Selection of GmSWEET39 for oil and protein improvement in soybean

Authors: ZHANG, HENGYOU - Danforth Plant Science Center; GOETTEL, WOLFGANG - Danforth Plant Science Center; Song, Qijian; JIANG, HE - Danforth Plant Science Center; HU, ZHENBIN - Danforth Plant Science Center; Wang, Ming; An, Yong-Qiang - Charles

Submitted to: PLoS Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2020
Publication Date: 11/11/2020
Citation: Zhang, H., Goettel, W., Song, Q., Jiang, H., Hu, Z., Wang, M.L., An, Y. 2020. Selection of GmSWEET39 for oil and protein improvement in soybean. PLoS Genetics. 16(11).e1009114. https://doi.org/10.1371/journal.pgen.1009114.
DOI: https://doi.org/10.1371/journal.pgen.1009114

Interpretive Summary: Soybean, one of the most important crop in the world, was domesticated from wild soybean and has been further improved as a dual-use seed crop to provide highly valuable oil and protein for human consumption and animal feed. Previously, a number of studies have reported a major locus controlling protein and oil content on Chromosome 15, however, the corresponding gene for the locus is unknown. In this study, we analyzed 631 soybean whole genome sequences, and determined that the sucrose transporter gene controls seed protein and oil content as well as seed weight in soybean. This is the first report of the gene responsible for the major locus controlling protein and oil content on chromosome 15. We demonstrated that the gene has been subjected to selection during domestication and all the North America elite cultivars involved in this study have the genic variants associated with low protein concentration. However, we discovered a set of germplasm with genic variants that can increase soybean protein content. The comprehensive knowledge on the molecular basis controlling the traits on Chromosome 15 is valuable to design new strategies for soybean seed quality improvement through breeding and biotechnological approaches.

Technical Abstract: Soybean [Glycine max (L.) Merr.] was domesticated from wild soybean (G. soja Sieb. and Zucc.) and has been further improved as a dual-use seed crop to provide highly valuable oil and protein for human consumption and animal feed. However, genes controlling these traits are unknown, and their underlying molecular basis remains less understood. Having combined high-confidence linkage mapping with high-power association analysis at single-nucleotide resolution based on 631 whole genome sequences, we mapped a major soybean protein and oil QTL on chromesome15 (GmSOP15). A two-nucleotide CC deletion truncating C-terminus of a sucrose transporter gene was strongly associated with high seed oil, seed weight and low seed protein. GmSOP15 was predominantly expressed in parenchyma and integument of the seed coat, suggesting that GmSOP15 likely regulates the three important soybean seed traits by affecting sucrose delivery from maternal seed coat to embryo. The CC deletion occurred during post domestication. The CC deletion-carrying haplotype H1 has been intensively selected and extensively used worldwide in soybean improvement and fixed in North American soybean cultivars, indicating that GmSOP15 plays an important role in soybean post-domestication improvement. In addition, a set of diverse GmSOP15 haplotypes in both G. soja and G. max accessions with potential use in reversing protein reduction in current soybean cultivars were also identified. The comprehensive knowledge on the molecular basis underlying the major QTL and GmSOP15 haplotypes associated with soybean improvement would be valuable to design new strategies for soybean seed improvement through breeding and biotechnological approaches.