The Membrane Continuum Governing Cadmium Uptake, Partitioning, and Detoxification in Plants

Cadmium (Cd) contamination threatens agro-ecological safety and food security; thus, elucidating mechanisms of Cd uptake and accumulation in plants is key to breeding low-Cd crops. Within the defensive network plants deploy against Cd stress, the plasma membrane and endomembrane system act as physical barriers to metal influx and as the core regulatory hub governing signal perception, transmembrane transport, and vacuolar compartmentalization for detoxification. This review examines the physiological and molecular mechanisms by which the cell membrane system influences Cd transport and accumulation in plants, focusing on five key dimensions: (1) the gating roles of plasma membrane transporters (e.g., ZIP, NRAMP, and HMA families) in root Cd uptake, efflux detoxification, and long-distance translocation to shoots; (2) compensatory mechanisms in intracellular homeostasis remodeling mediated by endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) and Golgi vesicle trafficking; (3) the vacuole as a central detoxification depot, achieving compartmentalized sequestration of free Cd²⁺ and macromolecular chelates through transmembrane transport networks comprising ABC, MTP, and CAX proteins; (4) profound effects of Cd-triggered dynamic remodeling of membrane lipid composition, lipid peroxidation, and membrane microdomain changes on physicochemical states and spatial distribution of transport channels; (5) membrane-initiated signaling networks (lipid sensors, Ca²⁺, ROS, NO) and their post-translational fine-tuning of transporter abundance and activity. This review integrates dynamic plant response mechanisms to heavy metal Cd from a multi-dimensional membrane biology perspective, aiming to provide theoretical references and novel insights for the molecular design and safe production of low-Cd crop varieties.