水稻胚乳中淀粉合成相关酶活性的变化对支链淀粉精细结构的影响

分析了水稻（Oryza sativa L．）籽粒发育过程淀粉生物合成途径中的关键酶——ADP-葡萄糖焦磷酸化酶、可溶性淀粉合酶、淀粉分支酶以及淀粉脱支酶活性变化,同时研究了淀粉结构形成动态．与野生型晚粳9522相比,转基因晚粳9522中直链淀粉的合成被显著抑制,而总淀粉含量和籽粒终重量没有改变．淀粉生物合成途径中关键酶活性表达时间不一致,存在明显的时段特征,这与淀粉积累动态密切相关．可溶性淀粉合酶活性表达最早,其在灌浆前期驱动淀粉合成起始;而淀粉粒结合态淀粉合酶在胚乳发育的中期活性最大．两水稻实验材料间,除淀粉脱支酶活性变化有所不同外,ADP-葡萄糖焦磷酸化酶和淀粉分支酶活性的变化没有明显差异．并且,支链淀粉的分支模式在水稻籽粒发育过程中变化较大,且与品种有关．以上结果揭示,支链淀粉的合成要先于直链淀粉,并且在控制支链淀粉各分支的形成过程中有不同的酶在起特异的作用．     

木薯淀粉合成相关酶基因的克隆及表达分析

根据核苷酸同源性设计简并引物,克隆了一段大小为665 bp的木薯腺苷二磷酸葡萄糖焦磷酸化酶小亚基基因(sAGP)片段,并根据已知序列设计特异引物,克隆分离得到GBSS基因和SBE基因的cDNA片段.半定量RT-PCR分析结果表明,在木薯不同生长时期,3种淀粉合成相关酶基因的时空表达规律不同,GBSS基因表达有时期特异性和组织特异性,只在块根形成期和块根成熟期表达,在组织部位茎中表达最多,并且在这3种基因中表达水平相对较低.而sAGP基因在这3种基因中表达水平最高,在木薯决根成熟期竟达超量表达水平,并且在华南124和辐选0l中有品种差异,差异明显,在辐选01中的表达要优于华南124的表达.SBE基因表达较平稳,在各个时期表达水平都处于中间水平,在4个时期中,块根成熟期时的表达水平相对较高,块根形成期和苗期其次,收获期最低,也具有品种间差异,在辐选01中的表达要优于华南124的表达.     

小麦籽粒淀粉分支酶遗传多样性及对支链淀粉含量的影响

采用非变性聚丙烯酰胺凝胶电泳,对90份小麦品种的淀粉分支酶同工酶(SBE)进行检测,以分析不同基因型对支链淀粉含量的遗传效应.结果表明:(1)SBEⅠ型显现出较为丰富的变异,具有A、B、Dⅰ和Dⅱ4个等位基因位点;SBEⅡ型仅具有SBEⅡa单一等位基因位点.根据SBEⅠ型4个基因位点在不同品种中的分布,可将90个品种分为7种基因型.不同基因型对支链淀粉含量的遗传效应分析表明,含有A位点的基因型(ADⅰDⅱ和ADⅰB)所对应的支链淀粉含量较高,且与由1个基因位点组成的基因型(Dⅰ)和2个基因位点组成的基因型(DⅰB和DⅰDⅱ)的支链淀粉含量差异显著.     

