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 centerpiece of the new work is the phenomenon known as adipose browning. White adipose tissue, the fat that stores energy in the body, can be converted under certain conditions into beige fat, a tissue type that burns energy rather than storing it. Beige fat is packed with mitochondria and expresses thermogenic programs, including the protein UCP1, that dissipate chemical energy as heat. In healthy people, browning is a response to cold exposure and helps maintain body temperature. In patients with cancer, however, inappropriate and persistent browning is thought to drain the body’s energy reserves, burning through calories and fat stores at a furious rate and contributing to the weight loss, weakness, and organ dysfunction that define cachexia. Understanding what switches browning on inside the tumors of a cachectic patient has therefore been a major goal of the field.

Chio and colleagues approached the problem from an unexpected angle: the chemistry of iron. Iron is an essential nutrient, central to oxygen transport, DNA synthesis, and mitochondrial respiration, but it is also chemically dangerous. Through the Fenton reaction, ferrous iron reacts with hydrogen peroxide to generate hydroxyl radicals, among the most reactive molecules in biology. Cells must therefore keep iron tightly sequestered and buffered, and when they fail, oxidative damage accumulates. Over the past decade, iron-driven lipid peroxidation has become famous as the trigger of ferroptosis, a form of regulated cell death, and iron overload has been linked to inflammation, fibrosis, and tumor progression. The new study extends this list dramatically, placing iron at the controls of a signaling axis that reaches deep into the metabolism of methionine, one of the twenty canonical amino acids.

Methionine is best known as the initiator amino acid of protein synthesis, but it carries a second, equally important identity as a redox-sensitive molecule. When oxidizing species attack methionine residues, they convert them to methionine sulfoxide, a chemical modification that can alter the structure and function of proteins in much the same way that phosphorylation or acetylation does, but with the direction reversed by a dedicated family of repair enzymes. Chief among these is methionine sulfoxide reductase A, or MSRA, an enzyme that restores oxidized methionine residues to their original form. For years, MSRA was studied primarily as a housekeeping antioxidant enzyme, valued for its role in protecting proteins from irreversible oxidative damage and for associations with aging and lifespan in model organisms. The new findings elevate it into a pathologically significant regulator of whole-body energy metabolism.

Through a combination of biochemical profiling, cell-culture experiments, and animal models of cancer-associated wasting, Chio and colleagues traced a pathway in which iron availability governs the degree of methionine oxidation within cells. When iron levels rise or iron handling is disrupted, the burden of methionine sulfoxide increases, and the balance between oxidation and reduction shifts. The team’s data indicate that this shift feeds into the transcriptional programs that drive adipocyte remodeling, promoting the browning of white fat depots. In other words, the iron-methionine redox axis behaves like a molecular thermostat for thermogenic fat, one that can be pushed into pathological overdrive during cancer. The investigators further showed that MSRA sits at a critical node: restoring or enhancing MSRA activity blunted the browning-associated events, whereas its loss made the pathological remodeling worse.

What makes the discovery especially exciting from a translational standpoint is that the pathway is, in the authors’ framing, targetable. MSRA is an enzyme with a defined catalytic activity, and enzymes are the kinds of molecules that medicinal chemistry knows how to engage. The study identifies MSRA as an important and actionable factor in the cachexia process, suggesting that boosting the methionine-sulfoxide-repair capacity of affected tissues could interrupt the energy-draining cascade. That possibility stands in sharp contrast to the current clinical landscape, where cachexia management remains largely supportive, relying on nutritional counseling, exercise where feasible, and a short list of drugs with modest and inconsistent benefits. No approved therapy has convincingly halted the syndrome, and the field has been searching for mechanisms upstream enough to intercept it early.

