Brassinosteroid-induced transcriptomic rearrangements unveiled the physiological mechanism of chromium stress tolerance in Brassica napus

Brassinosteroid (BR), a plant hormone regulating growth, development, and stress responses, emerges as a promising tool for maintaining agricultural production under abiotic stress conditions. In this study, we conducted RNA-seq profiling and morpho-physiological analysis to investigate the molecular cross-talk involved in 24-epibrassinolide (EBR) mediating alleviation of chromium (Cr) stress. EBR inhibited Cr accumulation and reversed Cr-induced phytotoxicity, thereby promoting plant growth. The photosynthetic pigments, chlorophyll fluorescence a, electron transport rate (ETR) and non-photochemical quenching (NPQ) were significantly higher in EBR+Cr treated plants compared to Cr alone. EBR application facilitated the recovery from Cr-induced structural deformities, including the disintegration of cell walls and membranes. Furthermore, under Cr stress, EBR application reduced malondialdehyde (MDA) and reactive oxygen species (ROS) production and accumulation. The levels of glutathione reductase (GR) and the activities of antioxidant enzymes were notably higher in plants subjected to EBR application following Cr stress. In addition, we established a transcriptomic database comprising 2345 differentially expressed genes (DEGs) (1255 upregulated and 1090 downregulated) as a result of EBR application under Cr stress. The transcriptome analysis unveiled key DEGs and the associated pathways, emphasizing the importance of defense responses, genes encoding photosystem I and II, jasmonate signaling, aquaporins, ABC transporters, and cell wall biogenesis-related genes in the response of EBR to Cr stress.