FAD2-silencing has pleiotropic effect on polar lipids of leaves and varied effect in different organs of transgenic tobacco

A microsomal ω-6 fatty acid desaturase gene (FAD2) of tobacco (Nicotiana tabaccum) was cloned by PCR-based method and a partial coding sequence of the putative FAD2 gene was used to create intron-containing construct expressing hairpin RNA for silencing endogenous FAD2 gene. In addition to a marked increase of oleic acid in phosphatidylcholine and phosphatidylethanolamine, the main lipid components of the extrachloroplastic membranes of plant cells, the silencing of FAD2 resulted in pleiotropic effect on polar lipids of leaves, i.e., a significant increase of oleic acid levels in sulfoquinovosyldiacylglycerol, phosphatidylglycerol, digalactosyldiacylglycerol and monogalactosyldiacylglycerol, located predominantly in the chloroplast, and a significant reduction of palmitic acid levels in some individual polar lipids. The significant increase of oleic acid only found in lipids of leaves and seeds of transgenic lines proved the diversity of the silencing effect in different organs. The possible mechanisms involved in the control of lipid unsaturation level in different organs of transgenic tobacco were discussed.