Hydrogen enhances adaptation of rice seedlings to cold stress via the reestablishment of redox homeostasis mediated by miRNA expression

AIMS: The role of hydrogen gas (H₂) in modulating cold tolerance was investigated. METHODS: A combination of physiological and molecular approaches was used to study the effect of H₂ on the alleviation of cold stress. RESULTS: Cold stress stimulated the production of H₂ in rice seedlings. The pretreatment with exogenous H₂ not only mimicked above physiological response, but also prevented cold-induced growth inhibition. With 0.39 mM H₂ pretreatment, rice seedlings exhibited the maximum improving responses, including alleviating the decrease of chlorophyll contents and photosynthetic activity. The lipid peroxidation and the overproduction of reactive oxygen species (ROS) were decreased as well. These results were supported by the changes of total and isozymatic activities of antioxidant enzymes. In comparison with cold stress alone, miR398 transcripts were down-regulated by H₂, and expression levels of its targets Cu/Zn-SOD1 (CSD1) and Cu/Zn-SOD2 (CSD2) were increased. By contrast, miR319 transcripts were differentially increased, showing a relatively negative correlation with its target genes PROLIFERATING CELL FACTOR5 (PCF5) and PROLIFERATING CELL FACTOR8 (PCF8). CONCLUSIONS: Our results suggested that endogenous H₂ might contribute to the enhancement of cold tolerance, at least partially, by the reestablishment of redox homeostasis via miR398 and miR319.