Toxicity becomes beneficial: CvSBP1 acts as a key receptor, responsible for converting the form of selenium

Cardamine violifolia (Brassicaceae) is a selenium (Se) hyperaccumulator widely recognized for its potential in environmental remediation and dietary Se biofortification. However, the genetic mechanisms underlying Se metabolism in this species remain poorly understood. In this study, six selenium-binding protein (CvSBP) genes were identified from the C. violifolia genome, all containing conserved SBP56 domains. Promoter analysis revealed the presence of light-responsive, abscisic acid (ABA)-responsive, and gibberellin (GA)-responsive elements, indicating dual regulation by environmental and hormonal signals. Expression profiling showed that CvSBP1 was most strongly correlated with Se content and was selected as the core candidate gene. Structural modeling identified two potential Se-binding pockets (Pocket 3 and Pocket 5) in the CvSBP1 protein. Subcellular localization indicated nuclear targeting of CvSBP1. The gene exhibited high expression in young tissues of C. violifolia. In Arabidopsis thaliana, overexpression of CvSBP1 affected Se methylation-related genes (AtMMT1, AtHMT1, and AtHMT3), facilitated the conversion of inorganic to organic Se, enhanced antioxidant enzyme activities, and improved tolerance to Se stress. These findings provide novel insights into the molecular basis of Se metabolism and adaptation in C. violifolia, and identify CvSBP1 as a promising genetic target for the development of Se-enriched and stress-resilient crops.