Strigolactones modulate iron uptake in plants.

Abstract

Strigolactone (SL) hormones influence a wide range of developmental and physiological processes but have not previously been linked to plant iron homeostasis. Here, we identify the gene underlying the iron-deficient maize mutant interveinal yellow (ivy) as ZmCCD8, a key enzyme in SL biosynthesis. Maize ivy/ccd8 mutants exhibit reduced expression of iron-regulated genes, including IRO2 and genes involved in iron chelator and transporter biosynthesis. Application of the synthetic SL rac-GR24 restores gene expression and alleviates chlorosis. Under iron-deficient conditions, ccd8 mutants show normal upregulation of iron uptake genes, indicating that SLs are not required for the deficiency response but are essential for maintaining basal iron gene expression under sufficient iron. Similar chlorosis in Arabidopsis and rice SL mutants under moderate iron suggests a conserved role for SLs in iron regulation, with potential agricultural applications. We propose that strigolactone signaling acts as an upstream regulatory input to the established FIT/IRO2-centered iron-deficiency network, with SMXL/D53 proteins functioning as negative regulators and iron deficiency providing the principal activating cue.

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