Finally, as noted in the press release (see the first link in this post), the researchers have not patented their technology as they want to make it freely available to everyone who needs access to the improved varieties of cassava.
Originally shared by Robert Woodman
Engineering Cassava to Combat Vitamin B6 Deficiency
Original research note: http://www.nature.com/nbt/journal/v33/n10/full/nbt.3318.html (paywall)
Vitamin B6 is an essential nutrient for humans. It is required for numerous biochemical processes in the human body, and deficiency in this vitamin is associated with numerous pathological conditions, including cardiovascular disease, diabetes, various neurological diseases, and nodding syndrome (NS), which is a childhood condition found rather commonly in eastern Africa in areas where vitamin B6 deficiency is endemic. (1,2)
A recent publication in Nature Biotechnology by a multinational group of scientists has found a possible way to solve vitamin B6 deficiency through genetic engineering of cassava. Cassava, also called Brazilian arrowroot, manioc, tapioca, and yuca (not the same as the unrelated plant known as yucca) is a New World plant that has become an important dietary staple throughout the tropical and subtropical world (3). Cassava is as important to African farmers as rice is to Asian farmers or as wheat and potatoes are to European farmers (4, citing a personal communication). Various researchers have suggested for some time that genetic engineering of cassava could be used to ameliorate malnutrition and dietary deficiencies (2, 4-7). The paper in Nature Biotechnology reports the successful engineering of cassava to produce vitamin B6 (1).
The enzymes PDX1 and PDX2 are needed to synthesize vitamin B6 in plants. Genes encoding PDX1 and PDX2 were taken from the plant Arabidopsis thaliana (8) and modified to put them under control of one of two promoters. One promoter (CaMV35S) allowed PDX1 and PDX2 to be expressed throughout the entire cassava plant, while the other promoter (Patatin) enhanced expression of the two genes in the cassava roots. Engineered cassava plants from each group, named 35S and PAT (based on the promoter that was used), were then grown from tissue culture in a greenhouse. Evaluation of the resulting plants showed no significant morphological differences but did show a large increase for vitamin B6 expressed in the plants’ leaves and roots (35S) or in the roots (PAT). The amount of vitamin B6 expressed in the transgenic leaves was increased from 3.9-fold to 48.2-fold over wild-type cassava, while the amount of vitamin B6 expressed in transgenic roots increased 1.9- to 5.8-fold over wild type cassava. Evaluation in a test field in Shanghai, China, showed that the genetically engineered plants were stable when grown in wild-type conditions.
One significant difference between engineered and wild-type cassava did emerge in the study. Using high-performance liquid chromatography (HPLC), the research group established that the vitamin B6 that accumulated in the engineered cassava plants’ leaves and roots was mostly in the unphosphorylated form. Only the phosphorylated esters of vitamin B6 are active in the body, but the unphosphorylated forms of vitamin B6 are more stable to storage and to heating. Cassava is typically boiled before eating to remove toxic compounds known as cyanogens, and quite a bit (15%, up to 75%) of the vitamin B6 in cassava can be lost due to boiling (9, see also 1, at page 1031). Thus, having a cassava plant with enhanced vitamin B6 production means that more vitamin B6 will be available to the eater after the plant is cooked.
Finally, the authors examined the bioavailability of the vitamin B6 produced by the genetically engineered plants and found that the vitamin B6 produced by the transgenic cassava was highly available to be absorbed by the consumer of the cassava. Indeed, the authors noted that “[u]sing bioavailable ‘vitamin B6 equivalents’, we calculated that the vitamin B6 recommended dietary allowance for an adult person (1.3 mg/day) would be reached with 51 g of boiled 35S-5 leaves or 505 g (~1.7 lb) of boiled PAT-12 storage roots” (1, at page 1031).
This paper shows that cassava, an important dietary staple, can be genetically engineered to produce more vitamin B6. The increased amounts of vitamin B6 will help alleviate nutritional deficiencies in Africa, improving the health and well-being of people who depend on cassava as a key component of their diet. Further, other modifications to cassava are possible to further improve the nutritional quality of this important plant. Finally, as noted in the press release (see the first link in this post), the researchers have not patented their technology as they want to make it freely available to everyone who needs access to the improved varieties of cassava. The groups involved in this research are now working with African scientists to try and introduce this modified cassava to African farmers.
(1) Kuan-Te Li, et al. Increased bioavailable vitamin B6 in field-grown transgenic cassava for dietary sufficiency. Nature Biotechnology 33, 1029–1032 (2015), doi:10.1038/nbt.3318. http://www.nature.com/nbt/journal/v33/n10/full/nbt.3318.html (paywall)
(2) Ian S. Blagbrough, Soad A.L. Bayoumi, Michael G. Rowan, and John R. Beeching. Cassava: An appraisal of its phytochemistry and its biotechnological prospects. Phytochemistry 71, 1940–1951 (2010), doi:10.1016/j.phytochem.2010.09.001
(3) Cassava. (2015, October 28). In Wikipedia, The Free Encyclopedia. Retrieved 20:23, November 1, 2015, from https://en.wikipedia.org/w/index.php?title=Cassava&oldid=687860962
(4) Montagnac, J. A., Davis, C. R. and Tanumihardjo, S. A. Nutritional Value of Cassava for Use as a Staple Food and Recent Advances for Improvement. Comprehensive Reviews in Food Science and Food Safety, 8, 181–194 (2009). doi: 10.1111/j.1541-4337.2009.00077.x. #openaccess paper available at http://onlinelibrary.wiley.com/doi/10.1111/j.1541-4337.2009.00077.x/full
5. Martina Newell McGloughlin. Modifying agricultural crops for improved nutrition. New Biotechnology 27(5), 494-504 (November 2010). Available at http://www.academyofsciences.va/content/dam/accademia/pdf/sv113/sv113-newell.pdf
6. Teresa B. Fitzpatrick, et al. Vitamin Deficiencies in Humans: Can Plant Science Help? The Plant Cell, 24, 395–414 (February 2012). #openaccess available at http://www.plantcell.org/content/24/2/395.long
7. Hervé Vanderschuren, et al. Strategies for vitamin B6 biofortification of plants. Front Plant Sci. 4, 143 (May 2013). Available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659326/
8. Arabidopsis thaliana. (2015, October 27). In Wikipedia, The Free Encyclopedia. Retrieved 20:42, November 1, 2015, from https://en.wikipedia.org/w/index.php?title=Arabidopsis_thaliana&oldid=687786836
9. A.Paula Cardoso, et al. Processing of cassava roots to remove cyanogens. Journal of Food Composition and Analysis, 18(5), 451-460 (August 2005). Available at http://www.sciencedirect.com/science/article/pii/S0889157504000705 and at https://www.researchgate.net/profile/Julie_Cliff/publication/222394748_Processing_of_cassava_roots_to_remove_cyanogens/links/09e415057672503c23000000.pdf