Reactive oxygen species mediate IAA-lnduced 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, ethyiene 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 ofVR- ACS1 andVR- ACS7 to encode ACC synthase, as well as ofVR- ACO1 andVR- ACO2, which encode ACC oxidase.