Effect of nitrogen fertilizer on distribution of starch granules in different regions of wheat endosperm

This study provided visual evidence of a nitrogen effect on starch granules(SGs) in wheat endosperm. Winter wheat(Titicum aestivum L.) cultivar Xumai 30 was cultured under no nitrogen(control) and 240 kg ha-1of nitrogen applied at the booting stage. The number, morphology, and size of Aand B-type SGs in subaleurone of dorsal endosperm(SDE), center of dorsal endosperm(CDE), modified aleurone(MA), subaleurone of ventral endosperm(SVE), and center of ventral endosperm(CVE) were observed under light and electron microscopes.(1) The distribution of SGs in SDE was similar to that in SVE, the distributions of SGs in CDE and CVE were similar, but the distribution of SGs in MA was different from those in the other four endosperm regions. The number of SGs in the five endosperm regions was in the order SDE > CDE > SVE > CVE > MA.(2) Nitrogen increased the number of Aand B-type SGs in SDE and SVE. Nitrogen also increased the number of B-type SGs but decreased the number of A-type SGs in CDE and CVE. Nitrogen decreased the numbers of A-type and B-type SGs in MA. The results suggest that increased N fertilizer application mainly increased the numbers of small SGs and decreased the numbers of large SGs, but that the results varied in different regions of the wheat endosperm.

Proteomics of Wheat Endosperm:a Tool to Find Genes Involved in Kernel Composition and Quality

The composition of the wheat kernel is the result of the expression of thousands of genes translated in enzymes involved in all the biochemical pathways that are needed for endosperm cell functions and also for the ac-

Characters of Cysteine Endopeptidases in Wheat Endosperm during Seed Germination and Subsequent Seedling Growth

The endopeptidases （EPs） in wheat endosperm during seed germination and subsequent seedling growth were characterized by gradient-polyacrylamide gel electrophoresis with gelatin copolymerized into the gel. Four cysteine EPs （EP1, EP2, EP3 and EP4） were detected in wheat endosperm during the 7 d growth after seed imbibition. The results also showed that the activities of all of these EPs increased continuously, and EP2 first appeared and had the highest proteolytic activity among the four EPs in this experimental process. The optimum pH and temperature of all four EPs were 4.0 and 40.0 ~C. All EPs were completely inhibited by 25 μmol/L E-64 and had no good thermal stabilities, especially EP1. In addition, these EPs had different substrate specificities to albumins, globulins, gliadins and glutenins; the main storage proteins of mature wheat endosperm. Among them, EP2 had the highest proteolytic activities on globulins, gliadins and glutenins, and might be the most important and specific EP with potential to be tightly correlated with seedling development.

Study on Plant Regeneration of Wheat Mature Embryos Under Endosperm-Supported Culture

To reveal the suitability of using mature embryos as an explant source in wheat tissue culture, mature embryos from eight common wheat cultivars （Triticum aestivum L. cv.） were cultured with or without endosperm to test their efficiency of callus induction and plant regeneration. When embryos were cultured together with endosperm （endosperm-supported culture, ES）, the percentage of callus induction was significantly lower than that when embryos were cultured in the absence of endosperm （non-endosperm-supported culture, NES）. This pattern was evident in most genotypes, regardless of whether 2 or 8 mg L^-1 2,4-D was added in the NES culture. However, in ES culture, more induced calli were differentiated into distinct green spots and they further developed into plantlets. Thus, more plants were regenerated in ES culture than in the NES treatment. Most of the eight tested genotypes showed a significant difference in callus induction rate and plantlet regeneration in both ES and NES cultures. In addition, the enzymatic activity of oxalate oxidase in the callus of ES culture condition was obviously higher than that in the callus of NES culture condition, suggesting that the activity of oxalate oxidase may be a parameter for selection of calli with potential for plantlet regeneration. These results indicate that wheat mature embryos are valuable explants for highly efficient callus induction and plant regeneration, if proper treatment and medium are used.

