Hydrogen Sulfide: A Novel Gaseous Molecule for Plant Adaptation to Stress

Hydrogen sulfide (H 2 S) has emerged as a novel gaseous signal molecule with multifarious effects on seed germination, plant growth, development, and physiological processes. Due to its dominant role in plant stress tolerance and cross-adaptation, it is getting more attention nowadays, although it has been largely referred as toxic and environmental hazardous gas. In this review work, we are highlighting the importance of H 2 S as an essential gaseous molecule to help in signaling, metabolism, and stress tolerance in plants. Firstly, production of H 2 S from different natural and artificial sources were discussed with its transformation from sulfur (S) to sulfate (SO 4 2− ) and then to sulfite (SO 3 2− ). The importance of different kinds of transporters that helps to take SO 4 2− from the soil solution was presented. Mainly, these transporters are SULTRs (H + /SO 4 2− cotransporters) and multigene family encodes them. Furthermore, these SULTRs have LAST (Low affinity transport proteins), HAST (High affinity transport proteins), vacuole transporters, and plastid transporters. Since it is well known that there is strong relationship between SO 4 2− and synthesis of hydrogen sulfide or dihydrogen sulfide or sulfane in plant cells. Thus, cysteine (Cys) metabolism through which H 2 S could be generated in plant cell with the role of different enzymes has been presented. Furthermore, H 2 S in interaction with other molecules could help to mitigate biotic and abiotic stress. Based on this review work, it can be concluded that H 2 S has potential to induce cross-adaptation to biotic and abiotic stress; thus, it is recommended that it should be considered in future studies to answer the questions like what are the receptors of H 2 S in plant cell, where in plants the physiological concentration of H 2 S is high in response to multiple stress and how it induces cross-adaptation by interaction with other signal molecules.