水稻粉质皱缩胚乳突变体fse4的表型分析与基因克隆

【目的】水稻种子主要以淀粉形式储藏能量。淀粉合成需要多种酶类和调控因子参与，机制较为复杂。本研究利用水稻胚乳发育缺陷突变体，克隆和鉴定新的调控淀粉合成相关基因，旨在为研究淀粉合成及其调控提供理论依据。【方法】从化学诱变剂甲基亚硝基脲（1-methyl-1-nitroso-urea, MNU）处理的宁粳3号(Ningjing 3, WT)突变体库中筛选到一个能稳定遗传的胚乳粉质皱缩突变体，命名为fse4 (floury and shrunken 4 )。与籼稻品种Dular杂交获得F1种子（F2），通过图位克隆的策略确定FSE4候选基因。利用杂合植株（FSE4fse4）分离出的粉质种子，观察形态学特征，分析其理化性质。使用扫描电镜和半薄切片技术观察胚乳结构。使用qRT-PCR和免疫印迹分析淀粉合成相关基因表达模式和淀粉合成相关酶类的蛋白积累量。利用全自动氨基酸分析仪测定成熟胚乳各氨基酸含量。【结果】突变体fse4籽粒宽度、厚度以及千粒重显著下降，同时胚乳中总淀粉、总蛋白、直链淀粉含量亦显著下降，而脂肪含量显著上升；淀粉黏度、崩解值和消减值显著低于野生型。突变体fse4中多为单粒型淀粉颗粒，且排列分散。FSE4定位于第5染色体长臂约252 kb的区间内，测序发现编码Δ1-吡咯啉-5-羧酸合成酶基因 （Delta 1-pyrroline-5-carboxylate synthetase, P5CS）第1外显子上发生单碱基替换，导致一保守的氨基酸发生变异。突变体fse4中大部分淀粉合成相关基因表达量下调，多种淀粉合成相关蛋白积累量减少。突变体fse4米粉中多种氨基酸含量发生显著变化，游离氨基酸含量是其野生型的3.6倍。此外，外源喷施脯氨酸能部分恢复突变体fse4种子萌发缺陷表型。【结论】FSE4编码脯氨酸合成关键限速酶P5CS，该基因对胚乳中氨基酸的合成及代谢起重要的调控作用，并影响淀粉的合成与积累。     

Phenotypic Analysis and Gene Cloning of Rice Floury Endosperm Mutant fse4

【Objective】Starch is the main energy reserve of rice endosperm. The biosynthesis of starch is complex, requiring a large number of synthetic enzymes and regulators. Screening rice endosperm defective mutants and cloning the underlying genes will lay theoretical basis for starch biosynthesis and its regulation. 【Method】 A stable genetic floury and shrunken endosperm mutant termed as fse4 (floury and shrunken4) were obtained from the mutant library of Ningjing 3 (WT), which was induced by N-methyl-N-nitrosourea (MNU). An F2 mapping population was generated by crossing the fse4 mutant with Dular (an indica rice variety) and the gene was finally isolated. The floury seeds segregated from the fse4 heterozygous plants were used to observe the morphological features, and the physicochemical properties of the brown rice flour were analyzed. The endosperm structure was observed with a scanning electron microscopy by the semi-thin section technology. The expression of starch synthesis related genes during grain filling was determined by qRT-PCR; Immunoblotting was used to detect the accumulation of proteins related to starch synthesis. The amino acids contents of each mature endosperm were determined with the fully automatic amino acid analyzer.【Result】The 1000-grain weight and grain size were significantly reduced in fse4. Compared with WT, the contents of total starch, amylose and total protein were signi?cantly lower in fse4, while the lipid content was signi?cantly higher. The starch viscosity, breakdown viscosity and setback viscosity of the fse4 mutant were lower than WT. The endosperm of the mutant had many single dispersed starch granules with large spaces between each other. Using 1568 recessive individuals, FSE4 was narrowed down to a 252 kb region. Sequencing revealed a single base substitution in the first exon of the delta 1-pyrroline-5-carboxylate synthetase (P5CS), resulting in a conserved amino acid variation. Most of the genes related to starch synthesis were downregulated in fse4 and the protein accumulation related to starch synthase were reduced. The contents of various amino acids in fse4 rice flour were increased or decreased, the total free amino acids contents in fse4 seeds was 2.6 times higher than those in WT. Exogenous proline was applied during the germination of fse4 seeds, and the embryonic lethal phenotype was partially recovered.【Conclusion】FSE4 encode the key rate-limiting enzyme P5CS of proline synthesis, which plays an important role in the biosynthesis and metabolism of amino acids in endosperm and affects the accumulation of starch.     