AFFINITY CHROMATOGRAPHIC PURIFICATION OF ACTIN FROM IMMATURE WHEAT ENDOSPERM AND PRELIMINARY STUDIES ON ITS CHARACTERISTICS

In recent investigation, we have found that there is an active intercellular movement of protoplasm in the nuceUus and endosperm tissue of the developing wheat caryopses, which can be inversely arrested by cytochalasin B, suggesting that actin may be involved in this movement. So, the detection of the existence of actin in the tissues having

Proteomic analysis reveals the differential proteins of endosperm between soft and hard wheat varieties

In this study,we revealed the differential proteins from the wheat endosperms using proteomic analysis and investigated their surface properties.The pattern of the polypeptides obtained from the Yangmai-15 and Yangmai-16 wheat varieties were compared using two-dimensional polyacrylamide gels.In addition,we compared the characteristics of the grain such as grain hardness,protein content,wet gluten,dough development time,dough stability,gliadin and glutenin contents between Yangmai-15 and Yangmai-16,and the results were significantly different.Notably,216 and 197 protein spots were separated from Yangmai-15 and Yangmai-16,respectively.The isoelectric points of the identified proteins ranged from 4 to 10 and the molecular weights of proteins varied from 10 to 100 kDa.Further,21 and 8 specific differential protein spots were identified fromthe flour of Yangmai-15 and Yangmai-16,respectively.The surface properties of identified peptides consisted of hydrophobic or hydrophilic residues,as well as randomly scattered residues.The proteomic analysis of the wheat endosperms provides a novel insight into the biochemical basis for the differences in physicochemical properties between the soft and hard wheat varieties.

Accumulation of glycolipids in wheat grain and their role in hardness during grain development

Grain hardness is an important parameter for wheat quality. To understand the role of glycolipids in the formation of grain hardness, the glycolipid contents in wholegrain wheat flour and the starch granule surfaces of oven-dried and freeze-dried hard and soft wheat grain were analyzed. Changes in endosperm structure and amyloplast membrane integrity during grain development were also examined by electron microscopy. The monogalactosyldigylcerol(MGDG) and digalactosyldigylcerol(DGDG) contents of the starch surface were significantly higher in soft wheat than in hard wheat, regardless of the drying method or developmental stage. Throughout grain development, MGDG content was significantly higher in the starch surface of freeze-dried hard wheat than in the starch surface of oven-dried hard wheat. In contrast, the MGDG content of the starch surface was significantly higher in freeze-dried soft grain at 14 and 35 days after anthesis. No significant difference was observed in puroindoline protein(PIN) accumulation in wholegrain flour from wheat that was dried using the two methods, whereas PIN accumulation on the starch surface of freeze-dried grain was lower than that on the starch surface of oven-dried grain.The gap between the amyloplast membrane and starch granules was larger in hard wheat than in soft wheat, as shown by transmission electron microscopy. For the same wheat cultivar, this gap was larger for oven-dried than for freeze-dried grain. The content of polar lipids in the starch surface was closely related to grain hardness, and the breakdown of the amyloplast membrane may determine the location of polar lipids on the starch surface.

营养胁迫对小麦幼苗生长和生理特性的影响

为了探究小麦幼苗生长潜力及其对营养胁迫的适应能力,通过沙培试验,设置了正常生长植株和种子营养物质缺失(仅去除胚乳、仅去除根系、胚乳和根系均去除)处理,考察了小麦苗期叶龄、生长速率、株高、根系、叶绿素含量(SPAD)、叶面积、干物质积累、生理特性的变化。结果显示,萌发36 h的小麦幼苗在营养缺失处理下均已具备独自存活能力。与未去除胚乳(正常植株和仅去除根系)的小麦幼苗相比,去除胚乳(仅去除胚乳以及胚乳和根系均去除)的小麦幼苗发育缓慢,需要更多时间才能达到与正常小麦相同的生长阶段,且在两叶一心时生长速率、株高、根长、SPAD、总叶面积和干重显著下降,长势明显较弱,可溶性蛋白、脯氨酸和丙二醛含量一直维持在较低的水平。与正常生长植株相比,仅去除根系的小麦幼苗能够快速适应营养胁迫,在两叶一心时生长速率、株高、根长和干重与正常植株基本一致,可溶性蛋白和脯氨酸含量显著增加,丙二醛含量显著降低。由此可见,苗期小麦种子营养物质缺失条件下幼苗生长迟缓,适应能力弱,影响小麦后期的生长和发育。

