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Salinity stress is one of the major environmental challenges which adversely affects plant growth and productivity. The acquisition of salinity stress tolerance has been an interesting area of investigation for plant abiotic stress management. Recently, we investigated the interdependency of reactive oxygen species (ROS) generating and scavenging system for offering salt stress adaptation in rice. In continuation to our earlier findings, in the present study we analyzed the transcript level expression of different respiratory burst oxidase homologs (Rbohs) genes in salt sensitive and salt tolerant cultivars of rice to corroborate this result with their activities. Brassinosteroid (BR) is known to confer abiotic stress tolerance by modulating ROS machinery, and hence in the present study, the expression of key genes associated in brassinosteroid biosynthesis and signaling in salt sensitive and tolerant cultivar of rice was also conducted. In the present investigation, the other stress markers involving proline catabolism and anabolism along with chlorophyllase has been analyzed to get a better insights to our understanding of salt stress adaptation mechanisms in rice.

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., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)

Brassinosteroids (BRs) are a class of steroidal plant hormones that play diverse roles in plant growth and developmental processes. Recently, the easy availability of biological resources, and development of new molecular tools and approaches have provided the required impetus for deeper understanding of the processes involved in BRs biosynthesis, transport, signaling and degradation pathways. From recent studies it is also evident that BRs interact with other phytohormones such as auxin, cytokinin, ethylene, gibberellin, jasmonic acid, abscisic acid, salicylic acid and polyamine in regulating wide range of physiological and developmental processes in plants. The inputs from these studies are now being linked to the versatile roles of BRs. The present review highlights the conceptual development with regard to BR homeostasis, signaling and its crosstalk with other phytohormones. This information will assist in developing predictive models to modulate various useful traits in plants and address current challenges in agriculture. [ABSTRACT FROM AUTHOR]