Lipid characterization of seed oils from high-palmitic, low-palmitoleic, and very high-stearic acid sunflower lines

摘要

Information obtained in recent years regarding the enzymes involved in FA synthesis can now be applied to develop novel sunflower lines by incorporating enzymes with specific characteristics into lines with a defined background. We have generated three highly saturated mutant lines in this way and characterized their FA content. The new high-palmitic, low-palmitoleic lines CAS-18 and CAS-25, the latter on a high-oleic background, have been selected from the high-stearic mutant CAS-3 by introducing a deficient stearic acid desaturase in a high-palmitic background from the previously developed mutant lines CAS-5 and CAS-12, respectively. As such, the desaturation of palmitic acid and the synthesis of palmitoleic acid and its derivatives (asclepic and palmitolinoleic acids) were reduced in these high-palmitic lines, increasing the stearic acid content. Likewise, introducing a FA thioesterase from a high-palmitic line (e.g., CAS-5) into the high-stearic CAS-3 increased the stearic acid content from 27 to 32% in the new high-stearic line CAS-31. As previously described in high-palmitic lines, high growth temperatures did not reduce the linoleic acid content of the oil. Furthermore, the FA composition of TAG, DAG, and phospholipids was modified in these lines. Besides a high degree of saturation, the TAG from these new vegetable oils have a low content of saturated FA in the sn-2 position. The α asymmetric coefficient obtained also indicates that the saturated FA are asymmetrically distributed within the TAG molecules. Indeed, the disaturated TAG content rose from 31.8 to 48.2%. These values of disaturated TAG are the highest to date in a temperate oilseed.