小麦胚乳发育及其养分输入的途径

观察研究了小麦胚乳细胞的发育,淀粉体的增殖变化和颖果中的输导系统。结果如下:(1)胚乳核的分裂分为有丝分裂与无丝分裂两种形式,以有丝分裂为主。分裂的速度显著受温度影响,在平均气温18℃时核分裂周期为9.2h,30℃时核的分裂周期为5.4h。小麦胚乳细胞分裂的持续时间为16d,即在籽粒鲜重达最大值的75％时分裂停止。(2)花后第3d,游离核在分裂末期产生成膜体,形成细胞壁。花后第7d,胚乳细胞中出现淀粉体,并开始积累淀粉;大小淀粉体数目在细胞间变幅很大。花后第9d,胚乳细胞中出现蛋白质体,蛋白质在粗糙内质网上形成,通过高尔基体转移,积累在液泡中。大的蛋白质体可由小的蛋白质体合并产生。(3)由腹部维管束卸出的灌浆物质需经过质外体后才能进入胚乳。

水稻和小麦胚乳发育的比较

以水稻盐粳 2 35和小麦扬麦 5号为研究材料 ,用整体解剖和树脂包埋切片等方法比较研究了这两种作物胚乳细胞分裂、分化和充实的特点 .两者发育的主要差异有 :(1)水稻胚乳囊呈香蕉形 ;小麦胚乳囊呈南瓜子形 .小麦的游离核与胚乳细胞要比水稻大 .(2 )水稻游离核的分裂以无丝分裂为主 ,而小麦游离核的分裂以有丝分裂为主 .水稻游离核及细胞的分裂速度较小麦快 .(3)水稻胚乳细胞中淀粉体约在花后第 4天出现 ,蛋白质体约在花后第 5天出现 ;小麦胚乳细胞中淀粉体约在花后第 7天出现 ,而蛋白质体约在花后第 9天出现 .(4 )水稻胚乳淀粉体中含有多个淀粉粒 ,而小麦胚乳淀粉体中仅含有一个淀粉粒 .(5 )水稻胚乳含两种蛋白质体类型 ,即PB1和PB2 ,而小麦胚乳只含一种蛋白质体 .(6 )水稻胚乳的背部有多层糊粉层细胞 ,其细胞壁上没有内突 ;而小麦腹部 (沟 )维管束的糊粉层细胞壁上有内突 。

小麦籽粒胚乳细胞增殖及物质充实动态

小麦籽粒胚乳细胞发育包括胚乳细胞的增殖和充实两个过程。胚乳细胞的增殖可用Richards方程模拟 ,增殖过程可划分为渐增期、快增期、缓增期。强势粒胚乳细胞数多于弱势粒 ,粒重亦高于弱势粒。胚乳细胞中淀粉积累动态可用方程y =(a +bx) x拟合。淀粉合成首先是蔗糖的降解 ,其合成与籽粒中蔗糖起始浓度及其降解速度密切相关 ,蔗糖起始浓度越高 ,降解越迅速 ,淀粉积累越多 ,强势粒最终淀粉含量高于弱势粒。

不同粒型小麦品种胚乳淀粉体的扫描电镜观察

对 3个不同粒型小麦品种胚乳淀粉体的大小、形状、分布和发育等特性进行了扫描电镜观察。结果表明 ,3个品种胚乳细胞淀粉体均为单粒淀粉 ,可根据淀粉体的大小分为三种类型 :Ⅰ、Ⅱ、Ⅲ型。Ⅰ型为椭球形 ,大粒淀粉 ;Ⅱ型为椭球形或橄榄球型、中粒淀粉 ;Ⅲ型为近圆球形 ,小粒淀粉。鄂恩 1号Ⅱ型淀粉体多为橄榄球型 ,明显异于其它品种。各品种颖果腹部Ⅰ、Ⅱ型淀粉体多 ,排列紧密 ;背部Ⅲ型淀粉体较多 ;中间胚乳细胞淀粉体以Ⅰ、Ⅲ型为主 ,排列疏松。颖果腹部淀粉体的发育和排列明显优于背部和中间。小粒型品种胚乳细胞淀粉体发育好 ,淀粉充实度高 ;大粒型品种相反 ,淀粉体排列疏松 ,发育差。

小麦胚乳A、B型淀粉粒理化特性研究

【目的】研究小麦胚乳A、B型淀粉粒对其理化特性的影响。【方法】利用扫描电镜对4个小麦品种籽粒发育不同时期自然断面和分离提纯的A、B型淀粉粒进行观察;用直链、支链淀粉试剂盒对籽粒不同发育时期胚乳中A、B型淀粉粒的直链、支链淀粉含量进行测定;成熟籽粒A、B型淀粉粒膨胀势依据McCormick的方法进行了测定。【结果】小麦胚乳淀粉粒形态出现规则形状和反常态,胚乳淀粉粒中直链淀粉形成早于支链淀粉,但最终积累量支链淀粉大于直链淀粉。供试的4个品种中,B型淀粉粒膨胀势均大于各自A型淀粉粒的膨胀势。【结论】小麦胚乳A型和B型淀粉粒从形态上分为常规型和反常型。成熟小麦胚乳A、B型淀粉粒中,支链淀粉的含量大于直链淀粉,且与总淀粉含量呈正相关趋势。B型淀粉粒的膨胀势大于A型淀粉粒。

