Reactive oxygen species mediate IAA-induced ethylene production in mungbean (Vigna radiata L.) hypocotyls

We reported previously that ROS may function as a downstream component for signaling auxin, a hormone that induces the ethylene production. Here we demonstrated that ROS can act upstream to promote auxin-induced ethylene production in mungbean hypocotyls. When plants were treated with AVG, ethylene biosynthetic inhibitor, or ACC, ethylene precursor, we found that little effect on the ROS generation. Hypocotyls exposed to H₂O₂ showed higher ethylene accumulations compared with untreated samples. Furthermore, auxin-induced ethylene production was reduced when tissues were pre-treated with a ROS scavenger, N-acetyl-L-cystein (NAC). We attributed this stimulatory effect to the activation of ethylene biosynthetic enzymes that results from transcriptional up-regulation of VR-ACS1 and VR-ACS7 to encode ACC synthase, as well as of VR-ACO1 and VR-ACO2, which encode ACC oxidase.