Handing off iron in plants: from uptake pathways to intracellular chaperones for biofortification
Qingnan ChuAbstract
Background
Plant iron (Fe) homeostasis has been extensively studied at the levels of soil uptake, long-distance transport, storage and deficiency signalling. A less resolved question is how Fe, once it crosses a membrane or is released from an intracellular store, is directed toward specific subcellular destinations and metalloprotein clients.
Scope
This Perspective synthesizes recent work on plant Fe acquisition, transporter dynamics, intracellular Fe pools, inter-organelle redistribution, nodule metal delivery and biofortification. It argues that classical transporter- and ligand-centred models remain essential, but may be complemented by selective intracellular routing mechanisms. Legume nodules are highlighted as a high-demand system in which Fe delivery to symbiosomes provides a useful test case for a proposed protein-mediated ionic Fe2+ handoff.
Conclusions
Current evidence supports a layered view of plant Fe trafficking in which membrane transport, soluble ligands, redox chemistry, storage compartments and candidate ionic Fe2+ chaperones cooperate to allocate Fe safely and selectively. The recently proposed Medicago truncatula ICHAP proteins provide an emerging model for the direct handoff of ionic Fe2+ between successive membrane-transport steps, a mechanism distinct from the established protein-mediated transfer of preassembled Fe-S clusters by the SUF, ISC and CIA mechineries. A routing-centred framework may help refine biofortification strategies by shifting attention from bulk Fe accumulation toward controlled deposition of nutritionally useful Fe in edible tissues.