水稻淀粉合成的分子生物学研究进展

本文综述了水稻淀粉合成的分子生物学研究的最新进展,主要内容是参与淀粉合成的酶鉴定及其基因表达调控,也介绍了对这些酶的遗传操作改良稻米淀粉品质等内容     

水稻淀粉合成的分子生物学研究进展

本文综述了水稻淀粉合成的分子生物学研究的最新进展,主要内容是参与淀粉合成的酶鉴定及其基因表达调控,也介绍了对这些酶的遗传操作改良稻米淀粉品质等内容。     

镉胁迫对水稻颖果充实和淀粉合成关键酶活性的影响

盆栽试验研究了Cd胁迫对水稻(扬稻6号和粳稻941)颖果充实过程中颖果鲜千重、可溶性糖和淀粉含量以及淀粉合成关键酶活性的影响,结果显示Cd胁迫:(1)降低了颖果淀粉合成关键酶的活性,缩短了颖果维持上述酶活性的天数;(2)降低了颖果可溶性糖的含量;(3)颖果灌浆减慢,鲜重、干重增加速率减缓,灌浆的天数变短,最终成熟颖果干重降低.说明,淀粉合成关键酶活性下降和维持活性的时间缩短使淀粉等贮藏物质的合成和积累降低是Cd胁迫降低颖果粒重的原因之一.     

RNAi沉默淀粉分支酶基因SEEI对玉米直链淀粉合成的影响

淀粉分支酶(SBE)是淀粉合成的限速酶.为了研究SBEI沉默对直链淀粉合成的影响,克隆了玉米(Zea mays)淀粉分支酶SBEI基因片段,构建了S8EI的RNAi表达载体pBAC418,用基因枪将其导入玉米自交系幼胚愈伤组织,经木糖筛选获得了7株转化再生植株.利用FAD2 intron和xylA基因探针对T<,0>代再生玉米植株进行DNA dot blot和PCR-Southern检测,证实5株为阳性植株,其中4株正常结实.SBEI基因沉默对阳性再生玉米株系籽粒的含油量没有显著影响;蛋白质含量显著高于受体对照;总淀粉含量与对照相比无显著差异,转基因株系直链淀粉含量平均提高了9.8%.     

RNAi沉默淀粉分支酶基因SBEI对玉米直链淀粉合成的影响

淀粉分支酶(SBE)是淀粉合成的限速酶。为了研究SBEI沉默对直链淀粉合成的影响, 克隆了玉米(Zea mays)淀粉分支酶SBEI基因片段, 构建了SBEI的RNAi表达载体pBAC418, 用基因枪将其导入玉米自交系幼胚愈伤组织, 经木糖筛选获得了7株转化再生植株。利用FAD2 intron和xylA基因探针对T₀代再生玉米植株进行DNA dot blot和PCR-Southern检测, 证实5株为阳性植株, 其中4株正常结实。SBEI基因沉默对阳性再生玉米株系籽粒的含油量没有显著影响; 蛋白质含量显著高于受体对照; 总淀粉含量与对照相比无显著差异, 转基因株系直链淀粉含量平均提高了9.8%。     

籼稻和粳稻中蜡质基因座位上微卫星标记的多态性及其与直链淀粉含量的关系

稻米直链淀粉是在由蜡质基因Wx编码的颗粒结合淀粉合成酶（GBSS）的催化下合成的。最近,在Wx基因的区段内发现了一段多态性微卫星序列（CT）n。对74个非糯籼稻和粳稻材料的（CT）n多态性进行了分析,并探讨了其与直链淀粉含量之间的关系。在74个品种（系）中共发现7种（CT）n片段（Wx等位基因）,即（CT）8,（CF）10,（CT）11,（CT）16,（CT）17,（CT）18,（Ch）19。在籼粳亚种间,不同（CT）n的分布存在差异较大：在籼稻中,以（CT）11和（CT）18为主,占92．6％,另有（CT）10和（CT）8各2份,（CT）17型1份;在粳稻中,以（CT）16、（CT）17为主,共占20份材料中的90．0％。在上述74个品种（系）中,以（CT）n表示的Wx基因型对稻米直链淀粉含量的决定系数R2达0．912,也即Wx基因型差异可解释这些材料直链淀粉含量变异的91．2％。还发现6份籼稻材料Wx座位上为杂合的（CT）18／（CT）11,其中2份为推广早籼优质品种浙9248和舟优903,并对其在遗传和育种研究中的意义作了探讨。     

Thermal and structural properties of unusual starches from developmental corn lines