小麦蛋白质含量和沉淀值的遗传研究

应用胚乳性状的遗传模型,以6×6双列设计研究了小麦蛋白质含量及沉淀值的遗传。结果表明:小麦F_2代籽粒的蛋白质含量的遗传符合加性-显性模型;沉淀值的遗传符合加性-显性-上位性模型。控制蛋白质含量和沉淀值的基因作用方式为超显性,显性作用大于加性作用。F_2群体中显性等位基因的频率与隐性等位基因的频率不等。本文还比较了二倍体模型与三倍体模型的异同,讨论了小麦蛋白质含量及沉淀值的改良与选择问题。

麦胚乳贮藏蛋白组分遗传研究进展

从本世纪 50年代至今 ,小麦及其近缘属物种的胚乳贮藏蛋白组分的遗传及生化研究已经取得长足的进步 ,并已被国外许多实验室用于小麦品质改良的实践 ,取得了一定的成绩。全面了解麦胚乳贮藏蛋白各组分的遗传及生化研究必然有助于小麦品质改良的研究。本文就麦胚乳贮藏蛋白的主要组成部分 ,即麦高分子量谷蛋白、麦醇溶蛋白、麦低分子量谷蛋白等 ,从小麦及其近缘属物种中各组分亚基编码基因的染色体定位及多态性变化、各组分亚基编码基因间的连锁关系。

小麦胚乳小淀粉粒是复粒淀粉的结构观察

为了查明小麦胚乳淀粉粒是单粒淀粉还是复粒淀粉,利用电子显微镜技术系统观察了小麦胚乳发育过程中淀粉粒的发育过程。结果表明,大淀粉粒在胚乳发育早期发生与发育,包含大淀粉粒的淀粉体通过缢缩进行增殖,每个淀粉体只包含一个大淀粉粒;小淀粉粒在胚乳发育的中、后期发生与发育,包含大淀粉粒的淀粉体被膜向细胞基质突起,出芽产生许多淀粉体,小淀粉粒在这些淀粉体内发生与发育;包含小淀粉粒的淀粉体也可以通过缢缩或被膜外突出芽产生新淀粉体,用来形成小淀粉粒;多个小淀粉粒可以同时在一个淀粉体内发生与发育;当淀粉体被淀粉粒所充满,淀粉体被膜降解消失,释放淀粉粒到细胞基质中。上述结果表明,小麦胚乳大淀粉粒为单粒淀粉,而小淀粉粒为复粒淀粉。

陕糯1号与非糯小麦西农1330胚乳发育及淀粉形态、粒径分析

目的比较分析糯小麦陕糯1号和非糯小麦西农1330胚乳发育及淀粉形态、粒径的差异,为糯性与非糯性小麦的品质改良和开发利用提供理论依据。方法选用陕糯1号(糯性)和西农1330(非糯性)2个小麦品种,取发育过程中籽粒(花后5、8、12、15、18、21、25和28 d)液氮速冻后横断,经戊二醛和锇酸固定、磷酸缓冲液漂洗、丙酮梯度脱水、Epon812胶包埋后,采用超薄切片机切成1μm厚的半薄切片,经1%甲苯胺蓝染色后采用光学显微镜观察胚乳细胞发育。提取2个小麦品种的淀粉粒,将其与成熟期籽粒横断面分别固定在样品台上,经离子溅射镀金后用扫描电镜观察成熟期胚乳结构及淀粉粒形态。采用MASTERSIZER-2000激光粒度仪分析淀粉粒粒径分布特征,每个样品重复3次,测定结果采用DPS统计软件进行数据统计分析,Sigmaplot 12.0作图。结果在小麦籽粒发育过程中,陕糯1号胚乳细胞体积大小及增大幅度均小于西农1330,发育早期,二者淀粉粒表面均能被甲苯胺蓝染色,发育中后期,陕糯1号淀粉粒仍能被染色,西农1330淀粉粒则不能被染色。与西农1330相比,陕糯1号胚乳细胞内蛋白基质较少,蛋白质与淀粉粒结合较疏松。陕糯1号B型淀粉粒形态多为不规则的多边形,西农1330B型淀粉粒大多呈圆球形,二者A型淀粉粒形态无明显差异。陕糯1号和西农1330淀粉粒粒径分布存在差异。陕糯1号淀粉粒体积分布呈四峰曲线变化,西农1330则呈双峰曲线变化,二者表面积分布均呈三峰曲线变化,数目分布均呈单峰曲线变化。陕糯1号A型(>10μm)淀粉粒体积、表面积百分比均低于西农1330,B型(<10μm)淀粉粒体积、表面积百分比均高于西农1330,二者A、B型淀粉粒数目百分比无明显差异。陕糯1号中SB型(<1μm)淀粉粒的体积、表面积、数目占总淀粉粒比例分别比西农1330低1.11%、11.60%和9.28%,LB型(1—10μm)淀粉粒的体积、表面积、数目占总淀粉粒比例分别比西农1330高8.27%、15.88%、9.27%。陕糯1号具有少量LA(>53μm)型淀粉粒,而西农1330没有。结论在小麦籽粒发育过程中,陕糯1号与西农1330的胚乳发育及淀粉形态存在明显差异。LB型淀粉粒对陕糯1号与西农1330 B型淀粉粒粒径分布影响较大。

