Stripe rust is a formidable adversary. Under favorable environmental conditions, the disease can strip wheat fields of up to 60 percent of their yield, and the pathogen’s highly dynamic populations continually evolve new races that overcome resistant cultivars. Because the fungus is an obligate biotroph, meaning it must feed on living host tissue, it has evolved sophisticated strategies to suppress plant defenses while quietly extracting nutrients. Farmers currently rely on a combination of fungicides and resistance genes, but the constant arms race between wheat and its attacker makes it essential to identify new layers of immune regulation that could be exploited for crop protection. The new study suggests that gas signaling, long overlooked in this context, may represent exactly such a layer.

The team began by testing whether exogenous hydrogen sulfide could influence disease outcomes directly. Wheat seedlings inoculated with the virulent Pst race V26 were treated with the hydrogen sulfide donor sodium hydrosulfide, or NaHS, at concentrations of 100, 300, and 500 micromolar. Compared with untreated inoculated plants, the treated seedlings showed markedly attenuated disease symptoms and reduced fungal proliferation, with the strongest protective effect at the highest dose. A slow-releasing hydrogen sulfide donor called GYY4137 produced similar suppression of pathogen development, while a chemical scavenger that removes hydrogen sulfide increased necrotic lesion area in an otherwise resistant interaction. Quantitative microscopy revealed that the gas treatment boosted the accumulation of reactive oxygen species and hypersensitive cell death at infection sites in a concentration-dependent manner, while fungal hyphal area and length correspondingly shrank. The effect was unambiguous: hydrogen sulfide enhances wheat immunity in a dose-dependent fashion.

To understand how the gas exerts this protection, the researchers turned to the molecular mechanism most commonly associated with hydrogen sulfide signaling: protein persulfidation. This post-translational modification converts the thiol groups of cysteine residues into persulfides, altering protein activity, interactions, and stability in a rapid and reversible way. Using comparative persulfidation proteomics, the team catalogued the persulfidated proteins in wheat leaves infected with Pst races CYR32 and V26 and compared them with uninfected controls. The scale of the modification was striking: 16,473 persulfidated proteins were identified in total, of which 1,053 were uniquely modified in infected samples. Gene ontology analysis showed that the proteins specifically persulfidated upon infection were enriched in biological processes tied to immunity and stress adaptation, including responses to other organisms, stress responses, and signal transduction.

Within the stress-response category, one protein stood out. TaATG6c, a wheat homolog of the conserved autophagy regulator ATG6/Beclin1, was the only protein with a direct functional association with the autophagy pathway. Autophagy is the cell’s recycling system, in which double-membraned vesicles called autophagosomes engulf damaged organelles, protein aggregates, and even invading pathogens for degradation. In plants, this process is intimately connected to immunity: it restricts pathogen invasion, modulates immune signaling, regulates programmed cell death, and maintains reactive oxygen species homeostasis. ATG6 serves as a central scaffold within the class III phosphatidylinositol-3-kinase complex that initiates autophagosome formation, making it a plausible point of control for a gas signal that needs to act quickly during infection.

Site-specific mass spectrometry pinpointed exactly where hydrogen sulfide attaches to TaATG6c. Two cysteine residues, Cys177 and Cys180, each displayed the characteristic mass shift of 31.97207 daltons that signals persulfidation. A modified biotin-switch assay confirmed the modification: NaHS treatment induced a concentration-dependent increase in TaATG6c persulfidation, the reducing agent DTT abolished the signal, and substituting the two cysteines with alanines completely eliminated the NaHS-induced modification. Notably, the two sister paralogs TaATG6a and TaATG6b showed no detectable persulfidation, underscoring the specificity of TaATG6c as the hydrogen sulfide-responsive member of the family. Structural modeling based on AlphaFold added a mechanistic dimension: both modified residues sit within the central coiled-coil domain, exposed on the protein surface at the interface where TaATG6c binds its partner ATG14. The modeling predicted that mutating these residues weakens the TaATG6c–ATG14 interaction by reducing hydrogen bonds at the interface, suggesting that persulfidation fine-tunes the assembly of the autophagy initiation complex without relocating the protein within the cell.

Functional experiments then established that TaATG6c is a genuine positive regulator of stripe rust resistance. Using virus-induced gene silencing targeting a conserved region shared by the three TaATG6 paralogs, the researchers suppressed TaATG6 expression by roughly 70 percent. When these silenced plants were challenged with the avirulent race CYR23, they developed more severe disease symptoms and carried significantly higher fungal biomass than controls. Microscopy revealed enlarged infection sites with increased hyphal growth. Intriguingly, the silenced plants accumulated more reactive oxygen species and more cell death, yet these responses failed to contain the fungus. The authors interpret this as evidence that excessive ROS arising from impaired autophagy is not sufficient to restrict pathogen proliferation, because autophagy normally helps maintain oxidative balance. Supporting this view, the autophagy activator lithium chloride suppressed Pst growth, while the inhibitor 3-methyladenine worsened necrotic lesions. TaATG6 expression itself was strongly induced during infection, peaking at 48 hours post-inoculation and reaching higher levels in the incompatible interaction than in the compatible one.

