The biosynthesis of ethylene in plants and its regulation by manipulating the expression of ACC synthase or ACC oxidase genes are discussed. Ethylene synthesis can be reduced by the introduction of antisense ACC synthase or antisense ACC oxidase genes. Expression genes of SAM hydrolase from bacteriofage T3, which catalyze the conversion of SAM to methylothioadenosine, also diminished ACC availability. Another possibility of ethylene biosynthesis control is the expression of gene encoding ACC deaminase from Pseudomonas.