Biological Functions of Hydrogen Sulfide in Plants

Hydrogen sulfide mechanism of action in plants; from interaction with regulatory molecules to persulfidation of proteins

Hydrogen sulfide (H2S), previously known as a toxic gas, is currently considered one of the most important gaseous transmitters in plants. This novel signaling molecule has been determined to play notable roles in plant growth, development, and maturation. In addition, pharmacological and genetic evidence indicated that this regulatory molecule effectively ameliorates various plant stress conditions. H2S is involved in these processes by changing gene expression, enzyme activities, and metabolite concentrations. During its regulatory function, H2S interacts with other signaling pathways such as hydrogen peroxide (H2O2), nitric oxide (NO), Ca2+, carbon monoxide (CO), phosphatidic acid (PA), phytohormones, etc. The H2S mechanism of action may depend on the persulfidation post-translational modification (PTM), which attacks the cysteine (Cys) residues on the target proteins and changes their structure and activities. This review summarized H2S biosynthesis pathways, its role in sulfide state, and its donors in plant biology. We also discuss recent progress in the research on the interactions of H2S with other signaling molecules, as well as the role of persulfidation in modulating various plant reactions.

"Light-Up" Near-Infrared Fluorescent Probe for Visualization of Hydrogen Sulfide Content and Abiotic Stress Response in Plants

Hydrogen sulfide (H2S) plays a vital role in plant physiology and stress adaptation, but the detection of endogenous H2S remains a challenge. In this work, a near-infrared fluorescent probe (NIR-BOD-HS) was synthesized using boron-dipyrromethene (BODIPY) as the raw material, which showed a good linear relationship in the concentration range of 0.1-70 μM and a detection limit of 56 nM. The long-wavelength emission (712 nm) reduced the interference of plant autofluorescence and improved the imaging quality. The probe combined with fluorescence imaging technology nondestructively realized the spatiotemporal distribution signal of H2S in the deep tissues of plants. In addition, the dynamic changes of H2S content during seed germination and seedling growth under abiotic stress were also demonstrated through the changes in fluorescence signals. This study helps to understand the physiological response mechanism of plants under abiotic stress and provides a scientific basis for further research on plant imaging and agricultural production.

Molecular mechanisms of cold stress response in cotton: Transcriptional reprogramming and genetic strategies for tolerance

Cold stress has a huge impact on the growth and development of cotton, presenting a significant challenge to its productivity. Comprehending the complex molecular mechanisms that control the reaction to CS is necessary for developing tactics to improve cold tolerance in cotton. This review paper explores how cotton responds to cold stress by regulating gene expression, focusing on both activating and repressing specific genes. We investigate the essential roles that transcription factors and regulatory elements have in responding to cold stress and controlling gene expression to counteract the negative impacts of low temperatures. Through a comprehensive examination of new publications, we clarify the intricacies of transcriptional reprogramming induced by cold stress, emphasizing the connections between different regulatory elements and signaling pathways. Additionally, we investigate the consecutive effects of cold stress on cotton yield, highlighting the physiological and developmental disturbances resulting from extended periods of low temperatures. The knowledge obtained from this assessment allows for a more profound comprehension of the molecular mechanisms that regulate cold stress responses, suggesting potential paths for future research to enhance cold tolerance in cotton by utilizing targeted genetic modifications and biotechnological interventions.

The ArcB kinase sensor participates in the phagocyte-mediated stress response in Salmonella Typhimurium

