Abstract: Grain shape is one of the most important influencing factor to rice grain yield. Among all of the cloned grain shape genes, GW2 is an important one controlling grain width. We obtained the sequences of the important grain shape gene GW2 using cDNA cloning strategy from rice variety TD70 and Kasalath and design its functional marker based on gene sequence difference to analyze genotype and phenotype of recombinant inbred lines(RILs) from TD70/Kasalath cross, some indica restorer lines and japonica rice cultivars in Jiangsu Province.  GW2TD70 shared 100% identity to GW2WY3 and 99.77% identity to GW2 sequence（GenBank: EF447275）and there exist a single nucleotide mutation at site 114 without changing amino acid, a single nucleotide deletion at site 316 which generate termination codon at site 346, 347 and 348,thus the expression of GW2 protein stopped in advance. The sequence of GW2Kasalath showed 99.92% identity to GW2 which is known, and there exists a single nucleotide change at site 114 without the variation in amino acid. Comparing with GW2 in TD70, the gene in Kasalath express the intact protein without advanced stop. For GW2 gene, the dCAPS marker was designed according to a base deletion of A in the 316 site of sequence. Digested by Apo I, TD70 showed 21 bp and 30 bp fragments and Kasalath showed 51 bp fragment. Among the 240 RILs, 82 contained GW2TD70 and 158 contain GW2Kasalath , there are significant differences between their phenotypic value. No GW2TD70 gene exit in 10 japonica rice cultivars from Jiangsu Province and 8 indica restorer lines. GW2 gene derived from TD70 may have regulatory effects on grain width，and we can use it to improve grain weight in rice breeding.

Key words: rice, extreme materials, GW2, sequence analysis, grain shape

摘要： 粒形是影响水稻产量的重要因子，对粒形相关基因的发掘和利用一直倍受重视。在已克隆的粒形基因中，GW2是一个控制粒宽的重要基因。通过同源克隆的方法，获得极端大粒水稻TD70和极端小粒水稻Kasalath的GW2基因cDNA片段，分析序列差异，设计功能标记，检测240个来源于TD70/Kasalath的重组自交系（RILs）和部分籼稻骨干恢复系、江苏省主栽粳稻品种的基因类型及其效应。结果表明，TD70的GW2与大粒粳稻WY3完全一致，与已知序列（GenBank: EF447275）相似性达99.77%，在碱基的第114位，T突变为C，但并不改变氨基酸性质；在第316位缺失碱基A，造成316位以后的所有碱基前移一位，氨基酸均发生变化，在碱基的第346、第347、第348位形成TAA的终止密码子，提前结束了TD70的GW2蛋白的表达。而Kasalath 的GW2序列仅在碱基的第114位，由T突变为C，但并不改变氨基酸性质；GW2Kasalath的316位没有突变，表达没有提前终止；设计的dCAPs标记，产物经内切酶Apo I酶切，TD70为21bp和30bp两个片段，而Kasalath条带为51 bp；240个RILs中含GW2TD70基因的株系有82个，含GW2Kasalath基因的株系有158个，两者在粒宽和粒重表型上存在显著差异；8个籼稻骨干恢复系和10个江苏省主栽粳稻品种中都不存在GW2TD70基因。GW2TD70基因对籽粒宽度有一定的调控作用，水稻育种中可以利用GW2TD70基因来提高籽粒粒重。

关键词: 水稻, 极端粒形； GW2基因, 序列分析, 粒形