Enhancing iron uptake and alleviating iron toxicity in wheat by plant growth-promoting bacteria: Theories and practices

Abstract

Though iron is a rich mineral in soil, its bioavailability for many crops is low. Considering the vital role of iron in all organisms, iron deficiency (ID) is one of the most widespread and common nutritional problem in the world. The hidden hunger caused by ID seriously affects the quality of human life and economic development. As one of the major staple foods, wheat grain is in short of iron as well. Iron absorbing in wheat is mainly through its root by the strategy II which gets iron from the rhizosphere through the release and uptake of Fe-chelating mugineic acid phytosiderophores. Meanwhile, there are versatile bacteria lived in both the rhizosphere and indigenous region of wheat root. Many of them are communistic or termed plant growth-promoting bacteria (PGPB), needing iron for growth and work as well. Contrasting to wheat, bacteria uptakes both dissociative inorganic and associative organic iron combined with siderophores more efficiently, mainly through different ATP binding cassette transporters. Laboratory and field experiments showed many PGPB improve wheat iron uptake when iron is deficient by producing different metabolites and regulating transporters, which provided basis for a microbiological strategy to iron biofortification. On the other side, many PGPB reduced iron toxicity to wheat as their strong bioleaching capacity and negative regulation of iron uptake or transport when iron is plenty