Integrated morpho-physiological, biochemical and transcriptomic analyses reveal wheat responses to antimony toxicity and brassinosteroid-mediated alleviation

• 25 µM Sb inhibited wheat seedling growth, with effects varying over time • Sb exposure increased MDA levels and activated the antioxidant defense system • Cell wall polysaccharides and metal(loid) transport proteins contributed to Sb detoxification • Sb-upregulated BIN2 expression suppresses BZR1/2 expression, impairing BR signal transduction • Exogenous BRs mitigated Sb-induced growth inhibition in wheat seedlings Antimony (Sb) induces detrimental toxicities on plant growth, yet the underlying mechanisms are under-explored. In this study, a comprehensive approach combining physiological and transcriptomic analyses was adopted to investigate the morpho-physiological, biochemical and molecular responses of wheat to Sb toxicity. The results showed that Sb treatments (> 10 μM) significantly reduced wheat biomass accumulation (by 52.2%-67.8% in shoots, and 24.9%-56.3% in roots) through inhibiting root development and impaired photosynthetic performance, accompanied by elevated malondialdehyde (MDA) levels. At 25 μM Sb, the antioxidant system and its corresponding genes responded dynamically to oxidative stress, while cell wall components and metal/metalloid transporter proteins synergistically contributed to Sb detoxification and tolerance. Notably, Sb stress upregulated BIN2-related genes in the brassinosteroid (BR) signaling pathway, thereby suppressing BZR1/2 expression and disrupting BR signal transducion. Furthermore, exogenous BR application mitigated Sb-induced growth inhibition by reducing MDA accumulation and restoring growth parameters. These findings reveal key molecular mechanisms underlying wheat’s response to Sb toxicity and highlight the potential of BR application as a strategy to enhance Sb tolerance in wheat.