Triacylglycerol Metabolism in Soybean Seed with Genetically Altered Unsaturated Fatty Acid Composition1

Abstract

Recurrent selection methodology has been utilized in the development of a soybean [Glycine max (L.) Merr.] genotype, designated as N78‐2245, that contains a high concentration of oleic acid (18:1) and lower concentrations of linoleic (18:2) and linolenic (18:3) acids compared to seed from typical soybean cultivars. Triacylglycerol (TG) is the predominant glycerolipid soybean oil. The nature of triacylglycerol deposition during the ontogeny of soybean seed with the high‐l8:l trait has not been shown previously. The objective of this study was to determine how expression of the high‐18:1 trait was affected through TG molecular species composition during seed development. To achieve that objective TG composition was evaluated in seed of N78‐2245 and ‘Dare’, a typical soybean cultivar, at four stages of reproductive growth. For both genotypes developmental changes in TG fatty acid composition primarily were reflected by the levels of nine TG species enriched in 18:1 (SM2, M3, and M2D), 18:2 (SD2, MD2, and D3) or 18:3 (MT2, D2T, and DT2); where S = palmitic (16:0) or stearic (18:0) acid, M = 18:1, D = 18:2, and T = 18.3. In N78‐2245 seed all designated species enriched in 18:1, 18:2 or 18:3 respectively accounted for 80.8 mol%, 12.8 mol%, and 6.4 mol% of the TG deposited between 30 and 45 days after flowering (DAF); but accounted for 17.0 mol%, 76.8 mol%, and 6.2 mol% of the TG deposited between 45 and 75 DAF. These data have indicated that factors associated with increased seed age have significantly influenced the expression of the high‐18:l trait in N78‐2245 by restricting the deposition of TG species enriched in 18:1.