Regional metabolomic profiling reveals lipid metabolic signatures associated with oil content in flue-cured tobacco

Introduction Flue-cured tobacco ( Nicotiana tabacum ) leaves exhibit substantial variation in oil content, yet the metabolic basis underlying these differences remains unclear. Methods In this study, we integrated physicochemical measurements, ultrastructural observation, and metabolomic profiling to investigate oil-associated metabolic characteristics. High-oil and low-oil leaves from Tongren (TR; TRH, high-oil; TRL, low-oil) and Weining (WN; WNH, high-oil; WNL, low-oil) were analyzed. Results High-oil leaves exhibited higher petroleum ether extract content (TRH 5.56%; TRL 4.63%; WNH 4.82%; WNL 4.15%) and lower softness value (TRH 34.7 mN; TRL 47.3 mN; WNH 21.7 mN; WNL 36.3 mN), with reduced luminosity (L*) and increased red-green axis (a*). Ultrastructural analysis revealed a greater abundance of lipid droplets in high-oil leaves, while starch granules persisted in low-oil leaves from TR. Metabolomic profiling identified 38 differential metabolites in TR (upregulated: triacylglycerols, phospholipids, fatty acid derivatives; downregulated: polyphenols, phenylpropanoids) and 47 in WN (upregulated: flavonoids, coumarins, sesquiterpene lactones; downregulated: organic acids, sugar alcohols, some fatty acid derivatives). Four metabolites—namely, marmesin, an arteannuin-like compound, isoferulic acid, and p-hydroxycinnamic acid—were found to be prevalent in both regions and exhibited a significant correlation with oil-related traits. Discussion Pathway enrichment analysis further indicated that high-oil leaves from TR and WN displayed distinct metabolic patterns despite similar oil phenotypes. These findings suggest that oil accumulation is associated with region-distinct metabolic profiles and provide potential metabolic markers for oil-related quality improvement.