Plant scientists from the University of Geneva and ETH Zurich have engineered the cassava plant (Manihot esculenta) to produce higher vitamin B6 in the leaves and roots of the plant. Cassava is better known in the U.S. as tapioca. It also goes by other names such as manioc, yuca, and Brazilian arrowroot. The results from the experiment were recently published in the journal Nature Biotechnology.
Cassava is considered a major carbohydrate source in many tropical and subtropical regions, such as sub-Saharan Africa. The roots are a popular starch and the leaves are also eaten as a vegetable. Both parts of the plant must be cooked to remove cassava’s toxic cyanide compounds.
In general, cassava only contains small amounts of vitamin B6. This means a person would have to consume 1.3 kilograms of cassava each day in order to obtain an adequate amount of vitamin B6. The researchers set out to discover a way to increase the vitamin B6 in the leaves and roots of cassava. Increasing the vitamin B6 in cassava is thought to protect people in Africa against the deficiency.
Vitamin B6 deficiency is linked with diabetes, cardiovascular disease, fatigue, anemia, malaise, seizures, convulsions, and a childhood condition in eastern Africa called nodding syndrome. Vitamin B6 deficiency is also common in many African regions where cassava is the main food in the diet.
ETH Zurich professor of plant biotechnology Wilhelm Grusissem commented on the modified cassava plant: “Using the improved variety, only 500 g of boiled roots or 50 g of leaves per day is sufficient to meet the daily vitamin B6 requirement.”
University of Geneva professor Teresa Fitzpatrick developed the basis of the genetically modified cassava. Fitzpatrick found the vitamin B6 biosynthesis in the model plant used for the experiment called Arabidopsis thaliana (also known as thale cress). The corresponding genes for the enzymes PDX1 and PDX2 were introduced into the cassava genome. The researchers also produced several new cassava lines to increase vitamin B6 levels.
The team conducted several in-field trails and greenhouse tests over many years to determine if the vitamin B6 production increase from the genetically modified cassava was stable in affected conditions.
The researchers confirmed that cassava lines contained greater vitamin B6 in the leaves and roots than the normal cassava when metabolites were measured. The transferred gene activity also played a part in the increased production of vitamin B6, regardless of if the plants were of the field or greenhouse variety. The greater amounts of vitamin B6 remained consistent even after vegetative propagation multiplied cassava twice.
A research team from the University of Utrecht had also confirmed that vitamin B6 from genetically modified foods is considered bioavailable. In other words, the vitamin B6 is easily absorbable by humans.
“Our strategy shows that increasing vitamin B6 levels in an important food crop using Arabidopsis genes is stable, even under field conditions. Making sure that the technology is readily available to laboratories in developing countries is equally important,” explained lead research on the study at ETH Zurich, Herve Vanderschuren. “We hope that these platforms can help spread the technology to farmers and consumers.”
It remains unclear when the genetically modified cassava will be available to consumers and farmers. Genetic engineering or traditional plant breeding will help cross the new vitamin B6 trait into modified cassava varieties preferred by farmers. It is hoped that the future experiments can be performed in African laboratories. The method is not patented, since the technology and gene construct is thought to be more beneficial if it is available to anyone interested.
Other plant-based sources of high vitamin B6 include avocados, spinach, kale, celery, bell peppers, garlic, tuna, cod, broccoli, potatoes, Brussels sprouts, nuts, oats, beans, brown rice, and beef liver.
Sources for Today’s Article:
Li, K.T., et al., “Increased Bioavailable vitamin B6 in field-grown transgenic cassava for dietary sufficiency,” Nature Biotechnology, 2015; 33, 1029-1032.
Ruegg, P., “A cure for vitamin B6 deficiency,” ETH zurich web site, October 9, 2015; https://www.ethz.ch/en/news-and-events/eth-news/news/2015/10/cure-for-vitamin-b6-deficiency.html.
Mateljan, G., The World’s Healthiest Foods: Essential Guide for the healthiest way of eating (Seattle: George Mateljan Foundation, 2007), 790-791.