The ArcAB two-component system includes a histidine kinase sensor (ArcB) and a regulator (ArcA) that respond to changes in cell oxygen availability. The ArcA transcription factor activates genes related to metabolism, membrane permeability, and virulence, and its presence is required for pathogenicity in Salmonella Typhimurium, which can be phosphorylated independently of its cognate sensor, ArcB. In this study, we aimed to characterize the transcriptional response to hypochlorous acid (HOCl) mediated by the presence of the ArcB sensor. HOCl is a powerful microbicide widely used for sanitization in industrial settings. We used wild-type S. Typhimurium and the mutant lacking the arcB gene exposed to NaOCl to describe the global transcriptional response. We also infected murine neutrophils to evaluate the expression levels of relevant genes related to the resistance and infection process while facing ROS-related stress. Our results indicate that the absence of the arcB gene significantly affects the ability of S. Typhimurium to grow under HOCl stress. Overall, 6.6% of Salmonella genes varied their expression in the mutant strains, while 8.6% changed in response to NaOCl. The transcriptional response associated with the presence of ArcB is associated with metabolism and virulence, suggesting a critical role in pathogenicity and fitness, especially under ROS-related stress. Our results show that ArcB influences the expression of genes associated with fatty acid degradation, protein secretion, cysteine and H2S biosynthesis, and translation, both in vitro and under conditions found within neutrophils. We found that protein carbonylation is significantly higher in the mutant strain than in the wild type, suggesting a critical function for ArcB in the response and repair processes. This study contributes to the understanding of the pathogenicity and adaptation mechanisms that Salmonella employs to establish a successful infection in its host.

The role of gasotransmitter hydrogen sulfide in plant cadmium stress responses

Cadmium (Cd) is a toxic heavy metal that poses a significant risk to both plant growth and human health. To mitigate or lessen Cd toxicity, plants have evolved a wide range of sensing and defense strategies. The gasotransmitter hydrogen sulfide (H2S) is involved in plant responses to Cd stress and exhibits a crucial role in modulating Cd tolerance through a well-orchestrated interaction with several signaling pathways. Here, we review potential experimental approaches to manipulate H2S signals, concluding that research on another gasotransmitter, namely nitric oxide (NO), serves as a good model for research on H2S. Additionally, we discuss potential strategies to leverage H2S-reguated Cd tolerance to improve plant performance under Cd stress.

Synergistic effects of hydrogen sulfide and nitric oxide in enhancing salt stress tolerance in cucumber seedlings

Salinity stress poses a significant threat to plant growth and agricultural productivity, affecting millions of hectares of land worldwide. The adverse effects of salt toxicity, primarily caused by high levels of sodium chloride in soil and water, disrupt essential physiological processes in plants, leading to reduced yields and degraded soil quality. The present study thoroughly investigated the potential involvement of hydrogen sulphide (H2S) and nitric oxide (NO) in facilitating salt stress tolerance in cucumbers. In this investigation, NaHS (sodium hydrogen sulfide), which is the donor of H2S, and SNP (sodium nitroprusside), which is the donor of NO, were used as treatments for cucumber seedlings exposed to salt stress. Additionally, L-NAME (N-nitro-L-arginine: 100 μM) and cPTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide), which are inhibitors and scavengers of NO respectively, were used to verify the involvement of NO in the presence of salinity. NaHS and SNP supplementation significantly boosted fresh weight, dry weight, plant height, and chlorophyll content, promoting growth under salt stress. These treatments raised endogenous H2S and NO levels, upregulating antioxidative enzymes like SOD, CAT, APX, GR, GPX, and GSTs. This response reduced oxidative damages by lowering reactive oxygen species (ROS) and lipid peroxidation. The combined application of NaHS and SNP under salt stress offers a promising and cost-effective strategy to improve plant resilience to salinity, reduce oxidative stress, and ultimately enhance crop productivity. These findings provide important insights into the potential use of H2S and NO donors for sustaining agricultural production in saline environments, addressing a critical global challenge for food security.

Hydrogen sulfide antagonizes cytokinin to change root system architecture through persulfidation of CKX2 in Arabidopsis

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule, which has been shown to play an important role in plant growth and development by coupling with various phytohormones. However, the relationship between H2S and cytokinin (CTK) and the mechanisms by which H2S and CTK affect root growth remain poorly understood. Endogenous CTK was analyzed by UHPLC-ESI-MS/MS. Persulfidation of cytokinin oxidase/dehydrogenases (CKXs) was analyzed by mass spectrometry (MS). ckx2/CKX2wild-type (WT), OE CKX2 and ckx2/CKX2Cys(C)62alanine(A) transgenic lines were isolated with the ckx2 background. H2S is linked to CTK content by CKX2, which regulates root system architecture (RSA). Persulfidation at cysteine (Cys)62 residue of CKX2 enhances CKX2 activity, resulting in reduced CTK content. We utilized 35S-LCD/oasa1 transgenic lines to investigate the effect of endogenous H2S on RSA, indicating that H2S reduces the gravitropic set-point angle (GSA), shortens root hairs, and increases the number of lateral roots (LRs). The persulfidation of CKX2Cys62 changes the elongation of cells on the upper and lower flanks of LR elongation zone, confirming that Cys62 of CKX2 is the specificity target of H2S to regulate RSA in vivo. In conclusion, this study demonstrated that H2S negatively regulates CTK content and affects RSA by persulfidation of CKX2Cys62 in Arabidopsis thaliana.

