Abstract
Activation of stress tolerance mechanisms demands transcriptional reprogramming. Salt stress, a major threat to plant growth, enhances ROS production and affects transcription through modulation of miRNAs and hormones. The present study delineates salt stress ameliorating action of thiourea (TU, a ROS scavenger) in Brassica juncea and provides mechanistic link between redox, microRNA and hormones. The ameliorative potential of TU towards NaCl stress was related with its ability to decrease ROS accumulation in roots and increase Na+ accumulation in shoots. Small RNA sequencing revealed enrichment of down-regulated miRNAs in NaCl + TU treated roots, indicating transcriptional activation. Ranking analysis identified three key genes including BRX4, CBL10 and PHO1, showing inverse relationship with corresponding miRNA expression, which were responsible for TU mediated stress mitigation. Additionally, ABA level was consistently higher till 24 h in NaCl, while NaCl + TU treated roots showed only transient increase at 4 h suggesting an effective stress management. Jasmonate and auxin levels were also increased, which prioritized defence and facilitated root growth, respectively. Thus, the study highlights redox as one of the “core” components regulating miRNA and hormone levels, and also strengthens the use of TU as a redox priming agent for imparting crop resilience to salt stress.
Highlights
Ability of thiourea (TU; a non-physiological thiol based ROS scavenger20,21) to restrict stress induced redox imbalance and associated damages in plants
TU improved source-to-sink relationship leading to increased crop yield[22,23] and at molecular level, it improved cellular energetics[24], co-ordinated calcium and abscisic acid (ABA) signaling events[25], maintained plant-water homeostasis[26], enhanced antioxidant defense[27] and improved sulphur metabolism[28]
The hormonal and redox signaling crosstalk has been demonstrated under different abiotic stress conditions[35]; little is known in Brassica juncea, especially under the context of salt stress
Summary
Ability of thiourea (TU; a non-physiological thiol based ROS scavenger20,21) to restrict stress induced redox imbalance and associated damages in plants. The hormonal and redox signaling crosstalk has been demonstrated under different abiotic stress conditions[35]; little is known in Brassica juncea, especially under the context of salt stress. Brassica juncea belongs to the family Brassicaeace and represent classical example of recursive whole genome duplication events. It is an allotetraploid (AABB) oilseed crop from the triangle of U (B. rapa (AA) and B. nigra (BB) and allotetraploids B. napus (AACC) and B. carinata (BBCC)[36]; of which, B. rapa genome is currently available. The present study highlights the mechanistic basis of TU mediated salt tolerance at the level of miRNA and hormone based regulations. The research outcome advances our understanding about the concept of redox mediated regulation of salt-tolerance; but, strengthens the applicability/adoptability of TU based technology for enhancing crop protection
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