Abstract
Cut flowers of a transgenic carnation (Dianthus caryophyllus L.) line (sACO-1 line), which was transformed with a carnation 1-aminocyclopropane-1-carboxylate (ACC) oxidase cDNA in sense orientation (sACO transgene), had a longer vase life than had flowers of the non-transformed plant and produced only a negligible amount of ethylene during natural senescence. The suppressed ethylene production in sACO-1 line was not accompanied with the accumulation of mRNA for ACC oxidase (DC-ACO1) gene in the gynoecium or mRNAs for DC-ACO1 and ACC synthase (DC-ACS1) genes in the petals. Previously, it was shown that in naturally senescing carnation flowers, ethylene is first produced from the gynoecium ; the evolved ethylene, acting as a diffusible signal which is perceived by petals, induces the expression of DC-ACO1 and DC-ACS1 genes that results in autocatalytic ethylene production in the petals (Shibuya et al., 2000). The results indicate that sACO transgene inhibits the expression of DC-ACO1, probably by cosuppression in the gynoecium, which then suppresses ethylene production in all flowers of sACO-1 line.
