1 - University of Freiburg; 2 - Universidad Politécnica de Madrid; 3 - Charles University; 4 - Ruhr University Bochum;
Abstract text: Plants acquire essential mineral nutrients from the soil, yet these elements must first traverse the extracellular matrix of the root before reaching the cell surface. How the physical properties of this extracellular compartment influence nutrient distribution and availability remains poorly understood. In plants, the extracellular matrix is formed by the cell wall, which carries a dynamically regulated negative charge that varies during development and in response to environmental cues.
Here, we show that cell wall charge functions as a tunable electrostatic gate that governs the partitioning of iron between retention and bioavailability. Genetic perturbation of pectin methylesterification indicates that increasing cell wall charge inherently enhances iron sequestration while restricting its mobility at the cell surface.
Moreover, iron limitation itself induces active remodeling of cell wall charge, dynamically shifting the balance toward increased iron accessibility. Together, these findings establish the plant cell wall as an active regulator of iron homeostasis rather than a passive barrier. By dynamically modulating extracellular electrostatics, roots regulate iron partitioning and bioavailability, revealing a new physical layer of control in plant mineral nutrition.