Context With the widespread use of transgenic soybeans (Glycine max (L. ) Merr.), their nutritional assessment for human food and animal feed is an important aspect of safety evaluation. WRINKLED 1 (WRI1) is a transcriptional activator of genes involved in fatty acid synthesis. Aims We aimed to evaluate the effect of overexpression of GmWRI1a in soybean on the nutritional profile of soybean seeds. Methods Using molecular biology techniques, we identified three transgenic soybean lines stably overexpressing GmWRI1a (GmWRI1a-OE). We quantified the nutritional and anti-nutritional components in seeds of GmWRI1a-OE and wild-type (DN50) soybean, and compared them on the basis of the principle of substantial equivalence. Key results The GmWRI1a and Bar genes were stably inherited in the three GmWRI1a-OE lines, and GmWRI1a protein content was higher in transgenic soybean seeds than in wild-type seeds. Overexpression of GmWRI1a resulted in changes in fatty acid composition, a significant increase in oil content, and a significant decrease in stachyose content in seeds. Contents of other nutritional components (proximates, amino acids and isoflavones) and anti-nutritional factors (phytic acid, trypsin inhibitors and raffinose) in seeds were not significantly different between the wild-type and GmWRI1a-OE lines. Conclusions Contents of nutritional and anti-nutritional components of GmWRI1a-OE seeds were all within the reference ranges reported for commercially available soybeans and, therefore, are substantially equivalent to those of wild-type seeds. Implications GmWRI1a-OE soybean seeds are a high-quality product for health-conscious consumers.

WRINKLED1 (WRI1), an APETALA2/ethylene-responsive-element-binding protein (AP2/EREBP) subfamily transcription factor, plays a crucial role in the transcriptional regulation of plant fatty acid biosynthesis. In this study, GmWRI1a was overexpressed in the soybean cultivar ‘Dongnong 50’ using Agrobacterium-mediated transformation to generate three transgenic lines with high seed oil contents. PCR and Southern blotting analysis showed that the T-DNA was inserted into the genome at precise insertion sites and was stably inherited by the progeny. Expression analysis using qRT-PCR and Western blotting indicated that GmWRI1a and bar driven by the CaMV 35S promoter were significantly upregulated in the transgenic plants at different developmental stages. Transcriptome sequencing results showed there were obvious differences in gene expression between transgenic line and transgenic receptor during seed developmental stages. KEGG analysis found that the differentially expressed genes mainly annotated to metabolic pathways, such as carbohydrated metabolism and lipid metabolism. A 2-year single-location field trial revealed that three transgenic lines overexpressing GmWRI1a (GmWRI1a-OE) showed a stable increase in seed oil content of 4.97–10.35%. Importantly, no significant effect on protein content and yield was observed. Overexpression of GmWRI1a changed the fatty acid composition by increasing the linoleic acid (C18:2) content and decreasing the palmitic acid (C16:0) content in the seed. The three GmWRI1a-OE lines showed no significant changes in agronomic traits. The results demonstrated that the three GmWRI1a overexpression lines exhibited consistent increases in seed oil content compared with that of the wild type and did not significantly affect the seed yield and agronomic traits. The genetic engineering of GmWRI1a will be an effective strategy for the improvement of seed oil content and value in soybean.