Physiological, biochemical, and transcriptomic analysis of castor (Ricinus communis L.) under foliar selenium treatment

BACKGROUND: ) on the physiological and molecular responses of castor (Ricinus communis L.) using transcriptomic analysis. RESULTS: Within the concentrations range of 20-40 mg/L, Se significantly enhanced SOD, CAT, and APX activities and upregulated the related genes. These treatments activated multiple hormone signaling pathways-including jasmone acid, salicylic acid, auxin, ethylene, and abscisic acid-and stimulated phenylpropanoid biosynthesis by upregulating key genes such as Phenylalanine ammonia-lyase-like (PAL), Cinnamoyl-CoA reductase 1-like (CCR), and Cinnamyl alcohol dehydrogenase (CAD). Additionally, several Se transporter gene families-phosphate transporters (PHTs), aquaporins (NIPs), and ABC families-were upregulated, facilitating Se uptake and detoxification. Conversely, a high Se concentration (60 mg/L) suppressed most antioxidant enzyme activities and related antioxidant gene expression, indicating toxicity. Overall, moderate Se application enhanced castor's stress tolerance and metabolic activity by coordinating antioxidant defense, hormone signaling, and secondary metabolism. In contrast, excessive Se induced physiological stress and gene repression. CONCLUSIONS: This study identified the optimal Se concentration (20-40 mg/L), which significantly improved the growth of castor and contributed to understanding the effects of Se treatment on the expression of genes in castor, providing valuable insights into the regulatory mechanisms of Se in alleviating abiotic stress in castor plants and inform optimal Se application strategies.