WOUND AND ETHYLENE INDUCTION OF THE ACC OXIDASE MELON GENE CM-ACO1 OCCURS VIA 2 DIRECT AND INDEPENDENT TRANSDUCTION PATHWAYS

The enzyme ACC oxidase catalyses the last step of ethylene biosynthesi s in plants. Expression of the melon ACC oxidase gene, CM-ACO1, is rap idly induced (within 10 min) by ethylene treatment or upon wounding in leaves. The inhibitor of ethylene action, 1-methylcyclopropene (1-MCP ), inhibited the accumulation of ethylene-induced CM-ACO1 mRNA transcr ipts, while wound-induced expression of the gene was not affected. The 5'-untranslated region of the CM-ACO1 gene was fused to the beta-gluc uronidase (GUS) reporter gene and the corresponding transgenic tobacco plants were analysed. Two separate regions of the CM-ACO1 promoter ac tivated GUS expression in response to ethylene treatment and wounding. These results suggest that induction of CM-ACO1 gene expression occur s via two separate signal transduction pathways in response to woundin g and ethylene treatment.