Abstract: A 0.9 kb fragment of ACC oxidase cDNA fragment prepared from total tomato RNA was amplified by polymerase chain reaction (PCR) and cloned into pGEM R T vector.The cloned ACC oxidase gene was further inserted into a binary vector,pBin438,in an inverted orientation between the CaMV 35S promoter and Nos 3’termination sequence (pBACO).Transgenic poplar plants were obtained by regeneration of agrobacteriummediated transformed leaves.PCR and Southern blot analyses confirmed the integration of a single antisense ACC oxidase gene in transformed poplar genome.The results from RTPCR of RNAs isolated from transgenic poplar leaves confirmed that the antisense RNA of ACC oxidase presented in these transgenic plants.The amount of ethylene released from transgenic poplars was reduced significantly to about 28% of that released from nontransformed controls.