Research
Proof of success is in the results
There are several benefits of using plants rather than general methods using cultured cells derived from animals or humans. (1) Production costs are calculated to be around 1/40 compared to using animal cells in the best case. Although productivity depends on the compatibility between the target protein molecules and host cells, proteins are usually produced in greater amounts in plants than in cultured cells. (2) The scalability is characteristic of the culturing of plants. When proteins are produced with cultured animal cells or microorganisms, it is crucial to estimate the required size of facilities and culturing tanks that are needed for commercialization. On the other hand, plants can be sown in fields or plant factories as necessary depending on the desired commercial scale. (3) Proteins derived from humans and produced in chloroplasts in plants are not glycosylated, resulting in a lower potential for allergic reactions when ingested by humans. This technology is based on discovery done using Arabidopsis and published in Proc. Natl. Acad. Sci. USA, 2010, and has been patented as “Constructs for Light-Switch for expressing genes of interest,” Japanese patent 6385644.
We are focusing on the production of biologics such as the world’s best-selling antibody drug adalimumab, otherwise known as Humira. This drug is used for the treatment of rheumatoid arthritis and the patents have just expired. We have succeeded in the production of the single-chain variable fragment (scFv) in tobacco chloroplasts with a yield of 35 mg/kg tobacco (fresh weight) and activity of Kd = 9.5 ×10-9 M against human tumor necrosis factor α (TNFα). Using this method to produce adalimumab gives a commercial value of approx. US$400 per square meter of field per year.
The proposal entitled “Production of biologics with lower costs by chloroplast engineering with Light-Switch to express foreign genes specifically” received the “Yamaha Motor Corp. Prize” at the Grand Prix of First Shizuoka Tech Planters sponsored by Leave a Nest, Inc., on July 7, 2018, in Hamamatsu, Japan. Another proposal, “Does Light-Switch serve mankind for a sustainable society?” was nominated as one of the finalists at the Agri Grand Prix 2018 on September 15, 2018, in Tokyo, Japan.
Salt accumulated on soil surfaces is a serious problem. Globally, salt-affected areas are presently the size of the United States and still expanding. As there is no rain in those areas, it has become impossible for farmers to continue to grow crops once salt has accumulated. It is thought that salt-tolerant genes could make plant cultivation possible in such areas, and it may be possible for agricultural products and biofuel to be produced. This technology is made possible with the genetic engineering of plants, and while genetically modified organisms are not well-received by society, in January 2017, the United States Department of Agriculture (USDA) ruled that GM grasses (Agrostis spp.) are not to be controlled as GM plants.
The salt-tolerant ability of plants is generally associated with drought-tolerance. The use of genes for salt tolerant callus (stc) and photoautotrophic salt tolerance (pst) revealed using Arabidopsis (published as two papers in PLOS ONE, 2015 and one in Plant Cell, 1999, respectively) can be applied to generate drought-tolerant grasses, which can then be used for greening building roofs and road slope faces. This technology has been patented as “Gene for ABC-transporter coffering salt tolerance on plants,” Japanese patent 5871222, as well as “A method for making transformant plants salt tolerant,” Japanese patent application 2007-065450, and “Polynucleotides imparting environmental stress-tolerance to plants,” Pub. No. WO/2006/098423 and International Application No. PCT/JP2006/305328.
Fig. 2. Phenotype of Arabidopsis with mutated PST2 gene
Plants were transferred to 200-mM NaCl (nearly half concentration of sea) containing medium and maintained for 3 weeks after growing on a standard medium for 3 weeks.
Fig. 3. Phenotypes of Arabidopsis ectopically expressing SUG genes
Enhancement of photosynthetic activity by degrading SUG genes was also observed.
3. Creation of productivity-enhanced plants by genome editing
“Genome editing” is the technology of editing the DNA of organisms to a status equivalent to that occurring in nature by specifically targeting genes, for example, disrupting genes. It is the beginning of a new era in Japan, as genome-edited foods can now be sold once they have been reported to the Ministry of Health, Labor and Welfare (MHLW). Although genome editing is a kind of genetic modification, genome-edited plants do not have the same regulation as other GM plants.
We found the genes responsible for suppressed greening (sug) using Arabidopsis, and knockout of these genes lets plants enhance their photosynthetic activity. It can be used to elevate the productivity of nutraceuticals and biofuel in plants. This technology has been patented as “Genes for suppressing photosynthetic activity and their application,” Japanese patent 5780506, and “A method for producing green callus cells,” Japanese patent application 2006-069547.
Plants have evolved to use environmental factors such as sunlight, water, and air to adapt to environmental change. Plants respond to different wavelengths of light. We found that blue and red LED light enhanced the content of polyphenols and saponins in Brassicaceae. This discovery can be applied in biofortification of pharmaceutics and nutraceuticals in plants.
We have three patent applications related to LED irradiation: “A method for enhancing expression of genes for saponin biosynthesis by exposure of plants to light illumination,” Japanese patent application 2007-087278, “A method for enhancing expression of genes for biosynthesis of lignans and lignins by exposure of plants to light illumination,” Japanese patent application 2008-089093, and “A method for enhancing expression of genes for flavonoid biosynthesis by exposure of plants to light illumination,” Japanese patent application 2008-089111.
