【作者】 李宗瑾；

【导师】 何光源； 汪越胜；

【作者基本信息】 华中科技大学 ， 生物化学与分子生物学， 2008， 硕士

【摘要】 小麦低分子量谷蛋白亚基(LMW-GS)约占种子贮藏蛋白的1/3,与高分子量谷蛋白亚基(HMW-GS)通过分子间二硫键形成谷蛋白聚合体,对小麦的加工品质有重要的影响。云南小麦(T. aestivum ssp.yunnanense King,AABBDD,2n=6x=42)是我国云南省特有的小麦种质资源,具有耐寒、耐瘠、抗条锈病、抗穗发芽等优异农艺性状,以及蛋白质含量高和品质好的优异品质性状,此外它还在普通小麦的起源和分类上有重要的研究价值。LMW-GS基因编码区不含有内含子,在N-和C-末端序列高度保守。由此,我们设计一对兼并引物(P1和P2),提取云南小麦YN11的基因组DNA,进行PCR扩增反应,得到长度约为900 bp和1100 bp的两条DNA片段,克隆测序后获得3个不同的LMW-GS基因序列,LMWYN-1、LMWYN-2和LMWYN-3。LMWYN-1和LMWYN-2编码区长度分别为1056 bp和960 bp,可分别编码330和299个氨基酸残基的成熟蛋白,而LMWYN-3由于在编码区存在3个提前终止密码子,不能编码成熟的蛋白质。这3个LMW-GS基因差异主要表现在重复区,而重复单元的不同及重复单元的插入和缺失又是造成序列大小差异的主要原因。根据N-末端氨基酸序列,三者都属于LMW-m型。序列一致性分析显示,这3个序列与小麦族物种的LMW-GS氨基酸序列有较高的一致性,可以表明其为LMW-GS基因。对其进行二级结构预测,预测结果显示,LMWYN-2的β-转角含量相对较高,这说明其可能为候选的优质基因。系统进化分析表明,LMWYN-1和LMWYN-3可能是由Glu-D3位点编码的基因,而LMWYN-2可能是由Glu-B3位点编码的基因。更多还原

【Abstract】 The low-molecular-weight glutenin subunits of wheat make up one third of the seed storage proteins, LMW-GS and HMW-GS produce glutenin polymers with the intermolecular disulphide bonds, and they have great effects on wheat processing quality. Yunnan wheat(T.aestivum ssp.yunnanense King,AABBDD,2n=6x=42) is an endemic wheat germplasm in Yunnan Province and possesses many desirable characters such as good quality, high protein content, resistance to reharvest sprouting and yellow rust, tolerance to cold and infertile soil, etc. Moreover, Yunnan wheat has the potential value in the study of wheat origin and classification. LMW-GS genes have no intron inframe and are conserved in the N-terminal and C- terminal sequences. Therefore, a pair of degenerate primers was designed, and the full coding regions of LMW-GS genes were amplified from the T.aestivum ssp.yunnanense King accession YN11. Three different genes, LMWYN-1, LMWYN-2 and LMWYN-3, were identified from the 900 bp and 1100 bp amplification products. The coding regions of LMWYN-1 and LMWYN-2 were 1056 bp and 960 bp, and encoded two mature proteins with 330 and 299 amino acid residues, respectively. LMWYN-3 was a pseudogene due to that three stop codons were in its coding region. There were many differences in repetitive domain among three genes. The numbers of repeats were responsible for some variation in amino sequence of LMW-GS. According to the N-terminal sequences, they might belong to LMW-m. Through identity of the deduced amino acid sequences, three sequences were homologous of wheat LMW-GS. Prediction for secondary structure suggested that high content ofβ-turn existed in LMWYN-2, and it might have positive influences on the quality of flour. Phylogenetic analysis indicated that LMWYN-1 and LMWYN-3 could be both located in Glu-D3 locus, while LMWYN-2 could be located within Glu-B3 locus.更多还原