玉米自交系齐319空间诱变系的生物学效应分析

以两份玉米子粒类型空间诱变系SP-M1、SP-M2以及野生型玉米自交系齐319为试验材料,对田间农艺性状、穗部性状、子粒的营养品质性状和胚乳内部显微结构进行分析。结果表明,与野生型相比,两个诱变系在株高、穗位高、粒长、百粒重等田间农艺性状和穗部性状上发生显著或极显著变异,且变异方向不同,SP-M1和SP-M2赖氨酸含量显著高于野生型,SP-M2淀粉含量显著高于野生型,蛋白质含量显著低于野生型。2个诱变系与齐319在胚乳边缘组织、胚乳内部组织、淀粉粒、基质蛋白等结构存在差异,淀粉粒的组成比例和排列顺序是影响胚乳超微结构差异的主要原因。     

水稻糖质胚乳突变体Sug-11籽粒灌浆过程的淀粉合成关键酶活性及其与淀粉理化特性关系

以水稻糖质胚乳突变体Sug-11与其野生型对照中花11为材料,通过对两者籽粒中可溶性总糖、蔗糖含量和淀粉含量以及有关淀粉品质理化指标的比较,结合籽粒灌浆过程中糖类物质含量、淀粉合成代谢关键酶活性和相关同工型基因转录表达水平的动态测定,从籽粒淀粉合成代谢角度,对水稻糖质突变体Sug-11的籽粒糖类含量变化和千粒重下降的生理原因进行了分析。结果表明,Sug-11糖质突变体与其野生型在灌浆初期的可溶性糖和蔗糖含量差异并不明显,随着籽粒灌浆进程,两者间的籽粒糖分含量差异在灌浆中后期逐步趋于明显;与野生型相比,Sug-11糖质胚乳突变体的稻米直链淀粉含量和直链淀粉碘蓝值显著下降,而淀粉溶解度和支链淀粉碘蓝值则显著升高,糖质胚乳突变对稻米淀粉的理化特性也产生了明显的影响;在籽粒淀粉合成代谢的几个关键酶中,Sug-11糖质突变体籽粒中的DBE活性及其在灌浆过程中的动态变化与其野生型存在明显差异,揭示了胚乳糖质突变体Sug-11籽粒中淀粉积累减少、糖分含量增加主要是由籽粒灌浆中后期的PUL转录表达水平和DBE活性的大幅下降所引起的,而Sug-11的籽粒灌浆不良和千粒重下降等现象,则与其ADPGase活性在籽粒灌浆前期的显著下降存在一定的联系。     

两个垩白突变体的鉴定及突变基因的图位克隆

【目的】研究两个水稻垩白突变体胚乳垩白的形成机制,为稻米品质改良提供理论基础。【方法】以从中花11的EMS突变体库中筛选出的两个稳定遗传的垩白突变体eb6、eb7为材料,对其进行农艺性状、稻米理化性质和遗传学分析,并利用eb6与南京11衍生的F2群体对控制垩白的基因进行图位克隆。同时对候选基因的表达模式及淀粉合成相关基因在突变体及野生型中表达情况进行了分析。【结果】与野生型相比,两个突变体胚乳中央部位呈现白色且不透明,淀粉复合颗粒形状不规则且排列疏松,而突变体胚乳边缘部位与野生型无异,都为半透明状,淀粉复合颗粒呈多面体且排列致密。相对于野生型,突变体eb6、eb7成熟种子中的直链淀粉含量和胶稠度显著降低,蛋白质含量显著升高。RVA谱分析显示突变体淀粉黏滞性明显低于野生型。同时,支链淀粉聚合度分析显示突变体eb6中聚合度(DP)小于16的短链显著增加,DP为16~23的中长链显著减少。遗传分析表明突变体eb6、eb7胚乳垩白表型由单隐性核基因控制,并且它们为一对等位突变体。利用突变体eb6与南京11杂交衍生的F2群体将突变体基因定位在第1染色体长臂上物理距离86.6 kb的区间内。该区间包含22个开放阅读框(ORF),其中ORF13编码腺苷二磷酸葡萄糖焦磷酸化酶大亚基2(Os AGPL2)。序列分析发现eb6与eb7分别在Os AGPL2第3、第7外显子上发生1个单碱基替换,并分别导致一个氨基酸替换。RT-PCR及原位杂交结果显示,Os AGPL2主要在水稻发育中的籽粒中表达。同时Os AGPL2的突变导致了多个淀粉合成相关基因在水稻籽粒灌浆过程中的表达模式发生改变。【结论】突变体eb6、eb7籽粒胚乳出现严重垩白表型为Os AGPL2突变所致。本研究进一步证明了Os AGPL2在调控水稻籽粒胚乳中淀粉的合成、淀粉复合颗粒的形成及稻米理化性质的平衡中起着重要的作用。     

