Molecular Farming in Plants


The commonly used term ‘molecular farming’ describes the large‐scale production of valuable proteins in transgenic plants, including antibodies, vaccines, other pharmaceuticals and industrial proteins. Compared to traditionally used systems such as microbial cultures, plants offer many advantages with respect to economy, quality and safety. Especially attractive is the possibility to power protein production using natural sunlight and atmospheric carbon dioxide. Furthermore, transient expression systems offer the possibility to rapidly produce personalised pharmaceuticals otherwise impossible. Several production systems including algae, mosses, tissue‐ and cell cultures have been reported, enabling contained protein production. Combining these cell‐based production systems with newly developed photo‐bioreactors promises powerful solutions for cost‐efficient and safe manufacturing of valuable proteins. However, constraints concerning protein yield and public acceptance must be overcome before the plant's full potential can be exploited.

Key Concepts:

  • Plant‐based production of proteins can be done in a wide range of systems including different species, tissues and organelles, for each protein the best combination must be identified.

  • Light‐driven production of bioactive‐proteins offers an eco‐friendly and sustainable alternative to conventional production systems.

  • Transient expression of proteins offers the possibility to cost efficiently produce customised pharmaceutical proteins.

Keywords: molecular farming; recombinant proteins; transgenic plants; biotechnology; plant transformation

Figure 1.

Different steps to generate transgenic plants suitable for molecular farming of pharmaceuticals: (a) choice of a target gene and insertion into plant expression vector; (b) transfer of the expression construct into Agrobacterium tumefaciens; (c) plant transformation and selection under sterile conditions; (d) generation of transgenic plants; (e) verification of protein accumulation, for example, by Western blot, ELISA, microscopy; (f) functional proof in animal model, for example, testing antibody formation after vaccination; (g) clinical studies; and (h) further development of the product and of the downstream processing technology as well as scaling‐up. P, promoter; G, gene; T, terminator.

Figure 2.

Sorting of plastids and isolation of genetically stable transplastomic plants: (a) chloroplast transformation by particle bombardment; (b) incorporation of the transforming DNA in only a single or a few out of several thousand plastid genome copies within a single chloroplast in a leaf cell (blue chloroplast); (c) Enrichment for plants with uniformly transformed plastid genomes during subsequent cell and organelle divisions under antibiotic selection leading to a transplastomic plant (d). P, particle gun; N, nucleus; green, untransformed chloroplast.

Figure 3.

Different transient expression systems: (a) Agro‐infiltration: Agrobacteria harbouring the binary construct with gene of interest are infiltrated into leaves leading to protein expression (light red); (b) virus infection: after localised infection, cell‐to‐cell movement, and systemic spread of the virus the protein is expressed at high levels (red) as a fusion to viral coat protein; (c) Agrobacterium‐mediated transfection of virus replicons: the viral vector with the gene of interest is delivered to the plant via Agrobacterium leading to gene amplification within each cell; after cell‐to‐cell movement performed by the replicon the protein of interest is expressed at very high levels (red). Pro, promoter; GoI, gene of interest; T, terminator; TMV, Tobacco mosaic virus; CP, coat protein; MP, movement protein.

Figure 4.

N‐linked glycosylation: (a) Structure of typical N‐linked glycans found in plants or mammals and (b) transfer and processing of plant‐specific N‐linked glycans in the ER and Golgi apparatus of plants.



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Further Reading

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Hoja, Ursula, and Sonnewald, Uwe(Jul 2012) Molecular Farming in Plants. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0003365.pub2]