Grain size is a major determinant of grain yield in sorghum and other cereals. Over 100 quantitative trait loci (QTLs) of grain size have been identified in sorghum. However, no gene underlying any grain size QTL has been cloned. Here, we describe the fine mapping and cloning of one grain size QTL. From an F₈ recombinant inbred line population derived from a cross between inbred lines 654 and LTR108, we identified 44 grain size QTLs. One QTL, qTGW1a, was detected consistently on the long arm of chromosome 1 in the span of 4 years. Using the extreme recombinants from an F_2:3 fine-mapping population, qTGW1a was delimited within a ~33 kb region containing three predicted genes. One of them, SORBI_3001G341700, predicted to encode a G-protein γ subunit and homologous to GS3 in rice, is likely to be the causative gene for qTGW1a. qTGW1a appears to act as a negative regulator of grain size in sorghum. The functional allele of the putatively causative gene of qTGW1a from inbred line 654 decreased grain size, plant height, and grain yield in transgenic rice. Identification of the gene underlying qTGW1a advances our understanding of the regulatory mechanisms of grain size in sorghum and provides a target to manipulate grain size through genome editing.

中文翻译：

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高粱qTGW1a编码一个G蛋白亚基，并充当晶粒尺寸的负调节剂。

谷物大小是高粱和其他谷物产量的主要决定因素。高粱中已鉴定出100多个晶粒大小的数量性状基因座。但是，尚未克隆出任何具有任何晶粒大小的QTL的基因。在这里，我们描述了一个粒度QTL的精细映射和克隆。从来自自交系654和LTR108之间杂交的F ₈重组自交系种群中，我们鉴定出44个晶粒大小的QTL。在4年的时间里，在1号染色体的长臂上一致地检测到一个QTL qTGW1a。使用来自F _2：3精细映射群体的极端重组子，qTGW1a被限定在一个包含三个预测基因的〜33 kb区域内。其中之一，SORBI_3001G341700预计在水稻中编码一个G蛋白γ亚基并与GS3同源，可能是qTGW1a的致病基因。qTGW1a似乎是高粱中晶粒大小的负调节剂。自交系654的qTGW1a推定致病基因的功能等位基因降低了转基因水稻的粒大小，株高和籽粒产量。qTGW1a潜在基因的鉴定使我们对高粱中晶粒大小的调控机制有了更深入的了解，并提供了通过基因组编辑来操纵晶粒大小的目标。