Biophysical characterization of hydrogen sulfide: A fundamental exploration in understanding significance in cell signaling

Hydrogen sulfide (H₂S) has emerged as a significant signaling molecule involved in various physiological processes, including vasodilation, neurotransmission, and cytoprotection. Its interactions with biomolecules are critical to understand its roles in health and disease. Recent advances in biophysical characterization techniques have shed light on the complex interactions of H₂S with proteins, nucleic acids, and lipids. Proteins are primary targets for H₂S, which can modify cysteine residues through S-sulfhydration, impacting protein function and signaling pathways. Advanced spectroscopic techniques, such as mass spectrometry and NMR, have enabled the identification of specific sulfhydrated sites and provided insights into the structural and functional consequences of these modifications. Nucleic acids also interact with H₂S, although this area is less explored compared to proteins. Recent studies have demonstrated that H₂S can induce modifications in nucleic acids, affecting gene expression and stability. Techniques like gel electrophoresis and fluorescence spectroscopy have been utilized to investigate these interactions, revealing that H₂S can protect DNA from oxidative damage and modulate RNA stability and function. Lipids, being integral components of cell membranes, interact with H₂S, influencing membrane fluidity and signaling. Biophysical techniques such as electron paramagnetic resonance (EPR) and fluorescence microscopy have elucidated the effects of H₂S on lipid membranes. These studies have shown that H₂S can alter lipid packing and dynamics, which may impact membrane-associated signaling pathways and cellular responses to stress. In the current work we have integrated this with key scientific explainations to provide a comprehensive review.

Post-Translational Modifications to Cysteine Residues in Plant Proteins and Their Impact on the Regulation of Metabolism and Signal Transduction

Cys is one of the least abundant amino acids in proteins. However, it is often highly conserved and is usually found in important structural and functional regions of proteins. Its unique chemical properties allow it to undergo several post-translational modifications, many of which are mediated by reactive oxygen, nitrogen, sulfur, or carbonyl species. Thus, in addition to their role in catalysis, protein stability, and metal binding, Cys residues are crucial for the redox regulation of metabolism and signal transduction. In this review, we discuss Cys post-translational modifications (PTMs) and their role in plant metabolism and signal transduction. These modifications include the oxidation of the thiol group (S-sulfenylation, S-sulfinylation and S-sulfonylation), the formation of disulfide bridges, S-glutathionylation, persulfidation, S-cyanylation S-nitrosation, S-carbonylation, S-acylation, prenylation, CoAlation, and the formation of thiohemiacetal. For each of these PTMs, we discuss the origin of the modifier, the mechanisms involved in PTM, and their reversibility. Examples of the involvement of Cys PTMs in the modulation of protein structure, function, stability, and localization are presented to highlight their importance in the regulation of plant metabolic and signaling pathways.

Elucidating the intricacies of the H2S signaling pathway in gasotransmitters: Highlighting the regulation of plant thiocyanate detoxification pathways

