摘   要水稻是我国主要的粮食作物之一。因此，水稻产量的提高一直是科学界研究的热门课题，也是普通百姓关注的焦点问题。那么究竟是什么因素会影响并且决定水稻的高产或是低产呢？目前认为，水稻的产量主要与以下几个方面有关。首先是水稻的穗数，其次是每条穗的颗粒数，最后是每个颗粒的大小。本次论文课题主要以突变体小圆粒水稻为研究对象，定位并克隆造成水稻小圆粒的基因，以及进一步研究小圆粒水稻相对于普通水稻，在蛋白表达及其他生理特性等方面的差异。89628

本实验首先从F2群体中选取20个突变表型植株，提取DNA，进行PCR扩增，凝胶电泳，根据双亲多态性不同进行筛选，多态性不同的引物即为候选引物，此时候选引物范围较大。接着选取200株本实验所研究的突变体的单株，利用事先合成的候选引物，先对该突变体进行初步定位，将SG1基因限定到染色体的一定区间内。之后，在限定区间内开发具有多态性的引物，进一步进行精细定位。最终SG1基因被限定在第5条染色体上PM446和YP320两对引物之间，物理距离约为33kb。该区间包括7个ORF，其中第四个ORF的第1212个碱基上，由胞嘧啶（C）突变为胸腺嘧啶（T），该密码子由CAG变为TAG，从而造成蛋白翻译的提前终止。定位并克隆出小圆粒突变基因后，利用该突变体为材料，通过水培，在水稻苗期研究外源添加不同浓度生长素（3-吲哚乙酸，IAA）对水稻地下部（根长）、地上部（株高）生长的影响。并通过Real-time qPCR方法检测SG1基因的表达模式。结果显示，sg1突变体相较于野生型对外源IAA的作用不敏感，且SG1基因在sg1突变体的倒一叶中表达水平比野生型低。

AbstractRice is one of the most important crops in china。 Therefore, the improvement of rice yield has been a hot topic both in the scientific research level and virtual breeding program。 Therefore, understanding of the molecular mechanism of yield is pivotal to create rice varieties。 There are three factors to determine rice yield, including of the grain size, the number of grains per panicle and the number of particles。 However, the molecular mechanism of grain size is still not clear。 In this thesis, we are mainly focus on the identification and cloning of the small round gene SG1, and the further study on the difference of sg1 with wild type on physiological characters and protein expression level。

Firstly, we selected 20 mutant plants from the F2 population crossing with sg1 and 9311, and their DNA was extracted。 The extracted DNA was then pooled together as template to do PCR amplification and gel electrophoresis with 198 pairs of polymorphic primers。 A few markers linkage with SG1 was picked up as candidate to do PCR with 200 more mutant phenotype inpiduals, then the SG1 was finally delimited to a single BAC by marker PM446 and YP320 with a physical distance of 33Kb。 In this region, there were 7 open reading frame (ORFs), and the fourth ORF, had a site mutation (Cytosine in wild type and thymine in mutant) in 1212th base after start codon ATG, which caused the premature stop code (CAG to TAG)。 To further explore the molecular mechanism of SG1 working in grain size regulation, we test whether SG1 is involved in auxin signaling pathway。 We treated both wild type and sg1 mutant with indoleacetic acid (IAA) and check the growth rate of roots and shoot。 We also detected the expression pattern of SG1 gene after IAA treatment。 The results showed that sg1 mutant was less sensitive to exogenous IAA than wild type, and the expression level of SG1 gene in sg1 mutant was lower than that of wild type。

毕业论文键词：水稻粒型； 连锁标记； 激素处理 ； 基因表达

Key words：Grain shape; linkage marker ; hormone treatment ; gene expression