Topic 22.5
Cloning of the Gene That Encodes ACC Oxidase
The gene that encodes ACC oxidase was cloned by a circuitous route. Researchers isolated a set of genes that are highly induced during tomato fruit ripening. They then blocked the expression of these genes by introducing an antisense version of each into transgenic tomatoes. Blocking of one such gene, pTOM13, repressed fruit ripening and inhibited ethylene production. Expression of pTOM13 in Xenopus oocytes as well as in yeast conferred the ability to convert ACC to ethylene, indicating that the gene encodes an ACC oxidase enzyme (Spanu et al. 1991). Using this gene, researchers then isolated ACC oxidase clones from numerous plant species.