Starches from exotic corn lines were screened by using differential scanning calorimetry (DSC) to find thermal properties that were significantly different from those exhibited by starches from normal Corn Belt lines. Two independent gelatinization transitions, one corresponding to the melting of a peak at 66 °C and the other to a peak melting at 69 °C, were found in some starches. The melting characteristics were traced to two separate types of granules within the endosperm. Strong correlations were found between DSC properties and proportion of large granules with equivalent diameter ≥17 μm. Starches with a lower peak onset gelatinization temperature (T_oG), had a lower normalized concentration of chains with a degree of polymerization (dp) of 15–24 and/or a greater normalized concentration of chains with a dp of 6–12. These studies will aid in understanding structure–thermal property relationships of starches, and in identifying corn lines of interest for commercial breeding.     

籼型杂交稻淀粉RVA谱特征值的杂种优势分析

以6个籼型三系不育系和5个籼型恢复系按不完全双列杂交设计配制的30个杂交稻组合及其亲本为材料,对其籽粒淀粉RVA谱各特征值进行了测定和分析。结果表明：（1）亲本间和杂交稻组合间的淀粉RVA谱各特征值均存在极显著的差异,其中变异最大的是消减值,最小的是糊化开始温度。（2）杂交稻组合淀粉RVA谱各特征值的变异系数均小于杂交稻亲本的变异系数;峰值粘度、崩解值、最低粘度和最终粘度的平均值杂交稻组合大于亲本,其他性状的平均值杂交稻组合小于亲本。（3）峰值粘度存在极显著的正向超亲优势;崩解值、最低粘度、最终粘度和回复值存在极显著的正向中亲优势;消减值和峰值时间存在极显著的负向中亲优势和正向低亲优势;糊化开始温度存在极显著的负向低亲优势;最终粘度、回复值和糊化开始温度表现为极显著的负向竞争优势,其他性状表现为正向竞争优势。（4）峰值粘度、崩解值、消减值和回复值等4个性状,各杂交稻组合与其母本、中亲值呈现极显著正相关,峰值时间与中亲值呈显著正相关。而与其父本的相关均未达显著水平。     

Particle size distribution of rice flour affecting the starch enzymatic hydrolysis and hydration properties

Rice flour is becoming very attractive as raw material, but there is lack of information about the influence of particle size on its functional properties and starch digestibility. This study evaluates the degree of dependence of the rice flour functional properties, mainly derived from starch behavior, with the particle size distribution. Hydration properties of flours and gels and starch enzymatic hydrolysis of individual fractions were assessed. Particle size heterogeneity on rice flour significantly affected functional properties and starch features, at room temperature and also after gelatinization; and the extent of that effect was grain type dependent. Particle size heterogeneity on rice flour induces different pattern in starch enzymatic hydrolysis, with the long grain having slower hydrolysis as indicated the rate constant (k). No correlation between starch digestibility and hydration properties or the protein content was observed. It seems that in intact granules interactions with other grain components must be taken into account. Overall, particle size fractionation of rice flour might be advisable for selecting specific physico-chemical properties.     

籼米淀粉粘滞性的基因型与环境互作研究

水稻精米中大约含有90%的淀粉,因此淀粉的特性对水稻的食味品质有很大的影响.淀粉粘滞性是预测稻米食用、蒸煮和加工品质的重要指标.本研究利用4个细胞质雄性不育系和8个恢复系配置的不完全双列杂交组合来分析淀粉粘滞性指标(崩解值、回复值和消减值)的胚乳、细胞质和母体基因效应及环境互作效应.结果表明在崩解值、回复值和消减值的遗传变异中,遗传主效应方差分量占了64%以上,表明它们主要受遗传主效应控制,同时也受到基因型与环境互作效应的影响.崩解值、回复值和消减值的总遗传率分别为67.8%、79.5%、79.5%,而且普通遗传率占了总遗传率的75%以上,表明对这些性状的早世代选择有效,且在不同环境中选择效果相对稳定.     

