H₂S regulates low oxygen signaling via integration with the unfolded protein response in Arabidopsis thaliana

Purpose: Hydrogen sulfide (H₂S) is an important signaling molecule in prokaryotes and eukaryotes. In higher plants, H₂S regulates different processes throughout development and stress responses. Here, we investigated the underlying mechanism of H₂S in modulating hypoxia response signaling in Arabidopsis. Methods: DAB (3,3-diaminobenzidine) and fluorescent probes were used to detect the accumulation of reactive oxygen species and H₂S. Evans blue staining was conducted to observe the cell death. Quantitative RT-PCR was performed to measure the relative gene expression levels. Results: Our data showed that endogenous H₂S production was induced by anoxia and appropriate application of exogenous H₂S mitigated the damage caused by submergence stress. Meanwhile, the histological staining, fluorescent microscope observation and molecular analysis demonstrated that H₂S metabolism-related mutants oasa1 and lcddes1-1 accumulated different ROS levels and exhibited different low oxygen sensitivities compared with the wild type. In addition, we observed that ER stress response genes were up-regulated in wild type upon anoxia, and different ER stress response-related mutants ero1-2, ero1-3, ero2-1, ero2-2 and bzip28bzip60 were more sensitive to submergence or anoxia than wild type. Moreover, the exogenous H₂S pretreatment could not alleviate submergence-induced leaf death in ero2-1 compared with wild type, indicating that hypoxia induced ER stress and activation of the unfolded protein response (UPR) signal pathway is important for plant hypoxia response. Conclusion: Our work demonstrates that H₂S regulates hypoxic stress response through the integration with UPR. This study provides new insights into H₂S function during plant low oxygen stress response.