The linin promoter is highly effective in enhancing punicic acid production in Arabidopsis.

KEY MESSAGE: Enhanced levels of punicic acid were produced in the seed oil of Arabidopsis over-expressing pomegranate FATTY ACID CONJUGASE driven by heterologous promoters, among which the linin promoter was the most efficient. Fatty acids with conjugated double bonds play a special role in determining both the nutritional and industrial uses of plant oils. Punicic acid (18:3Δ9cis,11trans,13cis ), a conjugated fatty acid naturally enriched in the pomegranate (Punica granatum) seeds, has gained increasing attention from the biotechnology community toward its production in metabolically engineered oilseed crops because of its significant health benefits. The present study focused on selecting the best heterologous promoter to drive the expression of the P. granatum FATTY ACID CONJUGASE (PgFADX) cDNA as a means of producing punicic acid in Arabidopsis seed oil. Among the four promoters of genes encoding seed storage proteins from different crop species, the linin promoter led to the highest accumulation of punicic acid (13.2% of total fatty acids in the best homozygous line). Analysis of the relative expression level of PgFADX in developing seeds further confirmed that the linin promoter was most efficient in Arabidopsis. In addition, a conserved profile of cis-regulatory elements were identified in four heterologous promoters by bioinformatic analysis, and their possible roles in regulating gene expression during plant development were also discussed based on the results of this study in combination with the literature. This study contributes to metabolic engineering strategies aimed at enhancing the production of bioactive fatty acids in oilseed crops.