The promotive and repressive effects of exogenous H2O2 on Arabidopsis seed germination and seedling establishment depend on application dose.

Abstract

Hydrogen peroxide (H₂O₂) displays significant and dual effects on seed germination and seedling development, depending on the application dosage. However, the definition of H₂O₂ thresholds and the mechanisms underlying the dual actions in Arabidopsis seed germination and seedling development are not yet clear. Here, we analyzed the Arabidopsis seed germination profiles in response to different concentrations of exogenous H₂O₂ and found that 2 mM functions as the key threshold, above this threshold, both seed germination and seedling establishment were gradually inhibited. By RNA-seq analysis and function verification, we identified pathways of abscisic acid (ABA) signalling, seed post-ripening, energy metabolism, ROS homeostasis, and cell wall loosening play positive roles in seed germination and seedling establishment downstream of the H₂O₂ signalling. Further physio-chemical approaches revealed that exogenous H₂O₂ affected the accumulation and distribution of O₂ ^•- and H₂O₂ in embryonic tissues by regulating the tissue-specific expression of SDH2-3, RHD2, and PRXs. Collectively, we found that germination rate and aerial growth were positively correlated with endogenous H₂O₂ content and root length was positively correlated with O₂ ^•- accumulation, demonstrating that different ROS signals played specific functions in different tissues and development processes. On the other hand, excessive H₂O₂ (10 mM) represses these two processes for radicle cell damage caused by oxidation stress. Finally, we put forward the mechanism model of the dual effects of exogenous H₂O₂ on seed germination and seedling establishment.