Antisense ACC Oxidase RNA Delays Carnation Petal Senescence

The phytohormone ethylene is essential for senescence in many fruits and flowers. In the biosynthesis of ethylene in plants, the conversion of S-adenosyl methionine (SAM) to 1-aminocyclopropane1-carboxylic acid (ACC) and the conversion of ACC to ethylene are catalyzed by ACC synthase (ACS) and ACC oxidase (ACO), respectively (Adams and Yang, 1979). Using a cDNA clone representing carnation ACO (from Dianthus caryophyllus L. cv. Scania), we have produced transgenic carnation plants containing an antisense ACO gene. Flowers of one transformant from each of two cultivars (‘Scania’ and ‘White Sim’) containing this antisense gene exhibit low climacteric ethylene production and a markedly delayed petal senescence. At the time after harvest when petal inrolling would normally take place, the antisense ACO flowers produce little or no detectable ACO mRNA or ACS mRNA. However, the ACS and ACO genes can be induced in these flowers by applying exogenous ethylene.