Interaction between endogenous H2O2 and OsVPE3 in the GA-induced PCD of rice aleurone layers.

KEY MESSAGE: Endogenous hydrogen peroxide (H2O2) is involved in regulating the gibberellic acid-induced programmed cell death (PCD) of the aleurone layers by cooperating with OsVPE3 during rice seed germination. Preliminary experiments revealed that H2O2 produced by the NOX pathway is the key factor affecting rice germination. Histochemical analysis indicated that H2O2 is located in the aleurone layer. Both the H2O2 scavenger DMTU and the NOX inhibitor DPI decreased H2O2 content and significantly slowed down vacuolation in a dose-dependent manner. Interestingly, DMTU down-regulated the OsNOX8 transcript or DMTU and DPI decreased the intracellular H2O2 level, resulting in a delay of PCD. In contrast, GA and H2O2 up-regulated the OsNOX8 transcript and intracellular H2O2 level, leading to premature PCD, and the effects of GA and H2O2 were reversed by DMTU and DPI, respectively. These results showed that the imbalance of intracellular H2O2 levels leads to the delayed or premature PCD. Further experiments indicated that GA up-regulated the OsVPE3 transcript and VPE activity, and the effect was reversed by DPI. Furthermore, Ac-YVAD-CMK significantly blocked H2O2 accumulation, and DPI + Ac-YVAD-CMK had a more significant inhibitory effect compared with DPI alone, resulting in the delayed PCD, suggesting that OsVPE3 regulates PCD by promoting H2O2 generation. Meanwhile, DPI significantly inhibited the OsVPE3 transcript and VPE activity, and in turn delayed PCD occurrence, suggesting that the H2O2 produced by the NOX pathway may regulate PCD by up-regulating the OsVPE3 transcript. Thus, the endogenous H2O2 produced by the NOX pathway mediates the GA-induced PCD of rice aleurone layers by interacting with OsVPE3.