Sunday, August 23, 2009

Transgenic Rice for Iron Deficiency

ETH Zurich has announced the development of a transgenic (GM) rice variety with a 6-times elevated level of iron, a nutrient that is one of the most important causes of malnutrition in the developing world.

Rice actually has a lot of iron in its seed coat, but it quickly spoils in tropical climates unless the seed coat is removed (aka "polished"). Additionally, eating polished rice is culturally important to most of these peoples (probably because brown rice tastes terrible!).

The team accomplished this by modifying the synthesis of two enzymes - one that pulls iron out of the soil and into the plant (nicotianamin synthase), and another that stores the iron in the endosperm of the seed (ferritin).

I was initially skeptical because the increased presence of a nutrient doesn't necessarily mean that humans will be able to absorb and use more of the nutrient. Plants are notorious for locking up nutrients (especially iron) in chemicals that bind (aka "chelate") the nutrients so strongly that the human digestive system can't separate them. The press release mentioned that ferritin is also used by human cells, so presumably this wouldn't be a problem.

At any rate, it'll be many years before this new variety is released to the public. As can be seen with ETH Zurich's previous work with Golden Rice, which has elevated levels of vitamin A, numerous laboratory and field trials are required before this plant can be approved for human consumption. Different cultures tend to be really picky about the varieties of rice they like to eat, so part of the development process will probably involve moving this trait into locally-adapted varieties.

Original: J. Wirth et al. (2009) Rice endosperm iron biofortification by targeted and synergistic action of nicotianamine synthase and ferritin. Plant Biotechnology Journal, 7: in press.

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