The Transcription Factor Basic Pentacysteine 5, RsBPC5, Enhances Lead Stress Tolerance in Raphanus sativus

Radish (Raphanus sativus), a commonly grown root vegetable prized for its nutrition and culinary use, is particularly vulnerable to lead (Pb) stress, which mainly results in Pb accumulation in the roots. However, the molecular mechanisms underlying Pb accumulation in radish remain largely unknown. In this study, we investigated the role of BASIC PENTACYSTEINE (BPC) genes in radish's response to Pb stress. Phylogenetic analysis revealed that radish contains 10 BPC genes, which are distinctly clustered in Cluster III. Expression analysis revealed that, except for RsBPC2, RsBPC4, and RsBPC7, the expression of most RsBPC genes was significantly altered under Pb stress. Notably, the expression of RsBPC5 gradually decreased with prolonged Pb exposure. Subcellular localization analysis confirmed that RsBPC5 is localized in the nucleus and acts as a transcriptional repressor. Functional assays demonstrated that transient overexpression of RsBPC5 enhanced the tolerance of radish plants to Pb stress via reducing Pb accumulation and activating the antioxidant defense system. Collectively, our findings suggest that RsBPC5 plays a key role in radish's response to Pb stress, potentially improving Pb tolerance by modulating Pb uptake and strengthening antioxidant defense mechanisms.