Film blowing of thermoplastic starch

Thermoplastic starch materials are often based on a combination of starch, glycerol and water. In the present study, two potato starch grades were employed; a native (natural) grade and an oxidised and hydroxypropylated grade of the native material, in order to produce the thermoplastic material. The primary aim of the study was to identify possible routes for film blowing thermoplastic starch on a laboratory scale by a suitable choice of processing conditions, amount of glycerol and moisture content. With an appropriate combination of these parameters, the thermoplastic material based on the modified starch could be film blown in a satisfactory manner. Film blowing of material based on the natural starch was significantly more difficult. The difficulties encountered were mainly related to a sticky surface of the film, insufficient tenacity and foaming. The processing window for thermoplastic starch (related to film blowing) is briefly outlined and discussed.     

Starch modification by iterated syneresis

Potato, tapioca, corn and wheat starches were solubilised in water and isolated from the solution by iterated syneresis and the effect of this physical modification on the physicochemical properties and structure was studied. The experimental starches were examined by chemical analysis, the Brabender rheological method, scanning electron or light microscopy, X-ray diffractometry, infrared spectroscopy, and differential scanning calorimetry. Physical modification was evidenced to the change starch–water interaction and the structure of starches. Pasting temperature shifted to lower values and the gelatinisation mechanism changed. All modified starches had a B-type of X-ray diffraction pattern. The melting temperature of starch crystallites was typical of retrograded starch, but the enthalpy change was higher. The correlation between the resistant starch content of modified starches and their crystal structure was discussed together with the thermal properties.     

On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. Part I. Pasting and calorimetric studies

Pasting and calorimetric studies of normal and waxy wheat starch were performed in the presence of a series of ionic (sulphates, trimethyl ammonium bromides) and non-ionic (monoglycerides, maltosides) short (12 carbon atoms) and long (16 carbon atoms) n-alkyl chain surfactants. With the exception of the alkyl ammonium bromides, all of the short chain surfactants lower the pasting temperature (PT) in normal wheat starch, while the long chain surfactants have the opposite effect. Contrary, regardless of their chain length, all ionic surfactants lower the PT in waxy wheat starch while the non-ionic surfactants induce small, sometimes almost negligible changes in the PT. Calorimetric studies revealed the absence of a direct connection between the effect of surfactants on the onset of the starch gelatinization transition and the PT. However, in the presence of all surfactants, except the alkyl ammonium bromides, the PT of normal wheat starch was found to lie within or very close the temperature range within which the dissociation of the amylose–surfactant complexes takes place. Waxy wheat starch, in contrast, pasted at temperatures that fell within the temperature range of the starch gelatinization transition. This is taken as evidence of the existence of a correlation between the PT and the dissociation of the amylose–surfactant complexes.     

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.     

Structural and enzymatic characterization of the isoamylase1 homo-oligomer and the isoamylase1–isoamylase2 hetero-oligomer from rice endosperm

The present study established that there are two distinct polymeric forms of isoamylase1 (ISA1) in rice endosperm: presumably a homo-pentamer of ISA1 and a hetero-hexamer composed of five ISA1 and one ISA2. The molecular sizes of the homo- and hetero-oligomers, which could be fractionated by hydrophobic chromatography, were approximately 420–480 and 510–550 kDa, respectively. The hetero-oligomer exhibited higher affinities for various branched polyglucans, especially for phytoglycogen, which had a K _m value that was approximately 12 times lower relative to that with the homo-oligomer, although no marked differences were found in chain preferences for debranching of amylopectin and phytoglycogen between these forms. The hetero-oligomer was active even when incubated at 50°C for 10 min, while the homo-multimer was completely inactivated at 40°C in 10 min. When the ISA1 homo-oligomer was incubated with the ISA2 protein expressed in Escherichia coli and applied onto a nondenature polyacrylamide gel, additional debranching activity bands which were specific for the purified ISA1–ISA2 preparation were also detected, indicating that ISA1 and ISA2 combine to form a hetero-oligomer. These results suggest that the hetero-oligomer plays a predominant role in the amylopectin biosynthesis in rice endosperm although the homo-oligomer can complement the function of the hetero-oligomer at least to some extent.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.