水稻粉质胚乳突变体ws的表型分析及基因克隆

从甲基亚硝基脲(1-Methyl-1-Nitrosourea,MNU)处理的粳稻品种滇粳优1号突变体库中,筛选到一个稳定遗传的胚乳粉质突变体ws,其籽粒的千粒重、籽粒大小、总淀粉含量、直链淀粉含量等指标均降低,淀粉在尿素溶液中的膨胀能力减弱。对成熟及发育中的胚乳淀粉结构进行观察,发现ws突变体的胚乳中产生大量小而不规则排布的单淀粉颗粒。利用F2群体中分离出的92个隐性极端个体将突变基因连锁在第8染色体近着丝粒位置,随后共用2025个极端个体将目标基因定位于95kb的区间。测序发现ws突变体中编码腺苷二磷酸葡萄糖焦磷酸化酶(Adenosine diphosphate glucose pyrophosphorylase,AGPase)小亚基S2的基因发生点突变,导致编码氨基酸的替换。基因表达分析发现,突变体胚乳中编码AGPase各亚基的相关基因表达量没有发生显著改变,而Western杂交分析显示突变体中AGPS2b的蛋白含量下降。同时,ws突变体的胚乳中AGPase活性下降为野生型的一半。研究结果表明,OsAGPS2的突变导致水稻胚乳中AGPase活性降低,从而影响了淀粉合成。     

Structural and Histochemical Characterization of Developing Rice Caryopsis

The development of pericarp, seed coat, starchy endosperm and aleurone of the rice caryopsis was investigated, histochemically and structurally, from the time of flowering to maturity. The results showed that during its growth, the maximum length of the caryopsis was attained first, followed by width and then thickness. Histochemical examination of the caryopsis showed that starch was mainly accumulated in the endosperm, but the endosperm showed no metabolic activity, while embryo and pericarp contained a few starch grains, and embryo and aleurone were strongly active. Aleuronic cells contained many aleurone grains and spherosomes, and aleurone in the dorsal region developed earlier and contained more layers of cells. Amyloplasts in endosperm contained many starch granules and were spherical at early stages but polyhedric at late stages. The protein bodies appeared later than amyloplasts, and the number of protein bodies in subaleurone was greater than those in the starchy endosperm. The white-belly portion of endosperm might be relative to the status of amyloplast development.     

水稻低淀粉粘滞性突变体的获得与特性分析

利用300 Gy [sup]60[/sup]Co-γ射线辐照早籼稻品系W8-1干种子,诱发产生了低淀粉粘滞性突变体[i]lsv-1[/i]。对其淀粉特性分析表明,突变体的表观直链淀粉含量、胶稠度和碱消值与原亲本相仿,但最高粘度、冷胶粘度、崩解值和消减值明显小于原亲本,达最高粘度时间更短,开始糊化温度更高。突变体糊化后的米粉特性和胚乳内淀粉粒的形态与原亲本显著不同。     

