Plant synthetic biology is an emerging field that uses engineering principles to genetically engineer plants, with the goal of producing products or enhancing plant traits. It has the potential to play an important role in improving agricultural crops and enabling novel bioproduction in plants, helping to produce food, biofuels, metabolites, therapeutics, and even completely synthetic life forms.
Recognizing the potential, U.S. and international agencies have begun to back plant synthetic biology efforts. The U.S. Dept. of Energy’s (DOE) Advanced Research Projects Agency-Energy (ARPA-E) is tasked with promoting and funding advanced energy technologies, and does so through the Plants Engineered to Replace Oil (PETRO) program. The National Science Foundation (NSF) has also funded several projects related to biofuel production. The Defense Advanced Research Projects Agency (DARPA) — part of the U.S. Dept. of Defense (DOD) — initiated the Living Foundries program, which seeks to leverage organisms, including plants, as manufacturing platforms. The DOD also backs the Biological Robustness in Complex Settings (BRICS) program, with a long-term goal of enabling the safe transition of synthetic biological systems from the lab into settings where they can achieve greater biomedical, industrial, and strategic potential.
The U.K. Dept. for Business, Innovation, and Skills (BIS), the Research Councils U.K. (RCUK), and other U.K.-based agencies have invested in various plant synthetic biology programs. With about 100 research institutes overseen by the Chinese Academy of Sciences, China is poised to become a global powerhouse in synthetic biology.
Plant synthetic biology and bioengineering research benefits the biomedical and therapeutics industries. Treating animal and human viral diseases with plant-made viral vaccines and plant-made viral antigens and monoclonal antibodies is one of the brightest prospects for success. The drug ZMapp — a cocktail of monoclonal antibodies that combat Ebola virus — is produced by tobacco plants (CEP, Sept. 2014, pp. 6–9). Viral vaccine candidates for treating hepatitis B, hepatitis C, influenza, human papillomavirus (HPV), human immunodeficiency virus (HIV), and bluetongue might also be produced in plants. Medicago, Inc., Caliber Biotherapeutics, and Mapp Bio-pharmaceuticals, Inc., are expanding quickly to serve the plant-made drugs market.
Agricultural crops can be made more stress resistant and compatible with biofuel production through plant synthetic biology and bioengineering. Plant biomass, which contains mostly cellulose, hemicellulose, and lignin, can be converted to biofuels as a source of renewable energy that can reduce dependence on fossil fuels. In addition, biofuels can be produced from a wide range of biomass sources.
A key challenge for plant bioengineers is creating more tools to enable bioengineering of plants, such as synthetic promoters and transcription factors for regulation of gene expression and advanced methods for DNA assembly and synthesis. CRISPR-Cas9, a precision genome-editing technology (see article on pp. 36–41), is able to integrate DNA into a specific site of a plant genome. Plant bioengineers need to adapt genome-editing technologies to the requirements of plant cells and tissues.
Plant genetic components such as promoters present another challenge, because they are more complex than prokaryotic (and some other eukaryotic) promoter systems used to engineer many organisms. Transcriptional regulation and precise control of gene expression in synthetic circuits is a major issue and a research priority for plant synthetic biologists. “BioBricks” — parts used to build biological systems in living cells — are being developed more slowly for plant databases than they are for other organisms, where development is rapid. The first quantitative characterization of plant BioBricks was published earlier in 2016 and only described approximately 600 components.
Most computational tools for designing and modeling organism systems are not optimized for plants, although they can be adapted for plant synthetic biology. Plant synthetic biologists must continually develop novel tools to address plant-specific questions.
Addressing these challenges will require the integration of viewpoints, knowledge, and technologies from plant biology and engineering academia and industry. The Society for Biological Engineering (SBE) is hosting the International Conference on Plant Synthetic Biology and Bioengineering (ICPSBB), Dec. 16–18, in Miami, FL, to bring leading researchers together to further this emerging field and provide an educational forum to train young researchers as future leaders. To submit an abstract or to participate to this conference, visit www.aiche.org/plantsynbio.
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