小麦胚乳Wx蛋白缺失对淀粉含量和淀粉特性的影响

为给面条小麦亲本材料的筛选提供可靠依据，用SDS-PAGE和STS-PCR结合的方法鉴定了24个品种的Wx蛋白亚基组成，测定了这些品种的淀粉含量、膨胀势和RVA参数。结果表明，与正常材料相比，Wx蛋白亚基缺失材料的胚乳中直链淀粉含量减少，支链淀粉和总淀粉含量变化不明显，Wx蛋白亚基缺失的数目越多，直链淀粉含量减少得就越多，糯麦的直链淀粉含量最少。在本研究参试材料特定遗传背景干扰的情况下，在Wx蛋白的三个亚基中Wx-A1蛋白亚基对直链淀粉含量影响最大。Wx蛋白亚基的缺失还使面粉的膨胀势、RVA参数的高峰粘度、崩解值增大，峰值时间延长，而使最终粘度、回生值和糊化温度降低，Wx蛋白亚基缺失的数目越多，这些特性变化的幅度越大。在缺失单个亚基的情况下，Wx-B1亚基的缺失使小麦粉的淀粉特性表现最好。相关分析表明，直链淀粉合成数量的减少是导致上述淀粉特性发生变化的主要原因。     

缺失不同Wx蛋白对普通小麦直链淀粉含量及淀粉特性的影响

为了明确普通小麦缺失不同W x蛋白对直链淀粉含量的影响以及部分糯小麦品系的淀粉特性,采用单向改良SDS-PAGE方法对1个非糯×糯杂交组合F2分离群体的196个单籽粒进行了W x蛋白筛选,测定了这批籽粒的直链淀粉含量,同时测定了1个部分糯小麦品系(缺失W x-B 1和W x-D 1)和2个正常型小麦品系粗面粉的直链淀粉含量、膨胀势和RVA粘度。结果表明,缺失1对W x蛋白的直链淀粉含量比正常型降低3.29~7.15个百分点,缺失2对W x蛋白的比正常型降低9.45~13.82个百分点,缺失3对W x蛋白的直链淀粉含量几乎为0;缺失W x-B 1和W x-D 1的部分糯小麦品系粗面粉的直链淀粉含量比正常型降低5.62~7.49个百分点,膨胀势则增加4.51~4.72,RVA高峰粘度显著高于正常型。     

硬粒小麦若干淀粉性状研究

为了解硬粒小麦品种不同磨粉样品和不同类型间的淀粉品质特性,测定了2个硬粒小麦品种4种不同磨粉样品的膨胀势和5个不同类型品种的膨胀势和直链淀粉含量。结果表明,2个硬粒小麦品种不同磨粉样品的膨胀势均以淀粉最高;缺失4A型和7A型的硬粒小麦品种具有膨胀势高、直链淀粉含量低的特性。文中还对我国硬粒小麦品质改良作了讨论。     

缺失不同Wx蛋白对小麦籽粒直链淀粉合成及淀粉特性的影响

以缺失不同Wx蛋白小麦为试验材料,研究缺失不同Wx蛋白对小麦籽粒直链淀粉合成及淀粉特性的影响。试验结果表明,缺失不同Wx蛋白对小麦籽粒直链淀粉含量、积累量和积累速率、束缚态淀粉合成酶基因（GBSSI）基因相对表达量以及束缚态淀粉合成酶（GBSS）活性的影响顺序表现为：缺ABD型>缺AB型>缺B型>缺D型>缺A型>正常型;对淀粉最终粘度、反弹值以及糊化温度影响的表现顺序与其一致;对淀粉峰值粘度、低谷粘度、稀懈值以及膨胀势影响的表现顺序与此相反。相关分析表明,直链淀粉积累速率峰值、GBSSI相对表达量最大值以及GBSS活性峰值三者之间相互呈极显著正相关。说明GBSSI基因可能通过编码GBSS酶,从而控制小麦籽粒中直链淀粉的合成。     

