Recombinant plants are plants which carry genes from other plants or organisms and can be used to produce certain proteins in large amounts, for lower costs, than in traditional fermentation units or by chemical processes. In 1986, human growth hormone was the first protein pharmaceutical made in plants, and in 1989 the first antibody (plantibody) was produced. These products were made by cloning genes and expressing them in tobacco plants instead of using bacteria (often E. coli is used for gene cloning) or other microorganisms. Since then, tobacco has dominated the industry as the most intensively studied and utilized GM plant species (Ma et al., 2003). Some plantigens (antigens produced by plants) and plantibodies have undergone clinical trials and FDA approval.
Over the years, however, scientists have discovered that there are certain advantages to using other plants, depending on the product and desired traits. For example, greater concentrations of proteins can be accumulated in cereal seeds and protein separations are easier with cereals than other parts of the plant. Seeds also offer stability to antibody products at ambient temperatures for prolonged periods of time (up to 3 years with no loss of activity).
Recombinant vaccines are being developed with the intent of growing them in edible plants for consumption by individuals in underdeveloped countries. Different plants are being considered, fruits and vegetables in particular, so they can be directly consumed.
Sources:
Ma, J., Drake, P. and Christou, P. 2003. The production of recombinant pharmaceutical proteins in plants. Nature Reviews Genetics 4:794-805. doi:10.1038/nrg1177.
Plantibodies: Human antibodies produced by field crops enter clinical trials. Trends in Plant Science 6(5):220. May 2001.
Phillips, T. Genetically modified organisms (GMOs): Transgenic crops and recombinant DNA technology. Nature Education 1(1):2008.
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