The decisive experiment connected all the threads. In control plants, NaHS treatment markedly alleviated disease symptoms caused by the compatible race CYR32, but this protective effect was substantially attenuated in TaATG6-silenced plants, demonstrating that the gas requires TaATG6c to deliver its full benefit. Conversely, transient overexpression of TaATG6 enhanced resistance, whereas overexpression of the C177A/C180A mutant failed to do so, proving that the two cysteine residues are critical for the protein’s resistance-promoting function. Endogenous biotin-switch assays showed that TaATG6c persulfidation follows a dynamic, pathogen-responsive pattern: it rises rapidly after infection, peaks at 24 hours, and gradually declines thereafter, while the cysteine mutant remained flat throughout. Finally, the team tracked the accumulation of lipidated ATG8, a hallmark of autophagosome formation. Both hydrogen sulfide treatment and Pst infection increased ATG8–PE levels in wild-type plants, and the combined treatment amplified the effect, but in TaATG6-silenced plants the basal level of ATG8–PE dropped and neither stimulus could induce it.

Taken together, the results sketch a coherent model of a redox-regulated immune circuit. When the stripe rust fungus attacks, hydrogen sulfide signaling surges, and the gas chemically tags TaATG6c at Cys177 and Cys180. This persulfidation strengthens the protein’s engagement with the autophagy initiation machinery, promoting autophagosome formation at precisely the moment the plant needs to deploy cellular recycling against the invader. Because the modification is rapid and reversible, it allows wheat to coordinate its defense within a precise temporal window rather than simply cranking up protein abundance. The work also resonates with earlier findings in Arabidopsis, where persulfidation of the autophagy protein ATG18a enhances autophagosome formation under stress, suggesting that sulfur-based control of autophagy may be a conserved feature of plant biology. For breeders and crop scientists, the study points to TaATG6c and its persulfidation sites as potential molecular targets for engineering or selecting wheat varieties with stronger, more durable resistance to stripe rust, and it elevates a humble, foul-smelling gas to the status of a key player in the global fight for food security.

Subject of Research: Hydrogen sulfide signaling and autophagy-mediated immunity in wheat against stripe rust

Article Title: Hydrogen sulfide promotes wheat immunity against stripe rust through TaATG6c persulfidation

Article References: Hydrogen sulfide promotes wheat immunity against stripe rust through TaATG6c persulfidation. (n.d.). https://doi.org/10.1007/s44154-026-00292-7

Image Credits: AI Generated

DOI: 10.1007/s44154-026-00292-7

Keywords: hydrogen sulfide, wheat, stripe rust, Puccinia striiformis, autophagy, TaATG6c, persulfidation, plant immunity, ATG8, redox signaling, crop disease resistance, post-translational modification

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

The research, led by Jiao Zhang, Xin Wang and Xiaofeng Zhang of Shanxi University in Taiyuan, China, under the corresponding authors Yanxi Pei and Zhuping Jin, focuses on an enzyme called electron transfer flavoprotein: ubiquinone oxidoreductase, or ETFQO. This protein sits in the inner mitochondrial membrane and serves as a metabolic escape hatch. When carbohydrates run low, the cell can break down amino acids such as lysine and branched-chain amino acids, and ETFQO channels the electrons liberated from that breakdown into the mitochondrial electron transport chain, allowing respiration to continue even when the usual fuel supply has collapsed.

What makes the new work striking is the discovery that hydrogen sulfide does not simply switch ETFQO on or off. Instead, it manipulates the enzyme at two levels simultaneously. At the transcriptional level, both hydrogen sulfide treatment and drought stress increase the expression of the ETFQO gene, producing more of the raw material for the protein. But the team’s transcriptome sequencing revealed something more subtle: hydrogen sulfide also changes how the ETFQO pre-messenger RNA is spliced, the process by which non-coding introns are removed and coding sequences are stitched together before a protein is made.

Alternative splicing is one of the most powerful sources of biological complexity in higher organisms. A single gene can yield multiple protein variants, called isoforms, each with potentially different structures and functions. In the case of ETFQO, the researchers found that hydrogen sulfide modulates splicing under stress conditions so that three distinct transcripts accumulate, which they named ETFQO.1, ETFQO.2 and ETFQO.3. These isoforms are not interchangeable, and the physiological experiments demonstrated that their roles diverge in ways that matter for survival.

