Synthesis and targeting of Brassica napus oleosin in transgenic tobacco

Abstract

A repeseed oleosin gene, Bn-III, containing a 3.44-kbp promoter region and the complete coding sequence, was introduced into tobacco explants via Agrobacterium-mediated transformation. Rapessed oleosin protein was synthesised in the transgenic tobacco plants, as detected by immunoblotting, and accumulated only in the embryo and endosperm tissues of the maturing tobacco seeds. The amounts of oleosin on a per seed basis were than 5-fold higher in the embryos than in the endosperm tissue. Rapeseed oleosin accumulated significantly later than the period of maximum storage oil deposition in the tobacco seeds and was correctly targeted to the surface layer of tobacco seed oil bodies, as shown by immunogold labelling. This is the first study to demonstrate the spatial and temperal accumulation pattern and correct targeting of a heterologous oleosin protein, under the control of its own gene promoter, in an unrelated plant species. The study also shows that transgenic tobacco is a useful model system in which to perform in vivo oleosin targeting experiments.