Root cell wall plasticity in iron homeostasis: an overlooked frontier in plant nutrition.

Iron (Fe) is an essential micronutrient for plant growth and development, yet its availability in soils is often limited or excessive, leading to widespread Fe deficiency or toxicity that constrains crop productivity. While Fe uptake, transport, and signaling pathways have been well characterized, the role of the root cell wall as a dynamic regulator of Fe homeostasis remains largely overlooked. This review presents the first comprehensive synthesis of how the structural and biochemical plasticity of the root apoplast and endodermis modulates Fe acquisition and distribution. We highlight key mechanisms, including pectin demethylation, proton extrusion, apoplastic acidification, callose deposition, Casparian strip formation, and suberization, that actively influence Fe solubility, binding, and radial movement across root tissues. By integrating recent findings on root cell-wall plasticity with Fe regulation, we identify regulatory hubs that link Fe status to cell-wall remodeling, as well as major knowledge gaps in the signaling pathways that mediate this connection. This timely review introduces a novel perspective that connects physical cell wall dynamics with molecular Fe signaling and underscores the potential of targeting cell wall traits to enhance Fe use efficiency and crop resilience, particularly on marginal soils.