H2 Enhances Arabidopsis Salt Tolerance by Manipulating ZAT10/12-Mediated Antioxidant Defence and Controlling Sodium Exclusion

Background: The metabolism of hydrogen gas (H-2) in bacteria and algae has been extensively studied for the interesting of developing H-2-based fuel. Recently, H-2 is recognized as a therapeutic antioxidant and activates several signalling pathways in clinical trials. However, underlying physiological roles and mechanisms of H-2 in plants as well as its signalling cascade remain unknown. Methodology/Principal Findings: In this report, histochemical, molecular, immunological and genetic approaches were applied to characterize the participation of H-2 in enhancing Arabidopsis salt tolerance. An increase of endogenous H-2 release was observed 6 hr after exposure to 150 mM NaCl. Arabidopsis pretreated with 50% H-2-saturated liquid medium, mimicking the induction of endogenous H-2 release when subsequently exposed to NaCl, effectively decreased salinity-induced growth inhibition. Further results showed that H-2 pretreatment modulated genes/proteins of zinc-finger transcription factor ZAT10/12 and related antioxidant defence enzymes, thus significantly counteracting the NaCl-induced reactive oxygen species (ROS) overproduction and lipid peroxidation. Additionally, H-2 pretreatment maintained ion homeostasis by regulating the antiporters and H+ pump responsible for Na+ exclusion (in particular) and compartmentation. Genetic evidence suggested that SOS1 and cAPX1 might be the target genes of H-2 signalling. Conclusions: Overall, our findings indicate that H-2 acts as a novel and cytoprotective regulator in coupling ZAT10/12-mediated antioxidant defence and maintenance of ion homeostasis in the improvement of Arabidopsis salt tolerance.