Folate or folic acid, also known as vitamin B9, is an essential nutrient involved in numerous body functions, including DNA synthesis and repair, production of red blood cells, and rapid cell division and growth, especially in infancy and pregnancy. Since the human body cannot make folate, our dietary supply must meet the daily requirement (~400 µg). Folate deficiency may result in diarrhea, depression, anemia, Alzheimer disease, neural tube defects and brain defects during pregnancy.
Folates naturally exists in a variety of foods, including leafy vegetables, fruits, nuts, legumes, dairy products, poultry, meat and seafood. Yet, in most crops like rice and other cereals, the amount of folate is very low. Due to the fact that rice is consumed by about half of the world’s population as single energy source, folate deficiency is very prevalent in developing countries with about a 10 fold higher occurrence of neural tube defects in some regions compared in Western countries.
Vitamins are unstable molecules and can degrade during food processing, preparation and storage, when exposed to oxygen, light, humidity, increase temperatures and acidity change. So, rice grains harvested in developing countries with high temperature and humidity suffer from the loss of vitamins during long-term storage. In 2007, a research lab from Ghent University (Belgium) developed the first generation of biofortified rice, by metabolic engineering, with a 100-fold higher folate level. The study showed the degradation of half of the folate content after a storage period of six months.
In order to solve this problem, a new rice prototype has been developed by the collaboration between the labs of Prof. Dominique Van Der Straeten, Prof. Willy Lambert, Prof. Christophe Stove, Dr. Hans De Steur and Prof. Xavier Gellynck and published in the journal Nature Biotechnology. In this generation of rice lines, high folate levels were not only achieved but also remained stable upon long term storage.
Comparable to a car assembly line, this new rice prototype is also created through metabolic engineering using specific enzymes to biosynthesize folate molecule from a certain start product with a series of consecutive changes. Two strategies were applied to stabilize folate. The first strategy was to bind folates with a folate binding protein. This protein has been well studied in mammals by presenting in milk and protecting folate from degradation. In this way, intact folates can be passed on from mother to her infant and its further development is also supported. So, by expressing a synthetic gene of a folate binding protein from bovine milk in the rice grain, folate levels are stabilized for long term storage under the same principle.
The second strategy involved the stimulation of the final step during folate formation. By extending the tail of the folate molecule, cellular retention and the binding to folate dependent proteins can be promoted. Besides, the new gene combination also increased the folate level up to 150 folds than that in normal rice. This transfer of genetic information into edible rice varieties is easy, as all genes involved in the study were placed next to each other on a single piece of DNA, which suggests further development of other fortifications such as the enhancement of other vitamins or minerals like iron. This technology can also be applied in other crops including both cereals and non-cereals.
References:
http://www.sciencedaily.com/releases/2015/09/150922104238.htm
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