Brassica rapa metal transporter BrMTP1 confers multi-metal tolerance

Plants require essential metal ions for growth and development, but excessive accumulation of these elements can be toxic. Metal tolerance proteins (MTPs) are key regulators of metal homeostasis, facilitating the sequestration and efflux of excess ions to maintain cellular balance. Brassica rapa is a globally important vegetable crop, yet the functional roles of its MTP family members in Zn, Co, and Mn transport remain poorly characterized. In this study, we identified BrMTP1 in B. rapa and elucidated its substrate specificity and transport mechanisms for Zn, Co, and Mn. Expression pattern analysis revealed that BrMTP1 is significantly upregulated under excessive Zn, Co, and Mn stress, and subcellular localization confirmed its tonoplast association. Functional characterization assays in Arabidopsis thaliana and yeast demonstrated that BrMTP1 mediates vacuolar sequestration of Zn, Co and Mn, thereby enhancing tolerance to metal toxicity. Moreover, BrMTP1 -overexpressing Arabidopsis lines exhibited enhanced accumulation of Zn, Co, and Mn in roots and reduced root-to-shoot translocation of these metals, suggesting a critical role in limiting their systemic distribution. Present findings provide novel insights into the molecular mechanisms of metal homeostasis in B. rapa and highlight BrMTP1 as a potential target for improving crop resilience to metal stress. • BrMTP1 is significantly upregulated under excess Zn, Co, and Mn stress, and subcellular localization confirmed its tonoplast association. • BrMTP1 mediates vacuolar sequestration of ions in yeast, thereby enhancing tolerance to metal toxicity. • BrMTP1 -overexpressing Arabidopsis lines exhibited reduced root-to-shoot translocation of Zn, Co, and Mn, suggesting a critical role in limiting their systemic distribution.