Abstract
Hydrogen sulfide (H2S) is predominantly considered as a gaseous transmitter or signaling molecule in plants. It has been known as a crucial player during various plant cellular and physiological processes and has been gaining unprecedented attention from researchers since decades. They regulate growth and plethora of plant developmental processes such as germination, senescence, defense, and maturation in plants. Owing to its gaseous state, they are effectively diffused towards different parts of the cell to counterbalance the antioxidant pools as well as providing sulfur to cells. H2S participates actively during abiotic stresses and enhances plant tolerance towards adverse conditions by regulation of the antioxidative defense system, oxidative stress signaling, metal transport, Na+/K+ homeostasis, etc. They also maintain H2S-Cys-cycle during abiotic stressed conditions followed by post-translational modifications of cysteine residues. Besides their role during abiotic stresses, crosstalk of H2S with other biomolecules such as NO and phytohormones (abscisic acid, salicylic acid, melatonin, ethylene, etc.) have also been explored in plant signaling. These processes also mediate protein post-translational modifications of cysteine residues. We have mainly highlighted all these biological functions along with proposing novel relevant issues that are required to be addressed further in the near future. Moreover, we have also proposed the possible mechanisms of H2S actions in mediating redox-dependent mechanisms in plant physiology.
Highlights
Abiotic stresses mainly comprise of numerous stresses such as heavy metal, drought, light, flooding, freezing, salinity, and many more abrupt environmental conditions
The instant reaction in plants occurs in the form of generation of reactive oxygen species (ROS), in the form of superoxide radicals, singlet oxygen species, malondialdehyde (MDA), hydrogen peroxide (H2O2), and various other free radicals that are notably increased during stressed conditions [2]
It led to coordinated action of antioxidative toolbox in the form of enhanced activities of superoxide dismutase (SOD), ascorbate peroxidase (APOX), catalase (CAT), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), guaiacol peroxidase (POD), and non-enzymatic antioxidants. These results clearly indicated the positive linkage among H2S and ROS; for instance, ascorbate peroxidase and catalase are specific targets for persulfidation and are altered by nitric oxide (NO) and post-translational modifications as well as S-nitrosylations and nitration, respectively [33]
Summary
Abiotic stresses mainly comprise of numerous stresses such as heavy metal, drought, light, flooding, freezing, salinity, and many more abrupt environmental conditions. Plants, due to their non-sessile nature, are exposed to these fluctuations at immediate pace [1]. A large body of literature determined the protective role of H2S to signal plant acclimation and resistance mechanism against abiotic stresses such as heavy metals, drought, salinity, freezing, flooding, heat, and osmotic stress [7,8,10]. It has been studied that H2S gets transported in membranes via the diffusion process without any carrier protein or facilitator [16] By this nature, H2S act as signaling molecule with its efficacy to participate in different physiological and metabolic processes for plant protection. The H2S-mediated mechanisms in plants in terms of post-translational modification of cysteine residues and protein persulfidation have been elucidated
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