Medicago truncatula Iron-chaperone 1 (ICHAP1) is required for symbiotic nitrogen fixation

Navarro-Gomez, C.; Collantes-Garcia, J. A.; Rodriguez-Simon, M.; Wen, J.; Castillo-Michel, H.; Imperial, J.; Escudero, V.; Gonzalez-Guerrero, M.

doi:10.64898/2026.03.29.714480

bioRxiv · 10.64898/2026.03.29.714480

Medicago truncatula Iron-chaperone 1 (ICHAP1) is required for symbiotic nitrogen fixation

Navarro-Gomez, C.·Collantes-Garcia, J. A.·Rodriguez-Simon, M.·Wen, J.·Castillo-Michel, H.·Imperial, J.·Escudero, V.·Gonzalez-Guerrero, M.

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Abstract

Hundreds of proteins in the cell require iron (Fe) or Fe-containing cofactors to function. However, how Fe2+ or Fe3+ are specifically allocated to each of these proteins in plant cells remains largely unknown. It has been proposed that Fe metalation could be driven by specific interactions with Fe-shuttling proteins known as Fe-chaperones. Here, we present the first family of plant Fe2+-chaperones (ICHAPs) with orthologues in dicots and monocots. The role of these proteins in Fe distribution to Fe-dependent metabolic processes has been illustrated using symbiotic nitrogen fixation in Medicago truncatula root nodules. ICHAP1 is a soluble Fe2+-binding protein that interacts with plasma membrane Fe2+ transporter NRAMP1, but not with symbiosome Fe2+-transporters. ICHAP1 mutants present altered Fe distribution in cells and they cannot fix nitrogen. A second family member, ICHAP2 is required to target Fe2+ to symbiosomes, as it accepts Fe2+ from ICHAP1 and interacts with symbiosome Fe2+-importer VTL8, but not with NRAMP1. These results indicate a path for Fe2+ allocation from the plasma membrane to the symbiosome through specific protein-protein interactions and Fe2+ exchange from NRAMP1 to ICHAP1, to ICHAP2, and to VTL8.

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Navarro-Gomez, C., Collantes-Garcia, J. A., Rodriguez-Simon, M., Wen, J., Castillo-Michel, H., Imperial, J., Escudero, V., Gonzalez-Guerrero, M.. 2026-03-31. Medicago truncatula Iron-chaperone 1 (ICHAP1) is required for symbiotic nitrogen fixation. https://doi.org/10.64898/2026.03.29.714480

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