Expression of biologically active human insulin-like growth factor 1 in Arabidopsis thaliana seeds via oleosin fusion technology. 
Novel protein expression in plant-based systems has become an important tool in producing and studying therapeutic proteins.  Among many plant-based systems developed so far, oleosin fusion technology is one of the most cost-effective and convenient methods.  In this study, an important therapeutic protein, human insulin-like growth factor 1 (hIGF-1), was expressed in Arabidopsis thaliana seeds via this technology.  The plant bias codon usage-optimized hIGF-1 gene was fused to the C-terminal of A. thaliana 18.5 kDa oleosin gene, and the fusion gene driven by an oleosin promoter was transferred into A. thaliana ecotype Col-0.  The accumulation of oleosin-hIGF-1 fusion protein in transgenic seeds was up to 0.75% of total seed protein (TSP) and the expression level of hIGF-1 was 0.17% of the TSP, which was eight times higher than previously reported using other plant-based hIGF-1 production systems.  The biological activity of the hIGF-1 as an oleosin-hIGF-1 fusion protein in vitro was demonstrated by using human SH-SY5Y neuroblastoma cells.