To test what each isoform actually does, the team generated Arabidopsis thaliana plants that overexpress each of the three transcripts individually. The results were clear-cut. Plants overexpressing ETFQO.3 showed improved drought tolerance, while those overexpressing ETFQO.1 or ETFQO.2 did not gain any such advantage. Yet the story does not end there. Both ETFQO.1 and ETFQO.3 participated in the hydrogen sulfide-modulated control of stomatal closure and mitochondrial respiration, and both responded more strongly to the gas than ETFQO.2 did. In other words, only one isoform directly confers drought resistance, but two of the three serve as responsive partners in the broader gasotransmitter-driven stress program.

The explanation for this functional specificity lies in a chemical modification known as persulfidation. Hydrogen sulfide can attach a sulfur atom to reactive cysteine residues on target proteins, converting their thiol groups into persulfides and thereby altering their activity, stability or interaction partners. This modification has emerged over the past decade as the principal way hydrogen sulfide transmits signals in cells, operating alongside better-known systems such as phosphorylation and nitric oxide-dependent S-nitrosylation. In guard cells, for example, persulfidation of the protein kinase SnRK2.6 has already been shown to link hydrogen sulfide to abscisic acid signaling, the central hormonal pathway governing stomatal behavior.

In the new study, the mechanistic experiments showed that hydrogen sulfide induces persulfidation of ETFQO.1 and ETFQO.3, but that the same modification is absent from ETFQO.2. This single biochemical difference appears to explain why the first two isoforms are responsive to the gas while the third is not, and why only ETFQO.3, the persulfidated variant that also carries the right structural features, delivers actual drought tolerance when overexpressed. The finding illustrates how alternative splicing and post-translational modification can act in concert: splicing generates a menu of protein variants, and persulfidation selects and tunes which of them participate in the stress response.

The broader significance of the work lies in how it reframes the role of hydrogen sulfide in plant energy metabolism. Previous research from the same and other groups had established that the gas regulates stomatal movements through multiple targets, including S-type anion channels via the OST1 kinase and calcium modules, potassium channels, and succinate dehydrogenase, which the same team showed is activated by persulfidation to induce stomatal closure in Arabidopsis. Hydrogen sulfide has also been shown to modulate alternative splicing of other targets, such as the succinate dehydrogenase gene BrSDH1-1 in Chinese cabbage and the splicing factors AtU2AF65a and BraATO2, which influence flowering. The new study extends this regulatory logic deep into the mitochondrion, showing that a gasotransmitter can coordinate the respiratory machinery that sustains the cell when photosynthesis falters.

This coordination is precisely what a drought-stressed plant needs. Closing stomata saves water but starves the leaf of carbon dioxide, so the tissue must re-balance its energy budget. By promoting ETFQO expression, reshaping its splicing pattern and persulfidating the resulting isoforms, hydrogen sulfide simultaneously supports the respiratory recycling of amino acids and the stomatal decisions that determine how much water the plant loses. The authors describe this as a coordinated transcriptional and post-translational mechanism that integrates alternative splicing with persulfidation to optimize drought adaptation, a model that advances understanding of how gasotransmitters function in stress responses.

The practical implications could be considerable. Drought is among the most damaging abiotic stresses for global agriculture, and engineering crops with enhanced stress resilience is a major goal of plant biotechnology. Because ETFQO.3 overexpression alone improved drought tolerance in Arabidopsis, the isoform represents a candidate target for breeding or genome editing programs aimed at producing crop varieties that endure water scarcity more effectively. More broadly, the study suggests that manipulating hydrogen sulfide signaling, or the splicing and persulfidation machinery it engages, could offer new strategies for crop improvement. As with all results established in a model organism, translating the findings into staple crops will require further work, but the identification of a single enzyme controlled through two converging regulatory layers provides a concrete molecular handle for that effort.

Subject of Research: Hydrogen sulfide regulation of ETFQO alternative splicing and persulfidation in plant drought tolerance

Article Title: H2S enhances drought resistance by orchestrating alternative splicing and persulfidation of ETFQO

Article References: Zhang, J., Wang, X., Zhang, X., Zhang, L., Pei, Y., & Jin, Z. (2026). H2S enhances drought resistance by orchestrating alternative splicing and persulfidation of ETFQO. Plant Cell Reports, 45(10), Article 312. https://doi.org/10.1007/s00299-026-04006-1

Image Credits: AI Generated

DOI: 10.1007/s00299-026-04006-1

Keywords: hydrogen sulfide, ETFQO, alternative splicing, persulfidation, drought stress, Arabidopsis thaliana, mitochondrial respiration, stomatal closure, gasotransmitter, plant stress signaling, energy metabolism, crop improvement