Hydrogen sulphide trapeze: Environmental stress amelioration and phytohormone crosstalk

Hydrogen sulphide (H2S) is recognized as the third endogenous gasotransmitter in plants after nitric oxide (NO) and carbon monoxide (CO). Though initially visualized as a toxic gaseous molecule, recent studies have illustrated its diverse role in regulating plant growth and developmental physiology. H2S is also a potent inducer of osmolytes and cellular antioxidants of enzymatic and non-enzymatic origins. It interacts with the Ca2+ and NO signaling pathways. Exogenous fumigation of H2S or application of the H2S donor, sodium hydrosulphide (NaHS) has been found to be beneficial in the amelioration of multiple abiotic stresses like salinity, drought, temperature, hypoxia and heavy metal toxicity. H2S also protects stress-sensitive proteins via persulphidation of cysteine residues, prone to reactive oxygen species (ROS)-mediated oxidation. It is well established that plants are highly dependent on phytohormone signaling during any physiological process. By virtue of the diversity of the H2S-mediated signaling network, interactions and crosstalks of this gasotransmitter with the plant hormones are evident. This article presents a detailed summary regarding the role of H2S in oxidative and environmental stress tolerance; and furthermore illustrates the reported interactions with crucial hormones like abscisic acid, auxins, gibberellic acid, ethylene and salicylic acid under physiologically differing circumstances.