GmNFYA14 negatively regulates soybean seed oil content by interacting with GmWRI1a

Introduction High oil content determines the commercial value of soybean, so the mechanisms that regulate oil accumulation are important targets for quality improvement. GmWRI1a is a core regulator of lipid biosynthesis in soybean, but the proteins that cooperate with it are still poorly defined. Methods Yeast two‑hybrid screening using truncated GmWRI1a as bait identified GmNFYA14. Multiple in-vitro and in-vivo protein interaction assays verified the physical interaction between GmNFYA14 and GmWRI1a. We generated GmNFYA14 overexpression and CRISPR/Cas9 knockout soybean lines to analyze seed storage components, and combined dual‑luciferase, EMSA and RNA‑seq assays to dissect the regulatory mechanism. Results Overexpression of GmNFYA14 reduced seed oil content by 2.96–4.13%, total fatty acid content by 9.90–10.78% and triacylglycerol content by 6.32–8.88%, while increasing protein content by 3.53–6.64%. Conversely, knockout of GmNFYA14 increased total fatty acid content by 13.51–13.90% and triacylglycerol content by 15.82%. GmNFYA14 did not occupy the promoters of these lipid genes itself. Instead, it interacted with GmWRI1a and attenuated both the transcriptional activity of GmWRI1a and its binding to the promoters of downstream lipid biosynthetic genes such as GmPKP-β1 and GmKAS1 . Consistent with this, transcriptome profiling showed that GmNFYA14 suppresses the expression of GmWRI1a-regulated lipid-related genes, restricting seed lipid accumulation. Discussion GmNFYA14 is a negative regulator of soybean oil accumulation that acts by dampening GmWRI1a activity rather than by binding target promoters directly. The GmNFYA14-GmWRI1a module adds a layer of control to fatty acid synthesis in seeds and provides candidate targets for molecular breeding to improve soybean oil content and agronomic traits.