Adaptation of an ecdysone-based genetic switch for transgene expression in soybean seeds.

Soybean was used as a model for studies of chemical induction of gene expression in seeds. A chimeric transcriptional activator, VGE, driven by the soybean seed glycinin G1 promoter, was used to induce the expression of an ER-targeted GFP(KDEL) reporter protein upon addition of the chemical ligand, methoxyfenozide. The chemical gene switch activated gene expression under in vitro conditions in somatic cotyledonary embryos and zygotic seed embryos cultured from transgenic soybean plants, as well as in seeds in planta under greenhouse conditions. The efficiency of induction of GFP expression under different growth conditions was strongly influenced by the developmental stage of the seed and availability of the inducer. The formation of ER-derived GFP-containing protein bodies in seed storage parenchyma cells was correlated with the level of induced expression.