Expression of yeast acyl-?9 desaturase for fatty acid biosynthesis in tobacco

Abstract:

Palmitoleic acid (16:1Δ9), an unusual monounsaturated fatty acid, is highly valued for human nutrition, medication and industry. Plant oils containing large amounts of palmitoleic acid are the ideal resource for biodiesel production. To increase accumulation of palmitoleic acid in plant tissues, we used a yeast (Saccharomyees cerevisiae) acyl-CoA-Δ9 desaturase (ScΔ9D) for cytosol- and plastid-targeting expression in tobacco (Nicotiana tabacum L.). By doing this, we also studied the effects of the subcellular-targeted expression of this enzyme on lipid synthesis and metabolism in plant system. Compared to the wild type and vector control plants, the contents of monounsaturated palmitoleic (16:1Δ9) and cis-vaccenic (18:1Δ11) were significantly enhanced in the ScΔ9D-transgenic leaves whereas the levels of saturated palmitic acid (16:0) and polyunsaturated linoleic (18:2) and linolenic (18:3) acids were reduced in the transgenics. Notably, the contents of 16:1Δ9 and 18:1Δ11 in the ScΔ9D plastidal-expressed leaves were 2.7 and 1.9 folds of that in the cytosolic-expressed tissues. Statistical analysis appeared a negative correlation coefficient between 16:0 and 16:1Δ9 levels. Our data indicate that yeast cytosolic acyl-CoA-Δ9 desaturase can convert palmitic (16:0) into palmitoleic acid (16:1Δ9) in high plant cells. Moreover, this effect of the enzyme is stronger with the plastid-targeted expression than the cytosol-target expression. The present study developed a new strategy for high accumulation of ω-7 fatty acids (16:1Δ9 and18:1Δ11) in plant tissues by protein engineering of acyl-CoA-Δ9 desaturase. The findings would particularly benefit the metabolic assembly of the lipid biosynthesis pathway in the large-biomass vegetative organs such as tobacco leaves for the production of high-quality biodiesel.