颗粒结合型淀粉合成酶研究进展

本文综述了小麦胚乳中合成直链淀粉的关键酶——颗粒结合型淀粉合成酶(GBSS)的研究进展，展望了GBSS的研究前景。小麦中的GBSS基因在种子中特异表达；控制3个Waxy，位点的基因Wx—A1、Wx—B1和Wx—D1，分别位于7AS、4AL和7DS上；六倍体小麦和二倍体小麦中3个GBSS的DNA序列从起始密码子到终止密码子，Wx—A1为2781bp，Wx-B1为2794bp，Wx—D1为2862bp。基因的完全编码区含有11个外显子和10个内含子，在核苷酸序列上三个糯基因彼此之间有惊人的同源性；研究表明，直链淀粉含量和淀粉糊化特性受Wx—B1的影响最大，其次是Wx-D1缺失蛋白，Wx-A1缺失蛋白的影响最小。GBSS的鉴定技术包括I2—KI染色、电泳和分子标记技术鉴定。     

糯性普通小麦的产生及其淀粉特性研究

以江苏白火麦（缺失Wx-Dl)和关东107（缺失Wx-Al和Wx-Bl）为亲本配制杂交组合，采用花粉和籽粒剖面染色、蛋白质电泳进行筛选和鉴定，人工创造得到自然界不存在的糯性小麦，并对其直链淀粉含量及淀粉品质性状进行研究。结果表明，所得到的两个糯性小麦吕系直链淀粉含量很低（小于1％），其糊化特性、膨胀势特性亦与普通小麦品种不同；RVA高峰粘度明显低于其亲本，其高峰粘度出现较快，而且反弹值不明显；其淀粉膨胀能力远大于亲本。     

青海高原春小麦糯性新品系的筛选及其直链淀粉含量

为了培育适合青海高原种植的春小麦糯性新品系,利用DNA分子标记技术检测了80株青春533×糯麦1号F2代材料的Wx基因缺失情况,同时测定了不同Wx基因缺失类型F2代材料的小麦籽粒直链淀粉含量。结果表明,在80株F2代分离群体材料中,单缺失WxA1或WxB1或WxD1基因的材料分别为8份、11份、9份;同时缺失WxA1和WxD1基因的材料为10份,同时缺失WxB1和WxD1基因的材料为12份,同时缺失WxA1和WxB1基因的材料为9份;WxA1、WxB1和WxD1基因全部缺失的材料为8份。Wx基因的缺失数量与直链淀粉含量的高低有密切关系,缺失1个Wx基因（部分糯小麦）,直链淀粉含量比对照（青春533）降低5.28%~11.35%;缺失2个Wx基因（部分糯小麦）,直链淀粉含量比对照降低10.73%~19.81%;缺失3个基因（糯小麦）的直链淀粉含量为0.97%,比对照降低30.53%。高原春小麦与糯性小麦杂交的F2代直链淀粉含量下降幅度要比前人所研究的材料下降幅度大,并且WxB1单缺失引起直链淀粉含量下降（11.35%）比WxA1和WxD1双缺失所引起的下降幅度要大（10.73%）。     

Wx-1基因变异和优质HMW-GS组合对中筋小麦品质的影响

高分子量谷蛋白亚基(HMW-GS)和Wx蛋白是两个影响小麦理化品质和制成品品质的重要因素。为研究HMW-GS和Wx基因变异对小麦理化品质、面条感官评分和质构特性的影响,以镇麦9号和扬糯麦1号为亲本的2个高代系为试验材料,研究了优质HMW-GS 5+10及Wx基因缺失对小麦理化品质及面条加工品质的效应。结果表明,品系1与品系2的湿面筋含量和SDS沉淀值与镇麦9号相近,但显著好于扬糯麦1号。相较于镇麦9号,品系1与品系2的直链淀粉含量分别降低了1.5%和2.5%,其峰值黏度和稀懈值均显著高于镇麦9号,膨胀势也高于镇麦9号。5+10亚基显著提高了面条质构参数中的硬度和咀嚼性,而Wx基因缺失显著提高了面条的软硬度评分和光滑性评分。综合来看,具有5+10亚基和 Wx-D1缺失型的品系2具有较高的SDS沉淀值、面团形成时间和稳定时间、较低的直链淀粉含量、较高的峰值黏度、稀懈值和膨胀势,蛋白质和淀粉综合品质表现较好。品系2面条总评分最高,显著高于镇麦9号和扬糯麦1号,其主要体现在适中的面条软硬度和较好的光滑性。推测Wx基因缺失和优质HMW-GS聚合可显著提高小麦淀粉品质和蛋白质品质,有效改善面条的蒸煮品质和感官评分。     

