Enhanced tolerance of rice to low iron availability in alkaline soils using barley nicotianamine aminotransferase genes

One of the widest ranging abiotic stresses in world agriculture arises from low iron (Fe) availability due to high soil pH, with 30% of arable land to o alkaline for optimal crop production. Rice is especially susceptible to l ow iron supply, whereas other graminaceous crops such as barley are not. A barley genomic DNA fragment containing two naat genes, which encode crucial enzymes involved in the biosynthesis of phytosiderophores, was introduced into rice using Agrobacterium-mediated transformation and pBIGRZ1. Phytosid erophores are natural iron chelators that graminaceous plants secrete from their roots to solubilize iron in the soil. The two transgenes were express ed in response to low iron nutritional status in both the shoots and roots of rice transformants. Transgenic rice expressing the two genes showed a hi gher nicotianamine aminotransferase activity and secreted larger amounts of phytosiderophores than nontransformants under iron-deficient conditions. C onsequently, the transgenic rice showed an enhanced tolerance to low iron a vailability and had 4.1 times greater grain yields than that of the nontran sformant rice in an alkaline soil.