Hydrogen Sulfide’s Hidden Hand: How a Tiny Gas Molecule Rewires Plant Proteins

For decades, hydrogen sulfide was known mostly as the gas with the unmistakable smell of rotten eggs, a toxic byproduct of industrial processes and decaying organic matter. Today, it occupies a very different place in biology. In plants, hydrogen sulfide has emerged as a genuine signaling molecule, and the mechanism by which it exerts much of its influence is a chemical modification of proteins known as persulfidation. A comprehensive review published in Plant Cell Reports by Di Yang, Dengjing Huang, Xinfang Chen, Ailing Li, Huan Chen and Weibiao Liao of Gansu Agricultural University synthesizes a decade of research and argues that persulfidation is not a peripheral curiosity but a central regulator that integrates hormone signaling, ion transport and stress adaptation across the plant kingdom.

The chemistry behind persulfidation is elegant in its simplicity. Cysteine residues within proteins carry reactive thiol groups, and when hydrogen sulfide reacts with these thiols, it converts them into persulfide groups, formally adding an extra sulfur atom. This seemingly small change can dramatically alter a protein’s behavior. Persulfidation can change a protein’s conformation, modify its enzymatic activity, alter its subcellular localization, protect cysteine residues from irreversible oxidation, or change how the protein interacts with partners and membranes. Because the modification is reversible, it functions as a dynamic molecular switch, allowing plant cells to respond rapidly and flexibly to developmental cues and environmental challenges without needing to synthesize new proteins.

Detecting this modification, however, has been one of the field’s greatest technical challenges, and the review devotes considerable attention to the methodological toolbox that has made persulfidation biology possible. The workhorse of the field is the modified biotin switch assay, an adaptation of a technique originally developed to detect S-nitrosylated proteins. In this approach, free thiols are blocked, persulfides are then selectively tagged, and the tagged proteins are pulled down and identified. Building on this foundation, researchers have developed mass spectrometry-based high-throughput workflows that can map persulfidation sites across thousands of proteins at once, generating whole-proteome persulfidation profiles in model plants such as Arabidopsis. These proteomic studies revealed that hundreds of proteins involved in wildly diverse processes carry the modification, hinting early on at the breadth of hydrogen sulfide’s regulatory reach.

Beyond the biotin switch family, the methodological landscape now includes antibody-dependent western blotting for targeted validation, electrophilic trapping strategies that exploit the distinctive nucleophilicity of persulfides, genetically encodable and small-molecule fluorescent probes that allow persulfidation to be visualized in living tissues, and alkylating compound-based approaches. Each technique comes with trade-offs in sensitivity, specificity and throughput, and the review emphasizes that careful controls remain essential. Notably, recent work has shown that some commonly used alkylating agents can convert persulfides into thioethers that escape detection, meaning that method choice can materially change experimental conclusions. Accurate detection, identification and quantification of persulfidation, the authors argue, is the indispensable foundation for understanding the modification’s biological functions and molecular mechanisms.

Where persulfidation truly shines, according to the synthesis, is in its role as a master fine-tuner of phytohormone signaling. The review documents how hydrogen sulfide modulates the pathways of ethylene, abscisic acid, auxin and melatonin by persulfidating key enzymes, receptors and transcription factors within each cascade. In the case of ethylene, the gas responsible for fruit ripening, hydrogen sulfide has been shown to negatively regulate ethylene biosynthesis by persulfidating the enzyme ACO in tomato plants under osmotic stress, creating a feedback loop that prevents runaway hormone production. Persulfidation of the transcription factor SlERF.D2 further interferes with ethylene signaling, while modification of the E3 ligase BRG3 delays tomato ripening by reducing ubiquitination of the ripening repressor WRKY71. Persulfidation and phosphorylation of the transcription factor SlWRKY6 have also been shown to differentially regulate tomato fruit ripening, illustrating how multiple post-translational modifications converge on the same regulatory proteins.

Abscisic acid, the hormone that governs stomatal closure and drought responses, provides perhaps the most mechanistically detailed examples. Hydrogen sulfide positively regulates abscisic acid signaling through persulfidation of SnRK2.6, a core protein kinase in guard cell signaling. Persulfidation-based modification of the cysteine desulfhydrase enzyme and the NADPH oxidase RBOHD controls guard cell abscisic acid signaling, linking sulfide production directly to the reactive oxygen species machinery that drives stomatal movement. Abscisic acid also triggers persulfidation of the cysteine protease ATG4, thereby regulating autophagy, while persulfidation of the glycosyltransferase UGT71C5 facilitates the reversible inactivation of abscisic acid itself. Through these targets, hydrogen sulfide influences everything from the opening and closing of stomata to the maintenance of hormone homeostasis, governing processes as visible as drought tolerance and as subtle as the balance of hormone pools within a single cell.