The findings also help explain a set of clinical observations that have long puzzled researchers. Cancers frequently induce systemic iron dysregulation, including the anemia of chronic disease and alterations in iron storage proteins such as ferritin and hepcidin. Tumors and their associated immune cells can also release inflammatory cytokines, including interleukin-6 and tumor necrosis factor, that reshape distant tissues. By connecting iron perturbation to methionine oxidation and then to adipose browning, the new work sketches a coherent chain of events that could link tumor-derived signals to the metabolic catastrophe unfolding in fat depots far from the tumor itself. It suggests that cachexia is not simply the passive consequence of appetite loss or competing tumor demand for nutrients, but the output of a regulated, mechanistically decipherable program.

Of course, important questions remain before the iron-methionine axis can be exploited in the clinic. The experiments establishing causality were performed largely in preclinical models, and animal models of cachexia, while valuable, do not capture the full heterogeneity of human disease, which varies enormously between patients with pancreatic cancer, lung cancer, colorectal cancer, and other malignancies. It is not yet clear which patient populations would benefit most from interventions aimed at iron handling or methionine redox repair, or how such interventions should be timed relative to tumor treatment. Iron itself is a double-edged sword: withholding it risks worsening anemia, while supplementing it could conceivably accelerate the very pathway the study identifies. The therapeutic window, as is so often the case in metabolism, will need careful mapping.

There are also broader implications for basic biology. If MSRA-mediated repair of oxidized methionine acts as a gatekeeper for thermogenic programs in fat, the same axis might operate in other contexts where browning or energy expenditure is relevant, including cold adaptation, exercise physiology, obesity, and perhaps even aging-related metabolic decline. The finding that a single amino acid’s redox chemistry can carry regulatory information of this magnitude adds weight to a growing view of methionine oxidation as a reversible signaling mechanism rather than mere collateral damage. It also intersects with the expanding literature on dietary methionine restriction, which has shown benefits in some metabolic and cancer models, and invites a reconsideration of how amino acid availability, iron status, and oxidative stress jointly shape systemic physiology.

For patients and their families, the immediate significance of the study is best expressed with appropriate caution: this is not a cure, but it is a genuine lead. Cachexia research has had few moments of genuine mechanistic clarity, and a targetable enzyme positioned within the pathway driving fat loss is exactly the kind of foothold the field has needed. Chio and colleagues have not only connected iron, methionine chemistry, and adipose browning in a single explanatory framework; they have also done so in a way that points toward concrete intervention. If follow-up studies confirm that enhancing methionine sulfoxide reductase activity can protect patients from the wasting of fat and muscle, the work could mark the beginning of a real shift in how medicine confronts one of cancer’s oldest and cruelest complications. Until then, the iron-regulated methionine redox axis stands as a vivid reminder that some of the most consequential discoveries in cancer biology emerge from the least glamorous corners of biochemistry, where a single sulfur atom in a single amino acid holds the balance between energy storage and energy loss.

Subject of Research: An iron-regulated methionine redox axis involving methionine sulfoxide reductase A that controls adipose browning and cancer cachexia

Article Title: An iron-regulated methionine redox axis governs adipose browning and cancer cachexia

Article References: Nam, J. S., Ahn, S. S., Shin, Y., Vargas-Castillo, A., Dixon, M. S., Ahmadi, P., Schilling, K., Zandkarimi, F., Chen, A., Yoon, N. A., Cullen, H., Sun, Y., Caffrey, T. C., Klute, K. A., Swanson, B. J., Lu, J., Pan, S., Chen, Y., Ichimiya, S., … Chio, I. I. C. (2026). An iron-regulated methionine redox axis governs adipose browning and cancer cachexia. Nature Cancer. https://doi.org/10.1038/s43018-026-01234-y

Image Credits: AI Generated

DOI: 10.1038/s43018-026-01234-y

Keywords: cancer cachexia, adipose browning, iron metabolism, methionine oxidation, methionine sulfoxide reductase A, MSRA, redox signaling, white adipose tissue, thermogenesis, Nature Cancer, oxidative stress, cancer metabolism