Phytosiderophore-based molecular approach for enhanced iron acquisition to increase crop production under high pH calcareous soils

Abstract

In the plant kingdom, two different Fe-deficiency chlorosis induced root strategies exist. Strategy I typical for dicots and monocots, with exception of grasses, is characterized by increased root reducing capacity (plasma membrane bound reductase), lowering the pH of the medium and in some instances enhanced release of phenolics. Strategy II iron acquisition mechanism of graminaceous monocots release iron-chelating mugineic acid family phytosiderophores (MAs in response to Fe deficiency) which solubilize inorganic Fe III compounds by chelation to form Fe3+-MA. These Fe3+- MAs are passed through a highly specific Fe transporter (yellow strip – YS I) present in the root plasma membrane. Further, notification of the key enzymes such as nicotianamine synthase (NAS) and/or nicotianaimine aminotransferase (NAAT) as well as deoxygenase gene IDS3 paved the way for the development of transgenic rice plants with enriched DMA both in shoot and root of chlorotic plants. Therefore, it is established that the genetic engineering can transfer traits from plants tolerant to adverse conditions to field crops for sustained productivity. Introduction of NAS, NAAT and IDS3 genes, respectively in rice has been found very effective in producing higher amount of phytosiderophores (MAs). Introduction of linearly combined genes NAS, NAAT and IDS3.Two cis-elements (iron deficiency-responsive elements) IDE 1 and IDE 2 have also been identified.