Genetic engineering approaches to improve the bioavailability and the level of iron in rice grains

Iron deficiency is the most widespread micro-nutrient deficiency world-wide . A major cause is the poor absorption of iron from cereal and legume-based diets high in phytic acid. We have explored three approaches for increasin g the amount of iron absorbed from rice-based meals. We first introduced a ferritin gene from Phaseolus vulgaris into rice grains, increasing their ir on content up to two-fold. To increase iron bioavailability, we introduced a thermotolerant phytase from Aspergillus fumigatus into the rice endosperm . In addition, as cysteine peptides are considered a major enhancer of iron absorption, we overexpressed the endogenous cysteine-rich metallothionein- like protein. The content of cysteine residues increased about seven-fold a nd the phytase level in the grains about 130-fold, giving a phytase activit y sufficient to completely degrade phytic acid in a simulated digestion exp eriment. High phytase rice, with an increased iron content and rich in cyst eine-peptide, has the potential to greatly improve iron nutrition in rice-e ating populations.