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

Abstract

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 O₂-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, β-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.

Key words: Arabidopsis thaliana, FAE1 promoter, stearoyl-acyl carrier protein desaturase (SAD), seed fatty acid composition.