METABOLIZATION OF IRON BY PLANT-CELLS USING O-TRENSOX, A HIGH-AFFINITY ABIOTIC IRON-CHELATING AGENT

A synthetic siderophore, O-Trensox (L), has been designed and synthesi zed to improve iron nutrition of plants. The affinity for iron of this ligand [pFe(III) = 29.5 and pFe(II) = 17.9] is very high compared wit h EDTA. In spite of its high and specific affinity for iron, O-Trensox was found to be able to prevent, and to reverse, iron chlorosis in se veral plant species grown in axenic conditions. It also allows the iro n nutrition and growth of Acer pseudoplatanus L. cell suspensions. The rate of iron metabolization was monitored by Fe-59 radioiron. Ferriti ns, the iron storage proteins, are shown to be the first iron-labelled proteins during iron metabolization and to be able to further dispatc h the metal. Using Fe(III)-Trensox, the rate of iron incorporation int o ferritin was found to be higher than when using Fe-EDTA, but slower than with Fe-citrate, the natural iron carrier in xylem. During a plan t cell culture, the extracellular concentrations of iron complex and f ree ligand were measured; changes in their relative amounts showed tha t the iron complex is dissociated extracellularly and that only iron i s internalized. This suggests a high affinity for iron of a putative c arrier on the plasmalemma. In contrast with Fe-citrate and Fe-EDTA com plexes, Fe(III)-Trensox is not photoreducible. Its ability to induce r adical damage as a Fenton reagent was tested using supercoiled DNA as target molecule. Unlike Fe-citrate and Fe-EDTA, Fe(II)-Trensox and Fe( III)-Trensox were proven to be harmless even during ascorbate-driven r eduction, while Fe-EDTA and Fe-citrate generate heavy damage to DNA.