Iron Biofortification

Iron deficiency is the most common nutritional deficiency disorder in Australia and the world. Over 2 billion people suffer from iron (Fe) deficiency, with symptoms ranging from poor mental development to depressed immune function and anaemia.

Meats, Fe-fortified cereals and vitamin C-rich foods are common dietary prescriptions for the 10% of Australian adults and children suffering from Fe deficiency. For billions of people in developing countries, however, meats and Fe-fortified foods are prohibitively expensive and difficult to obtain.

Rice provides up to 80% of daily calories for people in developing countries yet the commonly consumed polished grain – also known as white rice – contains nutritionally insufficient concentrations of Fe and other micronutrients. Large-scale screening of rice seed banks for Fe content has identified germplasm with up to 8 ppm Fe in white rice. Nutritional studies indicate, however, that women and children in rice-based societies require at least 14.5 ppm Fe in white rice to meet Fe intake requirements.

In collaboration with the HarvestPlus Challenge Program (www.harvestplus.org), the High-Iron Rice group is using biotechnology to generate new rice varieties that load increased concentrations of Fe into the grain, an approach known as “biofortification.”

As opposed to mineral supplements, which cost money and require a highly functional health infrastructure for dispersal, biofortified crops offer a cheap, reliable and sustainable solution to Fe and other micronutrient deficiencies.

Research Strategies

Nicotianamine (NA) chelates and transports metals throughout plant tissues and into developing seed. The possibility that elevated NA may increase the concentration of Fe in rice grain makes the NA synthase (NAS) genes an attractive target for biofortification programmes.

We are using a variety of biotechnological tools to increase expression of the three rice NAS genes – OsNAS1, OsNAS2 and OsNAS3 – in transgenic rice. Our initial work has yielded exciting results with increases of up to 3-fold more Fe in white rice, and we recently demonstrated that this increase is correlated with nicotianamine content.

We are currently using facilities at the Australian Synchrotron to visualize Fe distribution in the high-Fe rice, and tissue culture methods to determine bioavailability of the elevated Fe.

This work relies on a wide variety of experimental approaches. Some of the techniques employed include:

• Generation of transgenic rice using Agrobacterium tumefaciens
• DNA analyses – Southern blots, restriction digestion and PCR
• RNA analyses – Quantitative PCR, RT-PCR
• Protein analyses – LC-MS, GC-MS
• Nutrient analyses – ICP-AES, x-ray fluorescence microspectroscopy, Caco-2 cell culture

PhD & Master Degree Supervisors

Dr Alex Johnson
Dr Mark Tester
Dr Trevor Garnett

Suggested reading

• Johnson AAT, Hibberd JM, Gay C, Essah PA, Haseloff J, Tester M, Guiderdoni E (2005) Spatial control of transgene expression in rice (Oryza sativa L.) using the GAL4 enhancer trapping system. Plant J. 41: 779-789.
• Kim, S., Takahashi, M., Higuchi, K., Tsunoda, K., Nakanishi, H., Yoshimura, E., Mori, S. and Nishizawa, N.K. (2005) Increased nicotianamine biosynthesis confers enhanced tolerance of high levels of metals, in particular nickel, to plants. Plant Cell Physiol., 46, 1809-1818.
• Lucca, P., Hurrell, R. and Potrykus, I. (2002) Fighting iron deficiency anemia with iron-rich rice. J Am. Coll. Nutr., 21, 184S-190.
• von Wiren, N., Klair, S., Bansal, S., Briat, J.-F., Khodr, H., Shioiri, T., Leigh, R.A. and Hider, R.C. (1999) Nicotianamine chelates both FeIII and FeII. Implications for metal transport in plants. Plant Physiol., 119, 1107-1114.