小麦胚乳A、B型淀粉粒分离纯化方法研究

为了能够准确研究小麦籽粒胚乳中A、B型淀粉粒的形成机理、化学组分及理化特性,对前人分离提纯A、B型淀粉粒的方法进行改进,提出了适于小麦A、B型淀粉粒分离提纯的常量法和微量法。用4个不同淀粉含量类型的小麦品种籽粒对此方法进行验证,结果表明4个品种A、B型淀粉粒在常量法中的分离纯度分别达到79.46%~85.23%和90.27%~96.43%,在微量法中的分离纯度分别达到92.68%~96.70%和96.48%~99.00%。在常量法和微量法中,A型淀粉粒的分离纯度与品种淀粉含量成正相关,B型淀粉粒分离纯度与品种淀粉含量成负相关;而A、B型淀粉粒在两种方法中的分离产率与品种淀粉含量没有显著关系。

小麦内胚乳细胞及其淀粉体的发育

为了探明小麦内胚乳细胞发育和淀粉体生长的规律,以不同发育天数的小麦颖果为材料,利用树脂半薄切片和胚乳细胞分离等方法研究了内胚乳细胞及其淀粉体的形态、数目和生长过程。结果如下:(1)小麦内胚乳细胞呈不规则的多面体形态,内含大、小两种淀粉体,大淀粉体呈鹅卵石形,小淀粉体呈圆球形;(2)内胚乳细胞的生长呈"S"型曲线,花后16～24d是细胞生长最快的时期;(3)大淀粉体的增殖和生长主要在花后4～16d进行,小淀粉体在花后16d大量出现并快速增殖,至胚乳发育后期小淀粉体数量占内胚乳细胞淀粉体总量的90%以上;(4)内胚乳细胞核在颖果发育中、后期发生衰亡,淀粉体在核衰亡过程中仍然能增殖和生长。

小麦胚乳传递细胞发育的结构观察

为从细胞学方面了解小麦产量和品质的形成机制,以扬麦5号为材料,利用光镜和透射电镜观察了小麦颖果发育过程中胚乳传递细胞的结构变化,并探讨了胚乳传递细胞的生理功能。结果表明：（1）胚乳传递细胞是胚乳发育过程中最早分化的细胞类型,它们发生在紧邻胚乳腔的胚乳表层,由位于外侧1~2层糊粉层传递细胞和位于内侧1~2层内胚乳传递细胞构成;（2）颖果发育成熟时,内胚乳传递细胞核衰亡,糊粉层传递细胞核依然完整;（3）胚乳传递细胞发育呈明显的极性,且具时空性;（4）糊粉层传递细胞胞质较浓,富含粗面内质网、线粒体、高尔基体和脂质体;质膜皱褶,在局部区域外翻,形成众多的原生质管;（5）内胚乳传递细胞胞质较稀,液泡化程度较高,富含淀粉体;（6）胚乳传递细胞未加厚以及未形成壁内突的壁区域分布有大量的胞间连丝;（7）胚乳传递细胞中线粒体呈极性分布,即质膜附近线粒体的密度较大。根据胚乳传递细胞的结构特点推测,经胚乳传递细胞的养分输送既可通过质外体途径又可通过共质体途径来完成。