Aim: H2S is emerging as a signaling molecule involved in the regulation of many physiological processes in plants. Here, we investigated the potential antioxidant role of H2S in soybean (Glycine max)-rhizobia (Sinorhizobium fredii) symbiotic root nodules.
Method: An endogenous H2S production deficit rhizobia mutant ∆CSE was constructed to study the effect of decreased content of H2S in soybean nodules. Fluorescent probes and confocal microscope were used to observe the production and accumulation of H2S and reactive oxygen species. Transmission electronic microscopy was conducted to study the structural changes in ∆CSE soybean nodules. Finally, qRT-PCR, enzymatic activity, and oxidative damage parameters were measured.
Result: The results demonstrated that abundant H2S was generated in the nitrogen-fixing zone of soybean nodules. The deletion of the cystathionine γ-lyase (CSE) gene in S. fredii (∆CSE) caused a sharp decrease in H2S production in both free-living rhizobia and soybean nodules. We found that decrease in the H2S level in nodule cells inhibited nitrogenase activity. In addition, to elevated H2O2 and malondialdehyde accumulation, increased protein carbonyl content and decreased O2 − scavenging ability was observed in ∆CSE root nodules. Transmission electron microscopy revealed that an H2S deficit caused the deformation of bacteroids and damage of peribacteroid membranes in nodule cells. Moreover, the expression of some rhizobial and soybean genes related to antioxidant defense was up-regulated in ∆CSE nodules.
Conclusion: H2S is crucial for the nitrogen-fixation ability of soybean nodules by acting as an antioxidant element that protects nodule cells and bacteroids from oxidative damage.
Scopus Subject Areas
- Soil Science
- Plant Science
- Antioxidant defense
- Hydrogen sulfide
- Nitrogenase activity
- Oxidative stress
- Soybean root nodule