早籼稻垩白形成中胚乳淀粉粒发育的电镜观察

对不同垩白度早籼品种中优早3号（少垩白）和泸红早1号（多垩白）的不同温度处理下的胚乳淀粉粒进行了扫描电镜观察,结果显示胚乳腹部淀粉粒形成的发育过程明显受温度条件的影响。在灌浆初始,高温促使淀粉粒发育进程提前,淀粉粒形状呈圆球形,边缘光滑,从而造成成熟时淀粉粒间的空隙明显,结构疏松,垩白率高。这在少垩白品种中优早3号中表现得尤为显著。     

鸟苷酸激酶OsGK1对水稻种子发育至关重要

【目的】对水稻粉质皱缩突变体fse2进行表型分析及基因克隆,为阐明水稻淀粉合成机制以及胚的发育奠定基础。【方法】fse2来自粳稻品种滇粳优1号的MNU(N-甲基-N-亚硝基脲)诱变突变体库。本研究考查了突变体fse2籽粒的理化性状,利用扫描电镜和半薄切片观察了淀粉颗粒的结构;构建了fse2与N22的F₂群体,通过图位克隆及转基因互补验证确定目标基因;通过qRT-PCR以及GUS活性染色对FSE2进行组织表达分析;免疫印迹分析了突变体中淀粉合成相关基因以及线粒体基因的蛋白变化。【结果】fse2籽粒粉质皱缩,千粒重显著下降;胚乳中淀粉颗粒变小变圆,排列松散,不能形成正常的复合淀粉颗粒;突变体中总淀粉、直链淀粉含量均显著下降,脂肪含量显著上升,突变体淀粉的糊化特性发生明显改变。FSE2编码一个线粒体和质体双定位的鸟苷酸激酶(guanylate kinase),命名为OsGK1。OsGK1在各器官中组成型表达,并在花后6 d的胚乳中表达水平最高。突变体胚乳中淀粉合成相关蛋白水平显著降低,尤其是AGPS2b和PHOI。此外,突变体fse2的胚发育严重受损,导致种子纯合致死;线粒体定位的AOX积累显著增强,而野生型中几乎检测不到,表明线粒体呼吸途径受损。【结论】由于OsGK1的功能缺陷,导致水稻种子中线粒体和造粉体发育异常,进而产生了胚致死以及胚乳粉质皱缩的表型,因此OsGK1对水稻种子的发育至关重要。     

Tryptophanyl-tRNA Synthetase Gene WRS1 Regulates Rice Seed Development

【Objective】Aminoacyl-tRNA synthetases (aaRSs) are closely related to the transmission of genetic information. Besides translation, aaRSs in plants participate in gametogenesis and embryo development, early plastid development, immune signal perception and disease defense. In this study, we used a rice endosperm defective mutant to analyze the function of tryptophanyl-tRNA synthase (WRS1) during seed development, proving that WRS1 gene encodes a key factor affecting rice endosperm development. 【Method】In this study, a stably-inherited rice floury endosperm mutant (wrs1) was screened from the mutant library of indica cultivar N22 (Oryza sativa subsp. indica) induced by ethyl methane sulfonate (EMS). Map-based cloning and complementation test identified the target gene. Morphological observation and starch physicochemical properties of wrs1 mature seeds were analyzed. Semi-thin sections were prepared to observe the developing endosperm structure with a scanning electron microscope. qRT-PCR and GUS staining were performed to analyze the expression of WRS1. The expression of starch synthesis related genes in the endosperm at 12 days after flowering was determined by qRT-PCR, and these protein expression levels in mature seed were detected by immunoblotting. The free amino acid contents of mature seeds were measured with a fully automatic amino acid analyzer. 【Result】The seedlings of wrs1 were featured by obvious delay in development and finally withered and died. The floury grains isolated from the heterozygous mutant (WRS1wrs1) showed shrunken belly, decreased grain thickness and thousand-grain weight. Total starch contents, the peak viscosity and breakdown viscosity of pasting starch were lower in wrs1. The compound starch granules in developing endosperm of wrs1 were smaller and loosely arranged. WRS1 was restricted to the 183 kb region of the long arm of chromosome 12. Sequencing revealed a single base substitution in exon 6 of the tryptophanyl-tRNA synthetase gene (WRS1), resulting in a substitution of methionine. The expression of most starch synthesis-related genes in wrs1 was down-regulated, while these proteins showed different accumulation levels. The contents of proteins in wrs1 grains were decreased, while free amino acids contents were significantly increased. 【Conclusion】WRS1 encodes tryptophanyl-tRNA synthase. Mutation of this gene affects amino acid homeostasis and protein synthesis in rice endosperm, resulting in abnormal expression of the genes in starch synthesis pathway which affects starch synthesis and accumulation, and eventually lead to seed development defects.     

