Hydrogen Sulfide Helps Plants Survive Drought by Reshaping a Key Metabolic Enzyme

When water becomes scarce, plants face a brutal energy crisis. Their stomata close to conserve moisture, cutting off carbon dioxide and throttling photosynthesis, while their cells still need fuel to keep essential processes running. A new study published in Plant Cell Reports reveals that hydrogen sulfide, a gas long dismissed as a toxic byproduct, acts as a master coordinator of this metabolic emergency response, working on a single mitochondrial enzyme through two entirely different molecular mechanisms at once.

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