Hydrogen sulphide (H₂S) in the hidden half: Role in root growth, stress signalling and rhizospheric interactions

Abstract

Apart from nitric oxide (NO) and carbon monoxide (CO), hydrogen sulphide (H 2 S) has emerged as a potential gasotransmitter that has regulatory roles in root differentiation, proliferation and stress signalling. H 2 S metabolism in plants exhibits spatiotemporal differences that are intimately associated with sulphide signalling in the cytosol and other subcellular components, e.g. chloroplast and mitochondria. H 2 S biosynthesis in plant organs uses both enzymatic and non-enzymatic pathways. H 2 S generation in roots and aerial organs is modulated by developmental phase and changes in environmental stimuli. H 2 S has an influential role in root development and in the nodulation process. Studies have revealed that H 2 S is a part of the auxin and NO signalling pathways in roots, which induce lateral root formation. At the molecular level, exogenous application of H 2 S regulates expression of several transcription factors, viz. LBD (Lateral organ Boundaries Domain), MYB (myeloblastosis) and AP2/ERF (Apetala 2/ Ethylene Response Factor), which stimulate upregulation of PpLBD16 (Lateral organ boundaries domain 16), thereby significantly increasing the number of lateral roots. Concomitantly, H 2 S acts as a crucial signalling molecule in roots during various abiotic stresses, e.g. drought, salinity heavy metals (HMs), etc., and augments stress tolerance in plants. Interestingly, extensive crosstalk exists between H 2 S, NO, ABA, calcium and ethylene during stress, which escalate plant defence and regulate plant growth and productivity. Hence, the present review will elaborate the role of H 2 S in root development, stress alleviation, legume-Rhizobium symbiosis and rhizosphere signalling. The review also examines the mechanism of H 2 S-mediated abiotic stress mitigation and cross-talk with other signaling molecules.

Emerging role of hydrogen sulphide as a signalling molecule in plant biology

“…As a novel gaseous signalling molecule, H 2 S interacts with other signalling molecules, such as nitric oxide (NO) and with reactive oxygen species (ROS), and boosts plant defence against biotic and abiotic stresses (Siddiqui et al 2021;Raza et al 2022). The review of Mathur et al (2022) discusses the regulatory role of H 2 S in root differentiation, proliferation and stress signalling. The generation of H 2 S in roots is influenced by the development stage and environmental stimuli.…”

“…The review of Mathur et al . (2022) discusses the regulatory role of H 2 S in root differentiation, proliferation and stress signalling. The generation of H 2 S in roots is influenced by the development stage and environmental stimuli.…”

Hydrogen sulfide alleviates osmotic stress‐induced root growth inhibition by promoting auxin homeostasis

“…Meanwhile, H 2 S which is accumulated in response to heavy metal Cr 6+ stress enhances glutathione generation and actives phytochelatins to promote plant Cr 6+ stress tolerance (Fang et al., 2017). Additionally, some studies have focused on the function of H 2 S in regulating root growth, especially with respect to alleviating root development inhibition under abiotic stress (Mathur et al., 2022). For example, the application of an H 2 S donor, NaHS, has alleviated the NH 4 + ‐toxic symptoms in terms of root biomass and growth inhibition in Oryza sativa (Guo et al., 2017).…”

Biological Functions of Hydrogen Sulfide in Plants

“…Hydrogen sulfide (H 2 S) is a colorless, flammable, toxic, and corrosive gas that gives rotten eggs their distinctive odor; it is involved in numerous physiological processes in the plant, such as seed germination [ 1 ], stomatal movement [ 2 ], root morphogenesis [ 3 ], photosynthesis [ 4 ], senescence and yield [ 5 ], and fruit ripening and quality [ 6 ]. One of the major targets of H 2 S signaling in eukaryotic cells is the mitochondria.…”