Folate Biofortification of Rice

Laboratory of Functional Plant Biology, Department of Physiology, Ghent University,
K.L. Ledeganckstraat, 35, 9000 Ghent, Belgium. E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it.
*Laboratory of Toxicology, Department of Bioanalysis, Ghent University,
Harelbekestraat 72, 9000 Ghent, Belgium.
**Department of Agricultural Economics, Faculty of Bioscience Engineering, Ghent University,Coupure Links 653, 9000 Ghent, Belgium.

Rice is a major staple crop providing 80% of the daily caloric intake to 3 billion people. It is a poor source of essential micronutrients, including folates (vitamin B9). Humans and higher animals cannot synthesize folate on their own, thus, they have to rely on plant food as the major source of folate in their diet. Hence, folate shortage is wide-spread, especially in developing countries. Folate deficiency results in serious disorders, including neural tube defects (NTD) such as spina bifida in infants and megaloblastic anemia. Adequate dietary folate intake can prevent onset of these conditions.

Folate biofortification through metabolic engineering can complement the current methods to fight folate deficiency, all of which have proven limited success. Recently, we have achieved successful biofortification of rice seeds, by simultaneous overexpression of two Arabidopsis genes involved in the pteridine and para-aminobenzoate branches of the folate biosynthesis pathway1. A maximum enhancement of folate content in polished grains as high as 100 times above wild type levels was reached, with 100g of polished raw grains containing up to 4 times the adult daily requirement. Taking into account the processing losses and folate bioavailability, it is likely that 100g of white cooked rice can satisfy the daily folate requirement for an average adult person.

Ex-ante evaluation of the folate biofortified rice introduction in China using Disability Adjusted Life Years (DALY) approach has shown clear benefits of this intervention in order to relieve the NTD burden2. Implementation of biofortified rice would save 116,090 and 257,345 DALYs per year according to a low- and a high-impact scenario, respectively.

Current research is focused on the stabilization of folate in the biofortified rice grains by manipulating the polyglutamyl tail length of folate molecules and/or by binding to folate-binding proteins. We are also interested in studying the influence of high folate levels on rice seed metabolism by looking at global transcript profiles of the biofortified seeds as compared to the wild type using the microarray technology. Folate biofortification of other crops as well as evaluation of bioefficacy and bioavailability of folate in the biofortified rice in animal feeding experiments are under way.

References

  1. Storozhenko, S., De Brouwer, V., Volckaert, M., Navarrete, O., Blancquaert, D., Zhang, G.F., Lambert, W. and Van der Straeten, D. (2007) Folate fortification of rice by metabolic engineering. Nature Biotechnology, 25, 1277-1279.

  2. De Steur, H., Gellynck, X., Storozhenko, S., Liqun, G., Lambert, W., Van Der Straeten, D. and Viaene, J. (2010) Health impact in China of folate-biofortified rice. Nature Biotechnology, 28, 554-556.