High-oleic oilseed rapes developed with seed-specific suppression of FAD2 gene expression

Vegetable oil is not only important for its edibility but for industrial purposes. High-oleic vegetable oil is especially useful for making biodiesel because it is highly stable against oxidation. Transgenic oilseed crops with modified fatty acid compositions have been developed with several biotechnological gene-silencing methods. The seed oils with the most successfully altered fatty acid compositions are produced from high-oleic oilseed crops in which FAD2 gene expression is suppressed. Vegetable oil from oilseed rape (Brassica napus) is one of the most commonly used vegetable oils throughout the world and its oleic acid content is moderately high (about 65 %). Therefore, oilseed rape can be modified to produce high-oleic oilseed crops. Oilseed rape has four FAD2 genes, originating from B. rapa and B. oleracea, with nucleotide identities of 88–97 %. To produce transgenic high-oleic oilseed rape, plant transformation vectors were constructed using antisense RNA and RNA interference (RNAi) to modify the BrFAD2-1 gene, and canola-type cultivar Youngsan was transformed with Agrobacterium carrying the vectors. The transgenic lines generated, AS9A, HP15, and HPAS29, showed high-oleic phenotypes, which were stably inherited. Their oleic acid contents increased from 67 (Youngsan) to 78, 85, and 86 %, respectively, and their polyunsaturated fatty acid (PUFA) contents decreased from 24 (Youngsan) to 13, 8, and 6 %, respectively. HPAS29, developed with a combined antisense RNA–RNAi method, produced seed oil with the highest oleic acid and lowest PUFA contents. These transgenic high-oleic oilseed rapes could be useful in the manufacture of high-temperature frying oils and high-quality biodiesel fuel.