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Crop Biotech Update

Constitutive Overexpression of the OsNAS Genes for Iron- and Zinc-Biofortification of Rice

September 15, 2011

Rice is the primary staple food for about half of the world's population. However, polished rice has insufficient amounts of iron, zinc, and beta carotene to meet daily requirements of the consumers. Rice plants absorb iron from the soil only when there is low iron available. Alexander Johnson of the University of Melbourne in Australia and colleagues conducted a study to help plants continuously absorb iron not only during low iron situations.

The team overexpressed all three genes of the OsNAS family, which have been known to encode production of nicotianamine (NA), a chemical compound naturally found in plants that facilitates the uptake and transport of iron. They assessed the utility of each gene for iron biofortification through single-transgene approach. Two OsNAS2 overexpression lines exhibited four-fold increases in iron concentration. This increase was mapped in unprecedented detail using synchrotron X-ray fluorescence spectroscopy. Characterization of 90 transgenic lines overexpressing these genes showed that the three genes increase not just iron levels, but also zinc concentration.

Based on the findings, rice cultivars overexpressing single rice OsNAS genes could provide sustainable and genetically simple solution to iron and zinc deficiency disorders, which are rampant throughout the world.

Read the research article at