小麦Wx蛋白及主要淀粉性状与面条品质的关系

为了研究小麦Wx蛋白及淀粉主要性状与面条品质的关系，对26个小麦品种的Wx蛋白含量、直链淀粉含量、峰值粘度、膨胀势进行了测定，并探讨了其与面条品质的关系。结果表明．三种Wx蛋白亚基的含量与面条品质均呈显著负相关．相关系数分别为-0．598、-0．446和-0．451；直链淀粉含量与面条品质呈显著负相关，相关系数为-0．711；峰值粘度和膨胀势与面条品质呈显著正相关，相关系数分别为0．614和0．601。表明三种Wx蛋白亚基及直链淀粉含量、峰值粘度、膨胀势均与面条品质有密切关系，呈显著相关（正向或负向）。     

扬麦系列品种的淀粉糊化特性及Wx蛋白缺失分析

为了明确扬麦系列品种(系)的淀粉品质特点,为生产应用和淀粉品质的改良提供依据,测定了扬麦系列品种(系)及国内部分其他小麦品种(系)的RVA参数,并分析了它们的Wx蛋白缺失情况及其对RVA参数的影响.结果表明,扬麦系列品种(系)的峰值粘度和稀懈值极显著高于供试的北方小麦;低谷粘度和最终粘度显著高于北方小麦和南方小麦;反弹值显著高于南方小麦.扬麦系列品种(系)的Wx-B1缺失比例较高,为18.18%.Wx-B1缺失的扬麦系列品种的峰值粘度和稀懈值显著高于不缺失Wx-B1的扬麦系列品种, 而其它RVA参数差异不显著,但部分Wx-B1不缺失的扬麦系列品种(系)也具有较好的淀粉糊化品质.     

利用Wx基因的分子标记筛选部分糯小麦的研究

为了筛选出更多用于培育优质面条小麦的Wx基因缺失材料,用分子标记技术对260份中国核心小麦种质资源进行了分析,并用SDS-PAGE进行了验证.筛选出缺失Wx-A1蛋白亚基的品种2份,缺失Wx-B1蛋白亚基的品种14份,得到1份不同于"白火麦"的Wx-D1蛋白亚基缺失的地方品种"秃芒麦".对它们的地区分布分析发现,长江以北各麦区的小麦品种Wx基因缺失多于长江以南各麦区,且分布更为集中.对收集的20对Wx基因的分子标记引物进行了筛选,并对PCR扩增条件和产物分析条件进行优化,得到了3对可以在相同条件下对Wx基因进行筛选的引物,且能用同一电泳条件对产物进行分析,提高了分析效率.     

Functionality of chemically modified wild-type,partial waxy and waxy starches from tetraploid wheats

Partial waxy (reduced-amylose) and fully waxy (amylose-free) tetraploid durum wheats (Triticum turgidum L. var durum) were developed by introgression of null alleles at the Wx-A1 and Wx-B1 loci from common hexaploid wheat (Triticum aestivum L.). Purified starches were obtained from each genotype, and chemically modified by: 1) cross-linking with phosphorus oxychloride, 2) substitution with propylene oxide, and 3) sequential cross-linking with phosphorus oxychloride followed by substitution with propylene oxide. Functional properties were compared to blends of waxy and wild-type durum starches of known amylose contents. Significant differences in functionality were observed amongst the genotypes and blends after each modification. Waxy (0% amylose) and wild-type (30% amylose) typically were at the extremes of the observed ranges of functional properties. In general, the functional properties of the chemically modified starches were dependent upon amylose content. Starches from Wx-B1 null lines (24% amylose), were an exception. After substitution, such starches had the significantly highest value for RVA final viscosity, and generally performed in a manner similar to starch blends of 12–18% amylose.     

