Overexpression of Soybean GmWRI1a Stably Increases the Seed Oil Content in Soybean

Abstract

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, <i>GmWRI1a</i> was overexpressed in the soybean cultivar 'Dongnong 50' using <i>Agrobacterium</i>-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 <i>GmWRI1a</i> and <i>bar</i> driven by the CaMV <i>35S</i> 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 <i>GmWRI1a</i> (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 <i>GmWRI1a</i> 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 <i>GmWRI1a</i> 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 <i>GmWRI1a</i> will be an effective strategy for the improvement of seed oil content and value in soybean.