SBE)、去分支酶(DBE)活性都呈单峰曲线变化。30～40 DAP,普通玉米的SS活性显著高于其他3种类型;类型间平均和最大SSS活性水平的顺序为普通玉米>糯玉米>爆裂玉米>甜玉米;30～40 DAP,普通玉米GBSS活性最高,糯玉米GBSS活性最低;20～40 DAP,糯玉米SBE活性最高;甜玉米的DBE活性很低,并且在40 DAP完全丧失。淀粉合成速率与SS、SSS、GBSS和SBE活性相关程度比较高,与腺苷二磷酸葡萄糖焦磷酸化酶(AGP酶)和DBE活性相关不显著。推测AGP酶虽然为淀粉合成提供直接前体ADPG,但可能SS活性过低致使其限速作用比AGP酶的还强,AGP酶潜在的限速作用无法表现,SS成为玉米籽粒淀粉合成的限速因子。GBSS对直链淀粉积累起重要的促进作用;SSS和SBE对支链淀粉积累起重要的促进作用。     

sh-2超甜玉米乳熟期籽粒重量和碳水化合物变化及与温度降雨量的回归分析

采用夏季不同播期,研究了sh-2型超甜玉米乳熟期籽粒重量和碳水化合物的变化,用多重回归分析方法对气温、降雨量与籽粒重量、碳水化合物含量的关系进行了分析．结果表明,两个播期的可溶性总糖、果糖、蔗糖含量变化趋势有明显差异．夏季早播,提高了乳熟期籽粒鲜重和干重,灌浆速率,可溶性总糖和淀粉含量．说明夏季早播有利于提高甜玉米的独特甜风味和产量构成．移栽-收获期的T（温差）、K（有效积温）和RF（降雨量）是影响乳熟期籽粒鲜重和干重及可溶性总糖、果糖、蔗糖、淀粉含量的主要因子,K、RF表现正相关效应;在授粉-收获期,K是影响的主要因子,K与籽粒鲜重和干重及果糖、淀粉含量呈正相关,与籽粒蔗糖含量呈负相关．     

sh-2甜玉米F2籽粒营养品质遗传特点、杂种优势及其亲子回归关系分析

研究了25个sh-2甜玉米自交系及其组配的15个sh-2型F_2籽粒的5个品质性状的遗传特点、杂种优势、亲子回归关系．结果表明,亲本间,除籽粒还原糖含量外,可溶性总糖、蔗糖、淀粉、可溶性蛋白含量是否存在显著差异,对F_2籽粒品质有明显影响．F_2籽粒可溶性总糖、还原糖、淀粉、可溶性蛋白含量近低亲遗传,而蔗糖含量近高亲遗传．杂种F_2籽粒可溶性总糖、淀粉、可溶性蛋白含量普遍介于双亲之间,杂种优势不强;还原糖含量普遍表现为低亲,没有超亲优势;蔗糖含量以超亲为主,有明显杂种优势．亲本对F_2杂交籽粒可溶性总糖、还原糖、蔗糖、淀粉、可溶性蛋白含量均表现为正效应;除还原糖品质外,其他品质性状受父本的影响较大．研究表明,了解sh-2甜玉米亲本营养品质性状,能很好的预测其F_2籽粒营养品质性状,使育种更有目的性．     

shsu双隐性甜玉米F2籽粒营养品质杂种优势分析

杂种优势是一种普遍的遗传学现象.甜玉米杂种优势在各性状上有不同程度的表现,该研究采用不完全双列杂交方法按照P(P-1)/2对5个shsu双隐性甜玉米自交系组配的10个杂交组合F2籽粒的4个品质性状的遗传特点、杂种优势进行分析.结果表明:F2籽粒的4个品质性状很难同时达到理想效果,可溶性总糖、蔗糖、淀粉、可溶性蛋白含量受双亲含量的影响较大,基本是近低亲本遗传.为能得到较高的F2籽粒可溶性总糖含量,可尽量选择具有高可溶性总糖含量的亲本;F2籽粒蔗糖、淀粉含量却受父本的影响较大.     

