The invention relates to methods for the directed, transgenic expression of nucleic acid sequences in the carbohydrate-storing sink tissues of plants using transgenic expression cassettes which comprise the Vicia faba plastidic 1,4-.alpha.-D-glucan:phosphate .alpha.-D-glucosyltransferase promoter. Furthermore, the invention relates to said transgenic expression cassettes and to transgenic expression vectors and transgenic organisms comprising them, and to the use of the same for the production of foodstuffs, feedstuffs, seed, pharmaceuticals or fine chemicals.