An intron sense suppression construct targeting soybean FAD2-1 requires a double-stranded RNA-producing inverted repeat T-DNA insert

We demonstrate that the transformation of soybean (Glycine max) with sense suppression constructs using intron sequences from the fatty acid oleyl Delta12 desaturase gene FAD2-1A leads to efficient and specific reduction of FAD2-1 transcripts in developing seeds, increased oleic acid, and decreased polyunsaturated fatty acids. The related FAD2-2 transcripts are only marginally affected. Despite screening a large number of independent transformants, no single-copy efficacious transformants could be found. Invariably, all the least complex transgenic loci have two T-DNA copies in an inverted repeat configuration, centered at the right borders. We show that this T-DNA configuration produces an inverted repeat transcript and that small interfering RNAs accumulate against the target sequence.