The activation of autophagy by molecular hydrogen is functionally associated with osmotic tolerance in Arabidopsis

The role of molecular hydrogen (H₂) in autophagy during inflammatory response is controversial in mammalian cells. Although the stimulation of H₂ production in response to osmotic stress was observed in plants, its synthetic pathway and the interrelationship between its induction and plant autophagy remain unclear. Here, the induction of autophagy was observed in Arabidopsis upon osmotic stress, assessing by the autophagosome formation and autophagy-related genes expression. Above responses were intensified by H₂ fumigation. Meanwhile, the reduction in seedling growth and roots vigor was obviously abolished, accompanied by reestablishing redox balance. These H₂ responses were markedly impaired in T-DNA knockout lines atg2, atg5, and atg18. Further evidence showed that the increased endogenous H₂ synthesis by genetic manipulation, not only stimulated autophagosome formation, but also triggered various plant responses toward osmotic stress. By contrast, these responses were obviously abolished by the disruption of endogenous H₂ synthesis with the addition of 2,6-dichloroindophenol sodium salt. Together, the integrated genetic and molecular evidence clearly illustrated the requirement of autophagy activation in H₂ control of plant osmotic tolerance.