不同透明度水稻籽粒横断面扫描电镜分析

【目的】探索单淀粉粒断面观察方法,并阐明稻米透明度与直链淀粉含量的关系以及造成稻米透明度下降的淀粉结构基础。【方法】采用扫描电镜对经过不同处理的具有不同透明度的籼稻和粳稻胚乳横断面进行淀粉粒结构观察研究。【结果】籼稻和粳稻稻米的透明度在直链淀粉含量低于15%的软米中明显下降。通过比较不同籽粒横断面断开方式,发现直接机械断裂法无法断开单个淀粉粒,机械断裂加玻璃刀刮刻法可以断开单个淀粉粒但断面结构变形且无法定量分析。液氮脆断法可以观察到单个断裂的淀粉粒以及其中的空腔。比较籼稻和粳稻胚乳横断面淀粉粒的排列方式和单个淀粉粒内部结构,表明所有品种稻米胚乳淀粉粒均规则且紧凑排列,但所有暗胚乳稻米籽粒横断面中淀粉粒内部存在明显的空腔且糯稻淀粉粒空腔的数目和大小均明显高于暗胚乳稻米。进一步通过梯度烘干实验,证明稻米淀粉粒中的空腔数目和大小随着水分的降低而增多和变大。【结论】液氮直接脆断法是观察水稻单个淀粉粒断面的有效方法。稻米透明度与胚乳淀粉粒的排列紧密程度无关而与稻米的含水量以及单个淀粉粒中间的气腔数目和大小直接相关。此外,直链淀粉含量越低,淀粉粒中间的空腔数目越多,孔径越大。     

Effect of High Temperature at Ripening Stage on the Reserve Accumulation in Seed in Some Rice Cultivars

Abstract

The resistance to high-temperature stress and the structural appearance of the imperfect grains caused by a high temperature at the ripening stage were studied using 13 selected cultivars of rice. High temperature treatment (daily maximum temperature range, 32-40°C) given from the 4th day after heading caused the decrease in panicle weight in all of the cultivars examined. The number of empty grains in the upper and lower parts of a panicle was increased by the high temperature in 10 cultivars. Cultivars KRN, Citanduy, Belle patna and BPB were tolerant to the high-temperature treatment at the ripening stage, and cvs. Koshihikari, Sanlicun, Tainung 67, Yamada-nishiki and Lady Wright were sensitive. Light microscopic observation showed that, the whole endosperm was covered with a nucellar epidermis (NE) under both high and natural temperature (26-31°C) conditions at the first week after heading (WAH). Under high-temperature conditions the NE degenerated earlier than under natural temperature conditions. Scanning electron microscopic observation showed that, the endosperm cells of the seeds with a specific gravity (s.g.) of higher than 1.06 had large amyloplasts filled with starch granules. However, the endosperm cells of seeds with a s.g. of 1.00-1.06 had many small amyloplasts containing small single starch granules and had numerous spaces among the amyloplasts. In the endosperm cells at the dorsal side of imperfect grain, layered structures showing progressive decomposition of starch granules were observed.     

Hyperphosphorylation of cereal starch

Plant starch is naturally phosphorylated at a fraction of the C6 and the C3 hydroxyl groups during its biosynthesis in plastids. Starch phosphate esters are important in starch metabolism and they also generate specific industrial functionality. Cereal grains starch contains little starch bound phosphate compared with potato tuber starch and in order to investigate the effect of increased endosperm starch phosphate, the potato starch phosphorylating enzyme glucan water dikinase (StGWD) was overexpressed specifically in the developing barley endosperm. StGWD overexpressors showed wild-type phenotype. Transgenic cereal grains synthesized starch with higher starch bound phosphate content (7.5 (±0.67) nmol/mg) compared to control lines (0.8 (±0.05) nmol/mg) with starch granules showing altered morphology and lower melting enthalpy. Our data indicate specific action of GWD during starch biosynthesis and demonstrates the possibility for in planta production of highly phosphorylated cereal starch.     

