Brassinosteroids in plant growth and stress adaptation: molecular mechanisms and physiological functions.

Climate change is intensifying heat, drought and salinity stresses, placing global food production at increasing risk and highlighting the need for stress-resilient crops. Brassinosteroids (BRs), key plant steroid hormones, have emerged as central regulators of growth and environmental adaptation through coordinated transcriptional, hormonal and redox-mediated responses. Recent advances have refined the classical view of BRs biology by elucidating key biosynthetic and regulatory mechanisms. At the signalling level, the BRASSINOSTEROID INSENSITIVE 1 (BRI1)-BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) receptor complex and the GLYCOGEN SYNTHASE KINASE 3 (GSK3)-like kinase BRASSINOSTEROID INSENSITIVE 2 (BIN2)-BRI1-EMS-SUPPRESSOR 1 (BES1)/BRASSINAZOLE-RESISTANT 1 (BZR1) transcriptional module remain core components. The discovery of ABCB-mediated BRs transport has introduced a new conceptual framework in which hormone distribution contributes to localized signalling and tissue-specific responses. BRs enhance stress tolerance by improving antioxidant defence, photosynthesis, ion homeostasis, nutrient utilization, and hormonal coordination. Genome editing and multi-omics approaches further highlight the dynamic and spatial regulation of BRs networks. This review integrates mechanistic, transport, and systems-level advances into a unified framework for climate-resilient crop improvement. The online version contains supplementary material available at https://doi.org/10.1007/s12298-026-01811-6.