State Key Laboratory of Crop Stress Biology in Arid Areas and College of Agronomy, Northwest A&F University, Yangling, 712100 Shaanxi, People's Republic of China.
Theor Appl Genet. 2012 Sep;125(5):1057-68. doi: 10.1007/s00122-012-1895-6. Epub 2012 May 29.
TaGW2, an orthologous gene of rice OsGW2, has been associated with kernel width and weight of bread wheat (Triticum aestivum). Difference in TaGW2 coding sequence was not found among different wheat varieties in previous researches. In this study, we found eight exons and seven introns in TaGW2 with a full-length cDNA sequence of 1,275 bp, which contains a conserved function domain and seven splice sites that shared homology with rice OsGW2. A single T-base insertion in the eighth exon of TaGW2 on chromosome 6A was detected in a large-kernel wheat variety, Lankaodali. This insertion mutation reduces the coding protein sequence from normal 424 amino acids (47.2 kDa) to 328 amino acids (37.1 kDa) by truncating 96 amino acids. The result was validated by identifying histidine-tagged TaGW2 proteins encoded by both alleles of the mutant and the wild types in SDS-PAGE. Allele-specific PCR markers were developed based on the single nucleotide polymorphism (SNP) site. The SNP markers were genotyped for an F(2) segregation population from the cross of Lankaodali × Chinese Spring. Seed traits of F(2:3) families were evaluated in three different environments. The association analysis indicated that F(2:3) families with the mutated TaGW2 allele significantly increased kernel width (KW) and thousand-kernel weight (TKW), and slightly improved kernel length (KL). Using the SNP markers, another two varieties harbored the mutated TaGW2 allele were successfully identified from 22 additional wheat varieties, and they both have large KW and TKW. Cloning and sequencing of the gene further confirmed the functions of the mutated allele of TaGW2 in the two large kernel varieties. The results suggested that TaGW2 may negatively regulate kernel size variation, which shares the same function as OsGW2 in rice. The successful development of SNP markers provides a useful tool for improving kernel yield in wheat.
TaGW2 是水稻 OsGW2 的同源基因，与小麦（Triticum aestivum）的粒宽和粒重有关。在以前的研究中，不同小麦品种之间没有发现 TaGW2 编码序列的差异。在本研究中，我们发现 TaGW2 有 8 个外显子和 7 个内含子，全长 cDNA 序列为 1275bp，包含一个保守功能域和 7 个与水稻 OsGW2 同源的剪接位点。在一个大粒小麦品种兰卡道力中，在第 6A 染色体上 TaGW2 的第 8 外显子中发现了单个 T 碱基插入。该插入突变使编码蛋白序列从正常的 424 个氨基酸（47.2kDa）缩短至 328 个氨基酸（37.1kDa），截短了 96 个氨基酸。通过 SDS-PAGE 鉴定突变型和野生型 TaGW2 蛋白的组氨酸标记，验证了这一结果。基于单核苷酸多态性（SNP）位点开发了等位基因特异性 PCR 标记。在兰卡道力×中国春杂交的 F2 分离群体中，对 SNP 标记进行了基因型分析。在三个不同的环境中评估了 F2:3 家系的种子性状。关联分析表明，携带突变 TaGW2 等位基因的 F2:3 家系显著增加了粒宽（KW）和千粒重（TKW），略微提高了粒长（KL）。利用 SNP 标记，从 22 个额外的小麦品种中成功鉴定出另外两个含有突变 TaGW2 等位基因的品种，它们的 KW 和 TKW 都很大。对基因的克隆和测序进一步证实了 TaGW2 突变等位基因在两个大粒品种中的功能。结果表明，TaGW2 可能负调控粒大小变异，与水稻中的 OsGW2 具有相同的功能。SNP 标记的成功开发为提高小麦粒产量提供了有用的工具。
