酿酒酵母脂酰-?9脱氢酶亚细胞定位表达及其对烟草脂肪酸合成的影响

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

摘要:

以烟草Nicotiana tabacum L.为宿主植物，分别在细胞质内质网和质体内定位表达酿酒酵母Saccharomyees cerevisiae脂酰-CoA-Δ9脱氢酶 (ScΔ9D)，以期提高植物组织中棕榈油酸 (16∶1Δ9) 的积累量和分析该酶不同亚细胞定位表达对油脂代谢的影响。与野生型和空载体 (对照) 植物相比，转基因烟草植株叶片中单不饱和的棕榈油酸及顺式十八碳烯酸 (18∶1Δ11) 含量明显提高，而饱和的棕榈酸 (16∶0) 含量相应减少，多不饱和的亚油酸 (18∶2Δ9,12) 和亚麻酸 (18∶3Δ9,12,15) 含量亦降低。ScΔ9D质体定位表达烟叶中棕榈油酸及顺式十八碳烯酸含量分别是ScΔ9D细胞质内质网定位表达烟叶的2.7和1.9倍。这表明酵母脂酰-Δ9脱氢酶能在高等植物细胞中正确催化棕榈酸 (16∶0) 转化为棕榈油酸 (16∶1Δ9)，而且在质体内表达的效应显著高于在细胞质内质网上的效应。新建立了一种应用脂酰-CoA-Δ9脱氢酶代谢工程培育植物组织高水平合成积累棕榈油酸等ω-7脂肪酸的策略，有助于在生物量大的烟叶等营养器官中组装ω-7脂肪酸合成途径以生产优质生物燃油。

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.