Expression of the human milk protein β-casein in transgenic potato plants

A 1177 bp cDNA fragment encoding the human milk protein β-casein was introduced into Solanum tuberosum cells under control of the auxin-inducible, bidirectional mannopine synthase (mas1'2') promoters using Agrobacterium tumefaciens-mediated leaf disc transformation methods. Antibiotic-resistant plants were regenerated and transformants selected based on luciferase activity carried by the expression vector containing the human β-casein cDNA. The presence of human β-casein cDNA in the plant genome was detected by PCR and DNA hybridization experiments. Human β-casein mRNA was identified in leaf tissues of transgenic plants by RT-PCR analysis. Human β-casein was identified in auxin-induced leaf and tuber tissues of transformed potato plants by immunoprecipitation and immunoblot analysis. Human β-casein produced in transgenic plants migrated in polyacrylamide gels as a single band with an approximate molecular mass of 30 kDa. Immunoblot experiments identified approximately 0.01% of the total soluble protein of transgenic potato leaf tissue as β-casein. The above experiments demonstrate the expression of human milk β-casein as part of an edible food plant. These findings open the way for reconstitution of human milk in edible plants for replacement of bovine milk in baby foods for general improvement of infant nutrition, and for prevention of gastric and intestinal diseases in children.