不同透明度水稻籽粒横断面扫描电镜分析

摘 要：【目的】探索单淀粉粒断面观察方法,并阐明稻米透明度与直链淀粉含量的关系以及造成稻米透明度下降的淀粉结构基础。【方法】采用扫描电镜对经过不同处理的具有不同透明度的籼稻和粳稻胚乳横断面进行淀粉粒结构观察研究。【结果】籼稻和粳稻稻米的透明度在直链淀粉含量低于15%的软米中明显下降。通过比较不同籽粒横断面断开方式,发现直接机械断裂法无法断开单个淀粉粒,机械断裂加玻璃刀刮刻法可以断开单个淀粉粒但断面结构变形且无法定量分析。液氮脆断法可以观察到单个断裂的淀粉粒以及其中的空腔。比较籼稻和粳稻胚乳横断面淀粉粒的排列方式和单个淀粉粒内部结构,表明所有品种稻米胚乳淀粉粒均规则且紧凑排列,但所有暗胚乳稻米籽粒横断面中淀粉粒内部存在明显的空腔且糯稻淀粉粒空腔的数目和大小均明显高于暗胚乳稻米。进一步通过梯度烘干实验,证明稻米淀粉粒中的空腔数目和大小随着水分的降低而增多和变大。【结论】液氮直接脆断法是观察水稻单个淀粉粒断面的有效方法。稻米透明度与胚乳淀粉粒的排列紧密程度无关而与稻米的含水量以及单个淀粉粒中间的气腔数目和大小直接相关。此外,直链淀粉含量越低,淀粉粒中间的空腔数目越多,孔径越大。     

色氨酰-tRNA合成酶基因WRS1调控水稻种子发育

【目的】氨酰-tRNA合成酶（aminoacyl-tRNA synthetases, aaRSs）与遗传信息传递密切相关,已发现植物中aaRSs家族蛋白在维持翻译功能之余,还参与配子发生与胚发育、质体的早期发育以及免疫信号的感知与病害防御等生物学过程。本研究利用水稻胚乳发育缺陷突变体,分析水稻色氨酰-tRNA合成酶（WRS1）在胚乳发育中的作用,证明WRS1基因编码一个影响水稻胚乳发育的关键因子。【方法】本研究通过甲烷磺酸乙酯（ethyl methane sulfonate, EMS）诱变籼稻（Oryza sativa subsp. indica）品种N22,筛选到一个稳定遗传的水稻粉质胚乳突变体（wrs1）,图位克隆获得目标基因。对wrs1成熟种子进行形态学观察以及淀粉相关理化性质测定,利用细胞学切片分析wrs1发育中胚乳的结构,利用实时荧光定量PCR（quantitative real-time PCR, qRT-PCR）和GUS活性染色分析基因表达模式,通过qRT-PCR比较野生型与突变体花后12 d胚乳中淀粉合成相关基因表达情况,免疫印迹检测野生型与突变体成熟种子中淀粉合成酶蛋白积累情况,使用全自动氨基酸分析仪测定游离氨基酸含量。【结果】 wrs1突变体幼苗表现出明显的发育滞后且逐渐蔫萎死亡,从杂合突变体（WRS1wrs1）中分离到的粉质籽粒呈现明显的腹部皱缩,粒厚、千粒重下降,同时总淀粉含量下降,糊化淀粉的峰值黏度和崩解值均低于野生型。wrs1突变体发育胚乳中复合淀粉颗粒变小,排列疏松。WRS1定位于第12染色体长臂约183 kb的区间内,测序发现编码色氨酰-tRNA合成酶（tryptophanyl-tRNA synthetase, WRS）基因的第6外显子上发生单碱基替换,导致一个保守位置上的甲硫氨酸被替换。wrs1突变体中大部分淀粉合成相关基因表达量下调,且野生型与突变体间基因表达的变化与相应蛋白积累的差异存在不一致的趋势。wrs1突变体籽粒中蛋白质积累降低,而游离氨基酸含量显著升高。【结论】 WRS1编码色氨酰-tRNA合成酶,该基因突变后通过影响氨基酸稳态和蛋白质合成,造成淀粉合成相关基因异常表达从而影响淀粉的合成与积累,导致种子发育缺陷。     