In recent decades, there has been increasing interest in elucidating the role of sulfur-containing compounds in plant metabolism, particularly emphasizing their function as signaling molecules. Among these, thiocyanate (SCN-), a compound imbued with sulfur and nitrogen, has emerged as a significant environmental contaminant frequently detected in irrigation water. This compound is known for its potential to adversely impact plant growth and agricultural yield. Although adopting exogenous SCN- as a nitrogen source in plant cells has been the subject of thorough investigation, the fate of sulfur resulting from the assimilation of exogenous SCN- has not been fully explored. There is burgeoning curiosity in probing the fate of SCN- within plant systems, especially considering the possible generation of the gaseous signaling molecule, hydrogen sulfide (H2S) during the metabolism of SCN-. Notably, the endogenous synthesis of H2S occurs predominantly within chloroplasts, the cytosol, and mitochondria. In contrast, the production of H2S following the assimilation of exogenous SCN- is explicitly confined to chloroplasts and mitochondria. This phenomenon indicates complex interplay and communication among various subcellular organelles, influencing signal transduction and other vital physiological processes. This review, augmented by a small-scale experimental study, endeavors to provide insights into the functional characteristics of H2S signaling in plants subjected to SCN--stress. Furthermore, a comparative analysis of the occurrence and trajectory of endogenous H2S and H2S derived from SCN--assimilation within plant organisms was performed, providing a focused lens for a comprehensive examination of the multifaceted roles of H2S in rice plants. By delving into these dimensions, our objective is to enhance the understanding of the regulatory mechanisms employed by the gasotransmitter H2S in plant adaptations and responses to SCN--stress, yielding invaluable insights into strategies for plant resilience and adaptive capabilities.

Natural H2S-donors: A new pharmacological opportunity for the management of overweight and obesity

The prevalence of overweight and obesity has progressively increased in the last few years, becoming a real threat to healthcare systems. To date, the clinical management of body weight gain is an unmet medical need, as there are few approved anti-obesity drugs and most require an extensive monitoring and vigilance due to risk of adverse effects and poor patient adherence/persistence. Growing evidence has shown that the gasotransmitter hydrogen sulfide (H2S) and, therefore, H2S-donors could have a central role in the prevention and treatment of overweight/obesity. The main natural sources of H2S-donors are plants from the Alliaceae (garlic and onion), Brassicaceae (e.g., broccoli, cabbage, and wasabi), and Moringaceae botanical families. In particular, polysulfides and isothiocyanates, which slowly release H2S, derive from the hydrolysis of alliin from Alliaceae and glucosinolates from Brassicaceae/Moringaceae, respectively. In this review, we describe the emerging role of endogenous H2S in regulating adipose tissue function and the potential efficacy of natural H2S-donors in animal models of overweight/obesity, with a final focus on the preliminary results from clinical trials. We conclude that organosulfur-containing plants and their extracts could be used before or in combination with conventional anti-obesity agents to improve treatment efficacy and reduce inflammation in obesogenic conditions. However, further high-quality studies are needed to firmly establish their clinical efficacy.

Hydrogen Sulfide in the Oxidative Stress Response of Plants: Crosstalk with Reactive Oxygen Species

Growing evidence suggests that exposure of plants to unfavorable environments leads to the accumulation of hydrogen sulfide (H2S) and reactive oxygen species (ROS). H2S interacts with the ROS-mediated oxidative stress response network at multiple levels. Therefore, it is essential to elucidate the mechanisms by which H2S and ROS interact. The molecular mechanism of action by H2S relies on the post-translational modification of the cysteine sulfur group (-SH), known as persulfidation. H2S cannot react directly with -SH, but it can react with oxidized cysteine residues, and this oxidation process is induced by H2O2. Evidently, ROS is involved in the signaling pathway of H2S and plays a significant role. In this review, we summarize the role of H2S-mediated post-translational modification mechanisms in oxidative stress responses. Moreover, the mechanism of interaction between H2S and ROS in the regulation of redox reactions is focused upon, and the positive cooperative role of H2S and ROS is elucidated. Subsequently, based on the existing evidence and clues, we propose some potential problems and new clues to be explored, which are crucial for the development of the crosstalk mechanism of H2S and ROS in plants.

Gaseous signaling molecule H2S as a multitasking signal molecule in ROS metabolism of Oryza sativa under thiocyanate (SCN-) pollution

