Fatty acid elongase 1 (FAE1) promoter as a candidate for genetic engineering of fatty acids to improve seed oil composition

As an important cis-regulatory element, a promoter plays a key role in plant gene expression and regulation, and has been widely used in plant genetic engineering. The fatty acid elongase 1 (FAE1) promoter was isolated from Arabidopsis thaliana. Sequence analysis showed that the FAE1 promoter contains two Skn-1 motifs, one O-2-site, and one G-box, which play important roles in controlling seed-preferred expression. Stearoyl-acyl carrier protein desaturase (SAD) catalyzes the conversion of stearic to oleic acid. 23 FAE1pro:GUS and 31 FAE1pro: SAD transgenic lines were obtained and confirmed by polymerase chain reaction (PCR). In the FAE1pro: GUS transgenic lines, beta-glucuronidase (GUS) staining was observed in immature leaves, young stems, flowers, and pods, indicating that FAE1 promoter is highly active in these tissues. Real-time PCR revealed that the FAE1 promoter-driven maize SAD gene was highly expressed in the seeds, followed by the pods and flowers; however, its expression level was low in the roots, stems, and leaves. Stearic acid and long-chain saturated fatty acid contents of seeds were significantly decreased; further, the ratio of total saturated fatty acids to unsaturated fatty acids was also reduced. These results indicate that FAE1 promoter is ideal for genetic engineering to improve seed oil composition.