【目的】籽粒大小是决定水稻产量的重要农艺性状之一,开展水稻籽粒大小相关基因的克隆和功能研究对于阐述水稻产量形成的遗传调控机制具有重要意义。【方法】利用甲基磺酸乙酯诱变粳稻品种中花11,筛选获得一小粒突变体,命名为sg101(small grain 101)。通过形态学、细胞学手段调查了SG101的突变对籽粒大小、穗部主要性状及颖壳细胞数目和大小的影响,通过测定叶夹角和胚芽鞘长度分析其对外施油菜素内酯的差异响应,结合定量PCR技术分析了油菜素内酯合成途径和信号途径相关基因表达情况,并利用图位克隆的手段精细定位了水稻小粒基因SG101。【结果】与野生型相比,突变体sg101粒长和粒宽均极显著减小,从而导致千粒重极显著降低。此外,sg101还表现出结实率降低、穗长变短、二次枝梗数减少、植株变矮等。细胞学观察发现sg101的颖壳细胞大小没有改变,但细胞数目明显减少。定量PCR检测表明sg101中的细胞周期相关基因表达显著下降。另外,突变体sg101对外施油菜素内酯响应迟钝,其油菜素内酯合成途径和信号途径相关基因表达亦显著降低。【结论】遗传分析表明sg101突变体由隐性单基因控制,通过图位克隆的方法将SG101精细定位于第1染色体上,物理距离为265 kb的区间内。这为该基因的克隆及深入的功能研究奠定了基础。 【Objective】 Grain size is one of the important agronomic traits that determine rice yield. It is of great significance to carry out the cloning and function studies of rice grain size related genes to elucidate the genetic regulation mechanism of rice yield. 【Method】 A small mutant named sg101 (small grain 101) was obtained by mutagenesis of japonica rice Zhonghua 11 with methyl methanesulfonate. Morphological and cytological methods were used to investigate the effects of SG101 mutation on the grain size, the main characters of panicles and the number and size of glume cells. The differential responses of brassinolide to applied isoflavones were analyzed by measuring the angle of the leaf and the length of the coleoptile , Combined with quantitative PCR analysis of brassinosteroid synthesis and signal pathway related gene expression, and the use of map cloning means fine mapping of rice grain gene SG101. 【Result】 Compared with the wild type, the grain length and grain width of mutant sg101 significantly decreased, resulting in a significant reduction of 1000-grain weight. In addition, sg101 also showed reduced seed setting rate, shorter spike length, fewer secondary branches and shorter plants. Cytological observation found that the size of the gliacyte cells of sg101 did not change, but the number of cells was significantly reduced. Quantitative PCR detection showed that the expression of cell cycle related genes in sg101 decreased significantly. In addition, mutant sg101 had a slow response to applied brassinosteroids, and its brassinolide synthesis pathway and signal pathway-related gene expression were also significantly reduced. 【Conclusion】 Genetic analysis showed that the sg101 mutant was controlled by a recessive single gene. The SG101 was finely mapped on chromosome 1 by the map-based cloning method with a physical distance of 265 kb. This laid the foundation for the cloning and in-depth functional studies of this gene.