The induction of disruption in the electronic transport chain by thiocyanate (SCN-) leads to an excessive generation of reactive oxygen species (ROS) within rice (Oryza sativa). Hydrogen sulfide (H2S) assumes a crucial role as a gaseous signaling molecule, holding significant potential in alleviating SCN--related stress. Nevertheless, there remains a dearth of understanding regarding the intricate interplay between H2S and ROS in Oryza sativa amidst SCN- pollution. In this investigation, a hydroponics-based experiment was meticulously devised to explore how H2S-mediated modifications influence the genetic feedback network governing ROS metabolism within the subcellular organelles of Oryza sativa when exposed to varying effective concentrations (EC20: 24 mg SCN/L; EC50: 96 mg SCN/L; EC75: 300 mg SCN/L) of SCN-. The findings unveiled the enhanced capacity of Oryza sativa to uptake SCN- under H2S + SCN- treatments in comparison to SCN- treatments alone. Notably, the relative growth rate (RGR) of seedlings subjected to H2S + SCN- exhibited a superior performance when contrasted with seedlings exposed solely to SCN-. Furthermore, the application of exogenous H2S yielded a significant reduction in ROS levels within Oryza sativa tissues during SCN- exposure. To elucidate the intricacies of gene regulation governing ROS metabolism at the mRNA level, the 52 targeted genes were categorized into four distinct types, namely: initial regulatory ROS generation genes (ROS-I), direct ROS scavenging genes (ROS-II), indirect ROS scavenging genes (ROS-III), and lipid oxidation genes (ROS-IV). On the whole, exogenous H2S exhibited the capacity to activate the majority of ROS-I ∼ ROS-IV genes within both Oryza sativa tissues at the EC20 concentration of SCN-. However, genetic positive/negative feedback networks emphasized the pivotal role of ROS-II genes in governing ROS metabolism within Oryza sativa. Notably, these genes were predominantly activated within the cytoplasm, chloroplasts, mitochondria, peroxisomes, and the cell wall.

Melatonin-regulated heat shock proteins and mitochondrial ATP synthase induce drought tolerance through sustaining ROS homeostasis in H2S-dependent manner

Drought is thought to be one of the major global hazards to crop production. Understanding the role of melatonin (Mel) during plant adaptive responses to drought stress (DS) was the aim of the current investigation. Involvement of hydrogen sulfide (H2S) was also explored in Mel-regulated mechanisms of plants' tolerance to DS. A perusal of the data shows that exposure of tomato plants to DS elevated the activity of mitochondrial enzymes viz. pyruvate dehydrogenase, malate dehydrogenase, and citrate synthase. Whereas the activity of ATP synthase and ATPase was downregulated under stress conditions. Under DS, an increase in the expression level of heat shock proteins (HSPs) and activation level of antioxidant defense system was observed as well. On the other hand, an increase in the activity of NADPH oxidase and glycolate oxidase was observed along with the commencement of oxidative stress and accompanying damage. Application of 30 μM Mel to drought-stressed plants enhanced H2S accumulation and further elevated the activity of mitochondrial enzymes, activation level of the defense system, and expression of HSP17.6 and HSP70. Positive effect of Mel on these attributes was reflected by reduced level of ROS and related damage. However, application of H2S biosynthesis inhibitor DL-propargylglycine reversed the effect of Mel on the said attributes and again the damaging effects of drought were observed even in presence of Mel. This observation led us to conclude that Mel-regulated defense mechanisms operate through endogenous H2S under DS conditions.

Exploring the potential role of hydrogen sulfide and jasmonic acid in plants during heavy metal stress

In plants, hydrogen sulfide (H2S) is mainly considered as a gaseous transmitter or signaling molecule that has long been recognized as an essential component of numerous plant cellular and physiological processes. Several subcellular compartments in plants use both enzymatic and non-enzymatic mechanisms to generate H2S. Under normal and stress full conditions exogenous administration of H2S supports a variety of plant developmental processes, including growth and germination, senescence, defense, maturation and antioxidant machinery in plants. Due to their gaseous nature, they are efficiently disseminated to various areas of the cell to balance antioxidant pools and supply sulphur to the cells. Numerous studies have also been reported regarding H2S ability to reduce heavy metal toxicity when combined with other signaling molecules like nitric oxide (NO), abscisic acid (ABA), calcium ion (Ca2+), hydrogen peroxide (H2O2), salicylic acid (SA), ethylene (ETH), jasmonic acid (JA), proline (Pro), and melatonin. The current study focuses on multiple pathways for JA and H2S production as well as their signaling functions in plant cells under varied circumstances, more specifically under heavy metal, which also covers role of H2S and Jasmonic acid during heavy metal stress and interaction of hydrogen sulfide with Jasmonic acid.

