Plant Physiology and Biochemistry xxx (xxxx) xxx Please cite this article as: Yamshi Arif, Plant Physiology and Biochemistry, https://doi.org/10.1016/j.plaphy.2020.11.045 Available online 26 November 2020 0981-9428/© 2020 Elsevier Masson SAS. All rights reserved. Hydrogen sulfide: A versatile gaseous molecule in plants Yamshi Arif a , Shamsul Hayat a, * , Mohammad Yusuf b , Andrzej Bajguz c a Aligarh Muslim University, Faculty of Life Sciences, Department of Botany, Plant Physiology Section, Aligarh, 202002, India b United Arab Emirates University, College of Science, Department of Biology, Al Ain, 15551, United Arab Emirates c Faculty of Biology, Department of Biology and Plant Ecology, University of Bialystok, 1J Ciolkowskiego St., 15-245, Bialystok, Poland A R T I C L E INFO Keywords: Antioxidant Biosynthesis Crosstalk Development Growth Stress tolerance ABSTRACT Hydrogen sulfide (H 2 S) is a gasotransmitter and signaling molecule associated with seed germination, plant growth, organogenesis, photosynthesis, stomatal conductance, senescence, and post-harvesting. H 2 S is produced in plants via both enzymatic and non-enzymatic pathways in different subcellular compartments. Exogenous application of H 2 S facilitates versatile metabolic processes and antioxidant machinery in plants under normal and environmental stresses. This compound interacts with phytohormones like auxins, abscisic acid, gibberellins, ethylene, jasmonic acid, and salicylic acid. Furthermore, H 2 S participates in signal transductions of other signaling molecules like nitric oxide, carbon monoxide, calcium, methylglyoxal, and hydrogen peroxide. It also mediates post-translational modification, which is a protective mechanism against oxidative damage of proteins. This review summarizes the roles of H 2 S as intriguing molecule in plants. 1. Introduction Hydrogen sulfide (H 2 S) is a small lipophilic molecule and colorless, toxic, and flammable gas with an unpleasant smell like that of rotten eggs (Fotopoulos et al., 2015). It inhibits mitochondrial respiration by impairing cytochrome C oxidase. However, H 2 S now emerges as the third important gas messenger and signaling molecule after nitric oxide (NO) and carbon monoxide (CO). Breakthrough in the research came when H 2 S endogenously cross cell membranes without receptors, and thus like NO and CO, H 2 S appeared as a novel gasotransmitter involved in signal transduction (Guo et al., 2016). H 2 S is found in both eukaryotes and prokaryotes. In animals, endogenous H 2 S functions as a neuro- modulator in brain cells (Jin and Pei, 2015). Recently, it was found that H 2 S is produced in plants under normal and stressful conditions, and modulates plant growth and developmental processes. Therefore, it is important in sustaining agriculture and improving crop production (Hancock and Whiteman, 2014; Pandey and Gautam, 2020). H 2 S plays a widespread potent role in seed germination, photosynthesis, stomatal conductance, root organogenesis, transpiration, and ultimately senes- cence under normal and stress condition (Li et al., 2014a, 2014b; Chen et al., 2018; Liu et al., 2019; Zhang et al., 2020b). It also has a major role in increasing the shelf life of extensive fruits and vegetables during post-harvesting. The favorable effects in plants are seen at lower doses of H 2 S, whereas higher concentration impairs growth and developmental processes (Ni et al., 2016). Rennenberg et al. (1987) firstly investigated that H 2 S is produced in plant sub-cellular compartments like cytosol, chloroplast, and mito- chondria. For H 2 S production, L/D-cysteine is catalyzed by L/D-cysteine desulfhydrase. It was discovered and characterized that specific cysteine desulfhydrase exhibit H 2 S biosynthesis and sulfur assimilation (Foto- poulos et al., 2015). H 2 S biosynthesis takes place in chloroplast, mito- chondria, and cytosol with the help of five enzymatic systems, i.e., L-cysteine desulfhydrase (L-CDes), D-cysteine desulfhydrase (D-CDes), β-cyanoalanine synthase (CAS), cysteine synthase (CS), and sulfite reductase (SiR) (Li, 2015). H 2 S signaling is generally mediated by post-translational modification on cysteine residues on the particular target protein site in a process called persulfidation (Paul and Snyder, 2015). A diversity of approaches to delivering H 2 S in plants, such as applying sodium hydrosulfide (NaHS) and sodium sulfide (Na 2 S), gives just little burst of H 2 S.Nevertheless, donors (e.g., GYY4137, AP97, AP105) that give H 2 S to a great extent, and target organelles are avail- able (Hancock and Whiteman, 2014). The current review focuses on the multifaceted safeguarding role of H 2 S in plant tolerance to different environmental stresses and its inter- action with reactive oxygen species (ROS), antioxidants, and osmopro- tectant. Moreover, this review also highlights H 2 S post-translational modifications, the crosstalk of H 2 S with phytohormones and other signaling molecules, as well as H 2 S biosynthesis in subcellular * Corresponding author. E-mail address: hayat_68@yahoo.co.in (S. Hayat). Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy https://doi.org/10.1016/j.plaphy.2020.11.045 Received 26 July 2020; Accepted 17 November 2020