H2O2 response gene 1/2 are novel sensors or responders of H2O2 and involve in maintaining embryonic root meristem activity in Arabidopsis thaliana.

Signal molecule hydrogen peroxide (H2O2) plays critical roles in various processes of plant development. However, H2O2 signaling network, especially the responders that sense and respond to the H2O2 signal remain largely unknown. Here we report two homologous genes H2O2 Response Gene 1 and 2 (HRG1/2) in Arabidopsis that could quickly respond to exogenous or endogenous H2O2. Knockdown of HRG1/2 facilitated seed germination while overexpression of HRG1/2 greatly retarded seed germination. ROS level in HRG1 overexpression roots was significantly lower than that in HRG1/2 mutants after H2O2 treatment. The expression level of enzymatic antioxidant DHAR3 was upregulated in HRG1 overexpression plants, suggesting that DHAR3 is downstream of HRG1. That the root meristem length and cell number were significantly reduced in hrg1-1 and hrg2-1 plants upon H2O2 treatment compared to that of HRG1 overexpression plants also approves the idea that HRGs function in H2O2 removal. Further evolutionary analysis indicates that this is a dicotyledon-specific pathway responsive to H2O2. Together, this work reveals HRG1/2 as novel H2O2 responders involved in ROS scavenging to ensure embryonic root meristem activity. These findings provide valuable clues for the of H2O2 signaling and root meristem regulation.