Senescence and protein remobilisation in leaves of maturing wheat plants grown on waterlogged soil

Nicotianamine (NA), the key precursor of the mugineic acid family phytosiderophores (MAs), is synthesized from S-adenosylmethionine (SAM). The NA synthase was strongly induced by Fe-deficiency treatment, and the activity increased to the maximum level faster than the time of maximum level of MAs secretion and also before the appearance of severest chlorosis. The enzyme was mainly localized in the roots of barley. NA synthase had the optimum pH at 9.0, a molecular weight of about 40,00050,000 estimated by gel filtration or about 30,000 by SDS-PAGE. Using hydrophobic chromatography, hydroxylapatite chromatography, and preparative SDS-PAGE, NA synthase was purified as one band on SDS-PAGE.