Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), Beijing, China.
Crop Genomics and Bioinformatics Center and National Key Lab of Crop Genetics and Germplasm Enhancement, College of Agricultural Sciences, Nanjing Agricultural University, Weigang, Nanjing, Jiangsu, China.
J Exp Bot. 2019 Mar 11;70(5):1497-1511. doi: 10.1093/jxb/erz032.
BRITTLE1 (BT1), responsible for unidirectional transmembrane transport of ADP-glucose, plays a pivotal role in starch synthesis of cereal grain. In this study, we isolated three TaBT1 homoeologous genes located on chromosomes 6A, 6B, and 6D in common wheat. TaBT1 was mainly expressed in developing grains, and knockdown of TaBT1 in common wheat produced a decrease in grain size, thousand kernel weight (TKW), and grain total starch content. High diversity was detected at the TaBT1-6B locus, with 24 polymorphic sites forming three haplotypes (Hap1, Hap2, and Hap3). Association analysis revealed that Hap1 and Hap2 were preferred haplotypes in modern breeding, for their significant correlations with higher TKW. Furthermore, β-glucuronidase (GUS) staining and enzyme activity assays in developing grains of transgenic rice with exogenous promoters indicated that the promoters of Hap1 and Hap2 showed stronger driving activity than that of Hap3. Evolutionary analysis revealed that BT1 underwent strong selection during wheat polyploidization. In addition, the frequency distribution of TaBT1-6B haplotypes revealed that Hap1 and Hap2 were preferred in global modern wheat cultivars. Our findings suggest that TaBT1 has an important effect on starch synthesis and TKW, and provide two valuable molecular markers for marker assisted selection (MAS) in wheat high-yield breeding.
BRITTLE1（BT1），负责 ADP-葡萄糖的单向跨膜运输，在谷物淀粉合成中起关键作用。本研究在普通小麦中分离到三个 TaBT1 同源基因，分别位于染色体 6A、6B 和 6D 上。TaBT1 主要在发育籽粒中表达，敲低 TaBT1 会导致小麦籽粒变小、千粒重（TKW）降低和籽粒总淀粉含量减少。在 TaBT1-6B 位点检测到高度多样性，有 24 个多态性位点形成 3 种单倍型（Hap1、Hap2 和 Hap3）。关联分析表明，Hap1 和 Hap2 是现代育种中更受欢迎的单倍型，因为它们与更高的 TKW 显著相关。此外，转 TaBT1-6B 基因水稻外源启动子的 GUS 染色和酶活性分析表明，Hap1 和 Hap2 的启动子比 Hap3 具有更强的驱动活性。进化分析表明，BT1 在小麦多倍化过程中经历了强烈的选择。此外，TaBT1-6B 单倍型的频率分布表明，Hap1 和 Hap2 在全球现代小麦品种中更受欢迎。本研究结果表明 TaBT1 对淀粉合成和 TKW 有重要影响，为小麦高产育种中的标记辅助选择（MAS）提供了两个有价值的分子标记。
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