shsu双隐性甜玉米F2籽粒营养品质杂种优势分析

杂种优势是一种普遍的遗传学现象。甜玉米杂种优势在各性状上有不同程度的表现,该研究采用不完全双列杂交方法按照P(P-1)/2对5个shsu双隐性甜玉米自交系组配的10个杂交组合F2籽粒的4个品质性状的遗传特点、杂种优势进行分析。结果表明:F2籽粒的4个品质性状很难同时达到理想效果,可溶性总糖、蔗糖、淀粉、可溶性蛋白含量受双亲含量的影响较大,基本是近低亲本遗传。为能得到较高的F2籽粒可溶性总糖含量,可尽量选择具有高可溶性总糖含量的亲本;F2籽粒蔗糖、淀粉含量却受父本的影响较大。     

玉米种子发育过程中直链淀粉积累规律的分析

淀粉是玉米种子的主要组成成分,它包括直链淀粉和支链淀粉。支链淀粉的合成需要淀粉合成酶、分支酶和脱支酶的共同作用,而直链淀粉的合成则是在颗粒结合型淀粉合成酶的作用下进行的。颗粒结合型淀粉合成酶基因的突变造成玉米种子的腊质（糯性）表型。与支链淀粉合成的分子机制的研究相比,目前对玉米种子中直链淀粉合成的分子机制了解相对较少。以野生型黄早4玉米自交系和突变体糯玉米为实验材料,研究了种子不同发育时期直链淀粉的积累规律。通过碘染色的方法,观察了玉米种子发育过程中淀粉积累的形态变化。定量分析表明,从授粉后10d至25d,黄早4种子中直链淀粉的含量逐渐增加,同时颗粒结合型淀粉合成酶（GBSS）的活性逐渐提高;而在糯玉米中,直链淀粉和GBSS活性均未检测到。进而,通过RT-PCR方法,从黄早4种子中分离出编码GBSSI的cDNA片段。在授粉后10d至25d的玉米胚乳中均可检测到GBSSI的表达,而在胚中直到授粉后25d才检测到该基因表达的微弱信号。在糯玉米种子中没有检测到该基因的表达。研究结果表明,在玉米种子发育过程中,GBSSI基因的表达通过控制GBSS的合成,最终控制直链淀粉的合成。研究工作为理解玉米种子中直链淀粉合成的分子机制提供了重要信息。     

玉米籽粒胚乳细胞增殖及其与淀粉充实的关系

用纤维素酶解离胚乳、滤膜法统计玉米胚乳细胞的数目,进一步借助Logistic方程模拟胚乳细胞增殖动态的结果表明,整个灌浆期间胚乳细胞增殖呈现“慢-快-慢”的变化趋势。授粉15d后,不同类型胚乳的细胞数目依序为普通玉米〉糯玉米〉甜玉米〉爆裂玉米;胚乳细胞数目主要取决于细胞的增殖速率,并与淀粉充实和粒重关系密切。胚乳发育前期以胚乳细胞增殖为主,后期以淀粉积累为主。     

红曲霉葡萄糖淀粉酶的底物特异性

红曲霉（Monascus sp.）As 3.3491的葡萄糖淀粉酶具有多型性,其中的两个主要组分 E3和 E4得到了凝胶电泳均一的样品。比较了它们的底物特异性,同时与粗酶液和未分纯的 E3+4作了比较。从酶对底物的分解限度来看,粗酶液能100%的分解可溶性淀粉、直链淀粉、支链淀粉、糖原、玉米淀粉、马铃薯淀粉、麦芽糖和麦芽三糖,也能分解茁霉多糖（Pullulan）（35.8%）,潘糖（Panose6-α-葡糖基麦芽糖）（27.3%）、异麦芽糖（9.6%）、右旋糖酐（5%）、龙胆二糖（1.9%）。纯北的 E3和 E4仅能100%地分解糖原,麦芽糖和麦芽三糖,对其他底物的分解限度则有不同程度的降低,E3,E4和 E3+4之间没有明显差别,可以看出粗酶液中有能分解α-1,6-糖苷键的酶存在。各种酶样品均不能分解环状糊精（α,β和γ）,纤维二糖、龙胆二糖和（?）糖。比较了各种酶样品对不同底物包括不同平均链长的糊精的反应初速度,在用同样的百分浓度下,对麦芽糖、麦芽三糖、支链淀粉,可溶性淀粉等的反应初速度高,而对直链淀粉的反应初速度要低得多,这与它没有分枝,非还原性末端较少有关。对不同平均链长的小分子糊精的反应初速度随着链长的增加而增加。而对异麦芽糖的水解速度仅相当于麦芽糖的1%左右,E3,E4和 E3+4之间无明显的差别。用麦芽糖和可溶性淀粉为底物,比较了 E3和 E4的 Km 值和 Vmax值。两种酶对麦芽糖的Km 值均为1.38×10-1（%）,对于可溶性淀粉的 Km 值均为1.05（%）,Vmax也基本相同。E3和 E4对可溶性淀粉的水解产物均为β-葡萄糖,两种酶均能催化葡萄糖合成少量寡糖。     

