Tissue specific expression of human calcitonin gene in potato tubers by an organ specific promoter

ABSTRACT

To increase the production level of heterologous proteins in plants, strategies such as choice of stronger promoters, optimization of codon usage and specific localization of foreign proteins are of major concern. Calcitonin [CT], a 32 amino acid polypeptide is a powerful and specific inhibitor of bone resorption and is used to treat several human diseases. Calcitonin activity is not species-specific which make it possible to produce in various animal sources, however, antibody formation in the prolonged application of animal CT leads to gradual decrease or loss of activity. That is why the long term treatment of human patients with CT requires homologous calcitonin. In this study, a human calcitonin [hCT] gene, driven by two different promoters [granule bound starch synthase I and Cauliflower mosaic virus 35S] was expressed in potato plants, using Agrobacterium-mediated transformation. Molecular analysis, including PCR, RT-PCR, Northern dot blot hybridizations showed that hCT could be successfully transcribed in transgenic potato plants. The immunoassay results showed that tissue specific expression in potato, led to almost five-fold more hCT accumulation than constitutively expression in all plant tissues