Exogenous application of brassinosteroid offers tolerance to salinity by altering stress responses in rice variety Pusa Basmati-1

• Detailed study of role of 24-epibrassinolide (EBL) on rice under salt stress.
• Using EBL as an alternative strategy for curbing ill effect of salt on the plants.
• Several biochemical parameters studied to derive conclusion about BR mode of action.
• Expression study of key antioxidant defence, BRs and salt responsive genes.

Plant steroidal hormones, brassinosteroids, play a pivotal role in variety of plant developmental processes and adaptation to various environmental stresses. The present work investigates the response of various stress markers upon exogenous application of 24-epibrassinolide (EBL) on Pusa Basmati-1, a commercially important rice variety, under salt stress conditions. Rice seeds after treatment with different concentrations of NaCl alone or in combination with different concentrations of 24-epibrassinolide (EBL) were analysed for various growth parameters, protein, proline and malondialdehyde content (MDA) and antioxidant enzymes activities. The seedlings exposed to NaCl exhibited a significant decline in growth parameters and changes in the levels of antioxidant enzymes, however, treatment with EBL showed an improvement in growth, levels of protein and proline content and antioxidant enzymes activity. The enhanced levels of MDA content during salt stress in rice seedlings was decreased with EBL treatment. Further, the treatment with EBL increased the expression of various oxidative stress marker genes, although to different levels. Expression of various brassinosteroids (OsBRI1, OsDWF4) and salt (SalT) responsive genes, revealed the down regulation of OsDWF4 with application of EBL and upregulation of SalT in presence of salt stress thereby confirming the efficacy of the treatments. Interestingly, a significant down regulation of SalT gene was observed on application of EBL along with salt compared to salt treatment alone. On the other hand, the application of EBL alone and in combination with salt has resulted in upregulation of OsBRI1.