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Abiotic stressors threaten the survival mechanism of plant life on Earth. Phytohormones are one of the defensive molecules produced by plants to counteract destructive effects elicited by abiotic stresses. In recent years, melatonin has gained prime importance in plant research because of its regulatory role in abiotic stress tolerance. Melatonin plays a central role in interacting with other phytohormones such as auxin, gibberellin, cytokinin, abscisic acid, ethylene, brassinosteroids, jasmonic acid, salicylic acid and plant growth regulators like nitric oxide, polyamines, γ-aminobutyric acid and serotonin to regulate stress alleviation for maintaining basal growth under harsh environmental conditions. The precise understanding of intricate web of crosstalk mechanisms among different phytohormones and their interconnected networks in terms of synergistic and antagonistic actions is crucial for maintaining cellular dynamics under unfavorable conditions. Therefore, in the present review, we mainly focused on crosstalk regulatory circuits operated by melatonin with other phytohormones at both physiological and molecular levels and their responses under known abiotic stress environment. The biosynthesis, signaling pathway and efficacy of melatonin in various stress avoidance are also enumerated in this review. Indeed, it would not be presumptuous to hope that this review will be helpful for designing climate-smart crop cultivars in the forthcoming years using melatonin as the major stress mitigator and endogenous signaling molecule during stressful situations. [Display omitted] • Biosynthesis of melatonin in plants is more complex than in animals. • Melatonin receptor CAND2/PMTR1 participates in melatonin-mediated signal perception, involving mitogen activated protein kinase-signaling cascades to enhance stress tolerance. • Melatonin interacts with different phytohormones for conferring stress protection. • Melatonin and phytohormones crosstalk operates synergistically or antagonistically, depending on the nature and complexity of stress, plant type and surrounding environment. [ABSTRACT FROM AUTHOR]

Drought is undoubtedly a major environmental constraint that negatively affects agricultural yield and productivity throughout the globe. Plants are extremely vulnerable to drought which imposes several physiological, biochemical and molecular perturbations. Increased generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in different plant organs is one of the inevitable consequences of drought. ROS and RNS are toxic byproducts of metabolic reactions and poise oxidative stress and nitrosative stress that are detrimental for plants. In spite of toxic effects, these potentially active radicals also play a beneficial role in mediating several signal transduction events that lead to plant acclimation and enhanced survival under harsh environmental conditions. The precise understanding of ROS and RNS signaling and their molecular paradigm with different phytohormones, such as auxin, gibberellin, cytokinin, abscisic acid, ethylene, brassinosteroids, strigolactones, jasmonic acid, salicylic acid and melatonin play a pivotal role for maintaining plant fitness and resilience to counteract drought toxicity. Therefore, the present review provides an overview of integrated systemic signaling between ROS, RNS and phytohormones during drought stress based on past and recent advancements and their influential role in conferring protection against drought-induced damages in different plant species. Indeed, it would not be presumptuous to hope that the detailed knowledge provided in this review will be helpful for designing drought-tolerant crop cultivars in the forthcoming times. [Display omitted] • Drought can cause serious threat to agricultural crop production, thereby affecting global food security. • Excess generation of ROS and RNS during drought act as a signal for phytohormone accumulation for ROS and RNS scavenging. • Crosstalk between ROS, RNS and phytohormone signaling plays pivotal role in understanding drought stress tolerance mechanism. • Drought-induced overproduction of ROS and RNS regulates stomatal closure. [ABSTRACT FROM AUTHOR]