Researchers study bioengineered vegetables with anti-inflammatory properties

Researchers tried to genetically modify potato and tomato plants to produce betacyanin.. (CREDIT: Creative Commons)

Betalains are a class of plant pigments responsible for the characteristic red-violet (betacyanin) or yellow (betaxanthin) color of some fruits and vegetables. These naturally occurring, water-soluble and nitrogen-containing pigments are commonly used as food colorings. Recently, research findings have highlighted the strong antioxidant potential of betalains, making them potential candidates for healthy food production and disease control.

At present, betalains are formed only in plants of the order Caryophyllales and higher fungi. Consequently, metabolic engineering has been studied to genetically modify cultivated non-Caryophyllales plants to increase the production and scalability of these pigments.

Although transgenic betalain-accumulating plants have been developed over many years, their application in health food production has yet to be explored.

To fill this gap, a joint research team from the Tokyo University of Science (TUS) and the Iwate Biotechnology Research Center, Japan, led by Professor Gen-ichiro Arimura of TUS, attempted to genetically modify potato and tomato plants to produce betacyanin. Their goal was to test the therapeutic efficacy of betacyanin-producing tomatoes and potatoes against mouse models of colitis and inflammation-inducing macrophages.

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Their findings were published in Biotechnology and bioengineering. Discussing the results of this study, Professor Arimura says: “We have 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 betanine and isobetanine—two common types of betacyanin—in these transgenic vegetables. The accumulation of these pigments made them dark red in color when mature compared to their wild-type counterparts.”

Since macrophages play an important role in several inflammatory diseases, the research team further tested the therapeutic efficacy of these transgenic vegetables in macrophage-like cells (RAW264.7) after stimulating the immune response with lipopolysaccharides (LPS).

Comparison of betalain tomato with wild-type tomato for color and anti-inflammatory activity. (TEACHER: Genichiro Arimura from Tokyo Science University)

They noticed that transgenic tomato fruit extracts had higher anti-inflammatory activity compared to their wild-type counterparts. This was associated with a decrease in LPS-stimulated transcription of the pro-inflammatory cytokine gene, the Tnf-α gene, in transgenic cells.

“These results were consistent with the anti-inflammatory effects of transgenic tomatoes that we observed in the gut of mouse models with dextran sulfate sodium (DSS) colitis. A marked improvement in body weight loss and disease activity index was observed due to the suppression of DSS-stimulated transcription of pro-inflammatory genes – Tnf-α, Il6 and Cox-2 genes, ”adds Professor Arimura, discussing the results. from another experiment on mice.

Metabolic engineering of betacyanin in vegetables for anti-inflammatory therapy. (TEACHER: Genichiro Arimura from Tokyo Science University)

Moreover, the additive and synergistic effects of betacyanin with natural fruit components (such as lycopene in tomatoes) further enhanced improvement in colitis in mouse models. Interestingly, while significant anti-inflammatory effects were observed in transgenic tomato extracts at 100-1000-fold dilution, this was not the case with transgenic potatoes despite significant production of betanine and isobetanine.

The reason for this is thought to be the presence in the transgenic potato of unknown antagonists that act against the anti-inflammatory function of betacyanin, but this has yet to be confirmed.

Transgenic tomato fruits and potato tubers co-expressing genes for betacyanin biosynthesis, CYP76AD1 from B. vulgaris, DOD (DOPA-4,5-dioxygenase), and 5GT (cyclo-DOPA-5-O-glucosyltransferase) from Mirabilis jalapa. (TEACHER: Genichiro Arimura from Tokyo Science University)

“Tomatoes genetically modified to produce betacyanins have been found to have significant health benefits. Although there are natural plant sources of betalains, such as beets, these pigments show poor stability at high temperatures and pH extremes. This indicates that betacyanin-producing transgenic tomato lines are more likely to be effective as a health food when eaten raw,” concludes Professor Arimura.

What are the potential applications of these discoveries? He further adds, “Although there is no commercial cultivation of edible genetically modified crops in Japan, we expect their use as a health food through production in closed 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 for improving the commercial production of healthy foods that increases food supply while delivering health benefits to consumers.

For more science news, visit our New Discoveries section at The bright side of the news.

Note: Materials provided by the Tokyo University of Science. Content can be edited for style and length.

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