【作者】 王芳；

【导师】 王宪泽；

【作者基本信息】 山东农业大学 ， 生物化学及分子生物学， 2004， 硕士

【摘要】 小麦胚乳直链淀粉含量对小麦面粉的品质和用途起着十分重要的作用。过去人们对小麦淀粉品质的研究主要集中在化学分析及生化水平上,对直链淀粉含量与合成相关酶基因的关系及遗传多样性研究较少。 蜡质基因(Wx)编码的颗粒结合型淀粉合成酶(GBSS, E. C. 2. 4. 1.21),也叫 Wx 蛋白,主要负责直链淀粉的合成(Chao,1989)。普通小麦(AABBDD,Triticum aestivum L.)有 3 个 Wx 蛋白亚基,把控制 3 个Wx 位点的基因分别命名为 Wx-A1,Wx-B1 和 Wx-D1,研究证明它们分别位于 7A、4A 和 7D 染色体上。已发现小麦胚乳中直链淀粉和支链淀粉的含量与这 3 个基因的表达有关,这组基因中有一个缺失时,即会导致淀粉合成酶活性下降,直链淀粉含量降低和支链淀粉含量增加(Clarka,1991;彭佶松,1997),从而改变小麦的淀粉构成、面粉品质和食品加工品质(Miura,1994)。 本研究选用山东省推广种植的 32 个冬小麦品种,首先对蜡质基因(Wx-A1,Wx-D1)3’端的一个简单重复序列(SSR)(AT(AT)nAT),在 32 个小麦品种中的多态性及其与直链淀粉含量的关系进行了研究。 并对 20个小麦品种蜡质基因(Wx-B1)5’端第四个内含子附近的多态性进行了分析,探讨了其与直链淀粉含量之间的关系,研究结果如下:1. 32 个小麦品种中均存在 Wx-A1a 和 Wx-D1a 基因,扩增片段中均出现 两条带,一条 204bp(Wx-D1a)位于 7DS 染色体上,另一条 225-346bp (Wx-A1a)位于 7AS 染色体上, 较长的片段显示了长度多态性。 1<WP=7>小麦 Wx 基因的遗传多样性研究2. 直链淀粉含量与 7AS 上 SSR 多态性高度相关,直链淀粉含量高的小麦 品种扩增的片段较长;直链淀粉含量低的小麦品种扩增的片段较短, 不同 SSR 基因型品种间直链淀粉含量差异显著。3. 对 20 个小麦品种 Wx-B1 研究发现, 扩增的 5’端近第四个内含子区域的 片段经 BamHI 酶切后出现了多态性,且酶切后的片段多态性与直链 淀粉含量高度相关。4. 直链淀粉含量在 22.5%-26.5%之间的小麦品种不能被 BamHI 酶切,而直链淀粉含量在 30%以上的小麦品种能被 BamHI 酶切。因此,该PCR-BamHI 分子标记可用于选育中等直链淀粉含量的小麦品种,改良小麦品质。5. 建立了以 PCR 为基础的小麦直链淀粉含量的分子标记辅助选择体系(MAS)。更多还原

【Abstract】 Wheat endosperm amylose content plays an important role in wheat flourquality and uses. In the past, the studies on wheat starch quality were mainlyconcentrated on chemistry analysis and biochemisty level, yet the correlationbetween amylose content and corresponding gene for synthesis and geneticdiversity were studied little. The waxy gene(abbreviated as Wx) encodes the granule bound starchsynthase(GBSS, EC. 3. 4. 1.11), which is also called the Wx protein,responsible for the synthesis of amylose in wheat. The common wheat hasthree different Wx proteins, and the sites of three Wx genes are named Wx-A1,Wx-B1, and Wx-D1, which has been locate on chromosomes 7A, 4A and 7D,respectively. It has been reported that amylose content and amylopectincontent are related to the expression of these three Wx genes. Lack of one ofthe three Wx genes will result in the decrease of synthase activity, which madethe amylose content decrease and the amylopectin content increase, and thestarch compontent, flour quality and food processing quality change. 32 wheat cultivars of Shangdong were used in this experiment. First, apolymorphic SSR of Wx in 3’end was studied, and the correlation betweenpolymorphic SSR and amylose content was also studied. Second, thepolymorphism of Wx-B1 genes near 4th intron in 5’end in 20 wheat cultivarswas studied, and their relationship to amylose content was discussed. Theresults are as follows:1. The result indicated that both Wx-A1a and Wx-D1a were present in all 32 cultivars. Two fragments were found in all cultivars by polymerase chain 3<WP=9>小麦 Wx 基因的遗传多样性研究 reaction amplification using primers. One fragment of PCR was 204bp, the expected size fragment, which had been located on chromosome 7DS, and the other fragment was 225-346bp, which had been located on chromosome 7AS, and showed length polymorphism.2. The analysis showed that the amylose level was highly correlated to the length of the fragment of polymorphic SSR. The length of fragment amplified was longer in cultivars of high amylose content, while the length of fragment amplified was shorter in cultivars of low amylose content. Amylose content among the various SSR genotypes was statistically significantly different as analyzed using genotypes of the SSR motifs.3. The fragment amplified near 4th intron region appeared polymorphic characteristic with BamHI digestion in 20 wheat cultivars,and the polymorphism of fragment is highly related to amylose content.4. The fragment in cultivars of amylose content about 22.5%-26.5% cann’t been digested by BamHI, while the others of amylose content beyond 30% can be digested. PCR-BamHI molecular marker can be used to select wheat cultivars of intermediate amylose content, and improve wheat quality.5. A molecular marker-assisted selection (MAS) system based on PCR was established.更多还原