Washington D.C., USA
September 9, 2011
More than half the world’s population relies upon rice for their daily “bread.” Yet, rice has the lowest iron concentration of the commonly cultivated cereal crops. Alex Johnson (photo), a scientist at the University of Melbourne, is trying to increase the amount of iron, which is essential to good health, in rice grain. In a research study just published in PloS ONE, Johnson and his team were able to increase the iron concentration in rice up to 19 parts per million (ppm), 4 times more than in current varieties—the highest ever reported. Experts estimate that about 14 ppm of iron is needed in rice to provide sufficient dietary iron in rice-based diets. This breakthrough could have a big impact on reducing iron deficiency in millions of poor people who eat rice daily.
Increasing minerals such as iron in rice is notoriously difficult to do through conventional breeding. There are just not enough varieties of rice with high enough iron concentration to breed with.
Johnson and his team, instead, focused on Nicotianamine (NA), a chemical compound naturally found in plants that facilitates the uptake and transport of iron. Genes that control the production of NA, known as NAS genes, only kick into action when there are low amounts of iron in the soil, enabling the roots to absorb iron that the plants need. “What we have been able to do is turn on the NAS genes all the time, not only during times of low iron,” Johnson says, “resulting in several times more iron in the grain than would be possible through conventional breeding methods.”
As an added benefit, the NAS genes also increased the concentration of zinc in the grain. Zinc is another micronutrient essential for good health, yet billions of people are at risk of zinc deficiency.
The next step is to test these new varieties over several seasons outside of the greenhouse and see if they continue to uptake and transport more iron—and zinc—from the roots and into the edible portion of the rice grain.
Johnson and his team are also concerned that climate change, while expected to increase crop yields, may cause a decline in nutritional quality. “We need to use a variety of modern methods to ensure that food crops can not only withstand the effects of climate change but also better provide people with the micronutrients they need to enjoy good health.”
Research Paper: Constitutive Overexpression of the OsNAS Gene Family Reveals Single-Gene Strategies for Effective Iron- and Zinc-Biofortification of Rice Endosperm
Free Open Access to this Paper in PloS ONE
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