Effects of two novel Wx-A1 alleles of common wheat (Triticum aestivum L.) on amylose and starch properties

Common wheat (Triticum aestivum L.) has three Wx proteins (Wx-A1, Wx-B1, and Wx-D1), which are granule-bound starch synthases I and are responsible for the amylose synthesis of flour starch. The effects of two novel Wx-A1 proteins identified by gel electrophoresis on amylose content and starch properties were analyzed. The variant Wx-A1 protein coded by the Wx-A1i allele was present in smaller amounts and produced less amylose (7.3%) compared to standard lines with the Wx-A1a allele (21.5%). Wx-A1i generated altered starch properties; greater swelling power (SP), glucoamylase digestibility, starch paste clarity, and gelatinization enthalpy in differential scanning calorimetry. The starch from Wx-A1i also showed an altered pasting profile on a Rapid Visco-Analyzer, greater peak viscosity, smaller final viscosity, and lower pasting temperature. The Wx-A1i allele is a novel genetic resource for reducing amylose content in wheat. The other Wx-A1 protein coded by the Wx-A1j allele showed a more basic isoelectric point compared to Wx-A1a on an electrophoretic gel. The amylose content of Wx-A1j did not differ from standard Wx-A1a. Starch SP, paste clarity, and glucoamylase digestibility also suggested that Wx-A1j produced amylose as much as Wx-A1a.     

Molecular characterization of two novel null waxy alleles in Mexican bread wheat landraces

Starch is composed of two glucose polymers: amylose, formed by long linear chains, and amylopectin, which is larger and highly branched. The ratio between the two polymers (usually 22–35% amylose, 68–75% amylopectin) affects the starch properties, thereby determining different aspects of wheat quality. Waxy protein, which is the sole enzyme responsible for amylose synthesis, showed polymorphism in a collection of one hundred and three Mexican landraces, including null alleles at Wx-A1 and Wx-B1 loci, respectively. Molecular characterization of these alleles showed that the null Wx-A1 allele presented in only one accession was novel (Wx-A1o) and involved a deletion spanning the three and a half last exons of the gene. Some of the accessions lacking the Wx-B1 protein contained the common allele Wx-B1b (12.6%) (deletion of approximately 67 kb), while four others (3.8%) possessed the novel Wx-B1l, characterized by the deletion of one cytosine in the second exon of the gene and leading to a change in the ORF. This novel allele is particularly interesting because the absence of the Wx-B1 protein in this case was not associated with the lack of the other genes included in the approximately 67 kb region lost with the common null allele Wx-B1b.     

小麦Wx-A1和Wx-B1亚基的生化与分子标记检测

为了解小麦品种(系)Wx亚基的缺失类型,为品质育种提供依据,利用SDS-PAGE和STS分子标记技术对99份国内外小麦品种(系)Wx-A1和Wx-B1亚基的缺失型进行检测.结果表明,供试小麦品种(系)中Wx-B1亚基缺失的有19份,未检测出Wx-A1亚基缺失材料.STS标记结果中,Wx-7A位点的显性标记引物在野生型中扩增出一条1 172 bp的特异带,即Wx-A1a基因出现;Wx-7A位点的共显性标记引物在野生型中扩增出一条593 bp的特异带,在缺失类型中扩增出一条574 bp的特异带.Wx-4A位点的显性标记引物在野生型中扩增出一条425 bp的特异带,即Wx-B1a亚基出现,而在缺失该亚基的突变材料中没有扩增出该特异带.     

Effect of the three waxy null alleles on enzymes associated to wheat starch granules using proteomic approach

In bread wheat (Triticum aestivum L.), waxy genes are present at three loci (Wx-A1, Wx-B1 and Wx-D1) and are responsible for amylose synthesis in the grain. Near isogenic lines (NILs) of the agronomic cultivar Tremie with either one, two or three waxy null alleles were used to study the genome response to these null alleles through proteomic analysis of starch granule associated proteins of mature grain. Among the 352 spots that were revealed, 86 varied significantly between NILs. The main differences were observed for the granule bound starch synthase (GBSS), product of the waxy genes. A strong relation (R² = 0.94) between the amount of GBSS per gram of starch granule and the amylose quantity in the grain was revealed through quantification of the GBSS in each NIL. The analysis of GBSS quantity for each NIL invalidated the additive hypothesis for the expression of this enzyme in (Wx-A1a Wx-D1a Wx-B1b) (Wx-D1a Wx-B1a Wx-A1b) and the normal form of Tremie. In addition, four proteins identified as inactive GBSS were increased (+144.9%) in the triple null isogenic form compared to the normal form of Tremie. The quantitative variations of the proteins present in starch granules support the idea of regulatory mechanisms between genomes.