Figure 1. Schematic depiction of possible functions of iron binding compounds (IBCs). (A) Chelation of Fe(III) mobilized from Fe(III) oxide with subsequent reduction of Fe(III) by FRO2. (B). Reduction of Fe(III) by reduced IBCs and subsequent recycling of the redox state via reduction of IBCs by FRO2 or other oxidoreductases. (C) IBCs that function in an independent Fe uptake system. After secretion, IBCs bind Fe(III) released from Fe(III) oxides and the Fe(III)-IBC complex is taken up as such without prior reduction. IBCOx, oxidized IBC; IBCRed, reduced IBC. Symbols represent proteins identified in Arabidopsis but functional orthologs may exist in other species.