胚乳外观标记与RVA谱理化指标相结合辅助改良早籼稻食用品质

对具有较低和中等表观直链淀粉含量的浙辐504和IR64的杂交后代进行观察,发现胚乳外观存在4种类型：乳白色、云雾状、透明状及各外观混合体。与胚乳外观紧密关联,表观直链淀粉含量(AAC)也相应有4种含量水平：明显低AAC变异型、浙辐504型、IR64型和介于双亲的中间型。RVA谱分析表明,不同胚乳外观的淀粉粘滞特性差异明显。透明状外观尽管AAC相仿,但个体间淀粉粘滞性分化明显,只有个别优良品系的RVA谱与优质亲本IR64相似。表明以胚乳外观标记和RVA谱理化指标辅助选择可有效控制表观直链淀粉含量和淀粉粘滞性,是改良早籼稻米品质的一条有效途径。     

糯小麦与酿酒谷物黏度特性的比较

为明确糯小麦与其他酿酒谷物糊化特性的差异,为糯小麦在白酒酿造中的应用提供参考依据,比较分析了CD糯麦-2、普通小麦、糯米、高粱和玉米籽粒的淀粉RVA黏度特性。结果表明,不同作物的糊化特性有很大的差异,高梁的峰值黏度最高,糯小麦次之,玉米最低,普通小麦比糯米高,但二者差异较小;到达峰值黏度的时间为5.2~11.2 min,其中糯米糊化最快,糯小麦与糯米接近,比普通小麦快近2 min,普通小麦与高粱相近,玉米最慢;到达峰值黏度的温度为67.2~92.2℃,其中糯小麦和糯米低,分别为70.3℃和67.2℃,普通小麦和高粱分别为84.6℃和83.1℃,玉米则高达92.2℃,糯小麦比普通小麦低约14.3℃。糯小麦配粉能改变谷物的黏度特性,对糊化温度和糊化时间的影响小于对峰值黏度的影响,从不同作物考虑,糯小麦配粉对糯米的黏度特性影响相对较小。结果显示,糯小麦像糯米一样直链淀粉含量极低,其淀粉易糊化,糊化温度低,耗能少;向其他谷物中添加糯小麦可改变其淀粉黏度特性;糯小麦具有代替其他谷物酿造新型风味白酒的潜在优势。     

同源四倍体水稻胚乳发育:糊粉层细胞壁纤维素物质发育、胚乳淀粉积累及胼胝质“套”的形成

 利用荧光显微术观察，发现同源四倍体水稻与其二倍体原种的糊粉层细胞壁纤维素物质都存在一个“充实”的过程。授粉后5～6 d，糊粉层开始分化形成，此时其细胞壁上未观察到纤维素物质；授粉后6～8 d，糊粉层细胞壁上开始积累纤维素物质；授粉后8～9 d，糊粉层细胞壁积累了大量的纤维素物质。胚乳淀粉的积累存在一个变化的过程：初生胚乳核周围可见一些淀粉体，随着胚乳游离核的增多，游离核周围淀粉体的数量逐渐减少，胚乳细胞化后，胚乳细胞内开始大量形成淀粉体。利用苯胺蓝染色连续切片荧光观察，发现同源四倍体水稻及其二倍体原种胚乳发育过程中，在珠心表皮和内珠被之间存在一层胼胝质物质，围绕着胚囊并包裹住珠心呈“套”状。这个结构的形成变化过程为：授粉后30 min在珠孔端珠心表皮细胞与内珠被之间开始积累少量的胼胝质，之后胼胝质逐渐增多并向合点端扩展延伸；授粉后1～2 d包裹着整个胚囊外的珠心而仅在维管束处断开；授粉后9～13 d，胼胝质“套”消失。该结构可能与胚和胚乳在发育期间的水分和养分的调节等有密切关系。同源四倍体水稻还存在糊粉层细胞壁发育不同步、糊粉层细胞壁结构异常以及胼胝质“套”不消失等异常现象。这些现象有可能会影响同源四倍体水稻的结实率。