A genome-wide association study revealed that GmRGD14 positively regulates the root dry weight in soybeans

Roots are vital for crop growth, development, yield, and tolerance to various types of environmental stress. Numerous genetic loci associated with soybean root morphological traits have been identified, but few genes associated with these traits have been reported. This study identified seven quantitative trait loci (QTLs) containing stable SNPs significantly associated with the root dry weight in soybeans through a genome-wide association study. Among these QTLs, qRDW14-2 presented the greatest significance. In qRDW14-2, the gene GmRGD14, encoding the lysophosphatidic acid acyltransferase LPAT4, was identified as a candidate. GmRGD14, in block63, which contained the significant SNP S14_6521715, had the highest expression level in soybean roots, and its Arabidopsis homologous mutant lpat4 presented more lateral roots than did the control Col-0. GmRGD14 was localized primarily to the cell membrane and endoplasmic reticulum. The heterologous overexpression of GmRGD14 in Arabidopsis significantly increased the lateral root number, which was similar to the phenotype of atlpat4. Furthermore, overexpression of GmRGD14 resulted in a greater total root length, root tip number, root surface area, and root volume in the hairy roots of transgenic soybean plants than in those of control soybean plants, whereas knockdown of the gene via RNA interference in soybean hairy roots resulted in the opposite phenotype. GmRGD14, which is highly genetically variable in wild soybean, has been gradually utilized during soybean domestication. Overall, this study revealed that GmRGD14 is a new key gene involved in root growth, providing a promising genetic target for breeding elite soybean varieties with strong root systems.