3个香蕉品种的果实淀粉形状与含量及风味物质比较

采用扫描电子显微镜对巴西蕉、宝岛蕉、红香蕉3个品种(AAA基因型)的淀粉颗粒形状及大小进行观察,并测定果实中总淀粉、直链淀粉、支链淀粉及风味物质的含量,以揭示不同品种间香蕉果实品质差异的内在机理。结果显示:(1)巴西蕉、宝岛蕉、红香蕉淀粉颗粒的形状分别为不规则三角形、圆形、棒形,大小分别为8.20~35.70μm、6.90~29.80μm、5.47~23.80μm。(2)巴西蕉、宝岛蕉、红香蕉总淀粉含量分别为(66.93±2.48)%、(90.38±2.46)%、(48.91±2.49)%;直链淀粉含量分别为(20.48±1.09)%、(21.48±1.08)%、(14.67±1.10)%;支链淀粉含量分别为(46.45±1.85)%、(68.90±1.25)%、(34.24±1.45)%;且3个品种总淀粉、支链淀粉及直链淀粉含量差异均达到显著水平。(3)巴西蕉、宝岛蕉、红香蕉Vc含量分别为(15.54±1.10)、(17.63±1.14)、(16.76±1.03)mg/100g FM;可溶性固形物含量分别为(15.50±0.22)%、(15.67±0.30)%和(16.17±0.30)%;糖/酸比分别为2.75∶1、2.74∶1、3.15∶1;差异显著性分析发现,3个品种Vc及可溶性固形物含量差异分别达到极显著、显著水平;巴西蕉和宝岛蕉糖/酸比差异不显著。研究认为,同一基因型(AAA)不同品种香蕉果实的淀粉形状、大小、总淀粉、直链淀粉、支链淀粉以及Vc和可溶性固形物含量均存在明显差异,为解释不同品种间香蕉果实品质差异提供了理论依据。     

碘使淀粉液变色的原理是什么？

答：淀粉以淀粉粒的形式储存在植物的根、茎、种子和果实等器官中。在酸的作用下淀粉的最终水解产物是葡萄糖。用热水溶解淀粉时,可溶的部分为直链淀粉,不溶的部分为支链淀粉。不同植物淀粉中直链淀粉和支链淀粉所含比例不同,如玉米淀粉中含直链淀粉的比例为27％,土豆淀粉中直链淀粉的含量为30％：豆类淀粉全为直链淀粉,糯米淀粉则全为支链淀粉。     

Dynamic and extensional properties of starch in aqueous dimethylsulfoxide

The effect of starch composition and concentration on the rheological properties of starch in a mixed solvent, water–DMSO, was investigated in dynamic shear and extensional mode. High amylose corn starch containing 70% amylose and 30% amylopectin, common corn starch containing 25% amylose and 75% amylopectin, and waxy corn starch containing about 99% amylopectin were used in this study. Concentrations of 2, 4, 6, and 8% (w/v) in 10% water-90% DMSO (v/v) were used for each starch type. An increase in the amylopectin content of starch from 30 to 99% caused a change in behavior from semidilute solution to viscoelastic solid at a concentration of 8% (w/v). At a concentration of 2%, an increase in the amylopectin content of starch from 30 to 99% caused a change from Newtonian to incipient gel-like behavior. Behavior at intermediate concentrations of 4 and 6% (w/v) varied from semidilute to critical gel-like with increasing amylopectin content. A power-law relaxation was observed for all concentrations of common and waxy corn starches with the slope decreasing with increase in concentrations. A 2% waxy corn starch solution displayed extension thinning behavior, while a 2% high amylose corn starch solution displayed Newtonian behavior.     

