Plant pigments are known for their health-promoting properties, including anti-inflammatory effects. Incorporating these pigments into vegetables can help to enhance their anti-inflammatory properties and provide a range of health benefits.
Metabolic engineering is a branch of plant biotechnology that aims to genetically modify plant metabolic pathways in order to create plant varieties with enhanced health benefits. Scientists recently engineered potato and tomato plants to express betalain, a plant pigment found only in Caryophyllales and higher fungi. They discovered that while betalain-tomatoes had anti-inflammatory effects on macrophages and murine colitis, betalain-potatoes did not.
Betalains are a type of plant pigment that gives certain fruits and vegetables their distinctive red-violet (betacyanin) or yellow (betaxanthin) color. These naturally occurring, nitrogen-containing, water-soluble pigments are commonly used as food coloring agents. Recent research findings have brought to light betalains’ strong antioxidant potential, making them potential candidates for producing health foods and combating various diseases. At the moment, betalains are only found in plants of the Caryophyllales order and higher fungi. As a result, metabolic engineering has been investigated in order to genetically modify cultivable non-Caryophyllales plants in order to increase the production and scalability of these pigments.
Despite the development of transgenic betalain-accumulating plants over the years, their applications in the production of healthcare food resources have yet to be explored.
These findings were in line with the anti-inflammatory effects of transgenic tomato that we observed in the intestines of murine models with dextran sulfate sodium (DSS)-induced colitis.
Prof. Arimura
To address this gap, a collaborative research team from Tokyo University of Science (TUS) and Iwate Biotechnology Research Center, Japan, led by Professor Gen-ichiro Arimura from TUS, attempted to genetically modify potato and tomato plants to produce betacyanin. Their aim was to test the therapeutic efficacy of betacyanin producing tomatoes and potatoes against murine models of colitis and inflammation-inducing macrophages.
Their findings were published in Biotechnology & Bioengineerin.. Discussing the results of this study, Prof. Arimura says, “We successfully engineered potato tubers and tomato fruits to co-express betacyanin biosynthesis genes [genes for CYP76AD1 from Beta vulgaris, DOD (DOPA 4,5-dioxygenase) and 5GT (cyclo-DOPA 5-O-glucosyltransferase) from Mirabilis jalapa] under the control of suitable promoters. This enhanced the endogenous accumulation of betanin and isobetanin – two common types of betacyanin — in these transgenic vegetables. The accumulation of these pigments made them appear dark red in color upon maturation, as compared to their wild-type counterparts.”
Because macrophages play an important role in a variety of inflammatory diseases, the researchers investigated the therapeutic efficacy of these transgenic vegetables in macrophage-like cells (RAW264.7) after stimulating the immune response with lipopolysaccharides (LPS). They discovered that transgenic tomato fruit extracts had higher anti-inflammatory activity than their wild-type counterparts. Within transgenic cells, this was attributed to a decrease in LPS-stimulated transcription of the proinflammatory cytokine gene — a Tnf-? gene.
“These findings were in line with the anti-inflammatory effects of transgenic tomato that we observed in the intestines of murine models with dextran sulfate sodium (DSS)-induced colitis. A marked improvement in their body weight loss and disease activity index was observed through the suppression of the DSS-stimulated transcription of proinflammatory genes — genes for Tnf-?, Il6 and Cox-2,” adds Prof. Arimura, while discussing the results derived from the other experiment in mice.
Furthermore, the additive and synergistic action of betacyanin with natural fruit components (such as lycopene in tomatoes) improved colitis in murine models. Interestingly, while transgenic tomato extracts had significant anti-inflammatory effects at 100-1000-fold dilutions, transgenic potatoes did not, despite significant betanin and isobetanin production. The presence of unknown antagonists in transgenic potatoes that work against betacyanin’s anti-inflammatory function is thought to be the cause, but this has yet to be confirmed.
“Tomatoes genetically engineered to produce betacyanins were found to have substantial health promoting effects. Although natural plant sources of betalains such as beetroots exist, these pigments demonstrate poor stability in high temperatures and extreme pH. This indicates that betacyanin producing transgenic tomato lines are more likely to be effective as health foods when ingested in their raw state,” summarizes Prof. Arimura.
What are the implications of these findings? “Although there is no commercial cultivation of edible genetically modified crops in Japan,” he continues, “we expect that their applications as health foods produced in enclosed plant factories and other facilities will lead to the widespread use of recombinant plants in Japan.”
We are confident that betalain engineering will soon become a promising avenue to improve the commercial production of health foods, that boost food supply while simultaneously conferring health benefits to its consumers.
