Spatio-temporal and chemical regulation of apoplastic barrier development confers low cadmium accumulation in Salvia miltiorrhiza

Cadmium (Cd) accumulation in crops and medicinal plants poses serious risks to human health. Root apoplastic barriers are critical for limiting cadmium (Cd) uptake in plants, yet their developmental dynamics and chemical plasticity under Cd stress remain poorly understood. Here, we compare two Salvia miltiorrhiza ecotypes with contrasting Cd accumulation and reveal that low Cd accumulation is associated with earlier barrier formation closer to the root tip and increased suberin deposition. Metabolic and transcriptomic analyses further show that Cd stress selectively induces key aliphatic suberin monomers—including p -hydroxy-cinnamic acid, C18:0, C16:1-OH, and the uniquely induced C14d—potentially mediated by HXXXD/BAHD acyltransferases. These compositional changes enhance barrier impermeability and reduce Cd 2+ influx. Our findings provide a mechanistic framework for breeding low-Cd medicinal crops and highlight candidate targets for genetic intervention. • Early apoplastic barrier formation in SC spatially restricts Cd 2+ influx. • Barrier function depends on chemical plasticity, not merely structural strength. • Suberin monomer composition is differentially remodeled under Cd stress. • HXXXD/BAHD acyltransferases are identified as potential regulatory targets.