The α(1–4)(1–6) glucans from sweet and normal corns

After removal of granular starch at low centrifugal force, the centrifugation, at increasing forces, of aqueous extracts of su₁ corn gave a series of α-glucan precipitates that contained amylose. The amylose content decreased as the force increased. In contrast, in normal corn all the α-glucan precipitated as starch granules at low forces. In the sweet corn precipitates, apart from the granular starch, the branched α-glucan was phytoglycogen. The MW of this decreased as the proportion of amylose decreased. It appears that, as well as starch granules and soluble phytoglycogen, sweet corn contains granules, smaller than starch, of a range of sizes, and these are made up of phytoglycogen and amylose. As granule size decreases, so does the MW of the phytoglycogen and the content of amylose. A method of quantitative extraction of starch giving minimal depolymerization is described. The isopotential iodine absorption of a quantitative extract of sweet corn flour indicated that the total ratio of linear (amylose) fraction to branched (amylopectin + phytoglycogen) fraction was near the normal value of 1:4.     

Internal structure and physicochemical properties of corn starches as revealed by chemical surface gelatinization

The organization of amylose and amylopectin within starch granules is still not well elucidated. This study investigates the radial distribution of amylose and amylopectin in different corn starches varying in amylose content (waxy corn starch (WC), common corn starch (CC), and 50% and 70% amylose corn starches (AMC)). Corn starches were surface gelatinized by 13 M LiCl at room temperature to different extents (approximately 10%, 20%, 30%, and 40%). The gelatinized surface starch and remaining granules were characterized for amylose content, amylopectin chain-length distribution, thermal properties, swelling power (SP), and water solubility index (WSI). Except for the outmost 10% layer, the amylose content in CC increased slightly with increasing surface removal. In contrast, amylose was more concentrated at the periphery than at the core for 50% and 70% AMC. The proportion of amylopectin A chains generally decreased while that of B1 chains generally increased with increasing surface removal for all corn starches. The gelatinization enthalpy usually decreased, except for 70% AMC, whereas the retrogradation enthalpy relatively remained unchanged for CC but increased for WC, 50% and 70% AMC with increasing surface removal. The SP and WSI increased with increasing surface removal for all corn starches, with WC showing a significant increase in SP after the removal of the outmost 10% layer. The results of this study indicated that there were similarities and differences in the distribution of amylose and amylopectin chains along the radial location of corn starch granules with varying amylose contents. More amylose-lipid complex and amylopectin long chains were present at the periphery than at the core for amylose-containing corn starches.     

不同品种玉米对草地贪夜蛾生长发育及繁殖的影响

为评价新入侵害虫草地贪夜蛾对我国不同品种玉米的为害潜能,本文采用组建实验种群生命表的方法研究了草地贪夜蛾对3种甜质型玉米(穗甜1号、正甜68和华金甜1号)以及3种糯质型玉米(京科糯2000、广黑甜糯和广糯1号)的生存适合度,分析了草地贪夜蛾生物学指标与玉米叶片主要营养物质及粗纤维含量间的相关性。结果表明: 取食甜质型玉米的草地贪夜蛾的幼虫存活率、蛹重、雌成虫产卵量均显著高于取食糯质型玉米;取食甜质型玉米草地贪夜蛾的内禀增长率介于0.1566～0.1843,净生殖力介于187.97～353.35,也均高于取食糯质型玉米(内禀增长率介于0.0998～0.1465,净生殖力介于25.89～95.34),表明取食甜质型玉米的草地贪夜蛾具有更高的种群增长能力。甜质型玉米叶片中主要营养物质维生素C、淀粉、可溶性糖、蛋白质、脂肪、总氨基酸及粗纤维的含量普遍高于糯质型玉米,草地贪夜蛾的净生殖力与维生素C、淀粉、可溶性糖、蛋白质及粗纤维的含量均存在显著正相关关系。草地贪夜蛾在甜质型玉米上具有更高的生存适合度。     

