Rotten-Egg Gas Arms Wheat Against Rust by Switching On Cellular Recycling

Hydrogen sulfide is best known as the gas that gives rotten eggs their unmistakable stench, but inside plant cells it is one of biology’s most versatile signaling molecules. A new study published in Stress Biology has now revealed a surprising role for this gas in one of agriculture’s most damaging diseases: wheat stripe rust. Researchers led by Ying Ma and Xiaojing Wang at Northwest A&F University in China report that hydrogen sulfide bolsters wheat’s immune defenses against the fungal pathogen Puccinia striiformis f. sp. tritici, the causative agent of stripe rust, by chemically modifying a central component of the plant’s autophagy machinery. The finding, published on 13 February 2026, provides the first evidence that the autophagy protein TaATG6c is regulated by persulfidation in wheat and uncovers a previously unrecognized mechanism linking sulfur-based redox signaling, cellular recycling, and disease resistance in the world’s most important cereal crop.

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