Abstract:An ACC synthase cDNA isolated from tomato ( Lycopersicum esculentum Mill. ) fruit was constructed in antisense orientation under the transcriptional control of CaMV 35S promoter and then introduced into tobacco ( Nicotiana tabacum L. ). PCR amplification demonstrated the integration of this antisense gene in tobacco genomes. Northern hybridization and reverse transcription-PCR analyses indicated the expression of this heterologous antisense gene in the transgenic tobacco tissues, which caused a decrease in the ethylene production, particularly when shoot regeneration exhibited. The ability of shoot regeneration of the transgenic plant during the culture process was enhanced remarkably as compared with that of the control. These results indicate at the molecular level that ethylene may play a regulatory role in shoot formation.