Locations of hypochlorite oxidation in corn starches varying in amylose content

The general oxidation mechanism by hypochlorite on starch has been well studied, but the information on the distribution of the oxidation sites within starch granules is limited. This study investigated the locations where the oxidation occurred within corn starch granules varying in amylose content, including waxy corn starch (WC), common corn starch (CC), and 50% and 70% high-amylose corn starch (AMC). Oxidized corn starches were surface gelatinized by 13 M LiCl at room temperature to different extents (approximately 10%, 20%, 30%, and 40%). The surface-gelatinized remaining granules were separated and studied for structural characteristics including carboxyl content, amylose content, amylopectin chain-length distribution, thermal properties, and swelling properties. Oxidation occurred mostly at the amorphous lamellae. More carboxyl groups were found at the periphery than at the core of starch granules, which was more pronounced in oxidized 70% AMC. More amylose depolymerization from oxidation occurred at the periphery of CC. For WC and CC, amylopectin long chains (>DP 36) were more prone to depolymerization by oxidation. The gelatinization properties as measured by differential scanning calorimetry also supported the changes in amylopectin fine structure from oxidation. Oxidized starches swelled to a greater extent than their unmodified counterparts at all levels of surface removal. This study demonstrates that the locations of oxidation and physicochemical properties of oxidized starches are affected by the molecular arrangement within starch granules.     

The influence of amylose and amylopectin characteristics on gelatinization and retrogradation properties of different starches

Physico-chemical properties of starch from wheat, rye, barley (waxy, high-amylose and normal-amylose), waxy maize, pea and potato (normal-amylose and high-amylopectin) were studied. Emphasis was given to the amylose (total, apparent and lipid-complexed) and amylopectin characteristics as well as to the gelatinization and retrogradation properties measured using differential scanning calorimetry. The total amylose content varied from ca. 1 % for waxy maize to 37% for high-amylose barley. The amylopectin characteristics were determined by high-performance size-exclusion chromatography after debranching with isoamylase. The weight-average degree of polymerization ( _w) was 26, 33 and 27 for the A-, B-, and C-type starches, respectively. In general, the potato starches exhibited the highest retrogradation enthalpies and the cereal starches the lowest, while the pea starch showed an intermediate retrogradation enthalpy. The data were analysed by principal component analysis (PCA). The _w showed positive correlation to the melting interval, the peak minimum, the offset temperatures of the retrogradation-related endotherm as well as to the gelatinization and retrogradation enthalpies. However, the high-amylose barley retrograded to a greater extent than the other cereal starches, despite low _w (24). The amylose content was negatively correlated to the onset and the peak minimum temperatures of gelatinization.     

胚乳中淀粉的合成

禾本科植物胚乳内所含有的淀粉根据其结构、组成可以分为两类：直链淀粉（由α-1,4糖苷键连接的多聚D-葡萄糖）和支链淀粉（在以α-1,4糖苷键连接的主链上通过形成α-1,6糖苷键引入支链的多聚D-葡萄糖）。前者是以一种线性无序状态存在,而支链淀粉则是构成淀粉半晶体结构的主要成分。其中,除了负责合成作为糖基直接供体的ADP—Glc的酶AGPase外,直链淀粉中链的延伸反应由GBSSI完成,而支链淀粉的合成则相对复杂,需要SS、SBE、DBE、SP等一些酶的协同调控来共同完成。本文综述了胚乳中淀粉合成过程中所涉及的一些关键酶的研究进展,并对此研究领域进行了展望。     

鲜食糯玉米采后糖代谢相关酶活性变化

鲜食糯玉米采后腺苷二磷酸葡萄糖焦磷酸化酶（ADPGPPase）、尿苷二磷酸葡萄糖焦磷酸化酶（UDPGPPase）、束缚态淀粉合成酶（GBSS）、淀粉脱分支酶（DBE）等活性均呈现单峰曲线变化,第1～2天出现峰值然后略有下降;可溶性淀粉合成酶（SSS）活性呈较大幅度上升趋势,活性远高于采收初期;淀粉分支酶（SBE）在第3天出现极高峰值。与20℃贮藏温度相比,采后0℃低温贮藏可增强UDPGPPase活性,促进蔗糖降解;降低SSS和GBSS活性,延缓淀粉合成进程;抑制SBE活性,增强DBE活性,促进直链淀粉生成。