OvHMA3 enhances cadmium tolerance in Onobrychis viciifolia by promoting root compartmentalization via active...

Cadmium (Cd) contamination poses a significant threat to agricultural safety and ecosystem health. Onobrychis viciifolia is a promising candidate for phytoremediation, yet the molecular mechanisms underlying its Cd tolerance remain unclear. Under Cd stress, this species demonstrated a strong capacity to sequester Cd in root tissues, as reflected by a strikingly low translocation factor. RNA-seq analysis revealed that Cd stress significantly induces the expression of heavy metal transport-related genes, particularly those encoding Heavy Metal ATPases (HMAs). Through genome-wide identification and expression analysis, we identified OvHMA3 as a key candidate gene, which was significantly upregulated by Cd in a concentration-dependent manner. We confirmed the tonoplast localization of OvHMA3. Heterologous overexpression of OvHMA3 significantly improved Cd tolerance in both yeast and Arabidopsis. Mechanistic studies demonstrated that OvHMA3 functions as a P-type ATPase, mediating ATP-dependent vacuolar sequestration of Cd²⁺. This process led to specific Cd retention in roots (root-to-shoot ratio ≈ 5.31) and a significant reduction in leaf oxidative damage in transgenic plants. Our findings elucidate the molecular basis of Cd detoxification in O. viciifolia via OvHMA3-mediated vacuolar compartmentalization, our work provides both theoretical foundations and a valuable genetic resource for the genetic improvement of heavy metal tolerance in crops.