Introduction: Drought stress is one of the most important abiotic stresses that negatively
influence crop performance and productivity. Plants acclimatize to drought stress conditions through
altered molecular, biochemical and physiological responses. Gene and/or protein expression and regulation
are thought to be modulated upon stress perception and signal transduction for providing requisite
endurance to plants.
Plant growth regulators or phytohormones are important molecules required for various biological
processes in plants and are also central to stress signalling pathways. Among various phytohormones,
Abscisic Acid (ABA) and Ethylene (ET) are considered to be the most vital growth regulators implicated
in drought stress signalling and tolerance. Besides the above two known classical phytohormones,
Salicylic Acid (SA) and Jasmonic Acid (JA) have also been found to potentially enhance abiotic
stress tolerance particularly that of drought, salinity, and heat stress tolerance in plants. Apart
from these several other growth regulators such as Cytokinins (CKs), Auxin (AUX), Gibberellic Acid
(GA), Brassinosteroids (BRs) and Strigolactones (SLs) have also been reported to actively participate
in abiotic stress responses and tolerance in plants. The abiotic stress signalling in plants regulated by
these hormones further depends upon the nature, intensity, and duration of exposure to various environmental
stresses. It has been reported that all these phytohormones are also involved in extensive
crosstalk and signal transduction among themselves and/or with other factors.
Conclusion: This review thus summarizes the molecular mechanism of drought signalling and its crosstalk
with various phytohormone signalling pathways implicated in abiotic stress response and tolerance.