2,4‐Epibrassinolide Alleviates Cd Toxicity in <scp><i>Vigna angularis</i></scp> by Boosting Antioxidant Defense, Detoxification, and Genome Stability

Cadmium is one of the most toxic heavy metal pollutants in the world, seriously affecting crop growth and human health. 2,4-Epibrassinolide (BRs) has been proven to promote plant growth, enhance abiotic stress resistance and improve crop quality and yield. In this study, adzuki bean (V. angularis) cultivar 'Zhen Zhuhong' was grown hydroponically in 1/2 Hoagland nutrient solution with 0, 1, and 2 mg L^-1 cadmium chloride (CdCl₂), and then treated with 0 or 1 μM BR at the V1 stage. Compared with Cd stress, ascorbic acid content, peroxidase (POD, EC 1.11.1.7), catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC1.15.1.1) activities in adzuki Cd-stressed bean roots under BR treatment were increased by 30.63%, 41.83%, 51.49%, and 29.48%, which alleviated intracellular ROS accumulation and DNA oxidative damage. In addition, proline content and free amino acid content in BR-treated adzuki bean seedling roots under Cd stress increased by 30.37% and 35.96%, which was conducive to maintaining cell membrane homeostasis and improving root activity. RNA-seq and real-time quantitative reverse transcription PCR analyses revealed that BR treatment regulates the absorption, transport, and accumulation processes of Cd²⁺ in adzuki bean seedling roots, reducing the nonspecific accumulation of Cd²⁺ within cells and alleviating the toxic effects of Cd on root cells. BR treatment enhances the DNA damage repair in the roots of adzuki beans under Cd stress by reducing the extent of DNA oxidative damage, and effectively promoting the transition of cells from the G1 phase to the S phase.