Auxin and melatonin signaling are likewise woven into the persulfidation network. Hydrogen sulfide alleviates osmotic stress-induced inhibition of root growth by promoting auxin homeostasis, and it alleviates salt stress through auxin signaling in Arabidopsis. The modification also antagonizes cytokinin signaling by persulfidating the cytokinin-degrading enzyme CKX2, reshaping root system architecture, and it acts downstream of methane to induce adventitious root development in cucumber. In the melatonin sphere, hydrogen sulfide aids osmotic stress resistance through the persulfidation of melatonin production-related enzymes in Arabidopsis, and the two molecules cooperate in modulating secondary metabolites and metal sequestration in arsenic-stressed tomato plants. Together, these findings paint a picture of hydrogen sulfide as a hub that sits at the intersection of multiple hormonal circuits, allowing a single gasotransmitter to coordinate root development, flowering, ripening and stress responses across the plant life cycle.

Beyond hormones, the review highlights a strikingly concrete mechanism by which persulfidation protects plants from salt and drought stress: the maintenance of cellular ion homeostasis. Excess sodium is toxic to plant cells, and survival under salinity depends on keeping sodium out while retaining potassium. Persulfidation executes what the authors describe as a coordinated ‘activate efflux, inhibit leak’ strategy. On the activation side, the modification enhances the activity of the plasma membrane H+-ATPase and the SOS1 Na+/H+ antiporter, the molecular pump that drives sodium extrusion from the cell. Persulfidation of PMA1, a plasma membrane proton pump, has been shown directly to improve salt tolerance in Arabidopsis. On the retention side, hydrogen sulfide inhibits inward potassium channels through persulfidation, preventing the loss of cellular potassium that would otherwise accompany salt stress. This dual action has been observed in systems ranging from Arabidopsis and cucumber to poplar and the salt-secreting mangrove Avicennia marina, suggesting an evolutionarily conserved ionic strategy.

The breadth of persulfidation’s targets extends even further. The modification maintains the activity of cytosolic glucose-6-phosphate dehydrogenases under salt stress by stabilizing their tetrameric structure and competing with cysteine sulfur oxidation, thereby protecting central carbon metabolism. Persulfidation of the flowering repressor BraFLCs promotes flowering in heading Chinese cabbage, and hydrogen sulfide-induced persulfidation has been implicated in barley’s resilience to drought and salinity. The review also situates plant persulfidation within a broader evolutionary context, noting that selective persulfide detection methods have revealed conserved anti-aging effects of protein S-sulfhydration in animals, and that hydrogen sulfide signaling through persulfidation regulates processes from autophagy to endoplasmic reticulum stress responses across kingdoms. What began as plant biochemistry is now clearly part of a universal redox signaling language.

The practical implications of this synthesis are considerable. Because persulfidation governs fruit ripening, stomatal movement, root development and osmotic stress adaptation, it represents a promising target for improving crop adaptation to the increasingly erratic conditions of a changing climate. Engineering or agronomically manipulating hydrogen sulfide signaling could, in principle, enhance salt and drought tolerance in staple and horticultural crops without the yield penalties often associated with conventional stress-resistance traits. The authors’ framework, supported by funding from the National Natural Science Foundation of China, provides researchers with a roadmap: refine detection methods to quantify persulfidation at specific sites, map the modification across crop genomes, and identify the persulfidation states that confer resilience. As the molecular details continue to accumulate, the once-maligned gas of rotten eggs looks increasingly like one of the most versatile regulatory molecules in the plant world, a sulfur-based switchboard quietly coordinating how plants grow, ripen and survive.

Subject of Research: Protein persulfidation as a hydrogen sulfide-mediated post-translational modification regulating plant hormone signaling, ion homeostasis and stress adaptation

Article Title: Protein persulfidation in plants: a central regulator of multiple signaling pathways

Article References: Yang, D., Huang, D., Chen, X., Li, A., Chen, H., & Liao, W. (2026). Protein persulfidation in plants: a central regulator of multiple signaling pathways. Plant Cell Reports, 45(9), Article 269. https://doi.org/10.1007/s00299-026-03954-y

Image Credits: AI Generated

DOI: 10.1007/s00299-026-03954-y

Keywords: persulfidation, hydrogen sulfide, post-translational modification, phytohormone signaling, abscisic acid, ethylene, auxin, melatonin, ion homeostasis, salt tolerance, drought stress, Plant Cell Reports