Six subspecies of hexaploid wheat (Triticum aestivum) have been identified, but the origin of Indian dwarf wheat (Triticum sphaerococcum), the only subspecies with round grains, is currently unknown. Here, we isolated the grain-shape gene Tasg-D1 in T. sphaerococcum via positional cloning. Tasg-D1 encodes a Ser/Thr protein kinase glycogen synthase kinase3 (STKc_GSK3) that negatively regulates brassinosteroid signaling. Expression of TaSG-D1 and the mutant form Tasg-D1 in Arabidopsis (Arabidopsis thaliana) suggested that a single amino acid substitution in the Thr-283-Arg-284-Glu-285-Glu-286 domain of TaSG-D1 enhances protein stability in response to brassinosteroids, likely leading to formation of round grains in wheat. This gain-of-function mutation has pleiotropic effects on plant architecture and exhibits incomplete dominance. Haplotype analysis of 898 wheat accessions indicated that the origin of T. sphaerococcum in ancient India involved at least two independent mutations of TaSG-D1. Our results demonstrate that modest genetic changes in a single gene can induce dramatic phenotypic changes.

普通小麦的六个亚种（小麦 小麦）已经确定，但印度矮小麦的起源（小麦sphaerococcum），与圆形颗粒唯一的亚种，目前尚不得而知。在这里，我们在T中分离出了粒状基因Tasg-D1。球菌通过定位克隆。Tasg-D1编码一个Ser / Thr蛋白激酶糖原合酶激酶3（STKc_GSK3），它负调控油菜素类固醇信号传导。的表达TaSG-D1和突变形式Tasg-D1（在拟南芥拟南芥）暗示TaSG-D1的Thr-283-Arg-284-Glu-285-Glu-286结构域中的单个氨基酸取代增强了对油菜素类固醇的响应的蛋白质稳定性，可能导致小麦中形成圆形颗粒。这种功能获得的突变对植物的结构具有多效性，并表现出不完全的优势。对898个小麦品种的单倍型分析表明T的起源。sphaerococcum在古印度参与的至少两个独立的突变TaSG-D1。我们的结果表明，单个基因中的适度遗传变化可以诱导剧烈的表型变化。