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

Introduction: ) 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.