EgEIN3 negatively regulates oil biosynthesis by repressing EgGPAT expression in Oil Palm (Elaeis guineensis Jacq.)

Oil palm ( Elaeis guineensis Jacq.) is a crucial global oil crop, with its mesocarp rich in palm oil and nutrients. An ethylene-insensitive protein 3 (EIN3), associated with fruit ripening, was identified through transcriptome analysis. Its expression pattern suggested a regulatory role in oil accumulation. To investigate this, EgEIN3 was cloned from the mesocarp and bioinformatically characterized as a nuclear-localized transcription factor. Using VIGS, silencing of EgEIN3 led to significant upregulation of EgGPAT —a key gene in triacylglycerol synthesis—and altered lipid profiles, including increased TAG and total oil content, and changes in fatty acid composition. Conversely, overexpression of EgEIN3 downregulated EgGPAT and reduced oil accumulation. Molecular experiments confirmed that EgEIN3 binds directly to the EgGPAT promoter at the ACCGTTC motif. These results demonstrate that EgEIN3 negatively regulates EgGPAT , thereby influencing lipid metabolism in oil palm. This study unveils the role of EgEIN3 in oil biosynthesis, establishes a regulatory network, and provides insights into ethylene-mediated lipid synthesis, supporting future breeding efforts for improved oil quality. In Brief The EgEIN3 transcription factor, localized in the nucleus, binds to the ACCGTTC motif in the EgGPAT promoter to repress its transcription. This repression leads to reduced LPA and TAG synthesis, ultimately resulting in lower total oil content in the oil palm mesocarp. The 'silencing' and 'overexpression' phenotypes are visually contrasted. • EgEIN3 cloned as a nuclear transcription factor in oil palm mesocarp. • Silencing EgEIN3 boosts EgGPAT expression and increases oil accumulation. • Overexpression of EgEIN3 suppresses EgGPAT and reduces lipid content. • EgEIN3 directly binds EgGPAT promoter at the ACCGTTC motif. • Study reveals EgEIN3 as a negative regulator of oil biosynthesis in oil palm.