Hydrogen Sulfide: An Emerging Regulator of Oxidative Stress and Cellular Homeostasis-A Comprehensive One-Year Review

Hydrogen sulfide (H2S), traditionally recognized as a toxic gas, has emerged as a critical regulator in many biological processes, including oxidative stress and cellular homeostasis. This review presents an exhaustive overview of the current understanding of H2S and its multifaceted role in mammalian cellular functioning and oxidative stress management. We delve into the biological sources and function of H2S, mechanisms underlying oxidative stress and cellular homeostasis, and the intricate relationships between these processes. We explore evidence from recent experimental and clinical studies, unraveling the intricate biochemical and molecular mechanisms dictating H2S's roles in modulating oxidative stress responses and maintaining cellular homeostasis. The clinical implications and therapeutic potential of H2S in conditions characterized by oxidative stress dysregulation and disrupted homeostasis are discussed, highlighting the emerging significance of H2S in health and disease. Finally, this review underscores current challenges, controversies, and future directions in the field, emphasizing the need for further research to harness H2S's potential as a therapeutic agent for diseases associated with oxidative stress and homeostatic imbalance. Through this review, we aim to emphasize H2S's pivotal role in cellular function, encouraging further exploration into this burgeoning area of research.

Regulation of Mitochondrial Respiration by Hydrogen Sulfide

Hydrogen sulfide (H2S), the third gasotransmitter, has positive roles in animals and plants. Mitochondria are the source and the target of H2S and the regulatory hub in metabolism, stress, and disease. Mitochondrial bioenergetics is a vital process that produces ATP and provides energy to support the physiological and biochemical processes. H2S regulates mitochondrial bioenergetic functions and mitochondrial oxidative phosphorylation. The article summarizes the recent knowledge of the chemical and biological characteristics, the mitochondrial biosynthesis of H2S, and the regulatory effects of H2S on the tricarboxylic acid cycle and the mitochondrial respiratory chain complexes. The roles of H2S on the tricarboxylic acid cycle and mitochondrial respiratory complexes in mammals have been widely studied. The biological function of H2S is now a hot topic in plants. Mitochondria are also vital organelles regulating plant processes. The regulation of H2S in plant mitochondrial functions is gaining more and more attention. This paper mainly summarizes the current knowledge on the regulatory effects of H2S on the tricarboxylic acid cycle (TCA) and the mitochondrial respiratory chain. A study of the roles of H2S in mitochondrial respiration in plants to elucidate the botanical function of H2S in plants would be highly desirable.

Transcriptomic analysis reveals the functions of H2S as a gasotransmitter independently of Cys in Arabidopsis

Numerous studies have revealed the gasotransmitter functions of hydrogen sulfide (H₂S) in various biological processes. However, the involvement of H₂S in sulfur metabolism and/or Cys synthesis makes its role as a signaling molecule ambiguous. The generation of endogenous H₂S in plants is closely related to the metabolism of Cys, which play roles in a variety of signaling pathway occurring in various cellular processes. Here, we found that exogenous H₂S fumigation and Cys treatment modulated the production rate and content of endogenous H₂S and Cys to various degrees. Furthermore, we provided comprehensive transcriptomic analysis to support the gasotransmitter role of H₂S besides as a substrate for Cys synthesis. Comparison of the differentially expressed genes (DEGs) between H₂S and Cys treated seedlings indicated that H₂S fumigation and Cys treatment caused different influences on gene profiles during seedlings development. A total of 261 genes were identified to respond to H₂S fumigation, among which 72 genes were co-regulated by Cys treatment. GO and KEGG enrichment analysis of the 189 genes, H₂S but not Cys regulated DEGs, indicated that these genes mainly involved in plant hormone signal transduction, plant-pathogen interaction, phenylpropanoid biosynthesis, and MAPK signaling pathway. Most of these genes encoded proteins having DNA binding and transcription factor activities that play roles in a variety of plant developmental and environmental responses. Many stress-responsive genes and some Ca²⁺ signal associated genes were also included. Consequently, H₂S regulated gene expression through its role as a gasotransmitter, rather than just as a substrate for Cys biogenesis, and these 189 genes were far more likely to function in H₂S signal transduction independently of Cys. Our data will provide insights for revealing and enriching H₂S signaling networks.