Sorghum qTGW1a encodes a G-protein subunit and acts as a negative regulator of grain size

Authors: ZOU, GUIHUA - Zhejiang Academy Of Agricultural Sciences; ZHAI, GUOWEI - Zhejiang Academy Of Agricultural Sciences; CHEN, HEYUN - Zhejiang Academy Of Agricultural Sciences; YAN, SONG - Jiangxi Academy Of Agricultural Sciences; ZHOU, LENGBO - Guizhou Academy Of Agricultural Sciences; DING, YANQING - Guizhou Academy Of Agricultural Sciences; LU, PING - Chinese Academy Of Agricultural Sciences; LIU, HEQUIN - Zhejiang Academy Of Agricultural Sciences; Chen, Junping; Xin, Zhanguo; ZHEN, XUEQIANG - Zhejiang Academy Of Agricultural Sciences; LIU, XIUHUI - Zhejiang Academy Of Agricultural Sciences

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2020
Publication Date: 6/4/2020
Citation: Zou, G., Zhai, G., Chen, H., Yan, S., Zhou, L., Ding, Y., Lu, P., Liu, H., Chen, J., Xin, Z., Zhen, X., Liu, X. 2020. Sorghum qTGW1a encodes a G-protein subunit and acts as a negative regulator of grain size. Journal of Experimental Botany. https://doi.org/10.1093/jxb/eraa277.
DOI: https://doi.org/10.1093/jxb/eraa277

Interpretive Summary: Sorghum is an annual tropical C4 grass and one of the first domesticated cereal crops. It is grown across a wide-range of environments and serves as an important source of food, fodder, fiber, fuel, and building materials. Current breeding efforts to increase sorghum yield are focused on traits controlling grain size, number of grains per panicle, and number of tillers per plant. Grain size is a complex trait controlled by a large number of genes. While it is known that multiple genes control grain size in sorghum, none of the specific genes have been identified. Rather, large segments of chromosomes called quantitative trait loci (QTL), which contain multiple genes have been identified. To further dissect which genes make up grain size QTL in sorghum, ARS scientists at Lubbock, Texas in collaboration with scientists from the Institute of Crop and Nuclear Technology Utilizatio and Zhejiang Academy of Agricultural Sciences in China used an inbred sorghum population to study grain size. The result of this work was the identification of a gene called SbGS3 which proved to be a key regulator of sorghum grain size. The identification of SbGS3 and its function significantly advances our understanding of the regulatory mechanisms of grain size in sorghum and provides a target to manipulate grain size and increase yield through genome editing.

Technical Abstract: Grain size is a major determinant of grain yield in sorghum [Sorghum bicolor (L.) Moench] and other cereals. Because of the importance of grain size to grain yield, many quantitative trait loci (QTLs) of grain size have been identified in sorghum. However, no gene underlying any grain size QTLs has been identified. Here, we describe a study of grain size QTLs under two locations over four years. From an F8 RIL population derived from a cross between a small grain sorghum inbred line 654 and a large grain sorghum inbred line LTR108, 44 QTLs for grain size were identified. One QTL, qTGW1a on the long arm of chromosome 1, which affected grain weight, grain length, and grain width, was detected consistently over four years. Using the extreme recombinants from a F2:3 fine-mapping population, we delimitated qTGW1a within a ~33-kb region, containing three predicted genes. One gene, SORBI_3001G341700, encodes a G-protein subunit, homologous to the GS3 in rice. The gene was, therefore, named SbGS3. Similar to its function in rice, SbGS3 appears to act as a negative regulator of grain size in sorghum. Over expression of the functional SbGS3 from the small seed inbred line 654 decreased the grain size, plant height, and grain yield in transgenic rice. Identification of SbGS3 underlying the grain size QTL qTGW1a advanced our understanding of the regulatory mechanisms of grain size in sorghum and provided a target to manipulate grain size through genome editing.