Six subspecies of hexaploid wheat (Triticum spp.) have been identified, but the origin of Indian dwarf wheat (Triticum sphaerococcum Perc.), the only subspecies with round grains, is currently unknown. Here, we isolated the grain-shape gene Tasg-D1 in T. sphaerococcum Perc. via positional cloning. Tasg-D1 encodes a serine/threonine protein kinase glycogen synthase kinase 3 (STKc_GSK3) that negatively regulates brassinosteroid signaling. Expression of TaSG-D1 and the mutant form Tasg-D1 in Arabidopsis thaliana suggested that a single amino acid substitution in the TREE 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 Perc. in ancient India involved at least two independent mutations of TaSG-D1. Our results demonstrate that modest genetic changes in a single gene can induced dramatic phenotypic changes.

已经鉴定出六倍体小麦（Triticum spp。）的六个亚种，但目前尚不知道仅有矮粒亚种的印度矮小麦（Triticum sphaerococcum Perc。）的起源。在这里，我们分离了球形球菌Perc中的粒状基因Tasg-D1。通过位置克隆。Tasg-D1编码一个丝氨酸/苏氨酸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。TaSG-D1及其突变体Tasg-D1在拟南芥中的表达表明，TaSG-D1的TREE结构域中的单个氨基酸取代增强了响应油菜素类固醇的蛋白质稳定性，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。898份小麦的单倍型分析表明球形球菌Perc的起源。在古代印度，至少涉及两个独立的TaSG-D1突变。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。